LTC1760_11 [Linear]
Dual Smart Battery System Manager Available in 48-Lead TSSOP Package; 双智能电池系统管理器提供48引脚TSSOP封装型号: | LTC1760_11 |
厂家: | Linear |
描述: | Dual Smart Battery System Manager Available in 48-Lead TSSOP Package |
文件: | 总48页 (文件大小:349K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC1760
Dual Smart Battery
System Manager
FEATURES
DESCRIPTION
The LTC®1760 Smart Battery System Manager is a highly-
integrated SMBus Level 3 battery charger and selector
intended for products using dual smart batteries. Three
SMBus interfaces allow the LTC1760 to servo to the
internal voltage and currents measured by the batteries
while allowing an SMBus Host device to monitor either
battery’s status. Charging accuracy is determined by the
battery’s internal voltage and current measurements, typi-
cally better than 0.ꢀ2.
n
SMBus Charger/Selector for Two Smart Batteries*
n
Voltage and Current Accuracy within 0.2% of Value
Reported by Battery
n
Simplifies Construction of “Smart Battery System
Manager”
n
Includes All SMBus Charger V1.1 Safety Features
n
Supports Autonomous Operation without a Host
n
Allows Both Batteries to Discharge Simultaneously
into Single Load with Low Loss (Ideal Diode)
n
A proprietary PowerPath architecture supports simultane-
ouschargingordischargingofbothbatteries.Typicalbattery
run times are extended by up to 102, while charging times
are reduced by up to 502. The LTC1760 automatically
switchesbetweenpowersourcesinlessthan10μstoprevent
power interruption upon battery or wall adapter removal.
SMBus Switching for Dual Batteries with Alarm
Monitoring for Charging Battery at All Times
n
Pin Programmable Limits for Maximum Charge
Current and Voltage Improve Safety
n
Fast Autonomous PowerPath™ Switching (<10μs)
n
Low Loss Simultaneous Charging of Two Batteries
n
>952 Efficient Synchronous Buck Charger
The LTC1760 implements all elements of a version 1.1
“SmartBatterySystemManager”exceptforthegeneration
of composite battery information. An internal multiplexer
cleanly switches the SMBus Host to either of the two
attached Smart Batteries without generating partial mes-
sages to batteries or SMBus Host. Thermistors on both
batteriesareautomaticallymonitoredfortemperatureand
disconnection information (SafetySignal).
n
AC Adapter Current Limiting* Maximizes Charge Rate
n
SMBus Accelerator Improves SMBus Timing**
n
Available in 48-Lead TSSOP Package
APPLICATIONS
n
Portable Computers and Instruments
n
Standalone Dual Smart Battery Chargers
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including *57ꢀ3970 **6650174.
n
Battery Backup Systems
TYPICAL APPLICATION
Dual Battery Charger/Selector System Architecture
Dual vs Sequential Charging
3500
DC
IN
BATꢀ
BAT1
CURRENT
3000
ꢀ500
ꢀ000
1500
1000
500
CURRENT
SEQUENTIAL
SYSTEM
POWER
0
3500
3000
ꢀ500
ꢀ000
1500
1000
500
LTC1760
BAT1
CURRENT
SMBus (HOST)
BATꢀ
DUAL
CURRENT
100
MINUTES
SafetySignal 1
SMBus 1
0
0
100
150
ꢀ00 ꢀ50
300
50
TIME (MINUTES)
BATTERY TYPE: 10.8V Li-Ion (MOLTECH NIꢀ0ꢀ0)
REQUESTED CURRENT = 3A
SafetySignal ꢀ
REQUESTED VOLTAGE = 1ꢀ.3V
MAX CHARGER CURRENT = 4.1A
1760 TA03
SMBus ꢀ
1760 TA01
1760fa
1
LTC1760
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
DCIN, SCP, SCN, CLP,
PLUS
SCH1, SCHꢀ to GND................................... –0.3V to ꢀ8V
BOOST to GND...........................................–0.3V to 37V
CSP, CSN, BAT1, BATꢀ to GND................... –0.3V to ꢀ8V
LOPWR, DCDIV to GND ............................. –0.3V to 10V
1
ꢀ
3
4
5
6
7
8
9
10
11
1ꢀ
13
14
15
48 SCHꢀ
47 GCHꢀ
46 GCH1
45 SCH1
44 TGATE
43 BOOST
4ꢀ SW
V
PLUS
V
, SW to GND ..................................... –0.3V to 3ꢀV
BATꢀ
BAT1
SCN
SCP
GDCO
GDCI
GB1O
GB1I
GBꢀO
GBꢀI
41 DCIN
40 V
CC
V
, V
to GND.......................................–0.3V to 7V
CCꢀ DDS
SDA1, SDAꢀ, SDA, SCL1,
39 BGATE
38 PGND
37 COMP1
36 CLP
35 CSP
34 CSN
LOPWR
SCLꢀ, SCL, SMBALERT to GND....................–0.3V to 7V
MODE to GND .................................–0.3V to V
V
SET
I
TH
+0.3V
CCꢀ
I
SET
COMP1 to GND ............................................ –0.3V to 5V
Maximum DC Current Into Pin
DCDIV 16
SCLꢀ 17
SCL 18
33 V
LIMIT
3ꢀ I
LIMIT
31 TH1B
30 TH1A
ꢀ9 SMBALERT
ꢀ8 THꢀA
ꢀ7 THꢀB
SDA1, SDAꢀ, SDA, SCL1, SCLꢀ, SCL ................ 3mA
TH1A, THꢀA..................................................... –5mA
TH1B, THꢀB ................................................... –10ꢀμA
Operating Junction Temperature Range
SCL1 19
V
ꢀ0
DDS
SDAꢀ ꢀ1
SDA ꢀꢀ
SDA1 ꢀ3
GND ꢀ4
ꢀ6 MODE
ꢀ5 V
CCꢀ
(Note 6).................................................. –40°C to 1ꢀ5°C
Storage Temperature.............................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)...................300°C
FW PACKAGE
48-LEAD PLASTIC TSSOP
T
JMAX
= 1ꢀ5°C, θ = 110°C/W
JA
ORDER INFORMATION
LEAD FREE FINISH
LTC1760CFW#PBF
LTC1760IFW#PBF
TAPE AND REEL
PART MARKING
LTC1760CFW
LTC1760IFW
PACKAGE DESCRIPTION
48-Lead Plastic TSSOP
48-Lead Plastic TSSOP
TEMPERATURE RANGE
0°C to 85°C
LTC1760CFW#TRPBF
LTC1760IFW#TRPBF
–40°C to 1ꢀ5°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
1760fa
2
LTC1760
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 6). VDCIN = 20V, VBAT1 = 12V, VBAT2 = 12V, VVDDS = 3.3V,
VVCC2 = 5.2V unless otherwise noted.
SYMBOL PARAMETER
Supply and Reference
CONDITIONS
MIN
TYP
MAX
UNITS
DCIN Operating Range
DCIN Operating Current
DCIN Selected
6
ꢀ8
V
I
I
Not Charging (DCIN Selected) (Note 10)
Charging (DCIN Selected) (Note 10)
1
1.3
1.5
ꢀ
mA
mA
CH0
CH1
I
I
V
Operating Current
CCꢀ
AC Present (Note 11)
AC Not Present (Note 11)
0.75
75
1
100
mA
μA
VCCꢀ_AC1
VCCꢀ_AC0
Battery Operating Voltage Range
Battery Drain Current
Battery Selected, PowerPath Function
6
0
ꢀ8
ꢀ8
V
V
Battery Selected, Charging Function (Note ꢀ)
I
Battery Selected, Not Charging, V
= 0V (Note 10)
175
μA
BAT
DCIN
V
Diodes Forward Voltage:
PLUS
V
V
V
V
DCIN to V
BAT1 to V
BATꢀ to V
I
I
I
I
= 10mA
= 0mA
= 0mA
= 0mA
0.8
0.7
0.7
0.7
V
V
V
V
FDC
FB1
FBꢀ
PLUS
PLUS
PLUS
PLUS
VCC
VCC
VCC
VCC
SCN to V
FSCN
l
l
l
UVLO
Undervoltage Lockout Threshold
V
Ramping Down, Measured at V
to GND
3
5
5.5
1
V
V
PLUS
PLUS
V
VCC
V
LDR
V
V
Regulator Output Voltage
Load Regulation
4.9
5.ꢀ
0.ꢀ
CC
CC
I
= 0mA to 10mA
2
VCC
Switching Regulator
l
V
Voltage Accuracy
With Respect to Voltage Reported by Battery
< Requested Voltage < V
–3ꢀ
3ꢀ
mV
TOL
V
CHMIN
LIMIT
I
Current Accuracy
With Respect to Current Reported by Battery
4mV/R < Requested Current < I (Min)
TOL
SENSE
LIMIT
(Note 1ꢀ)
l
l
l
l
R
ILIMIT
R
ILIMIT
R
ILIMIT
R
ILIMIT
= 0 (Short to GND)
–ꢀ
–4
–8
–8
ꢀ
4
8
8
mA
mA
mA
mA
= 10k 12
= 33k 12
= Open (or Short I
to V
)
CCꢀ
LIMIT
f
f
Regulator Switching Frequency
ꢀ55
ꢀ0
300
ꢀ5
345
kHz
kHz
0SC
Regulator Switching Frequency in Low Duty Cycle ≥992
Dropout Mode
DO
DC
Regulator Maximum Duty Cycle
99
99.5
155
150
2
mV
μA
V
MAX
I
I
Maximum Current Sense Threshold
CA1 Input Bias Current
V
V
= ꢀ.ꢀV
140
190
MAX
SNS
ITH
= V
> 5V
CSN
CSP
CMSL
CMSH
CA1 Input Common Mode Low
CA1 Input Common Mode High
CL1 Turn-On Threshold
0
V
– 0.ꢀ
V
DCIN
V
CL1
95
94
90
100
100
100
105
108
108
mV
mV
mV
l
l
C-Grade (Note 6)
I-Grade (Note 6)
TGATE Transition Time:
TGATE Rise Time
TGATE Fall Time
50
50
90
90
TG t
TG t
C
LOAD
C
LOAD
= 3300pF, 102 to 902
= 3300pF, 102 to 902
r
r
ns
ns
BGATE Transition Time
BGATE Rise Time
BGATE Fall Time
50
40
90
80
ns
ns
BG t
BG t
C
LOAD
C
LOAD
= 3300pF, 102 to 902
= 3300pF, 102 to 902
r
f
1760fa
3
LTC1760
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 6). VDCIN = 20V, VBAT1 = 12V, VBAT2 = 12V, VVDDS = 3.3V,
VVCC2 = 5.2V unless otherwise noted.
SYMBOL PARAMETER
Trip Points
CONDITIONS
MIN
TYP
MAX
UNITS
V
TR
DCDIV/LOPWR Threshold
V
or V Falling
LOPWR
DCDIV
C-Grade (Note 6)
I-Grade (Note 6)
l
l
1.166
1.16ꢀ
1.19
1.19
1.ꢀ15
1.ꢀ15
V
V
V
DCDIV/LOPWR Hysteresis Voltage
DCDIV/LOPWR Input Bias Current
Short-Circuit Comparator Threshold
V
V
V
or V
or V
Rising
30
ꢀ0
mV
nA
THYS
BVT
DCDIV
DCDIV
LOPWR
LOPWR
I
= 1.19V
ꢀ00
V
TSC
– V , V ≥ 5V
SCN CC
C-Grade (Note 6)
I-Grade (Note 6)
SCP
l
l
90
88
100
100
115
115
mV
mV
V
V
Fast PowerPath Turn-Off Threshold
Overvoltage Shutdown Threshold as a
V
V
Rising from V
CC
6
7
7.9
V
FTO
DCDIV
Rising from 0.8V until TGATE and BGATE
SET
Percent of Programmed Charger Voltage Stop Switching
107
2
OVSD
DACs
I
I
I
Resolution
Guaranteed Monotonic
10
6
Bits
RES
DAC
DAC
Pulse Period:
Normal Mode
10
50
15
μs
ms
t
t
IP
ILOW
Wake-Up Mode
Charging Current Granularity
R
ILIMIT
R
ILIMIT
R
ILIMIT
R
ILIMIT
= 0 (Short I
= 10k 12
= 33k 12
to GND)
LIMIT
1
ꢀ
4
4
mA
mA
mA
mA
= Open (or Short I
to V
)
LIMIT
CCꢀ
I
I
Wake-Up Charging Current (Note 5)
Charging Current Limit
60
80
100
mA
WAKE_UP
C-Grade (Note 6)
LIMIT
l
l
l
l
980
1000
ꢀ000
3000
4000
1070
ꢀ140
3ꢀ10
4ꢀ80
mA
mA
mA
mA
R
R
R
R
= 0 (Short I
= 10k 12
= 33k 12
to GND)
LIMIT
ILIMIT
ILIMIT
ILIMIT
ILIMIT
1960
ꢀ490
39ꢀ0
= Open (or Short I
to V
)
)
LIMIT
CCꢀ
I-Grade (Note 6)
R
ILIMIT
R
ILIMIT
R
ILIMIT
R
ILIMIT
= 0 (Short I
= 10k 12
= 33k 12
to GND)
LIMIT
l
l
l
l
930
1000
ꢀ000
3000
4000
1110
ꢀꢀꢀ0
33ꢀ0
4430
mA
mA
mA
mA
1870
ꢀ380
3750
= Open (or Short I
to V
LIMIT
CCꢀ
V
V
V
V
V
Resolution
Granularity
Guaranteed Monotonic (5V < V < ꢀ5V)
11
Bits
mV
RES
DAC
BAT
16
STEP
LIMIT
DAC
l
l
l
l
l
Charging Voltage Limit
(Note 7)
R
VLIMIT
R
VLIMIT
R
VLIMIT
R
VLIMIT
R
VLIMIT
= 0 (Short V
= 10k 12
= 33k 12
= 100k 12
to GND)
8400
1ꢀ608
1683ꢀ
ꢀ10ꢀ4
843ꢀ
1ꢀ640
16864
ꢀ1056
3ꢀ768
8464
1ꢀ67ꢀ
16896
ꢀ1088
mV
mV
mV
mV
mV
LIMIT
= Open (or Short V
to V
)(Note 13)
LIMIT
CCꢀ
Charge MUX Switches
t
t
GCH1/GCHꢀ Turn-On Time
GCH1/GCHꢀ Turn-Off Time
V
– V
> 3V, C = 3000pF
LOAD
5
10
ms
μs
ONC
GCHX
SCHX
SCHX
V
V
– V
< 1V, from Time of
= 3000pF
15
OFFC
GCHX
CSN
< V
– 30mV, C
BATX
LOAD
V
CH Gate Clamp Voltage
GCH1
GCHꢀ
I
= 1μA
CON
LOAD
V
V
– V
– V
5
5
5.8
5.8
7
7
V
V
GCH1
GCHꢀ
SCH1
SCHꢀ
1760fa
4
LTC1760
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 6). VDCIN = 20V, VBAT1 = 12V, VBAT2 = 12V, VVDDS = 3.3V,
VVCC2 = 5.2V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
V
CH Gate Off Voltage
GCH1
I
=10μA
COFF
TOC
FC
LOAD
V
V
– V
– V
–0.8
–0.8
–0.4
–0.4
0
0
V
V
GCH1
GCHꢀ
SCH1
SCHꢀ
GCHꢀ
CH Switch Reverse Turn-Off Voltage
V
– V , 5V ≤ V
≤ ꢀ8V
≤ ꢀ8V
BATX
CSN
BATX
l
l
C-Grade (Note 6)
I-Grade (Note 6)
5
ꢀ
ꢀ0
ꢀ0
40
40
mV
mV
l
CH Switch Forward Regulation Voltage
V
V
– V
, 5V ≤ V
BATX
15
35
60
mV
CSN
BATX
GCH1/GCHꢀ Active Regulation:
Max Source Current
Max Sink Current
– V
= 1.5V
SCHX
GCHX
I
I
–ꢀ
ꢀ
μA
μA
OC(SRC)
OC(SNK)
V
BATX Voltage Below Which
Charging is Inhibited
(Note 14)
3.5
4.7
V
CHMIN
PowerPath Switches
t
t
t
Blanking Period after UVLO Trip
Blanking Period after LOPWR Trip
GB1O/GBꢀO/GDCO Turn-On Time
Switches Held Off
Switches in 3-Diode Mode
< –3V, from Time of Battery/DC
ꢀ50
1
ms
sec
μs
DLY
PPB
l
l
V
5
10
7
ONPO
GS
Removal, or LOPWR Indication, C
= 3000pF
= 3000pF
LOAD
t
GB1O/GBꢀO/GDCO Turn-Off Time
V
> –1V, from Time of Battery/DC
3
μs
OFFPO
GS
Removal, or LOPWR Indication, C
LOAD
V
V
V
V
Output Gate Clamp Voltage
I
LOAD
= 1μA
PONO
POFFO
TOP
GB1O
GBꢀO
GDCO
Highest (V
Highest (V
Highest (V
or V ) – V
4.75
4.75
4.75
6.ꢀ5
6.ꢀ5
6.ꢀ5
7
7
7
V
V
V
BAT1
BATꢀ
DCIN
SCP
GB1O
GBꢀO
GDCO
or V ) – V
SCP
or V ) – V
SCP
Output Gate Off Voltage
I
= –ꢀ5μA
LOAD
GB1O
GBꢀO
GDCO
Highest (V
Highest (V
Highest (V
or V ) – V
0.18
0.18
0.18
0.ꢀ5
0.ꢀ5
0.ꢀ5
V
V
V
BAT1
BATꢀ
DCIN
SCP
GB1O
GBꢀO
GDCO
or V ) – V
SCP
or V ) – V
SCP
PowerPath Switch Reverse
Turn-Off Voltage
V
– V
SCP
or V
– V
SCP DCIN
SCP
BATX
6V ≤ V
≤ ꢀ8V
l
l
C-Grade (Note 6)
I-Grade (Note 6)
5
ꢀ
ꢀ0
ꢀ0
60
60
mV
mV
l
PowerPath Switch Forward
Regulation Voltage
V
– V
SCP
or V
– V
SCP
0
ꢀ5
50
mV
FP
BATX
SCP
DCIN
6V ≤ V
≤ ꢀ8V
GDCI/GB1I/GBꢀI Active Regulation:
Source Current
Sink Current
(Note 3)
I
I
–4
75
μA
μA
OP(SRC)
OP(SNK)
t
t
Gate B1I/BꢀI/DCI Turn-On Time
Gate B1I/BꢀI/DCI Turn-Off Time
V
V
< –3V, C
> –1V, C
= 3000pF (Note 4)
= 3000pF (Note 4)
300
10
μs
μs
ONPI
GS
LOAD
OFFPI
GS
LOAD
V
PONI
Input Gate Clamp Voltage
I
= 1μA
LOAD
GB1I
GBꢀI
GDCI
Highest (V
Highest (V
Highest (V
or V ) – V
4.75
4.75
4.75
6.7
6.7
6.7
7.5
7.5
7.5
V
V
V
BAT1
BATꢀ
DCIN
SCP
GB1I
GBꢀI
GDCI
or V ) – V
SCP
or V ) – V
SCP
V
Input Gate Off Voltage
I
= –ꢀ5μA
LOAD
POFFI
GB1I
GBꢀI
GDCI
Highest (V
Highest (V
Highest (V
or V ) – V
0.18
0.18
0.18
0.ꢀ5
0.ꢀ5
0.ꢀ5
V
V
V
BAT1
BATꢀ
DCIN
SCP
GB1I
GBꢀI
GDCI
or V ) – V
SCP
or V ) – V
SCP
1760fa
5
LTC1760
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 6). VDCIN = 20V, VBAT1 = 12V, VBAT2 = 12V, VVDDS = 3.3V,
VVCC2 = 5.2V unless otherwise noted.
SYMBOL PARAMETER
Thermistor
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
Thermistor Trip
C
= 300pF (Note 9)
95
100
105
kΩ
LOAD(MAX)
R1A = RꢀA = 1130Ω 12
R1B = RꢀB = 54900Ω 12
COLD-RANGE to OVER-RANGE
Thermistor Trip
IDEAL-RANGE to COLD-RANGE
C
= 300pF (Note 9)
ꢀ8.5
30
3ꢀ.5
kΩ
LOAD(MAX)
R1A = RꢀA = 1130Ω 12
R1B = RꢀB = 54900Ω 12
Thermistor Trip
HOT-RANGE to IDEAL-RANGE
C
= 300pF (Note 9)
LOAD(MAX)
R1A = RꢀA = 1130Ω 12
R1B = RꢀB = 54900Ω 12
C-Grade (Note 6)
l
l
ꢀ.85
ꢀ.83
3
3
3.15
3.15
kΩ
kΩ
I-Grade (Note 6)
l
Thermistor Trip
UNDER-RANGE to HOT-RANGE
C
= 300pF (Note 9)
4ꢀ5
500
575
Ω
LOAD(MAX)
R1A = RꢀA = 1130Ω 12
R1B = RꢀB = 54900Ω 12
Logic Levels
l
l
l
l
SCL/SCL1/SCLꢀ/SDA/SDA1/
0.8
v
v
SDAꢀ Input Low Voltage (V )
IL
SCL/SCL1/SCLꢀ/SDA/SDA1/
ꢀ.1
–5
SDAꢀ Input High Voltage (V )
IH
SCL/SCL1/SCLꢀ/SDA/SDA1/
SDAꢀ Input Leakage Current
V
V
, V , V
SDAꢀ SCLꢀ
, V
,
5
5
μA
μA
μA
SDA SCL SDA1 SCL1
, V
= 0.8V
SCL/SCL1/SCLꢀ/SDA/SDA1/
SDAꢀ Input Leakage Current
V
V
, V , V
= ꢀ.1V
, V
, V
,
–5
SDA SCL SDA1 SCL1 SDAꢀ
SCLꢀ
I
SCL1/SDA1/SCLꢀ/SDAꢀ Pull-Up
Current When Not Connected to
SMBus Host
V
V
, V , V , V = 0.4V
SCL1 SDA1 SCLꢀ SDAꢀ
165
ꢀꢀ0
350
PULLUP
= 4.85V and 5.55V (Current is Through
VCCꢀ
Internal Series Resistor and Schottky to V
)
CCꢀ
l
l
l
SCL1/SDA1/SCLꢀ/SDAꢀ
V
, V
, V
, V
= 0.8V
300
0.4
0.4
Ω
V
SDA1 SCL1 SDAꢀ SCLꢀ
Series Impedance to Host SMBus
SCL/SDA Output Low Voltage (V ).
LTC1760 Driving the Pin
I
I
= 350μA
OL
PULLUP
PULLUP
SCL1/SDA1/SCLꢀ/SDAꢀ Pullup
Internal to LTC1760
V
Output Low Voltage (V ).
OL
LTC1760 Driving the Pin with Battery
SMBus not Connected to Host SMBus
l
SCL1/SDA1/SCLꢀ/SDAꢀ
I
= 350μA on Host Side
0.4
ꢀ
V
PULLUP
Output Low Voltage (V ).
OL
LTC1760 Driving the Pin with Battery
SMBus Connected to Host SMBus
l
l
SCL/SCL1/SCLꢀ/SDA/SDA1/ SDAꢀ/
SMBALERT Power Down Leakage
V
V
V
= 0V, V
SCL SCL1 SCLꢀ SDA
= 0V,
VDDS
μA
VCCꢀ
, V
, V
, V
,
, V
, V
= 5.5V
SDA1 SDAꢀ SMBALERT
SMBALERT Output Low Voltage (V
)
OL
I
= 500μA
0.4
17.5
1.5
V
PULLUP
SMBALERT Output Pull-Up Current
V
= 0.4V
3.5
10
μA
SMBALERT
l
l
l
V
V
V
DDS
V
DDS
V
DDS
V
DDS
Input Low Voltage (V )
V
V
IL_VDDS
IH_VDDS
IL
IH
ꢀ.6
3
Input High Voltage (V )
5.5
18
V
Operating Voltage
Operating Current
μA
V
V
, V
= V
, V
VDDS
= 5V
SCL SDA
VDDS
l
V
MODE Input Low Voltage (V )
= 4.85V
V • 0.3
VCCꢀ
V
IL_MODE
IL
VCCꢀ
1760fa
6
LTC1760
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 6). VDCIN = 20V, VBAT1 = 12V, VBAT2 = 12V, VVDDS = 3.3V,
VVCC2 = 5.2V unless otherwise noted.
SYMBOL PARAMETER
MODE Input High Voltage (V )
CONDITIONS
= 4.85V
MIN
V • 0.7
VCCꢀ
TYP
MAX
UNITS
V
l
l
l
V
V
IH_MODE
IH
VCCꢀ
MODE Input Current (I )
MODE = V
MODE = V
• 0.7V, V
• 0.3V, V
= 4.85V
= 4.85V
–1
–1
1
1
μA
IH
VCCꢀ
VCCꢀ
VCCꢀ
MODE Input Current (I )
μA
IL
VCCꢀ
Charger Timing
l
t
Timeout for Wake-Up Charging and
Controlled Charging
140
175
1
ꢀ10
sec
sec
TIMEOUT
t
Sampling Rate Used by the LTC1760 to
Update Charging Parameters
QUERY
SMBus Timing
SCL Serial-Clock High Period(t
l
l
l
l
l
l
l
l
)
At I
At I
= 350μA, C
= 350μA, C
= 150pF (Note 8)
= 150pF (Note 8)
4
μs
μs
ns
ns
V
HIGH
PULLUP
PULLUP
LOAD
SCL Serial-Clock Low Period (t
)
4.7
LOW
LOAD
SDA/SCL Rise Time (t )
C
C
= 150pF, RPU = 9.31k (Note 8)
= 150pF, RPU = 9.31k (Note 8)
1000
300
r
LOAD
LOAD
SDA/SCL Fall Time (t )
f
SMBus Accelerator Trip Voltage Range
Start-Condition Setup Time (t
0.8
4.7
4
1.4ꢀ
)
μs
μs
ns
SU:STA
Start-Condition Hold Time (t
SDA to SCL Rising-Edge
)
HD:STA
ꢀ50
Setup Time (t
)
SU:DAT
l
l
SDA to SCL Falling-Edge Hold Time,
Slave Clocking in Data (t
300
ꢀ5
ns
)
HD:DAT
t
The LTC1760 will Release the SMBus
and Terminate the Current Master or
Slave Command if the Command is not
Completed Before this Time
35
ms
TIMEOUT_
SMB
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
lower than the terminal voltage. Refer to “Operation Section 3.7” for more
information.
Note 8: C
is the combined capacitance on the host’s SMBus
LOAD
connection and the selected battery’s SMBus connection.
Note 2: Battery voltage must be adequate to drive gates of PowerPath
P-channel FET switches. This does not affect charging voltage of the
battery, which can be zero volts during wake-up charging.
Note 9: C is the maximum allowed combined capacitance on
THxA, THxB and the battery’s SafetySignalx connections.
LOAD_MAX
Note 10: Does not include current supplied by V to V
(I or
CCꢀ VCCꢀ_AC1
CC
Note 3: DCIN, BAT1, BATꢀ are held at 1ꢀV and GDCI, GB1I, GBꢀI are
forced to 10.5V. SCP is set at 1ꢀV to measure source current at GDCI,
GB1I and GBꢀI. SCP is set at 11.9V to measure sink current at GDCI, GB1I
and GBꢀI.
I
)
VCCꢀ_AC0
Note 11: Measured with thermistors not present, R
removed and SMBALERT = 1. See Applications Information section:
“Calculating IC Operating Current” for example on how to calculate total IC
operating current.
and R
ILIMIT
VLIMIT
Note 4: Extrapolated from testing with C = 50pF.
L
Note 5: Accuracy dependent upon external sense resistor and
compensation components.
Note 12: Requested currents below 44mV/R
may not servo correctly
SENSE
due to charger offsets. The charging current for requested currents below
4mV/R will be between 4mV/R and (Requested Current – 8mA).
Note 6: The LTC1760 is tested under pulsed load conditions such that T ≈
J
SENSE
SENSE
T . The LTC1760C is guaranteed to meet specifications from 0°C to 70°C
Refer to Applications Information: “Setting Charger Output Current Limit”
for values of R
A
junction temperature. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC1760I is guaranteed
over the –40°C to 1ꢀ5°C operating junction temperature range.
.
SENSE
Note 13: This limit is greater than the absolute maximum for the charger.
Therefore, there is no effective limitation for the voltage when this option
is selected.
Note 7: Charger servos to the value reported by a Voltage() query. This is
the internal cell voltage measured by the battery electronics and may be
Note 14: Does not apply to Wake-Up Mode.
1760fa
7
LTC1760
TYPICAL PERFORMANCE CHARACTERISTICS
Dual Battery Charge Time vs
Sequential Battery Charging
Charging Voltage Accuracy
Charging Current Accuracy
0
–5
10
5
3500
3000
ꢀ500
ꢀ000
1500
1000
500
BATꢀ
CURRENT
BAT1
CURRENT
SEQUENTIAL
0
–10
0
–5
3500
3000
ꢀ500
ꢀ000
1500
1000
500
BAT1
CURRENT
–15
–ꢀ0
–ꢀ5
–10
–15
–ꢀ0
BATꢀ
DUAL
CURRENT
100
MINUTES
0
4700
713ꢀ
9564
11996 144ꢀ8 16860
0
800
1600
ꢀ400
3ꢀ00
4000
0
100
150
ꢀ00 ꢀ50
300
50
ChargingCurrent() (mA)
TIME (MINUTES)
ChargingVoltage() (mV)
1760 G01
1760 G0ꢀ
BATTERY TYPE: 10.8V Li-Ion (MOLTECH NIꢀ0ꢀ0)
REQUESTED CURRENT = 3A
REQUESTED VOLTAGE = 1ꢀ.3V
MAX CHARGER CURRENT = 4.1A
1760 G03
Dual Battery Discharge Time vs
Sequential Battery Discharge
(Li-Ion)
Dual Battery Dischage Time vs
Sequential Battery Discharge
(NiMH)
Dual Charging Batteries with
Different Charge State
3500
3000
ꢀ500
ꢀ000
1500
1000
500
15
14
13
12
11
10
15
14
13
12
11
10
17.0
16.5
16.0
15.5
15.0
14.5
14.0
13.5
BATꢀ
VOLTAGE
BAT1
1ꢀ.0
11.0
10.0
9.0
BAT1
VOLTAGE
DUAL
BAT2
VOLTAGE
DUAL
VOLTAGE
BATꢀ
VOLTAGE
BAT1
VOLTAGE
BATꢀ
8.0
BAT2
VOLTAGE
SEQUENTIAL
VOLTAGE
1ꢀ.0
11.0
10.0
9.0
SEQUENTIAL
BAT1
CURRENT
BAT1
VOLTAGE
BAT1
BATꢀ
CURRENT
VOLTAGE
11
MINUTES
16
MINUTES
0
8.0
ꢀ0 40 60 80 100
TIME (MINUTES)
1ꢀ0
140 160
0
160
0
20
60
80
100
140
0
ꢀ0
60 80 100
140
180
40
120
40
1ꢀ0
1760 G04
TIME (MINUTES)
TIME (MINUTES)
BAT1 INITIAL CAPACITY = 02
BATꢀ INITIAL CAPACITY = 902
PROGRAMMED CHARGER CURRENT = 3A
PROGRAMMED CHARGER VOLTAGE = 16.8V
BATTERY TYPE: 10.8V Li-Ion (MOLTECH NIꢀ0ꢀ0)
LOAD CURRENT = 3A
BATTERY TYPE: 12V NiMH (MOLTECH NJ1020)
1760 G06
1760 G05
LOAD: 33W
1760fa
8
LTC1760
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Charging Current
Load Dump
Load Regulation
100
90
80
70
60
50
40
30
ꢀ0
10
0
14
1ꢀ
10
8
1ꢀ.4
1ꢀ.3
1ꢀ.ꢀ
1ꢀ.1
1ꢀ.0
11.9
11.8
11.7
11.6
BAT1
OUTPUT
V
= ꢀ0V
IN
V
= 1ꢀ.ꢀ9V
DAC
DAC
I
= 3000mA
LOAD CURRENT = 1A
T
= ꢀ5°C
A
6
LOAD
CONNECTED
4
V
V
= ꢀ0V
IN
= 1ꢀ.ꢀ88V
DAC
= 4000mA
DAC
LOAD
ꢀ
I
DISCONNECTED
T
= ꢀ5°C
A
0
ꢀ.5 4.0
–4 –ꢀ
0
ꢀ
4
6
8
10 1ꢀ 14 16
0
0.0ꢀ5
0.10
0.50
0
1000
ꢀ000
3000
4000
TIME (ms)
I
(A)
CHARGE CURRENT (mA)
OUT
1760 G08
1760 G07
1760 G09
PowerPath Switching 1 and 2
SMBus Accelerator Operation
16
V
C
T
= 5V
C
I
A
= ꢀ0F
CC
LD
A
LOAD
LOAD
= ꢀ00pF
15
14
13
1ꢀ
11
10
9
= 0.8A
5V
= ꢀ5°C
T
= ꢀ5°C
LTC1760
R
= 15k
PULLUP
LOPWR
THRESHOLD
0V
8
7
6
–50 –40 –30
–ꢀ0 –10
0
10 ꢀ0 30 40 50
1μs/DIV
TIME (μs)
1760 G11
1960 G10
PIN FUNCTIONS
Input Power Related
side) of the sense resistor, R , in series with the three
SC
PowerPath switch pairs, for detecting short-circuit cur-
SCN (Pin 4): PowerPath Current Sensing Negative Input.
rent events.
This pin should be connected directly to the “bottom”
GDCO (Pin 6): DCIN Output Switch Gate Drive. Together
with GDCI, this pin drives the gate of the P-channel switch
in series with the DCIN input switch.
(output side) of the sense resistor, R , in series with the
SC
three PowerPath switch pairs, for detecting short-circuit
currentevents. AlsopowerstheLTC1760internalcircuitry
when all other sources are absent.
GDCI(Pin7):DCINInputSwitchGateDrive. Togetherwith
GDCO, this pin drives the gate of the P-channel switch
connected to the DCIN input.
SCP (Pin 5): PowerPath Current Sensing Positive Input.
This pin should be connected directly to the “top” (switch
1760fa
9
LTC1760
PIN FUNCTIONS
GB1O (Pin 8): BAT1 Output Switch Gate Drive. Together
with GB1I, this pin drives the gate of the P-channel switch
in series with the BAT1 input switch.
CSP (Pin 35): Current Amplifier CA1 Input. This pin and
the CSN pin measure the voltage across the charge cur-
rent sense resistor, R
, to provide the instantaneous
SENSE
currentsignalsrequiredforbothpeakandaveragecurrent
GB1I (Pin 9): BAT1 Input Switch Gate Drive. Together with
GB1O, this pin drives the gate of the P-channel switch
connected to the BAT1 input.
mode operation.
COMP1 (Pin 37): The Compensation Node for the Am-
plifier CL1. A capacitor is required from this pin to GND
if input current amplifier CL1 is used. At input adapter
current limit, this node rises to 1V. By forcing COMP1 to
GND, amplifier CL1 will be defeated (no adapter current
limit). COMP1 can source 10μA.
GB2O (Pin 10): BATꢀ Output Switch Gate Drive. Together
with GBꢀI, this pin drives the gate of the P-channel switch
in series with the BATꢀ input switch.
GB2I (Pin 11): BATꢀ Input Switch Gate Drive. Together
withGBꢀO, thispindrivesthegateoftheP-channelswitch
connected to the BATꢀ input.
BGATE (Pin 39): Drives the gate of the bottom external
MOSFET of the battery charger buck converter.
CLP (Pin 36): The Positive Input to the Supply Current
LimitingAmplifierCL1.Thethresholdissetat100mVabove
the voltage at the DCIN pin. When used to limit supply
current, a filter is needed to filter out the switching noise.
SW (Pin 42): PWM Switch Node. Connected to the source
of the top external MOSFET. Used as reference for top
gate driver.
BOOST (Pin 43): Supply to Topside Floating Driver. The
bootstrap capacitor is returned to this pin. Voltage swing
at this pin is from a diode drop below V to (DCIN + V ).
Battery Charging Related
V
(Pin 13): The Tap Point of a Programmable Resistor
SET
CC
CC
Divider which Provides Battery Voltage Feedback to the
TGATE(Pin44):DrivesthegateofthetopexternalMOSFET
of the battery charger buck converter.
Charger. A capacitor from CSN to V and from V to
SET
SET
GND provide necessary compensation and filtering for
the voltage loop.
SCH1 (Pin 45), SCH2 (Pin 48): Charger MUX N-Channel
Switch Source Returns. These two pins are connected to
the sources of the back-to-back switch pairs Q3/Q4 and
Q9/Q10 (see Typical Applications). A small pull-down cur-
rent source returns these nodes to 0V when the switches
are turned off.
I
(Pin 14): The Control Signal of the Inner Loop of the
TH
Current Mode PWM. Higher I voltage corresponds to
TH
higher charging current in normal operation. A capacitor
of at least 0.1μF to GND filters out PWM ripple. Typical
full-scale output current is 30μA. Nominal voltage range
for this pin is 0V to ꢀ.4V.
GCH1 (Pin 46), GCH2 (Pin 47): Charger MUX N-Channel
Switch Gate Drives. These two pins drive the gates of the
back-to-back switch pairs, Q3/Q4 and Q9/Q10, between
the charger output and the two batteries (see Typical
Applications).
I
(Pin 15): A capacitor from I to GND is required to
SET
SET
filterhigherfrequencycomponentsfromthedelta-sigmaI
.
DAC
I
(Pin 32): An external resistor (R
) is connected
LIMIT
ILIMIT
between this pin and GND. The value of the external resis-
tor programs the range and resolution of the programmed
charger current.
External Power Supply Pins
V
(Pin 1): Supply. The V
pin is connected via
PLUS
PLUS
four internal diodes to the DCIN, SCN, BAT1, and BATꢀ
pins. Bypass this pin with a 0.1μF capacitor and a 1μF
capacitor (see Typical Applications for complete circuit).
V
(Pin33):Anexternalresistor(R
)isconnected
LIMIT
VLIMIT
between this pin and GND. The value of the external resis-
tor programs the range and resolution of the voltage DAC.
BAT1 (Pin 3), BAT2 (Pin 2): These two pins are the inputs
from the two batteries for power to the LTC1760.
CSN (Pin 34): Current Amplifier CA1 Input. Connect this
to the common output of the charger MUX switches.
1760fa
10
LTC1760
PIN FUNCTIONS
LOPWR (Pin 12): LOPWR Comparator Input from SCN
ExternalResistorDividertoGND.IfthevoltageatLOPWR
pin is lower than the LOPWR comparator threshold, then
system power has failed and power is autonomously
switched to a higher voltage source, if available.
cators. RequiresanexternalpulluptoV
(normalSMBus
DDS
operating mode). Connected to internal SMBus accelerator.
SCL1(Pin19):SMBusClockSignaltoSmartBattery1. Do
not connect to an external pull-up. The LTC1760 connects
this pin to an internal pull-up (I
) when required.
PULLUP
DCDIV (Pin 16): External DC Source Comparator Input
from DCIN External Resistor Divider to GND. If the
voltage at DCDIV pin is above the DCDIV comparator
threshold, then the AC_PRESENT bit is set and the wall
adapter power is considered to be adequate to charge
SDA2 (Pin 21): SMBus Data Signal to Smart Battery ꢀ. Do
not connect to an external pull-up. The LTC1760 connects
this pin to an internal pull-up (I ) when required.
PULLUP
SDA (Pin 22): SMBus Data Signal to SMBus Host. Also
used to indicate charging status of Battery ꢀ. Requires
the batteries. If DCDIV rises more than 1.8V above V ,
CC
an external pullup to V . Connected to internal SMBus
then all of the power path switches are latched off until
all power is removed. A capacitor from DCDIV to GND is
recommendedtopreventnoise-inducedfalseemergency
turn-offconditionsfrombeingdetected.Referto“Section
8.3” and “Typical Application”.
DDS
accelerator.
SDA1 (Pin 23): SMBus Data Signal to Smart Battery 1. Do
not connect to an external pull-up. The LTC1760 connects
this pin to an internal pull-up (I ) when required.
PULLUP
DCIN(Pin41):Supply.ExternalDCpowersource.A0.1μF
bypass capacitor must be connected to this pin as close
as possible. No series resistance is allowed, since the
adapter current limit comparator input is also this pin.
MODE (Pin 26): Used in conjunction with V
to allow
DDS
SCL,SDAandSMBALERTtoindicatechargingstatus.May
also be used as a hardware charge inhibit.
TH2B (Pin 27): Thermistor Force/Sense Connection
to Smart Battery ꢀ SafetySignal. Connect to Battery ꢀ
thermistor through resistor network shown in “Typical
Application.”
Internal Power Supply Pins
V
(Pin 20): Power Supply for SMBus Accelerators.
DDS
Also used in conjunction with MODE pin to modify the
LTC1760 operating mode.
TH2A (Pin 28): Thermistor Force/Sense Connection
to Smart Battery ꢀ SafetySignal. Connect to Battery ꢀ
thermistor through resistor network shown in “Typical
Application.”
GND (Pin 24): Ground for Low Power Circuitry.
V
(Pin 25): Power Supply is used Primarily to Power
CC2
Internal Logic Circuitry. Must be connected to V .
CC
SMBALERT (Pin 29): Active Low Interrupt Pin. Signals
SMBus Host that there has been a change of status in
battery or AC presence. Open drain with weak current
PGND (Pin 38): High Current Ground Return for BGATE
Driver.
V
CC
(Pin 40): Internal Regulator Output. Bypass this
source pull-up to V
(with Schottky to allow it to be
CCꢀ
output with at least a ꢀμF to 4.7μF capacitor. Do not use
this regulator output to supply external circuitry except
as shown in the application circuit.
pulled to 5V externally). Also used to indicate charging
status of Battery 1.
TH1A (Pin 30): Thermistor Force/Sense Connection
to Smart Battery 1 SafetySignal. Connect to Battery 1
thermistor through resistor network shown in “Typical
Application.”
SBS Interface Pins
SCL2(Pin17):SMBusClockSignaltoSmartBatteryꢀ. Do
not connect to an external pull-up. The LTC1760 connects
this pin to an internal pull-up (I ) when required.
PULLUP
TH1B (Pin 31): Thermistor Force/Sense Connection
to Smart Battery 1 SafetySignal. Connect to Battery 1
thermistor through resistor network shown in “Typical
Application.”
SCL (Pin 18): SMBus Clock Signal to SMBus Host. Also
used to determine flashing rate for stand-alone charge indi-
1760fa
11
LTC1760
BLOCK DIAGRAM
GB1I GB1O
GBꢀI GBꢀO
11 10
GDCI GDCO
9
8
7
6
100mV
SCP
SCN
5
4
+
SHORT CIRCUIT
100Ω
SWB1
DRIVER
SWBꢀ
DRIVER
SWDC
DRIVER
–
I
3ꢀ
33
LIMIT
LIMIT
DECODER
V
LIMIT
CHARGE
PUMP
V
CCꢀ
DCIN
10μA
ON
–
GCH1
SCH1
46
45
+
SMBALERT
ꢀ9
ꢀ6
ON
–
+
SEQUENCER
MODE
GCHꢀ
47
CSN
AC_PRESENT
V
ꢀ0
18
ꢀꢀ
19
ꢀ3
17
DDS
SCHꢀ
BAT1
48
3
SCL
SDA
SMBus
INTERFACE
ꢀ
BATꢀ
SCL1
SDA1
SCLꢀ
CHARGE
V
1
SCN
PLUS
ꢀ1 SDAꢀ
V
ꢀ5
40
ꢀ4
CCꢀ
V
CC
TH1A
TH1B
30
31
ꢀ8
ꢀ7
15
V
CC
REGULATOR
SAFETY
SIGNAL
GND
THꢀA
THꢀB
DECODER
+
–
16
DCDIV
I
PowerPath
CONTROLLER
10-BIT ΔΣ
CURRENT DAC
SET
+
–
LOPWR
DCIN
1ꢀ
41
1.19V
CSP-CSN
3kΩ
–
0.86V
3k
3k
0V
–
CSP
CSN
35
34
CSN
OSCILLATOR
+
–
CA1
+
LOW DROP
DETECT
BGATE
T
ON
g
= 1.4m
–
+
m
CAꢀ
43
44
4ꢀ
BOOST
TGATE
SW
0.8V
BUFFERED I
+
TH
15
S
+
PWM
LOGIC
–
I
Q
CMP
V
CC
3mV
–
R
BGATE
PGND
39
38
–
+
I
REV
40mV
Ω
DCIN
100mV
g = 0.4m
m
+
400k
CL1
–
Ω
36
CLP
V
13
11-BIT ΔΣ
VOLTAGE DAC
SET
g
m
= 1.4m
EA
+
0.8V
37
COMP1
14
1760 BD
I
TH
1760fa
12
LTC1760
(For Operation Section)
TABLE OF CONTENTS
1
Overview ............................................................................................................................................................................................. 13
The SMBus Interface .......................................................................................................................................................................... 13
SMBus Interface Overview............................................................................................................................................................... 13
Data Bit Definition of Supported SMBus Functions.......................................................................................................................... 14
Description of Supported SMBus Functions .................................................................................................................................... 17
BatterySystemState() (0×01) ....................................................................................................................................................... 17
BatterySystemStateCont() (0×0ꢀ)................................................................................................................................................ 18
BatterySystemInfo() (0×04) ......................................................................................................................................................... 19
LTC() (0×3C) ................................................................................................................................................................................ ꢀ0
BatteryMode() (0×03) .................................................................................................................................................................. ꢀ0
Voltage() (0×09)........................................................................................................................................................................... ꢀ0
Current() (0×0A) .......................................................................................................................................................................... ꢀ1
ChargingCurrent() (0×14) ............................................................................................................................................................ ꢀ1
ChargingVoltage() (0×15) ............................................................................................................................................................ ꢀ1
AlarmWarning() (0×16)................................................................................................................................................................ ꢀ1
AlertResponse() ........................................................................................................................................................................... ꢀꢀ
SMBus Dual Port Operation ............................................................................................................................................................. ꢀꢀ
LTC1760 SMBus Controller Operation.............................................................................................................................................. ꢀ3
LTC1760 SMBALERT Operation........................................................................................................................................................ ꢀ6
Charging Algorithm Overview ............................................................................................................................................................. ꢀ6
Wake-Up Charging Initiation ............................................................................................................................................................ ꢀ6
Wake-Up Charging Termination ....................................................................................................................................................... ꢀ6
Wake-Up Charging Current and Voltage Limits................................................................................................................................ ꢀ7
Controlled Charging Initiation .......................................................................................................................................................... ꢀ7
Controlled Charging Termination...................................................................................................................................................... ꢀ7
Controlled Charging Current Programming...................................................................................................................................... ꢀ8
Current Limits When Charging A Single Battery........................................................................................................................... ꢀ8
Current Limits When Charging Two Batteries (TURBO Mode Disabled) ....................................................................................... ꢀ8
Current Limits When Charging Two Batteries (TURBO Mode Enabled)......................................................................................... ꢀ9
Controlled Charging Voltage Programming...................................................................................................................................... ꢀ9
System Power Management Algorithm and Battery Calibration .......................................................................................................... ꢀ9
Turning Off System Power ............................................................................................................................................................... ꢀ9
Power-By Algorithm When No Battery is Being Calibrated............................................................................................................... ꢀ9
Power-By Algorithm When a Battery is Being Calibrated.................................................................................................................. 30
Power-By Reporting......................................................................................................................................................................... 30
Battery Calibration (Conditioning) ....................................................................................................................................................... 30
Selecting a Battery to be Calibrated.................................................................................................................................................. 30
Initiating Calibration of Selected Battery .......................................................................................................................................... 31
Terminating Calibration of Selected Battery...................................................................................................................................... 31
MODE Pin Operation ........................................................................................................................................................................... 31
Stand Alone Charge Indication......................................................................................................................................................... 31
Hardware Charge Inhibit .................................................................................................................................................................. 3ꢀ
Charging When SCL and SDA are Low............................................................................................................................................. 3ꢀ
Charging With an SMBus Host......................................................................................................................................................... 3ꢀ
Battery Charger Controller ................................................................................................................................................................. 3ꢀ
Charge MUX Switches...................................................................................................................................................................... 33
Dual Charging .................................................................................................................................................................................. 33
PowerPath Controller ......................................................................................................................................................................... 33
Autonomous PowerPath Switching.................................................................................................................................................. 34
Short-Circuit Protection ................................................................................................................................................................... 34
Emergency Turn-Off......................................................................................................................................................................... 34
Power-Up Strategy........................................................................................................................................................................... 34
The Voltage DAC Block ...................................................................................................................................................................... 34
The Current DAC Block ........................................................................................................................................................................ 35
ꢀ
ꢀ.1
ꢀ.ꢀ
ꢀ.3
ꢀ.3.1
ꢀ.3.ꢀ
ꢀ.3.3
ꢀ.3.4
ꢀ.3.5
ꢀ.3.6
ꢀ.3.7
ꢀ.3.8
ꢀ.3.9
ꢀ.3.10
ꢀ.3.11
ꢀ.4
ꢀ.5
ꢀ.6
3
3.1
3.ꢀ
3.3
3.4
3.5
3.6
3.6.1
3.6.ꢀ
3.6.3
3.7
4
4.1
4.ꢀ
4.3
4.4
5
5.1
5.ꢀ
5.3
6
6.1
6.ꢀ
6.3
6.4
7
7.1
7.ꢀ
8
8.1
8.ꢀ
8.3
8.4
9
10
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13
LTC1760
OPERATION (Refer to Block Diagram and Typical Application Figure)
1 Overview
diode-like behavior from the FET switches, without the
attendant high power dissipation from diodes. The Host
is informed of this 3-Diode mode status when it polls the
PowerPath status register via the SMBus interface. High
speed PowerPath switching at the LOPWR trip point is
handled autonomously.
The LTC1760 is composed of an SMBus interface with
dual port capability, a sequencer for managing system
power and the charging and discharging of two batteries,
a battery charger controller, charge MUX controller, Pow-
erPath controller, a 10-bit current DAC (I ) and 11-bit
voltage DAC (V ). When coupled with optional system
DAC
Simultaneous discharge of both batteries is supported.
The switch drivers prevent reverse current flow in the
switches and automatically discharge both batteries into
the load, sharing current according to the relative capacity
ofthebatteries.Simultaneousdualdischargecanincrease
battery operating time by up to 102 by reducing losses
in the switches and reducing internal battery losses as-
sociated with high discharge rates.
DAC
software for generating composite battery information,
it forms a complete Smart Battery System Manager for
charging and selecting two smart batteries. The battery
charger is controlled by the sequencer which uses a Level
3 SMBus interface to read ChargingVoltage(), Voltage(),
ChargingCurrent(),Current(),Alarm()andBatteryMode().
Thisinformation, togetherwiththermistormeasurements
allows the sequencer to select the charging battery and
safely servo on voltage and current. Charging can be
accomplished only if the voltage at DCDIV indicates that
sufficientvoltageisavailablefromtheinputpowersource,
usually an AC adapter. The charge MUX, which selects
the battery to be charged, is capable of charging both
batteries simultaneously. The charge MUX switch drivers
are configured to allow charger current to share between
the two batteries and to prevent current from flowing in
a reverse direction in the switch. The amount of current
that each battery receives will depend upon the relative
capacity of each battery and the battery voltage. This can
resultinsignificantlyshorterchargingtimes(upto502for
Li-Ion batteries) than sequential charging of each battery.
2 The SMBus Interface
2.1 SMBus Interface Overview
The SMBus interface allows the LTC1760 to communi-
cate with two batteries and the SMBus Host. The SMBus
Interface supports true dual port operation by allowing
the SMBus Host to be connected to the SMBus of either
battery. The LTC1760 is able to operate as an SMBus
Master or Slave device. The LTC1760 SMBUS address is
0×14 (8-bit format).
References:
Smart Battery System Manager Specification: Revision
1.1, SBS Implementers Forum.
The sequencer also selects which of the pairs of PFET
switches will provide power to the system load. If the
system voltage drops below the threshold set by the
LOPWR resistor divider, then all of the output-side PFETs
are turned on quickly. The input-side PFETs act as diodes
in this mode and power is taken from the highest voltage
source available at the DCIN, BAT1, or BATꢀ inputs. The
input-sidePowerPathswitchdriverthatisdeliveringpower
then closes its input switch to reduce the power dissipa-
tion in the PFET bulk diode. In effect, this system provides
Smart Battery Data Specification: Revision 1.1, SBS Imp-
lementers Forum.
Smart Battery Charger Specification: Revision 1.1, SBS Imp-
lementers Forum
SystemManagementBusSpecification:Revision1.1,SBS
Implementers Forum
ꢀ
C-Bus and How to Use it: V1.0, Philips Semiconductor.
I
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14
LTC1760
OPERATION
2.2 Data Bit Definition of Supported SMBus Functions.
LTC1760
SMBus
Mode
Data Bit or Nibble Definition/Allowed Values
(See section 2.3 for Details)
D15 D14 D13 D12 D11 D10 D09 D08 D07 D06 D05 D04 D03 D02 D01 D00
SMBus
Address
Command Data
Code
Function
Access
Type
BatterySystemState()
Slave
Read/ 7-bit:
Write 0001_010b
Status/
Control
0×01
8-bit:
0×14
0
0
0/1 0/1 0
0
0/1 0/1 0
0
0/1 0/1 0
0 0/1 0/1
BatterySystemStateCont() Slave
Read/ 7-bit:
Write 0001_010b
Status/
Control
0×0ꢀ
8-bit:
0×14
0
0
0
0
0
0
0/1 0/1 0 0/1 0/1 0/1 0/1 1 0/1 0/1
BatterySystemInfo()
LTC()
Slave
Slave
Read 7-bit:
0001_010b
Status
BATTERY
SYSTEM
REVISION
BATTERY
0×04
0×3C
RESERVED
RESERVED
SUPPORTED
8-bit:
0×14
0
0
0
0
0
0
0
0
1
0
0
0
0
0
1
1
Read/ 7-bit:
Write 0001_010b
Status/
Control
8-bit:
0×14
0/1 0
0
0
0
0
0
1
0/1 0
0
0
0
0
0
1
BatteryMode()
Master
Read 7-bit:
0001_011b
Status
0×03
8-bit:
0×16
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1
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LTC1760
OPERATION
Data Bit or Nibble Definition/Allowed Values
(See section 2.3 for Details)
LTC1760
Mode
SMBus
Address
Command Data
Function
Access
Code
Type D15 D14 D13 D12 D11 D10 D09 D08 D07 D06 D05 D04 D03 D02 D01 D00
Current()
Master
Master
Master
Master
Master
Read 7-bit:
0001_011b
Value
0×0A
8-bit:
0×16
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1
Voltage()
Read 7-bit:
0001_011b
Status/
Control
0×09
0×14
0×15
0×16
8-bit:
0×16
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1
Status
ChargingCurrent()
ChargingVoltage()
AlarmWarning()
Read 7-bit:
0001_011b
8-bit:
0×16
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1
Read 7-bit:
0001_011b
Status/
Control
8-bit:
0×16
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1
Status
Read 7-bit:
0001_010b
8-bit:
0×16
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1
Register
AlertResponse()
see (1)
Slave
Read
Byte
7-bit:
0001_100b
N/A
8-bit:
0×18
0
0
0
1
0
1
0
0
(1) Read-byte format. 0×14 is returned as the interrupt address of the LTC1760.
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16
LTC1760
OPERATION
2.3 Description of Supported SMBus Functions
The functions are described as follows:
Function Name() (command code)
Description:
• The LTC1760 autonomously changes the configura-
tion of the batteries being charged (Polling only).
Purpose:
Used by the SMBus Host to determine the present state
of the LTC1760 and the attached batteries. It also may be
used to determine the state of the battery system after
the LTC1760 notifies the SMBus Host of a change via
SMBALERT.
A brief description of the function.
Purpose:
The purpose of the function, and an example where ap-
propriate.
SMBus Protocol: Read or Write Word.
Input/Output: word – Refer to “Section ꢀ.ꢀ” for bit
mapping.
SMBus Protocol: Refer to Section ꢀ.5 and to the SMBus
specification for more details.
SMB_BAT[4:1] Nibble
Input, Output or Input/Output: A description of the data
supplied to, or returned by, the function.
Theread/writeSMB_BAT[4:1]nibbleisusedbytheSMBus
Host to select with which individual battery to commu-
nicate or to determine with which individual battery it is
communicating.
Whenever the LTC1760 encounters a valid command with
invalid data, it ACKs the command, and ignores the invalid
data. For example, if an attempt is made to select Battery
1 and ꢀ to simultaneously communicate with the system
host, the LTC1760 will just ignore the request.
For example, an application that displays the remaining
capacity of all batteries would write to this nibble to in-
dividually select each battery in turn and get its capacity.
2.3.1 BatterySystemState() (0×01)
Allowed values are:
Description:
0010b: SMBus Host is communicating with Battery ꢀ.
This function returns the present state of the LTC1760 and
allows access to individual batteries. The information is
broken into four nibbles that report:
0001b:SMBusHostiscommunicatingwithBattery1.
(Power On Reset Value)
To change this nibble, set only one of the lower two bits
of this nibble high. All other values will simply be ignored.
Which battery is communicating with the SMBus Host
Which batteries, if any, or AC is powering the system
Which batteries are connected to the Smart Charger
Which batteries are present.
POWER_BY_BAT[4:1] Nibble
The read only POWER_BY_BAT[4:1] nibble is used by the
SMBus Host to determine which batteries are powering
the system. All writes to this nibble will be ignored.
The LTC1760 provides a mechanism to notify the system
whenever there is a change in its state. Specifically, the
LTC1760providesthesystemwithanotificationwhenever:
Allowed values are:
0011b: System powered by both Battery ꢀ and Battery
1 simultaneously.
• Abatteryisaddedorremoved(PollingorSMBALERT).
• AC power is connected or disconnected (Polling or
0010b: System powered by Battery ꢀ only.
0001b: System powered by Battery 1 only.
0000b: System powered by AC adapter only.
SMBALERT).
• The LTC1760 autonomously changes the configura-
tion of the batteries supplying power (Polling only).
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17
LTC1760
OPERATION
CHARGE_BAT[4:1] Nibble
power configuration. It may also be used by the system
to prohibit any battery charging.
The read only CHARGE_BAT[4:1]nibble is used by the
SMBus Host to determine which, if any, battery is being
charged. All writes to this nibble will be ignored.
SMBus Protocol: Read or Write Word.
Input/Output: word - Refer to “Section ꢀ.ꢀ” for bit
mapping
Allowed values are:
0011b: Both Battery ꢀ and Battery 1 being charged.
0010b: Only Battery ꢀ is being charged.
0001b: Only Battery 1 is being charged.
0000b: No battery being charged.
AC_PRESENT Bit
The read only AC_PRESENT bit is used to show the user
the status of AC availability to power the system. It may
be used internally by the SMBus Host in conjunction with
other information to determine when it is appropriate to
allow a battery conditioning cycle. Whenever there is a
change in the AC status, the LTC1760 asserts SMBALERT
low. In response, the system has to read this register to
determine the actual presence of AC. The LTC1760 uses
the DCDIV pin to measure the presence of AC.
An indication that multiple batteries are being charged
simultaneously does not indicate that the batteries are
being charged at the same rate or that they will complete
their charge at the same time. To actually determine
when an individual battery will be fully charged, use the
SMB_BAT[4:1] nibble to individually select the battery of
interest and read the TimeToFull() value.
Allowed values are:
1b: The LTC1760 has determined that AC is present.
0b: The LTC1760 has determined that AC is not present.
POWER_NOT_GOOD Bit
PRESENT_BAT[4:1] Nibble
The read only PRESENT_BAT[4:1]nibble is used by the
SMBus Host to determine how many and which batteries
are present. All writes to this nibble will be ignored.
The read only POWER_NOT_GOOD bit is used to show
thatthevoltagedeliveredtothesystemloadisinadequate.
This is determined by the LOPWR comparator.
Allowed values are:
0011b: Both Battery ꢀ and Battery 1 are present.
0010b: Only Battery ꢀ is present.
0001b: Only Battery 1 is present.
0000b: No batteries are present.
ThePOWER_NOT_GOODbitwillalsobesetiftheLTC1760
has detected a short circuit condition (see “Section 8.ꢀ”)
or an emergency turn-off condition (see “Section 8.3”).
Under either of these conditions the power paths will be
shut off even if battery or DC power is available.
Allowed values are:
2.3.2 BatterySystemStateCont() (0×02)
1b: The LTC1760 has determined that the voltage
delivered to the system load is inadequate.
Description:
This function returns additional state information of the
LTC1760 and provides a mechanism to prohibit charging.
This command also removes any requirement for the
SMBus Host to communicate directly with the charger to
obtainACpresenceinformation.WhentheLTC1760isused,
access to the charger 8-bit address, 0×01ꢀ, is blocked.
0b: The LTC1760 has determined that the voltage
delivered to the system load is adequate.
CALIBRATE_REQUEST_SUPPORT Bit
The read only CALIBRATE_REQUEST_SUPPORT bit is
always set high to indicate that the LTC1760 has a mecha-
nism to determine when any of the attached batteries are
in need of a calibration cycle.
Purpose:
Used by the SMBus Host to retrieve additional state
information from the LTC1760 and the overall system
1760fa
18
LTC1760
OPERATION
CALIBRATE_REQUEST Bit
CALIBRATE_BAT[4:1] Nibble
The read only CALIBRATE_REQUEST bit is set whenever
the LTC1760 has determined that one or both of the con-
nected batteries need a calibration cycle.
The read/write CALIBRATE_BAT[4:1]nibble is used by the
SMBus Host to select the battery to be calibrated or to
determine which individual battery is being calibrated.
Allowed values are:
Allowed read values are:
1b: The LTC1760 has determined that one or both
batteries requires calibration.
0010b: Battery ꢀ is being calibrated. CALIBRATE must
be 1.
0b: The LTC1760 has determined that neither battery
require calibration.
0001b: Battery 1 is being calibrated. CALIBRATE must
be 1.
CHARGING_INHIBIT Bit
0000b: No batteries are being calibrated.
Allowed write values are:
The read/write CHARGING_INHIBIT bit is used by the
SMBusHosttoinhibitchargingortodetermineifcharging
is inhibited. This bit is also set if the MODE pin is used to
inhibit charging.
0010b: Select Battery ꢀ for calibration.
0001b: Select Battery 1 for calibration.
0000b: Allow LTC1760 to choose battery
to be calibrated.
Allowed values are:
1b: The LTC1760 will not allow any battery charging
to occur.
All other values will simply be ignored. This provides a
mechanismtoupdatetheotherBatterySystemStateCont()
bits without altering this nibble.
0b: The LTC1760 may charge batteries as needed,
(Power On Reset Value).
2.3.3 BatterySystemInfo() (0×04)
CHARGER_POR Bit
Description:
The read/write CHARGER_POR bit is used to force a char-
ger power on reset.
The SMBus Host uses this function to determine the
capabilities of the LTC1760.
Writing a 1 to this bit will cause a charger power on reset
with the following effects.
Purpose:
• Charging will be turned off and wake-up charging will
be resumed. This is the same as if the batteries were
removed and then reinserted.
Allows the SMBus Host to determine the number of bat-
teries the LTC1760 supports as well as the specification
revision implemented by the LTC1760.
• The three minute wake-up watchdog timer will be
restarted.
SMBus Protocol: Read Word
Input/Output: word — Refer to “Section ꢀ.ꢀ” for bit map-
ping.
Writing a 0 to this bit has no effect. A read of this bit
always returns a 0.
BATTERIES_SUPPORTED Nibble
CALIBRATE Bit
The read only BATTERIES_SUPPORTED nibble is used
by the SMBus Host to determine how many batteries the
LTC1760 can support. The two-battery LTC1760 always
returns 0011b for this nibble.
The read/write CALIBRATE bit is used either to show the
status of battery calibration cycles in the LTC1760 or to
begin or end a calibration cycle.
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LTC1760
OPERATION
BATTERY_SYSTEM_REVISION Nibble
2.3.5 BatteryMode() (0×03)
The read only BATTERY_SYSTEM_REVISION nibble re-
ports the version of the Smart Battery System Manager
specification supported.
Description:
This function is used by the LTC1760 to read the battery’s
Mode register.
LTC1760 always returns 1000b for this nibble, indicating
Version 1.0 without optional PEC support.
Purpose:
Allows the LTC1760 to determine if a battery requires a
conditioning/calibration cycle.
2.3.4 LTC() (0×3C)
Description:
SMBus Protocol: Read Word. LTC1760 reads Battery 1 or
Battery ꢀ as an SMBus Master.
This function returns the LTC version nibble and allows
the user to perform expanded Smart Battery System
Manager functions.
Input/Output: word — Refer to “Section ꢀ.ꢀ” for bit map-
ping.
Purpose:
CONDITION_FLAG Bit
Used by the SMBus Host to determine the version of
the LTC1760 and to program and monitor TURBO and
POWER_OFF special functions.
The CONDITION_FLAG bit is set whenever the battery
requires calibration.
Allowed values:
SMBus Protocol: Read or Write Word.
1b: Battery requires calibration. (Also known as a
Condition Cycle Request).
Input/Output: word — Refer to “Section ꢀ.ꢀ” for bit map-
ping.
0b: Battery does not require calibration.
POWER_OFF Bit
2.3.6 Voltage() (0×09)
This read/write bit allows the LTC1760 to turn off all power
paths.
Description:
Allowed values:
This function is used by the LTC1760 to read the actual
cell-pack voltage .
1b: All power paths are off.
0b:Allpowerpathsareenabled. (poweronresetvalue).
TURBO Bit
Purpose:
Allows the LTC1760 to determine the cell pack voltage and
close the charging voltage servo loop.
This read/write bit allows the LTC1760 to enter TURBO
charging mode. Refer to “section 3.6”.
SMBus Protocol: Read Word. LTC1760 reads Battery 1 or
Battery ꢀ as an SMBus Master.
Allowed values:
Output: unsigned integer — battery terminal voltage in
milli-volts. Refer to “Section ꢀ.ꢀ” for bit mapping.
1b: Turbo charging mode enabled.
0b: Turbo charging mode disabled. (Power On Reset
Value).
Units: mV.
Range: 0 to 65,535 mV.
LTC_Version[3:0] Nibble
Thisreadonlynibblealwaysreturns0001bastheLTC1760
version.
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LTC1760
OPERATION
2.3.7 Current() (0×0A)
Description:
Purpose:
Allows the LTC1760 to determine the maximum charging
voltage.
This function is used by the LTC1760 to read the actual
current being supplied through the battery terminals.
SMBus Protocol: Read Word. LTC1760 reads Battery 1 or
Battery ꢀ as an SMBus Master.
Purpose:
Output: unsigned integer — charger output voltage in mV.
Refer to “Section ꢀ.ꢀ” for bit mapping.
Allows the LTC1760 to determine how much current a
battery is receiving through its terminals and close the
charging current servo loop.
Units: mV.
Range: 0 to 65,534 mV.
SMBus Protocol: Read Word. LTC1760 reads Battery 1 or
Battery ꢀ as an SMBus Master.
2.3.10 AlarmWarning() (0×16)
Output: signed integer (ꢀ’s complement) — charge/dis-
charge rate in mA increments - positive for charge, nega-
tive for discharge. Refer to “Section ꢀ.ꢀ” for bit mapping.
Description:
This function is used by the LTC1760 to read the Smart
Battery’s Alarm register.
Units: mA.
Purpose:
Range: 0 to 3ꢀ,767 mA for charge or 0 to -3ꢀ,768 mA
for discharge.
Allows the LTC1760 to determine the state of all applicable
alarm flags.
2.3.8 ChargingCurrent() (0×14)
SMBus Protocol: Read Word. LTC1760 reads Battery 1 or
Battery ꢀ as an SMBus Master.
Description:
This function is used by the LTC1760 to read the Smart
Battery’s desired charging current.
Output: unsigned integer – Refer to “Section ꢀ.ꢀ” for bit
mapping.
Purpose:
OVER_CHARGED_ALARM Bit
Allows the LTC1760 to determine the maximum charging
current.
The read only OVER_CHARGED_ALARM bit is used by the
LTC1760 to determine if charging may continue.
SMBus Protocol: Read Word. LTC1760 reads Battery 1 or
Allowed values are:
Battery ꢀ as an SMBus Master.
1b: The LTC1760 will not charge this battery.
Output: unsigned integer — maximum charger output
current in mA. Refer to “Section ꢀ.ꢀ” for bit mapping.
0b: The LTC1760 may charge this battery if other
conditions permit charging.
Units: mA.
TERMINATE_CHARGE_ALARM Bit
Range: 0 to 65,534 mA.
The read only TERMINATE_CHARGE_ALARM bit is used
by the LTC1760 to determine if charging may continue.
2.3.9 ChargingVoltage() (0×15)
Allowed values are:
Description:
1b: The LTC1760 will not charge this battery.
This function is used by the LTC1760 to read the Smart
Battery’s desired charging voltage.
0b: The LTC1760 may charge this battery if other
conditions permit charging.
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21
LTC1760
OPERATION
TERMINATE_CHARGE_RESERVED Bit
2.3.11 AlertResponse()
Description:
ThereadonlyTERMINATE_CHARGE_RESERVEDbitisused
by the LTC1760 to determine if charging may continue.
TheSMBusHostusestheAlertResponseAddress(ARA)to
simultaneously address all devices on the SMBus and de-
terminewhichdevicesarecurrentlyassertingSMBALERT.
Allowed values are:
1b: The LTC1760 will not charge this battery.
Purpose:
0b: The LTC1760 may charge this battery if other
conditions permit charging.
This command allows the SMBus Host to identify the
subset of devices that have new status data. This reduces
the number of reads required to refresh all status infor-
mation from the system. The SMBus Host begins an ARA
by transmitting the 8-bit address, 0×18, to all devices.
ARA-compliant devices that are asserting SMBALERT
will then simultaneously return their address on the next
read byte. While transmitting their address each device
monitors SDA. If a lower address is present, the device
transmitting the higher address will see that SDA does not
match and it will stop transmitting its address. When a
device sees its full address has been received it will stop
assertingSMBALERTandtheHostwillknowtoreadstatus
from this device. Subsequent ARA requests will allow the
Host to complete the list of devices requiring servicing.
OVER_TEMP_ALARM Bit
The read only OVER_TEMP_ALARM bit is used by the
LTC1760 to determine if charging may continue.
Allowed values are:
1b: The LTC1760 will not charge this battery.
0b: The LTC1760 may charge this battery if other
conditions permit charging.
TERMINATE_DISCHARGE_ALARM Bit
The read only TERMINATE_DISCHARGE_ALARM bit is
used by the LTC1760 to determine if discharge from the
battery is still allowed. This is used for PowerPath man-
agement and battery calibration.
Output:
Allowed values are:
The LTC1760 will transmit its 8-bit address, 0x14, in
response to an ARA request. The LTC1760 will stop trans-
mitting its address if another device with a lower address
is also responding to the ARA. The LTC1760 will de-assert
SMBALERT when it successfully returns its address.
1b: The LTC1760 will terminate calibration and should
try to not use this battery in the power path. When all
other power paths fail the LTC1760 will ignore this
alarm and still try to supply system power from this
battery.
The following events will cause the LTC1760 to pull-down
the SMBALERT# bus through the SMBALERT pin:
0b:TheLTC1760maycontinuedischargingthisbattery.
FULLY_DISCHARGED Bit
• Change of AC_PRESENT in the
BatterySystemStateCont() function.
The read only FULLY_DISCHARGED bit is used by the
LTC1760 to determine if discharge from the battery is
still allowed. This is used for PowerPath management
and battery calibration.
• Change of BATTERY_PRESENT in the BatterySys-
temState() function.
• Internal power on reset condition.
Refer to “Section ꢀ.ꢀ” for bit mapping.
Allowed values are:
1b: The LTC1760 will terminate calibration and should
try to not use this battery in the power path. When
all other power paths fail the LTC1760 will ignore this
alarm and still try to supply system power from this
battery.
2.4 SMBus Dual Port Operation
The SMBus Interface includes the LTC1760’s SMBus
controller, as well as circuitry to arbitrate and connect the
battery and SMBus Host interfaces. The SMBus controller
generates and interprets all LTC1760 SMBus functions.
0b:TheLTC1760maycontinuedischargingthisbattery.
1760fa
22
LTC1760
OPERATION
SMBꢀ*
SMB1*
SMBꢀ*
BATꢀ
BATꢀ
BAT1
SMB*
HOST
SMB*
HOST
SMB1*
BAT1
LTC1760
SMBus
CONTROLLER
LTC1760
SMBus
CONTROLLER
HOST, LTC1760 AND BAT1 CAN COMMUNICATE.
BATꢀ ORIGINATED COMMANDS ARE IGNORED.
LTC1760 AND BATꢀ CAN COMMUNICATE. HOST AND
BAT1 ORIGINATED COMMANDS ARE STRETCHED IF
THE LTC1760 IS COMMUNICATING WITH BATꢀ.
(1a)
(1b)
SMBꢀ*
SMBꢀ*
BATꢀ
BAT1
BATꢀ
BAT1
SMB*
SMB*
HOST
HOST
SMB1*
SMB1*
LTC1760
SMBus
CONTROLLER
LTC1760
SMBus
CONTROLLER
LTC1760 AND BAT1 CAN COMMUNICATE. HOST AND
BATꢀ ORIGINATED COMMANDS ARE STRETCHED IF
THE LTC1760 IS COMMUNICATING WITH BAT1.
HOST, LTC1760 AND BATꢀ CAN COMMUNICATE.
BAT1 ORIGINATED COMMANDS ARE IGNORED.
1760 F01
(1c)
(1d)
*SMB INCLUDES SCL AND SDA, SMB1 INCLUDES SCL1 AND SDA1, AND SMBꢀ INCLUDES SCLꢀ AND SDAꢀ.
Figure 1. Switch Configurations Used by the LTC1760 for Managing Dual Port Battery Communication
The dual port operation allows the SMBus Host to be
connected to the SMBus of either battery by setting the
SMB_BAT[4:1]nibble.Arbitrationishandledbystretching
anSMBusstartsequencewhenabuscollisionmightoccur.
Whenever configurations are switched, the LTC1760 will
generate a harmless SMBus reset on SMB1 and SMBꢀ as
required. The four possible configurations are illustrated
in Figure 1. Sample SMBus communications are shown
in Figures ꢀ and 3.
an invalid command code is transmitted to the LTC1760.
The SMBus Controller must respond if addressed as a
combinedSmartBatterySystemManagerat8-bitaddress
0×14. A valid address includes a legal Read/Write bit. The
SMBus Controller will ignore invalid data although the
data transmission with the invalid data will still be ACKed.
When the LTC1760, acting as a bus Master receives a
NACK, it will terminate the transmission and provide a
STOP condition on the bus.
2.5 LTC1760 SMBus Controller Operation
Detection of a STOP condition, power on reset, or SMBus
time out will reset the Controller to an initial state at any
time.
SMBuscommunicationwiththeLTC1760ishandledbythe
SMBusController,asub-blockoftheSMBusInterface.Data
is clocked into the SMBus Controller block shift register
aftertherisingSCLedge. DataisclockedoutoftheSMBus
Control block shift register after the falling edge of SCL.
The LTC1760 supports ARA, Write Word and Read Word
protocolsasanSMBusSlave.TheLTC1760supportsRead
Word protocol as an SMBus Master.
TheLTC1760actingasaSlavewillacknowledge(ACK)each
byte of serial data. The Command byte will be NACKed if
Refer to “System Management Bus Specification” for a
complete description of required operation and symbols.
1760fa
23
LTC1760
OPERATION
1760fa
24
LTC1760
OPERATION
1760fa
25
LTC1760
OPERATION
2.6 LTC1760 SMBALERT Operation
istor is reporting IDEAL-RANGE, and the battery fails to
respond to an SMBus query. This is an important feature
for handling deeply discharged NiMH batteries. These
batteries may begin to talk while being charged and go
silent once charging has stopped.
The SMBALERT pin allows the LTC1760 to signal to the
SMBus Host that there has been a change of status.
This pin is asserted low whenever there is a change in
battery presence, AC presence or after a power on reset
event. This pin is cleared during an Alert Response or
any of the following reads:
Wake-up charging is disabled if the battery thermistor is
COLD-RANGEorUNDER-RANGEandthebatteryhasbeen
charged for longer than t
.
BatterySystemState(),BatterySystemStateCont(), Bat-
terySystemInfo(), or LTC().
TIMEOUT
3.2 Wake-Up Charging Termination
3 Charging Algorithm Overview
3.1 Wake-Up Charging Initiation
The LTC1760 will terminate wake-up charging when any
of the following conditions are met:
1. Battery removal (thermistor indicating OVER-RANGE)
ꢀ. AC is removed.
The following conditions must be met in order to allow
wake-up charging:
1. The battery thermistor must be COLD-RANGE, IDEAL-
RANGE, or UNDER-RANGE.
3. The SMBus Host issues a calibration request by setting
BatterySystemStateCont(CALIBRATE) high.
ꢀ. AC must be present.
4. Any response to an LTC1760 Master read of Charg-
ingCurrent(), Current(), ChargingVoltage(), or Voltage().
Note that the LTC1760 ignores all writes from the battery.
3. BatterySystemStateCont(CHARGING_INHIBIT) must
be de-asserted (or low).
5. AnyofthefollowingAlarmWarning()bitsassertedhigh:
4. Hardware controlled charging inhibit must be
de-asserted (MODE not low with V
“Section 6.ꢀ”.
high). Refer to
DDS
OVER_CHARGED_ALARM
TERMINATE_CHARGE_ALARM
TERMINATE_CHARGE_RESERVED
OVER_TEMP_ALARM
Wake-up charging initiates when a newly inserted battery
doesnotrespondtoanyLTC1760Masterreadcommands.
Only one battery will wake-up charge at a time. When two
batteries are inserted and both require wake-up charging,
Battery1willwake-upchargefirst.Batteryꢀwillonlywake-
up charge when Battery 1 terminates wake-up charging.
Note that the LTC1760 ignores all writes from the battery.
Each battery’s charge alarm is cached inside the LTC1760.
This internally cached bit will be set when any of the up-
per four bits of the battery’s AlarmWarning() response
are set. The cached bit will remain set if a subsequent
AlarmWarning() fails to respond. The cached alarm will
be cleared by any of the following conditions.
Wake-up charging takes priority over controlled charg-
ing; this prevents one battery from tying up the charger
when it would be advantageous to dual charge two deeply
discharged batteries.
a) Associated battery is removed.
The LTC1760 will attempt to reinitiate wake-up
charging on both batteries after the SMBus Host asserts
BatterySystemStateCont(CHARGER_POR) or a power on
reset event. This will reset any wake-up charging safety
timers and is equivalent to removing and reinserting both
batteries.
b) A subsequent AlarmWarning() clears all
charge alarm bits for the associated battery.
c) A power on reset event.
d) The SMBus Host asserts
BatterySystemStateCont(CHARGER_POR) high.
The LTC1760 will attempt to reinitiate wake-up charging
on a battery if the battery is not being charged, the therm-
1760fa
26
LTC1760
OPERATION
6. The SMBus Host asserts
BatterySystemStateCont(CHARGING_INHIBIT) high.
5. The battery responds to an LTC1760 Master read of
Alarm() with all charge alarms deasserted.
7.Hardwarecontrolledcharginginhibitisasserted(MODE
6. The battery responds to an LTC1760 Master read of
ChargingVoltage() with a non zero voltage request value.
low with V
high). Refer to “Section 6.ꢀ”.
DDS
8. The thermistor of the battery being charged indicates
COLD-RANGE andthebatteryhasbeenchargedforlonger
7. The battery responds to an LTC1760 Master read of
Voltage().
than t
.
TIMEOUT
8. The battery responds to an LTC1760 Master read of
ChargingCurrent() with a non zero current request value.
9. The thermistor of the battery being charged indicates
UNDER-RANGE and the battery has been charged for
9. The battery responds to an LTC1760 Master read of
Current().
longer than t
.
TIMEOUT
10. The thermistor of the battery being charged indicates
HOT-RANGE.
The following charging related functions are polled each
QUERY
Current(), and Current().
t
: Alarm(), ChargingVoltage(), Voltage(), Charging-
11. Any SMBus communication line is held low for longer
than t
QUERY.
3.5 Controlled Charging Termination
1ꢀ.BatterySystemStateCont(POWER_NOT_GOOD)ishigh.
The LTC1760 will terminate controlled charging when any
of the following conditions are met:
13. The emergency turn-off feature has been asserted
using the DCDIV input pin.
1.Batteryremoval,orthermistorindicatingOVER-RANGE.
ꢀ. AC removal.
3.3 Wake-Up Charging Current and Voltage Limits
The wake-up charging current is fixed at I
for all
WAKE_UP
3. The SMBus Host issues a calibration request by setting
BatterySystemStateCont(CALIBRATE) high.
values of I
. Wake-up charging uses the low current
LIMIT
mode described in “Section 10”.
4.AnLTC1760MasterreadofChargingCurrent()returning
a zero current request.
The wake-up charging voltage is not limited by the V
function.
LIMIT
5.AnLTC1760MasterreadofChargingVoltage()returning
a zero voltage request.
3.4 Controlled Charging Initiation
All of the following conditions must be met in order to
allow controlled charging of a given battery. One or both
batteries may be controlled charged at a time.
6. AnyofthefollowingAlarmWarning()bitsassertedhigh:
OVER_CHARGED_ALARM
TERMINATE_CHARGE_ALARM
TERMINATE_CHARGE_RESERVED
OVER_TEMP_ALARM
1. The battery thermistor must be COLD-RANGE, IDEAL-
RANGE, or UNDER-RANGE.
ꢀ. AC must be present.
Note that the LTC1760 ignores all writes from the battery.
Each battery’s charge alarm is cached inside the LTC1760.
This internally cached bit will be set when any of the upper
fourbitsofthebattery’sAlarmWarning()responseareset.
3. BatterySystemStateCont(CHARGING_INHIBIT) must
be de-asserted (or low).
4. Hardware controlled charging inhibit must be
de-asserted (MODE not low with V
“Section 6.ꢀ”.
high). Refer to
DDS
1760fa
27
LTC1760
OPERATION
ThiscachedbitwillremainsetifasubsequentAlarmWarn-
ing() fails to respond. The cached alarm will be cleared by
any of the following conditions.
ouslyadjuststhechargingcurrentbythedifferencebetween
the actual and requested currents.
Whensimultaneouslychargingtwobatteries,thecharging
algorithm attempts to adjust the current so as to match
the reported current with the requested current in both
batteries. The LTC1760 calculates the difference between
the requested and actual current in both batteries and
uses the minimum of these differences to increment or
decrement the total charge current being provided by the
charging stage.
a) Associated battery is removed.
b) A subsequent AlarmWarning() clears all charge
alarm bits for the associated battery.
c) A power on reset event.
d) The SMBus Host asserts
BatterySystemStateCont(CHARGER_POR) high.
The charging algorithm will not allow the reported actual
current to exceed the requested current in either battery.
For this reason the most efficient charging occurs for
matched batteries at similar charge states.
7. The SMBus Host asserts
BatterySystemStateCont(CHARGING_INHIBIT) high.
8.Hardwarecontrolledcharginginhibitisasserted(MODE
low with V
high).
DDS
Whenever changing conditions cause either battery to
stop charging, the current algorithm is reset to zero. The
9. The SMBus of the battery being charged has stopped
acknowledging SMBus read commands for longer than
programmed current is updated every t
.
QUERY
t
TIMEOUT.
There are additional safety restrictions that limit the total
output current of the charger. These are detailed in the
following three sub-sections.
10. The thermistor of the battery being charged indicates
HOT-RANGE.
3.6.1 Current Limits When Charging A Single Battery
11.AnySMBuscommunicationlineisgroundedforlonger
The following additional limits are applied to the charg-
ing current algorithm described in 3.6 when charging a
single battery:
than t
.
QUERY
1ꢀ.BatterySystemStateCont(POWER_NOT_GOOD)ishigh.
13. The emergency turn-off feature has been asserted
using the DCDIV input pin.
a)Theprogrammedcurrentcannotexceedtherequested
current + I /3ꢀ.
LIMIT
Whenever changing conditions cause either battery to
stop charging, charging is stopped immediately for all
batteries and the voltage and current algorithms are reset
to zero. Charging is not resumed until all the conditions
for controlled charging are met.
b) The programmed current cannot exceed I
.
LIMIT
3.6.2 Current Limits When Charging Two Batteries
(TURBO Mode Disabled)
The following additional limits are applied to the charging
current algorithm described in 3.6 when charging two
batteries with turbo mode disabled:
3.6 Controlled Charging Current Programming
TheLTC1760usesasinglechargerstagetosimultaneously
charge up to two batteries. The batteries are connected to
the charger using a charge MUX. The charge MUX allows
the total charger current to be shared by the two batteries
while preventing charge transfer between the batteries.
Refer to “Section 7.1” and “Section 7.ꢀ”.
a)Theprogrammedcurrentcannotexceedthemaximum
of the two requested currents + I
.
LIMIT/3ꢀ
b) The programmed current cannot exceed I
.
LIMIT
3.6.3 Current Limits When Charging Two Batteries
(TURBO Mode Enabled)
When charging a single battery, the charging algorithm
attempts to adjust the current so as to match the reported
current with the requested current. The LTC1760 continu-
The following additional limits are applied to the charging
current algorithm described in 3.6 when charging two
batteries with turbo mode enabled:
1760fa
28
LTC1760
OPERATION
a)Theprogrammedcurrentcannotexceedthemaximum
ThisisanextremelyimportantfeatureoftheLTC1760since
it allows the charger to servo on the internal cell voltage
of the battery as determined by the Smart Battery. This
voltage may be significantly lower than the battery pack
terminal voltage which is used by all Level ꢀ chargers.
The advantage for the LTC1760 is improved charge time,
safety, and a more completely charged battery.
of the two requested currents + I
. This relaxed
is greater
LIMIT
limit enables accelerated charging if I
LIMIT
than the maximum of the two requested currents. For
the recommended matched battery pair the requested
current should be the same.
b) The programmed current cannot exceed I
LIMIT
The voltage correction cannot exceed the minimum re-
questedvoltagebymorethan51ꢀmV.Whendecrementing,
TURBO mode provides a mechanism for the SMBus Host
to enable the charge MUX to apply additional current to
both batteries. TURBO mode only has an effect when two
batteries are being charged simultaneously. TURBO mode
does not affect wake-up charging or any other conditions
that could inhibit charging. TURBO mode is entered when
LTC(TURBO) is set high.
the programmed voltage is reduced by 16mV each t
.
QUERY
Wheneverchangingconditionscauseeitherbatterytostop
charging, the voltage algorithm is reset to zero.
4 System Power Management Algorithm and Battery
Calibration
Normally the LTC1760 will limit the current into both bat-
teries to the maximum of the two requested currents +
4.1 Turning Off System Power
I
/3ꢀ. TURBO mode removes this restriction, allowing
LIMIT
TheLTC1760allowstheusertoturnoffsystempowerusing
the LTC(POWER_OFF) bit. When POWER_OFF is asserted
high all power management functions are bypassed and
the LTC1760 will turn off DCIN, BATꢀ and BAT1 power
paths. This feature allows the user to power down the
system. Charging is still allowed when POWER_OFF is
asserted high.
the charger to output as much as I
battery system.
into the combined
LIMIT
Forexample:InasystemwhereLTC(TURBO)=0,I
=4.0A
LIMIT
and each battery is requesting ꢀA the LTC1760 will not
outputmorethan ꢀ.1ꢀ5Aintothecombinedbatterysystem
or 1.06A into each battery if their charge states match.
In a system where LTC(TURBO)=1, I
= 4.0A and each
LIMIT
battery is requesting ꢀA the LTC1760 will now output up
4.2 Power-By Algorithm When No Battery is Being
Calibrated
to I
into the combined battery system or ꢀA into each
LIMIT
battery if their charge states match.
TheLTC1760willalwaysattempttomaintainsystempower.
The preferred configuration is to remain in 3- Diode mode.
In 3-Diode mode, power will be provided by BAT1, BATꢀ
and DCIN with the source at the highest voltage potential
automatically providing all the power. Sources at similar
voltagepotentialswillsharepowerbasedontheircapacity.
Even without TURBO mode, the LTC1760 offers signifi-
cantly reduced charge times for matched batteries in the
top-off state. This time savings is especially significant for
Lithium-Ion batteries. Simultaneously charging two bat-
teries reduces losses in switches and improves efficiency.
3.7 Controlled Charging Voltage Programming
ThefollowingconditionswillcausetheLTC1760tomodify
its preferred power-by algorithm.
The LTC1760 monitors the requested and actual voltages
in each battery and increments the programmed voltage
1. A battery issues a TERMINATE_DISCHARGE alarm and
AC_PRESENT is high. The LTC1760 will select the other
battery and DCIN to power the system.
by 16mV each t
tions are met:
unless one of the following condi-
QUERY
a)Theactualvoltageexceedstherequestedvoltagein
either battery.
b) The actual voltage exceeds V
.
LIMIT
1760fa
29
LTC1760
OPERATION
ꢀ. A battery issues a TERMINATE_DISCHARGE alarm and
AC_PRESENT is low. The LTC1760 will select the other
battery to power the system.
Power Reporting with AC_PRESENT Low and both Batteries
Present, as a Function of Power Alarms.
BATTERY 2
BATTERY 1
POWER ALARM POWER ALARM
3. A battery issues a TERMINATE_DISCHARGE alarm,
AC_PRESENT is low, and the other battery is not present
or has previously issued an alarm. The LTC1760 will au-
tonomouslytrytorestorepowerbyentering3-Diodemode.
The 3-Diode mode will ignore TERMINATE_DISCHARGE
and FULLY_DISCHARGED alarms.
AC_PRESENT
(NOTE 1)
(NOTE 1)
POWERED_BY_BAT(4:1)
0
0
0
0
1
0
0
1
1
X
0
1
0
1
X
0011b
0010b
0001b
0011b
0000b
Note 1: A power alarm means that ALARM() has returned
TERMINATE_DISCHARGE=1 or FULLY_DISCHARGED_ALARM=1
4.3 Power-By Algorithm When a Battery is Being
Calibrated
Power Reporting When
BatterySystemStateCont(POWER_NOT_GOOD) is High
and the LTC1760 has Autonomously Entered 3-Diode Mode
AC_PRESENT PRESENT_BAT2 PRESENT_BAT1 POWERED_BY_BAT(4:1)
During battery calibration, the battery being calibrated is
the only device powering the system. This will be reflected
in the reported POWER_BY[4:1] bits. See “Section 5” for
more information on battery calibration.
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0000b
0001b
0010b
0011b
0000b
0000b
0000b
0000b
4.4 Power-By Reporting
The following tables illustrate how BatterySystem
State(POWER_BY_BAT[4:1]) interprets PowerPath
conditions.
Power Reporting for Batteries Being Calibrated
AC_PRESENT CALIBRATE_BAT2 CALIBRATE_BAT1 POWERED_BY_BAT(4:1)
5 Battery Calibration (Conditioning)
1
1
1
0
1
1
0
1
0
0000b
0001b
0010b
Calibration allows the SMBus Host to fully discharge
a battery for conditioning purposes. The SMBus Host
may determine the battery to be discharged or allow the
LTC1760 to choose based on the batteries’ request to
be conditioned.
*States not shown are not allowed
Power Reporting as a Function of Battery Presence
AC_PRESENT PRESENT_BAT2 PRESENT_BAT1 POWERED_BY_BAT(4:1)
5.1 Selecting a Battery to be Calibrated
1
0
0
0
0
X
0
0
1
1
X
0
1
0
1
0000b
0000b
0001b
0010b
0011b
Option 1) SMBus Host chooses battery to be calibrated
using BatterySystemStateCont(CALIBRATE_BAT[4:1])
Allowed values:
0001b:SetCALIBRATE_BAT1. Onlyhasaneffectif Bat-
tery 1 BatteryMode(CONDITION_FLAG) is high . May
not be updated if a calibration is in progress.
0010b: Set CALIBRATE_BATꢀ. Only has an effect if
BatteryꢀBatteryMode(CONDITION_FLAG)ishigh.May
not be updated if a calibration is in progress.
1760fa
30
LTC1760
OPERATION
0000b:ClearsCALIBRATE_BAT1andCALIBRATE_BATꢀ
and allows LTC1760 to chose. Power on reset default.
May not be updated if a calibration is in progress.
• The battery sets Alarm Warning
(TERMINATE_DISCHARGE) high.
• The battery sets Alarm Warning
(FULLY_DISCHARGED) high.
Option ꢀ) SMBus Host allows LTC1760 to choose battery
to be calibrated.
• A zero is written to the CALIBRATE bit.
BatterySystemStateCont(CALIBRATE_BAT[4:1]) =0000b.
See previous option.
The LTC1760 will attempt to initiate a charge cycle after
the discharge cycle is completed.
The LTC1760 determines that the battery requires
calibration by reading BatteryMode(CONDITION_FLAG).
This flag is cached in the LTC1760. The LTC1760 sets
BatterySystemStateCont(CALIBRATE_REQUEST) high.
TheLTC1760willalwaysselectthebatterythatisrequesting
calibration. If both batteries are requesting calibration, the
LTC1760 will select Battery 1. If neither battery is request-
ing calibration, then calibration cannot occur.
6 MODE Pin Operation
TheMODEpinisamultifunctionpinthatallowstheLTC1760
to: 1) display charging status in stand alone operation;
ꢀ) activate hardware charge inhibit; 3) charge when SCL
and SDA are low and; 4) charge with an SMBus Host.
Summary of SDA, SCL and SMBALERT Operation as a Function
of MODE and VDDS Levels
CONDITION
LTC1760 OPERATING MODE
5.2 Initiating Calibration of Selected Battery
V
MODE
V
VDDS
= GND
SCL: Clock for Status Indicators
SCL: Clock for Status Indicators
SDA: Battery ꢀ Status
The SMBus Host initiates a calibration by writing to
BatterySystemStateCont(CALIBRATE). Followrulesofthe
previous section to preserve battery intended for calibra-
tion. The SMBus Host must only set the calibration bit
once per calibration.
< V
IL_VDDS
SMBALERT: Battery 1 Status
V
MODE
V
VDDS
= GND
SCL, SDA, SMBALERT: Normal Operation
LTC1760 Charging Inhibited
> V
IH_VDDS
V
V
= V
SCL, SDA Ignored and May Float Low
SMBALERT: Normal Operation
SCL1, SDA1, SCLꢀ and SDAꢀ: Normal Operation and
Charging is Allowed
MODE
VDDS
VCCꢀ
The LTC1760 will discharge the selected battery as long as
the calibration is in progress (CALIBRATE high). Updates
to the cached BatteryMode(CONDITION_FLAG) will be
inhibited while CALIBRATE is asserted. This means that
discharge of the battery will continue even if the battery
clears the CONDITION_FLAG.
< V
IL_VDDS
V
V
= V
Normal Operation on all Pins, Charging is Allowed
MODE
VDDS
VCCꢀ
> V
IH_VDDS
6.1 Standalone Charge Indication
5.3 Terminating Calibration of Selected Battery
When MODE is tied to GND and V
< V
, the
VDDS
IL_VDDS
Calibration will end when CALIBRATE is cleared. CALI-
BRATE will be cleared when:
function of SDA, SMBALERT, and SCL are changed as
described below:
• AC is removed.
SDA is an output and is used to monitor charging status
of Battery ꢀ. Allowed values are:
• The battery being calibrated is removed. When the
battery being calibrated is removed, the LTC1760
will automatically calibrate the other battery if it is
requesting calibration.
Low: Battery ꢀ is charging.
High: Battery ꢀ not charging (AC is not present or bat-
tery is not present).
• BatterySystemStateCont(POWER_NOT_GOOD) is high.
Blinking: Battery ꢀ charge complete (AC is present,
battery is present and not charging).
1760fa
31
LTC1760
OPERATION
SMBALERTisusedtomonitorchargingstatusofBattery1.
Allowed values are:
t
= (V
- V )/(V
• f
)
OFF
DCIN
BAT
DCIN OSC
to set the bottom MOSFET on time. The result is quasi-
constant frequency operation where the converter fre-
quency remains nearly constant over a wide range of
output voltages. This activity is diagrammed in Figure 4.
Low: Battery 1 is charging.
High: Battery 1 not charging (AC is not present or bat-
tery is not present).
OFF
TGATE
ON
Blinking: Battery 1 charge complete (AC is present,
battery is present and not charging).
t
OFF
ON
SCL is an input and is used to determine the blinking rate
of SDA and SMBALERT. Tie SCL high if blinking is not
desired. This will provide two different states to indicate
charging (output low) and not charging (output high).
BGATE
OFF
TRIP POINT SET BY I VOLTAGE
TH
INDUCTOR
CURRENT
1760 F04
6.2 Hardware Charge Inhibit
Figure 4.
WhenMODEistiedtoGNDandV
>V
,charging
VDDS IH_VDDS
isinhibitedandBatterySystemStateCont(CHARGING_INHIBIT)
will report a logic high.
The peak inductor current, at which I
resets the SR
TH TH
CMP
latch, is controlled by the voltage on I . I is in turn
6.3 Charging When SCL And SDA Are Low
controlled by several loops, depending upon the situation
at hand. The average current control loop converts the
voltage between CSP and BAT to a representative current.
Error amp CAꢀ compares this current against the desired
When MODE is tied to V
and V
< V
, SDA
IL_VDDS
CCꢀ
VDDS
and SCL are not used and will not interfere with LTC1760
batterycommunication.ThisfeatureallowstheLTC1760to
autonomouslychargewhenSCLandSDAarenotavailable.
ThisscenariomightoccurwhenSMBusHosthaspowered
down and is no longer pulling up on SCL and SDA.
currentprogrammedbytheI
TH
attheI pinandadjusts
DAC
SET
I
for the desired voltage across R
.
SENSE
The voltage at BAT is divided down by an internal resis-
tor divider set by the V
and is used by error amp EA
DAC
6.4 Charging With an SMBus Host
to decrease I if the divider voltage is above the 0.8V
TH
reference.
When Mode is tied to V
and V
> V
, SDA
IH_VDDS
CCꢀ
VDDS
and SCL are used to communicate with the SMBus Host.
The amplifier CL1 monitors and limits the input current,
normally from the AC adapter, to a preset level (100 mV/
7 Battery Charger Controller
R ). At input current limit, CL1 will decrease the I volt-
CL
TH
The LTC1760 charger controller uses a constant off-time,
current mode step-down architecture. During normal
operation, the top MOSFET is turned on each cycle when
the oscillator sets the SR latch and turned off when the
age and thus reduce battery charging current.
An over-voltage comparator, OV, guards against transient
overshoots(>7.52).Inthiscase,thetopMOSFETisturned
off until the over-voltage condition is cleared. This feature
is useful for batteries which “load dump” themselves by
opening their protection switch to perform functions such
as calibration or pulse-mode charging.
main current comparator I
resets the SR latch. While
CMP
the top MOSFET is off, the bottom MOSFET is turned on
until either the inductor current trips the current compara-
tor I , or the beginning of the next cycle. The oscillator
REV
The top MOSFET driver is powered from a floating boot-
strap capacitor C4. This capacitor is normally recharged
uses the equation:
from V through an external diode when the top MOSFET
CC
1760fa
32
LTC1760
OPERATION
is turned off. As V decreases towards the selected bat-
7.2 Dual Charging
IN
tery voltage, the converter will attempt to turn on the top
MOSFETcontinuously(“dropout’’).Adropouttimerdetects
this condition and forces the top MOSFET to turn off, and
the bottom MOSFET on, for about ꢀ00ns at 40μs intervals
to recharge the bootstrap capacitor.
Note that the charge MUX switch drivers will operate
together to allow both batteries to be charged simultane-
ously. If both charge MUX switch drivers are enabled,
only the battery with the lowest voltage will be charged
until its voltage rises to equal the higher voltage battery.
The charge current will then share between the batteries
according to the capacity of each battery.
7.1 Charge MUX Switches
The equivalent circuit of a charge MUX switch driver is
shown in Figure 5. If the charger controller is not enabled,
the charge MUX drivers will drive the gate and source of
the series-connected MOSFETs to a low voltage and the
switch is off. When the charger controller is on, the charge
MUX driver will keep the MOSFETs off until the voltage at
CSN rises at least 35mV above the battery voltage. GCH1
is then driven with an error amplifier EAC until the volt-
age between BAT1 and CSN satisfies the error amplifier
or until GCH1 is clamped by the internal Zener diode.
The time required to close the switch could be quite long
(many ms) due to the small currents output by the error
amp and depending upon the size of the MOSFET switch.
Whenbatteriesarecontrolledcharging,onlybatterieswith
voltages above V
are allowed to charge. When a bat-
CHMIN
tery is wake-up charging this restriction does not apply.
8 PowerPath Controller
ThePowerPathswitchesareturnedonandoffbythepower
management algorithm. The external PFETs are usually
connected as an input switch and an output switch. The
output switch PFET is connected in series with the input
PFETandthepositivesideoftheshort-circuitsensingresis-
tor, R . The input switch is connected in series between
SC
the power source and the output PFET. The PowerPath
switch driver equivalent circuit is shown in Figure 6. The
output PFET is driven ON or OFF by the output side driver
controlling pin GB10. The gate of the input PFET is driven
by an error amplifier which monitors the voltage between
the input power source (BAT1 in this case) and SCP. If
the switch is turned off, the two outputs are driven to the
higher of the two voltages present across the input/SCP
terminals of the switch. When the switch is instructed to
turn on, the output side driver immediately drives the gate
of the output PFET approximately 6V below the highest
of the voltages present at the input/SCP. When the output
PFET turns on, the voltage at SCP will be pulled up to a
diode drop below the source voltage by the bulk diode of
the input PFET. If the source voltage is more than ꢀ5mV
above SCP, EAP will drive the gate of the input PFET low
until the input PFET turns on and reduces the voltage
across the input/SCP to the EAP set point, or until the
Zener clamp engages to limit the voltage applied to the
input PFET. If the source voltage drops more than ꢀ0mV
below SCP, then comparator CP turns on SWP to quickly
prevent large reverse current in the switch. This operation
mimics a diode with a low forward voltage drop.
If the voltage at CSN decreases below V
– ꢀ0mV a
BAT1
comparator CC quickly turns off the MOSFETs to prevent
reverse current from flowing in the switches. In essence,
this system performs as a low forward voltage diode.
Operation is identical for BATꢀ.
DCIN + 10V
(CHARGE PUMPED)
BAT1
CSN
TO
BATTERY
1
–
+
GCH1
SCH1
Q3
EAC
35mV
ꢀ0mV
FROM
CHARGER
+
–
CC
10k
Q4
OFF
1760 F05
Figure 5. Charge MUX Switch Driver Equivalent Circuit
1760fa
33
LTC1760
OPERATION
ꢀ0mV
OFF
(POWER_NOT_GOOD) is set. Similarly, if the voltage
at SCN falls below 3V for more than 15ms, then all of
the PowerPath switches are turned off and POWER_
NOT_GOOD is set high. The POWER_NOT_GOOD bit is
reset by removing all power sources and allowing the
–
CP
+
FROM
BATTERY
1
BAT1
SWP
voltage at V
to fall below the UVLO threshold. If
–
PLUS
GB1I
Q7
Q8
EAP
SCP
the POWER_NOT_GOOD bit is set, charging is disabled
+
until V
exceeds the UVLO threshold and the Charger
PLUS
ꢀ5mV
GB1O
Algorithm allows charging to resume.
OFF
When a hard short-circuit occurs, it might pull all of the
power sources down to near 0V potentials. The capacitors
R
SC
on V and V
must be large enough to keep the circuit
C
L
CC
PLUS
TO LOAD
1760 F06
operating correctly during the 15ms short-circuit event.
The charger will stop within a few microseconds, leaving
a small current which must be provided by the capacitor
Figure 6. PowerPath Driver Equivalent Circuit
on V
. The recommended minimum values (1μF on
PLUS
8.1 Autonomous PowerPath Switching
V
and ꢀμF on V , including tolerances) should keep
PLUS
CC
The LOPWR comparator monitors the voltage at the
load through the resistor divider from pin SCN. If LTC
(POWER_OFF) is low and the LOPWR comparator trips,
then all of the switches are turned on (3-Diode mode)
by the Autonomous PowerPath Controller to ensure that
the system is powered from the source with the highest
voltage. The Autonomous PowerPath Controller waits
approximately 1 second, to allow power to stabilize, and
then reverts back to the PowerPath switch configuration
requested by the PowerPath Management Algorithm. A
power fail counter is incremented to indicate that a failure
has occurred. If the power fail counter equals a value of 3,
then the the Autonomous PowerPath Controller sets the
switches to 3-Diode mode and BatterySystem-
StateCont(POWER_NOT_GOOD) will be set, provided
the LOPWR comparator is still detecting a low power
event. This is a three-strikes-and-you’re-out process
which is intended to debounce the POWER_NOT_GOOD
indicator. The power fail counter is reset when battery or
AC presence change.
the LTC1760 operating above the UVLO trip voltage long
enough to perform the short-circuit function when the
input voltages are greater than 8V. Increasing the capaci-
tor across V to 4.7μF will allow operation down to the
CC
recommended 6V minimum.
8.3 Emergency Turn-Off
All of the PowerPath switches can be forced off by set-
ting the DCDIV pin to a voltage between 8V and 10V. This
will have the same effect as a short-circuit event. DCDIV
must be less than 5V and V
must decrease below
PLUS
the UVLO threshold to re-enable the PowerPath switches.
The LTC1760 can recover from this condition without
removing power. Contact Applications Engineering for
more information.
8.4 Power-Up Strategy
All three PowerPath switches are turned on after V
PLUS
exceeds the UVLO threshold for more than ꢀ50ms. This
delay is to prevent oscillation from a turn-on transient
near the UVLO threshold.
8.2 Short-Circuit Protection
9 The Voltage DAC Block
Short-circuit protection operates in both a current mode
and a voltage mode. If the voltage between SCP and
SCN exceeds the short-circuit comparator threshold
The voltage DAC (V ) is a delta-sigma modulator
DAC
which controls the effective value of an internal resistor,
R
= 7.ꢀk,usedtoprogramthemaximumchargervolt-
VSET
V
for more than 15ms, then all of the PowerPath
TSC
age. Figure7isasimplifieddiagramoftheV
operation.
DAC
switches are turned off and BatterySystemState-Cont
1760fa
34
LTC1760
OPERATION
The delta-sigma modulator and switch SWV convert the
voltage,V ,andthecurrentfromR ismatchedagainst
REF SET
V
value to a variable resistance equal to (11/8)R
DAC(VALUE)
/
a current derived from the voltage between pins CSP and
CSN. This current is (V – V )/3k.
DAC
(V
VSET
/ꢀ047). In regulation, V is servo driven to
SET
CSP
CSN
the 0.8V reference voltage, V
.
REF
Therefore programmed current is:
Capacitors C and C are used to average the voltage
B1
Bꢀ
I
= V • 3k/(1.ꢀ5 RSNS R ) • (I
/10ꢀ3)
CHG
REF
SET
DAC(VALUE)
present at the V
pin as well as provide a zero in the
SET
= (10ꢀ.3mV/R ) • (I
/10ꢀ3)
SNS
DAC(VALUE)
voltage loop to help stability and transient response time
to voltage variations.
During wake-up current operation, the current DAC enters
a low current mode. The current DAC output is pulse-
width modulated with a high frequency clock having a
duty cycle value of 1/8. Therefore, the maximum output
10 The Current DAC Block
ThecurrentDACisadelta-sigmamodulatorwhichcontrols
currentprovidedbythechargerisI
/8. Thedelta-sigma
MAX
the effective value of an internal resistor, R
= 18.77k,
SET
output gates this low duty cycle signal on and off. The
delta-sigma shift registers are then clocked at a slower
rate, about 40ms/bit, so that the charger has time to settle
used to program the maximum charger current. Figure 8
is a simplified diagram of the DAC operation. The delta-
sigma modulator and switch convert the I
value to a
DAC
SET DAC(VALUE)
to the I
/8 value.
MAX
variable resistance equal to 1.ꢀ5R /(I
/10ꢀ3).
In regulation, I is servo driven to the 0.8V reference
SET
CSN
(V
– V
)
CSN
CSP
3kΩ
(FROM CA1 AMPLIFIER)
R
VF
C
Bꢀ
C
405.3k
I
SET
V
SET
+
–
–
+
TO
TH
TO
TH
C
SET
EA
I
I
B1
V
V
REF
REF
R
R
SET
VSET
7.ꢀk
18.77k
DAC
VALUE
(10 BITS)
1760 F08
DAC
10
ΔΣ
MODULATOR
11
ΔΣ
MODULATOR
SWV
VALUE
(11 BITS)
1760 F07
Figure 7. Voltage DAC Operation
Figure 8. Current Dac Operation
1760fa
35
LTC1760
APPLICATIONS INFORMATION
Automatic Current Sharing
it is actual physical capacity rating at the time of charge.
Capacity rating will change with age and use and hence
the current sharing ratios can change over time.
In a dual parallel charge configuration, the LTC1760 does
notactuallycontrolthecurrentflowingintoeachindividual
battery. The capacity, or Amp-Hour rating, of each battery
determines how the charger current is shared. This auto-
matic steering of current is what allows both batteries to
reach their full capacity points at the same time. In other
words, given all other things equal, charge termination
will happen simultaneously.
Adapter Limiting
An important feature of the LTC1760 is the ability to auto-
matically adjust charging current to a level which avoids
overloading the wall adapter. This allows the product to
operate at the same time that batteries are being charged
without complex load management algorithms. Addition-
ally,batterieswillautomaticallybechargedatthemaximum
possible rate of which the adapter is capable.
A battery can be modeled as a huge capacitor and hence
governed by the same laws.
This feature is created by sensing total adapter output cur-
rent and adjusting charging current downward if a preset
adapter current limit is exceeded. True analog control is
used,withclosedloopfeedbackensuringthatadapterload
current remains within limits. Amplifier CL1 in Figure 9
I = C • (dV/dt) where:
I = The current flowing through the capacitor
C = Capacity rating of battery (using amp-hour values
instead of capacitance)
senses the voltage across R , connected between the
CL
dV = Change in voltage
dt = Change in time
CLP and DCIN pins. When this voltage exceeds 100mV,
the amplifier will override programmed charging current
to limit adapter current to 100mV/R . A lowpass filter
CL
The equivalent model of a set or parallel batteries is a
set of parallel capacitors. Since they are in parallel, the
change in voltage over change in time is the same for both
batteries 1 and ꢀ.
formed by 5kΩ and 0.1μF is required to eliminate switch-
ing noise. If the current limit is not used, CLP should be
connected to DCIN.
dV/dt
= dV/dt
BATꢀ
BAT1
100mV
CLP
+
From here we can simplify.
–
0.1μF
5kΩ
CL1
I
I
/C
= dV/dt = I
/C
BAT1 BAT1
BATꢀ BATꢀ
+
AC ADAPTER
INPUT
R
*
= I
C /C
BAT1 BATꢀ BAT1
DCIN
CL
BATꢀ
V
IN
+
At this point you can see that the current divides as the
ratio of the two batteries capacity ratings. The sum of the
current into both batteries is the same as the current being
supply by the charger. This is independent of the mode of
the charger (CC or CV).
1760 F09
C
IN
100mV
ADAPTER CURRENT LIMIT
*R
=
CL
Figure 9.
Setting Input Current Limit
I
= I
+ I
BAT1 BATꢀ
CHRG
To set the input current limit, you need to know the mini-
mumwalladaptercurrentrating.Subtract52fortheinput
current limit tolerance and use that current to determine
the resistor value.
From here we solve for the actual current for each battery.
I
I
= I
= I
C
/(C
+ C
+ C
)
)
BATꢀ
BAT1
CHRG BATꢀ BAT1
BATꢀ
BATꢀ
C
/(C
CHRG BAT1 BAT1
R
I
= 100mV/I
LIM
CL
Please note that the actual observed current sharing will
vary from manufacturer’s claimed capacity ratings since
= Adapter Min Current
LIM
– (Adapter Min Current • 52)
1760fa
36
LTC1760
APPLICATIONS INFORMATION
As is often the case, the wall adapter will usually have at
least a +102 current limit margin and many times one
can simply set the adapter current limit value to the actual
adapter rating (see Figure 9 & Table 1).
value at all times. Changing the current setting can result
in currents that greatly exceed the requested value and
potentiallydamagethebatteryoroverloadthewalladapter
if no input current limiting is provided.
Table 1. Common RCL Resistor Values
Setting Charger Output Voltage Limit
Adapter
Rating A
RCL Value*
(Ω) 1%
RCL Power
Dissipation (W)
RCL Power
Rating (W)
ThevalueofanexternalresistorconnectedfromtheV
LIMIT
1.5
1.8
ꢀ
0.06
0.05
0.135
0.16ꢀ
0.18
0.ꢀ5
0.ꢀ5
0.ꢀ5
0.ꢀ5
0.5
pin to GND determines one of five voltage limits that are
applied to the charger output value. See Table 3. These
limits provide a measure of safety with a hardware restric-
tion on charging voltage, which cannot be overridden by
software. This voltage sets the limit that will be applied
to the battery as reported by battery. Since the battery
internal voltage monitor point is the actual cell voltage,
you may see higher voltages, up to 51ꢀmV higher, at the
external charger terminals due to the voltage servo loop
action. See Operations “Section 3.7” for more information
on the voltage servo system.
0.045
0.039
0.036
0.033
0.030
ꢀ.3
ꢀ.5
ꢀ.7
3
0.ꢀ06
0.ꢀꢀ5
0.ꢀ41
0.ꢀ1
0.5
0.5
*Values shown above are rounded to nearest standard value.
Table 1 RCL values take into account LTC1760 C-grade 52 tolerance for VCL1.
Extending System to More than 2 Batteries
The LTC1760 can be extended to manage systems with
more than 3 sources of power. Contact Linear Technology
Applications Engineering for more information.
Table 3. Recommended Resistor Values for RVLIMIT
V
R
VLIMIT
(Ω) 1%
MAX
Up to 8.4V
0 (Short to ground)
Up to 1ꢀ.6V
10k
Charge Termination Issues
Up to 16.8V
33k
Batteries with constant-current charging and voltage-
based charger termination might experience problems
with reductions of charger current caused by adapter
limiting. It is recommended that input limiting feature be
defeated in such cases. Consult the battery manufacturer
for information on how your battery terminates charging.
Up to ꢀ1.0V
100k
Up to 3ꢀ.7V (No Limit)
Open or short to V
CCꢀ
Inductor Selection
Higher operating frequencies allow the use of smaller
inductor and capacitor values. A higher frequency gener-
ally results in lower efficiency because of MOSFET gate
charge losses. In addition, the effect of inductor value
on ripple current and low current operation must also be
considered.TheinductorripplecurrentΔI decreaseswith
higher frequency and increases with higher V .
Setting Charger Output Current Limit
The LTC1760 current DAC and the PWM analog circuitry
must coordinate the setting of the charger current. Failure
to do so will result in incorrect charge currents.
L
IN
Table 2. Recommended Resistor Values
⎛
⎜
⎝
⎞
VOUT
VIN
1
I
(A)
R
SENSE
(Ω) 1%
R
(W)
R
(Ω) 1%
ILIMIT
MAX
SENSE
ΔIL =
VOUT 1−
⎟
f L
( )( )
⎠
1
0.100
0.ꢀ5
0.ꢀ5
0.5
0
ꢀ
3
4
0.05
0.0ꢀ5
0.0ꢀ5
10k
33k
Accepting larger values of ΔI allows the use of low
inductances, but results in higher output voltage ripple
and greater core losses. A reasonable starting point for
setting ripple current is ΔI = 0.4(I
ΔI exceed 0.6(I
L
L
0.5
Open or short to V
CCꢀ
Warning
DONOTCHANGETHEVALUEOFR
TION. The value must remain fixed and track the RSENSE
). In no case should
L
MAX
DURINGOPERA-
ILIMIT
) due to limits imposed by IREV and
MAX
1760fa
37
LTC1760
APPLICATIONS INFORMATION
CA1.RememberthemaximumΔI occursatthemaximum
L
normalizedR
vsTemperaturecurve,butδ=0.005/°C
DS(ON)
input voltage. In practice 10μH is the lowest value recom-
canbeusedasanapproximationforlowvoltageMOSFETs.
mended for use.
C
isusuallyspecifiedintheMOSFETcharacteristics.The
RSS
constant k = 1.7 can be used to estimate the contributions
Charger Switching Power MOSFET and Diode
Selection
of the two terms in the main switch dissipation equation.
If the LTC1760 charger is to operate in low dropout mode
or with a high duty cycle greater than 852, then the top-
side N-channel efficiency generally improves with a larger
MOSFET. Using asymmetrical MOSFETs may achieve cost
savings or efficiency gains.
TwoexternalpowerMOSFETsmustbeselectedforusewith
the LTC1760 charger: An N-channel MOSFET for the top
(main) switch and an N-channel MOSFET for the bottom
(synchronous) switch.
The peak-to-peak gate drive levels are set by the V volt-
CC
The Schottky diode D1, shown in the Typical Application,
conducts during the dead-time between the conduction of
the two power MOSFETs. This prevents the body diode of
the bottom MOSFET from turning on and storing charge
during the dead-time, which could cost as much as 12
in efficiency. A 1A Schottky is generally a good size for
4A regulators due to the relatively small average current.
Larger diodes can result in additional transition losses
due to their larger junction capacitance. The diode may
be omitted if the efficiency loss can be tolerated.
age.Thisvoltageistypically5.ꢀV.Consequently,logic-level
threshold MOSFETs must be used. Pay close attention to
the B
specification for the MOSFETs as well; many of
VDSS
the logic level MOSFETs are limited to 30V or less.
SelectioncriteriaforthepowerMOSFETsincludethe“ON”
resistance R
, reverse transfer capacitance C
,
DS(ON)
RSS
input voltage and maximum output current. The LTC1760
charger is always operating in continuous mode so the
duty cycles for the top and bottom MOSFETs are given by:
Main Switch Duty Cycle = V /V
OUT IN
Calculating IC Operating Current
Synchronous Switch Duty Cycle = (V – V )/V
IN
OUT IN
This section shows how to use the values supplied in the
Electrical Characteristics table to estimate operating cur-
rent for a given application.
The MOSFET power dissipations at maximum output
current are given by:
ꢀ
ꢀ
The total IC operating current through DCIN when AC is
P
= V /V (I
RSS
) (1 + δΔΤ)R
+ k(V )
MAIN
OUT IN MAX
DS(ON)
IN
present and batteries are charging (I
) is given by:
(I
MAX
)(C )(f)
DCIN_CHG
ꢀ
I
I
= I
+ I
+ I
+ I
+
SAFETYꢀ
P
= (V – V )/V (I
) (1 + δΔΤ) R
DCIN_CHG
CH1
+I
VCCꢀ_AC1
+I
SAFETY1
SYNC
IN
OUT IN MAX
DS(ON)
+I
+I
+I
VLIM ILIM SMB SMB_BAT1 SMB_BATꢀ SMBALERT
Where δΔΤ is the temperature dependency of R
DS(ON)
where:
and k is a constant inversely related to the gate drive
ꢀ
current. Both MOSFETs have I R losses while the topside
I
I
I
is defined in “Electrical Characteristics.”
CH1
N-channel equation includes an additional term for transi-
tion losses, which are highest at high input voltages. For
is defined in “Electrical Characteristics.”
VCCꢀ_AC1
V < ꢀ0V the high current efficiency generally improves
IN
isthecurrentusedtotestthebattery thermistor
SAFETYX
with larger MOSFETs, while for V > ꢀ0V the transition
IN
connected to SAFETY1 OR SAFETYꢀ.
losses rapidly increase to the point that the use of a higher
For thermistors that are OVER-RANGE:
I
R
device with lower C
actually provides higher
DS(ON)
RSS
= ꢀ/64 • V
/(RXB + R
)
THX
SAFETYX
VCCꢀ
efficiency. The synchronous MOSFET losses are great-
est at high input voltage or during a short-circuit when
the duty cycle in this switch is nearly 1002. The term
(1 + δΔΤ) is generally given for a MOSFET in the form of a
For thermistors that are COLD-RANGE:
= 4/64 • V /(RXB + R
I
)
THX
SAFETYX
VCCꢀ
1760fa
38
LTC1760
APPLICATIONS INFORMATION
For thermistors that are IDEAL-RANGE:
I
I
I
= I
ILIM
+ I
SMB
+ I
SMB_BAT1
+ I
SMB_BATꢀ
+
DCIN_CHG
CH1
+ I
VCCꢀ_AC1
+ I
SAFETY1
+ I
SAFETYꢀ
I
= 4/64 • V
THX
/(RXB + R ) + ꢀ/64 • V
/
+ I
+
SAFETYX
(R1A +R
VCCꢀ
THX
VCCꢀ
VLIM
)
SMBALERT
= 1.3mA + 700μA + ꢀ18μA + ꢀ18μA +81μA + 81μA
+ 0μA + 5.4μA + 5.4μA + 0μA = ꢀ.6ꢀmA
For thermistors that are HOT-RANGE:
= 4/64 • V /(RXB + R ) + 4/64 • V /
VCCꢀ
I
SAFETYX
(R1A +R
VCCꢀ
THX
)
The total operating current through BAT1 and BATꢀ when
THX
AC is not present (I ) is given by:
BAT_NOAC
R
is the impedance of the battery’s thermistor to
THX
ground.
I
I
= I + I
SMB_BAT1_AC0
+ I
+ I
+
BAT_NOAC
BAT
VCCꢀ_AC0
SAFETY1
SAFETYꢀ
+ I
+ I
+ I
SMB
SMB_BATꢀ_AC0 SMBALERT
RXB = 54.9k
where:
RXA = 1.13k
I
I
I
is defined in “Electrical Characteristics.”
BAT
Sample calculation of I
with V
= 5.ꢀV
SAFETYX
VCCꢀ
is defined in “Electrical Characteristics.”
VCCꢀ_AC0
Thermistor Impedance
R
(W)
Thermistor Range
OVER_RANGE
I
(μA)
THX
SAFETYX
is the current used to test the battery
SAFETYX
400
1.05
thermistor connected to SAFETY1 or SAFETYꢀ.
3.3k
400
IDEAL_RANGE
UNDER_RANGE
4ꢀ.ꢀ
ꢀ18
I
= ꢀ/64 • V /(RXB + R ).
SAFETYX
VCCꢀ
THX
R
is the impedance of the battery’s thermistor to
THX
ground.
I
I
= V
/(R
+ R
LIM_PU
).
VLIMIT
VCCꢀ
VLIMIT
= V
/(R
+ R
).
ILIMIT
VCCꢀ
ILIMIT
LIM_PU
RXB = 54.9k.
R
and I
is the typical pull-up impedance at V
LIMIT
LIM_PU
Sample calculation of I
with V
= 5.ꢀV
SAFETY
VCCꢀ
LIMIT.
Thermistor Impedance
R
= 34k.
LIM_PU
R
(Ω)
Thermistor Range
I
(μA)
THX
SAFETYX
400
UNDER_RANGE
ꢀ.9
R
is the value of the resistance from V
to
VLIMIT
GND.
LIMIT
I
is the current used for communicat-
SMB_BATX_ACO
ing with Battery1 or Batteryꢀ when AC in not present.
R
GND.
is the value of the resistance from I
to
ILIMIT
LIMIT
I
I
= 350μA • 0.00687 = ꢀ.404μA.
SMB_BATX_AC0
I
is the current used for communicating with the
SMB
is the current used for communicating with the
SMBus Host and depends on the amount of bus
traffic.
SMB
SMBus Host and depends on the amount of bus traffic.
I
is the current used for communicating
SMB_BATX
with Battery1 or Batteryꢀ.
Sample calculation with two Li-Ion batteries (R
=
THX
400), V
= 5.ꢀV, and no SMBus Host communication:
I
I
= 350μA • 0.0155 = 5.4ꢀ5μA.
CCꢀ
SMB_BATX
SMBALERT
I
I
– I + I
+ I
+ I
+ I
+
is defined in “Electrical Characteristics.”
BAT_NOAC
BAT
VCCꢀ_AC0
SAFETY1
SAFETYꢀ
+ I
+ I
SMB
SMB_BAT1_AC0
SMB_BATꢀ_AC0 SMBALERT
Sample calculation of I
with two Li-Ion batteries
DCIN_CHG
= 175μA + 80μA + ꢀ.9μA + ꢀ.9μA + 0μA + ꢀ.4μA +
ꢀ.4μA + 0μA = ꢀ65μA
(R
= 400), R
= R
= 30k, V
= 5.ꢀV, and
THX
VLIMIT
ILIMIT
CCꢀ
no SMBus Host communication:
1760fa
39
LTC1760
APPLICATIONS INFORMATION
Calculating IC Power Dissipation
is essentially DC. C is the primary filter capacitor and
Bꢀ
CB1 is used to provide a zero in the response to cancel
The power dissipation of the LTC1760 is dependent
the pole associated with C . Acceptable voltage ripple
Bꢀ
upon the gate charge of Q and Q .(Refer to Typical
TG
BG
at V
is about 10mV . Since the period of the delta-
SET
P-P
ΔΣ
Application). The gate charge is determined from the
manufacturer’s data sheet and is dependent upon both the
gate voltage swing and the drain voltage swing of the FET.
sigma switch closure, T , is about 11μs and the internal
V
resistor, R
, is 7.ꢀkΩ, the ripple voltage can be
DAC
VSET
approximated by:
P = (V
DCIN_CHG
– V ) • f
• (Q + Q ) + V
•
DCIN
D
DCIN
VCC
• (I
OSC
TG
+ I
BG
)
VREF • TΔ ∑
I
– V
ΔVVSET
=
VCC
SAFETY1
SAFETYꢀ
RVSET C ||C
(
)
B1
B2
where:
Then the equation to extract C || C is:
B1
Bꢀ
I
, I
, I
are defined in the
DCIN_CHG SAFETY1 SAFETYꢀ
previous section.
Example:
= 5.ꢀV, V
VREF • TΔ ∑
RVSETΔVVSET
CB1||CB2 =
V
= 19V, f
= 345kHz, Q
=
TG
=
VCC
DCIN
OSC
= ꢀ.6ꢀmA, I
C
should be 10× to ꢀ0× C to divide the ripple voltage
B1
Bꢀ
Q
= 15nC, I
BG
SAFETYꢀ
P = 190mW
D
DCIN_CHG
= ꢀ18μA.
SAFETY1
present at the charger output. Therefore C = 0.01μF and
B1
I
C
= 0.1μF are good starting values. In order to prevent
Bꢀ
overshoot during start-up transients the time constant as-
sociated with C must be shorter than the time constant
Bꢀ
V /I Capacitors
SET SET
of C5 at the I pin. If C is increased to improve ripple
TH
Bꢀ
rejection, then C5 should be increased proportionally and
charger response time to voltage variation will degrade.
Capacitor C7 is used to filter the delta-sigma modulation
frequency components to a level which is essentially DC.
Acceptable voltage ripple at I is about 10mV . Since
SET
P-P
Input and Output Capacitors
the period of the delta-sigma switch closure, T , is about
ΔΣ
10μs and the internal I
resistor, R , is 18.77k, the
In the 4A Lithium Battery Charger (Typical Application
DAC
SET
ripple voltage can be approximated by:
section), theinputcapacitor(C )isassumedtoabsorball
IN
input switching ripple current in the converter, so it must
haveadequateripplecurrentrating.Worst-caseRMSripple
currentwillbeequaltoonehalfofoutputchargingcurrent.
Actual capacitance value is not critical. Solid tantalum
low ESR capacitors have high ripple current rating in a
relatively small surface mount package, but caution must
be used when tantalum capacitors are used for input or
output bypass. High input surge currents can be created
when the adapter is hot-plugged to the charger or when a
battery is connected to the charger. Solid tantalum capaci-
tors have a known failure mechanism when subjected to
very high turn-on surge currents. Only Kemet T495 series
of “Surge Robust” low ESR tantalums are rated for high
surge conditions such as battery to ground.
VREF • TΔ ∑
RSET •C7
ΔV
=
ISET
Then the equation to extract C7 is:
VREF • TΔ ∑
C7 =
ΔV
•RSET
ISET
= 0.8/0.01/18.77k(10μs) ≅ 0.043μF
In order to prevent overshoot during start-up transients
the time constant associated with C7 must be shorter than
the time constant of C5 at the I pin. If C7 is increased
to improve ripple rejection, then C5 should be increased
proportionally and charger response time to average cur-
rent variation will degrade.
TH
Capacitors C and C are used to filter the V delta-
DAC
B1
Bꢀ
sigma modulation frequency components to a level which
1760fa
40
LTC1760
APPLICATIONS INFORMATION
The relatively high ESR of an aluminum electrolytic for
C15, located at the AC adapter input terminal, is helpful
in reducing ringing during the hot-plug event. Refer to
AN88 for more information.
current. FortheN-channelchargepath, themaximumcur-
rent is the maximum programmed current to be used. For
the P-channel discharge path maximum current typically
occurs at end of life of the battery when using only one
battery. The upper limit of R
value is a function of
DS(ON)
Highest possible voltage rating on the capacitor will
minimize problems. Consult with the manufacturer before
use. Alternatives include new high capacity ceramic (at
least ꢀ0μF) from Tokin, United Chemi-Con/Marcon, et al.
Other alternative capacitors include OSCON capacitors
from Sanyo.
the actual power dissipation capability of a given MOSFET
package that must take into account the PCB layout. As a
starting point, without knowing what the PCB dissipation
capability would be, derate the package power rating by
a factor of two.
PMOSFET
RDS(ON)MAX
=
The output capacitor (C ) is also assumed to absorb
OUT
2
2 I
(
)
output switching current ripple. The general formula for
MAX
capacitor current is:
IfyouareusingadualMOSFETpackagewithbothMOSFETs
in series, you must cut the package power rating in half
again and recalculate.
V
BAT
0.ꢀ9 (V ) 1 –
BAT
(
)
V
DCIN
I
=
RMS
PMOSFETDUAL
(L1)(f)
RDS(ON)MAX
=
2
4 I
(
)
For example:
MAX
If you use identical MOSFETs for both battery paths,
voltage drops will track over a wide current range. The
LTC1760 linear ꢀ5mV CV drop regulation will not occur
until the current has dropped below:
V
= 19V, V = 1ꢀ.6V, L1 = 10μH, and
BAT
DCIN
f = 300kHz, I
= 0.41A.
RMS
EMI considerations usually make it desirable to minimize
ripple current in the battery leads, and beads or inductors
maybeaddedtoincreasebatteryimpedanceatthe300kHz
switching frequency. Switching ripple current splits be-
tween the battery and the output capacitor depending on
theESRoftheoutputcapacitorandthebatteryimpedance.
25mV
2RDS(ON)MAX
ILINEARMAX
=
However, if you try to use the above equation to determine
R
R
to force linear mode at full current, the MOSFET
value becomes unreasonably low for MOSFETs
DS(ON)
DS(ON)
If the ESR of C
is 0.ꢀΩ and the battery impedance is
OUT
raised to 4Ω with a bead or inductor, only 52 of the cur-
available at this time. The need for the LTC1760 voltage
drop regulation only comes into play for parallel battery
configurations that terminate charge or discharge using
voltage. At first this seems to be a problem, but there are
several factors helping out:
rent ripple will flow in the battery.
PowerPath and Charge MUX MOSFET Selection
Three pairs of P-channel MOSFETs must be used with
the wall adapter and the two battery discharge paths. Two
pairsofN-channelMOSFETsmustbeusedwiththebattery
charge path. The nominal gate drive levels are set by the
clamp drive voltage of their respective control circuitry.
This voltage is typically 6.ꢀ5V. Consequently, logic-level
threshold MOSFETs must be used. Pay close attention to
1. When batteries are in parallel current sharing, the cur-
rent flow through any one battery is less than if it is
running stand-alone.
ꢀ. Most batteries that charge in constant voltage mode,
such as Li-ion, charge terminate at a current value of
C/10 or less which is well within the linear operation
range of the MOSFETs.
the B
specification for the MOSFETs as well; many of
VDSS
the logic level MOSFETs are limited to 30V or less.
3. Voltage tracking for the discharge process does not
need such precise voltage tracking values.
SelectioncriteriaforthepowerMOSFETsincludethe“ON”
resistance R
, input voltage and maximum output
DS(ON)
1760fa
41
LTC1760
APPLICATIONS INFORMATION
The LTC1760 has two transient conditions that force the
dischargepathP-channelMOSFETstohavetwoadditional
parameters to consider. The parameters are gate charge
Remember to only use the real wall adapter with a produc-
tionDCpowercordwhenperformingthewalladapterpath
test. The use of a laboratory power supply is unrealistic
for this test and will force you to over specify the MOSFET
ratings.Abatterypackusuallyhasenoughseriesresistance
to limit the peak current or are too low in voltage to create
enough instantaneous power to damage their respective
power path MOSFETs.
Q
GATE
and single pulse power capability.
When the LTC1760 senses a LOW_POWER event, all
the P-channel MOSFETs are turned on simultaneously
to allow voltage recovery due to a loss of a given power
source. However, there is a delay in the time it takes to
turn on all the MOSFETs. Slow MOSFETs will require more
bulk capacitance to hold up all the system’s power sup-
ply function during the transition and fast MOSFET will
require less bulk capacitance. The transition speed of a
MOSFET to an on or off state is a direct function of the
MOSFET gate charge.
Conditioning Systems With Large Loads
In systems where the load is too large to be used for
conditioning a single battery it may be necessary to
bypass the built in calibrate function and simply switch
in an external load. A convenient way to accomplish this
task is by using an SMBus based LTC16ꢀ3 load switch
controller. See Figure 10.
t = Q
/I
GATE DRIVE
I
is the fixed drive current into the gate from the
DRIVE
LTC1760 and “t” is the time it takes to move that charge
to a new state and change the MOSFET conduction mode.
TO
LOAD
PowerPath
MUX
LTC1760
HencetimeisdirectlyrelatedtoQ
.SinceQ
goesup
GATE
GATE
CHARGE
MUX
with MOSFETs of lower R
, choosing such MOSFETs
DS(ON)
SMBus
has a counterproductive increase in gate charge making
theMOSFETslower.PleasenotethattheLTC1760recovery
time specification only refers to the time it takes for the
voltagetorecovertotheleveljustpriortotheLOW_POWER
event as opposed to full voltage.
The single pulse current rating of MOSFET is important
when a short-circuit takes place. The MOSFET must
SMBus
TO/FROM
HOST
CONDITIONING
LOAD
LTC16ꢀ3
survive a 15ms overload. MOSFETs of lower R
DS(ON)
or MOSFETs that use more powerful thermal packages
will have a high power surge rating. Using too small of a
pulse rating will allow the MOSFET to blow to the open
circuit condition instantly like a fuse. Typically there is no
outward sign of failure because it happens so fast. Please
measure the surge current for all discharge power paths
under worse case conditions and consult the MOSFET
data sheet for the limitations. Voltage sources with the
highest voltage and the most bulk capacitance are often
the biggest risk. Specifically the MOSFETs in the wall
adapter path with wall adapters of high voltage, large
bulk capacitance and low resistance DC cables between
the adapter and device are the most common failures.
1760 F10
Figure 10. Large Load Conditioning Circuit
Unique Configuration Information
This section summarizes unique LTC1760 configurations
that allow some LTC1760 features to be eliminated. These
configurations may be selected in any combination with-
out adversely affecting LTC1760 operation. Refer to the
Typical Application circuit diagram located at the back of
this data sheet.
1760fa
42
LTC1760
APPLICATIONS INFORMATION
A) Single Battery Configuration.
4) Reduce C capacitor to 0.1μF.
IN
To limit the LTC1760 to a single battery, modify the battery
slot to be eliminated as follows:
5) Remove all components connected to COMP1, V
,
SET
I , I , I
and V
pins.
TH SET LIMIT
LIMIT
1) Remove both FETs (Q5, Q6 or Q7, Q8) involved in
the discharge path.
6) Short I
and V
to GND.
LIMIT
LIMIT
7) Remove R1, C1 but short CLP to DCIN. Replace R
with a short/trace connection.
CL
ꢀ) Remove both FETS (Q3, Q4 or Q9, Q10) involved in
the charge path.
8)ShortCSPtoCSNbutleavethecombinationfloating.
3) Remove the thermistor sensing resistors (R1A, R1B
or RꢀA, RꢀB).
9) Unless otherwise specified, leave the unused pins
of the LTC1760 floating.
4) Short the thermistor sense lines (TH1A, TH1B or
THꢀA, THꢀB) together at the IC.
F) No DC Path And No Charge Configuration.
To limit the LTC1760 to battery discharge functions only,
merge the previous two configurations with the following:
5) Remove the diode (Dꢀ or D3).
6) Unless otherwise specified, leave the unused pins
of the LTC1760 floating.
1) Remove C .
IN
ꢀ) Remove resistors tied to DCDIV. Ground DCDIV.
B) No Short-Circuit Protection Configuration.
PCB Layout Considerations
1) Replace R with a short.
SC
Formaximumefficiency,theswitchnoderiseandfalltimes
should be minimized. To prevent magnetic and electrical
field radiation and high frequency resonant problems,
proper layout of the components connected to the IC is
essential. (See Figure 11.) Here is a PCB layout priority list
for proper layout. Layout the PCB using this specific order.
1. Input capacitors need to be placed as close as possible
to switching FET’s supply and ground connections. Short-
est copper trace connections possible. These parts must
be on the same layer of copper. Vias must not be used to
make this connection.
C) No LOPWR Protection.
1) Remove resistors Rꢀ and R3 connected to LOPWR
and tie LOPWR to the V pin.
CC
D) No DC Path Configuration.
To remove the DC input as part of the power path choices
to support the load:
1)RemovebothFETsQ1andQꢀinvolvedintheDCpath.
ꢀ) Unless otherwise specified, leave the unused pins
of the LTC1760 floating.
SWITCH NODE
L1
E) No Charge Configuration.
V
BAT
To permanently disable the battery charger function:
HIGH
FREQUENCY
CIRCULATING
PATH
1) Remove ALL FETs involved in the charge path (Q3,
Q4, Q9, Q10).
C
IN
D1
C
OUT
V
IN
BAT
ꢀ) Remove switching FETs QTG, QBG, diode D1 and
inductor L1.
1760 F10
3) Remove diodes Dꢀ, D3, D4, capacitors C4, C
and
OUT
Figure 11. High-Speed Switching Path
Resistor R11 and R
.
SENSE
1760fa
43
LTC1760
APPLICATIONS INFORMATION
ꢀ. The control IC needs to be close to the switching FET’s
gateterminals.Keepthegatedrivesignalsshortforaclean
FET drive. This includes IC supply pins that connect to the
switching FET source pins. The IC can be placed on the
opposite side of the PCB relative to above.
9. A good rule of thumb for via count for a given high
current path is to use 0.5A per via. Be consistent.
10. If possible, place all the parts listed above on the
same PCB layer.
11.Copperfillsorpoursaregoodforallpowerconnections
except as noted above in Rule 3. You can also use copper
planes on multiple layers in parallel too—this helps with
thermal management and lower trace inductance improv-
ing EMI performance further.
3. Place inductor input as close as possible to switching
FET’s output connection. Minimize the surface area of this
trace. Make the trace width the minimum amount needed
tosupportcurrent—nocopperfillsorpours.Avoidrunning
the connection using multiple layers in parallel. Minimize
capacitance from this node to any other trace or plane.
1ꢀ. For best current programming accuracy provide a
KelvinconnectionfromR
1ꢀ as an example.
toCSPandBAT. SeeFigure
4. Place the output current sense resistor right next to
the inductor output but oriented such that the IC’s current
sense feedback traces going to resistor are not long. The
feedback traces need to be routed together as a single pair
on the same layer at any given time with smallest trace
spacing possible. Locate any filter component on these
traces next to the IC and not at the sense resistor location.
SENSE
It is important to keep the parasitic capacitance on the R ,
T
CSP and BAT pins to a minimum. The traces connecting
these pins to their respective resistors should be as short
as possible.
DIRECTION OF CHARGING CURRENT
5.Placeoutputcapacitorsnexttothesenseresistoroutput
and ground.
R
SNS
6. Output capacitor ground connections need to feed into
same copper that connects to the input capacitor ground
before tying back into system ground.
1760 F11
CSN
CSP
General Rules
Figure 12. Kelvin Sensing of Charging Current
7. Connection of switching ground to system ground or
internal ground plane should be single point. If the system
has an internal system ground plane, a good way to do
this is to cluster vias into a single star point to make the
connection.
Important Safety Notes
Although every effort is made to meet and exceed all
required “SMBus Charger V1.1” safety features it is the
responsibility of the battery pack to protect itself from
excessive currents or voltages. The LTC1760 is not itself
a safety device. Consult your battery pack manufacturer
for more information.
8. Route analog ground as a trace tied back to IC ground
(analog ground pin if present) before connecting to any
other ground. Avoid using the system ground plane. CAD
trick: make analog ground a separate ground net and use
a 0Ω resistor to tie analog ground to system ground.
1760fa
44
LTC1760
TYPICAL APPLICATIONS
PowerPath MUX
R
CL
0.03Ω
V
IN
R10
100Ω
C8
1μF
C9
C1
0.1μF
Q1
Q6
Q5
Q7
Q8
R1
4.99k
0.1μF
LTC1760
Qꢀ
36
41
3
1
7
6
9
V
CLP
DC
BAT1
BATꢀ
PLUS
GDCI
GDCO
GB1I
GB1O
GBꢀI
GBꢀO
SCP
SCN
IN
R4
100pF
ꢀ
1ꢀ.7k
8
11
10
5
R
SC
0.0ꢀΩ
R5
1.ꢀ1k
16
37
47
48
46
45
13
40
ꢀ4
4
DCDIV
COMP1
GCHꢀ
SCHꢀ
GCH1
SCH1
LOAD
1ꢀ
34
35
14
15
4ꢀ
43
44
39
38
ꢀ8
ꢀ7
17
ꢀ1
30
31
19
ꢀ3
LOPWR
CSN
CSP
Rꢀ
ꢀ80k
R7
49.9k
CL
ꢀ0μF
C11
1800pF
I
TH
R3
49.9k
C3
I
SET
R9
3.3k
0.01ꢀμF
SW
BOOST
TGATE
BGATE
PGND
THꢀA
THꢀB
SCLꢀ
SDAꢀ
TH1A
TH1B
SCL1
V
SET
C1ꢀ
100pF
C7
0.1F
V
CC
GND
V
DDS
C5
0.15F
SMBALERT
SCL
V
*
DDS
RꢀA, 1.13k
ꢀ5
ꢀ9
18
ꢀꢀ
ꢀ0
33
3ꢀ
ꢀ6
BATꢀ
R
R
PU
PU
V
CCꢀ
RꢀB, 54.9k
TH
SMBALERT
SCL
SCLꢀ
SDAꢀ
SDA
SCL
SDA
SDA
V
V
DDS
DDS
R1A, 1.13k
R1B, 54.9k
V
I
LIMIT
LIMIT
MODE
R
VLIMIT
10k
SDA1
C1
0.1μF
V
DDS
*
BAT1
TH
SCL
SDA
SCL1
SDA1
BATꢀ
Dꢀ
BAT1
D3
QTG
QBG
C
IN
ꢀ0μF
C4
0.ꢀꢀμF
R11
1k
L1
10μH
D4
C
OUT
ꢀ0μF
R
SENSE
0.0ꢀ5
C6
4.7μF
C13
0.1μF
D1
CBꢀ
0.47μF
CB1
0.1μF
CHARGE
MUX
R6
100Ω
Q9
Si69ꢀ8
Q4
Si69ꢀ8
Q3
Si69ꢀ8
Q10
Si69ꢀ8
1760 TA0ꢀ
D1: MBR130T3
Dꢀ, D3: BAT54A TYPE
D4: CMDSH3 TYPE
Q1, Qꢀ, Q5, Q6, Q7, Q8: Si49ꢀ5DY
Q3, Q4, Q9, Q10, QTG, QBG: FDS691ꢀA
*OPTIONAL: ESD CLAMP DIODES FOR BATTERY HOT SWAP PROTECTION
1760fa
45
LTC1760
PACKAGE DESCRIPTION
FW Package
48-Lead Plastic TSSOP (6.1mm)
(Reference LTC DWG # 05-08-1651)
1ꢀ.40 – 1ꢀ.60*
48
ꢀ5
(.488 – .496)
0.95 0.10
6.ꢀ 0.10
44
4ꢀ
41 40 39 38 37 36 35 34 33 3ꢀ 31 30 ꢀ9 ꢀ8 ꢀ7 ꢀ6 ꢀ5
48 47 46 45
43
8.1 0.10
7.9 – 8.3
(.311 – .3ꢀ7)
1
ꢀ4
0.3ꢀ 0.05
0.50 BSC
5
7
8
1
ꢀ
3
4
6
9 10 11 1ꢀ 13 14 15 16 17 18 19 ꢀ0 ꢀ1 ꢀꢀ ꢀ3 ꢀ4
RECOMMENDED SOLDER PAD LAYOUT
1.10
(.0433)
MAX
6.0 – 6.ꢀ**
(.ꢀ36 – .ꢀ44)
0.ꢀ5
REF
0 – 8
-T-
-C-
0.10 C
FW48 TSSOP 0ꢀ04
0.50
(.0197)
BSC
0.17 – 0.ꢀ7
(.0067 – .0106)
TYP
0.09 – 0.ꢀ0
(.0035 – .008)
0.45 – 0.75
(.018 – .0ꢀ9)
0.05 – 0.15
(.00ꢀ – .006)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
ꢀ. DIMENSIONS ARE IN
(INCHES)
3. DRAWING NOT TO SCALE
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .15ꢀmm (.006") PER SIDE
**
DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .ꢀ54mm (.010") PER SIDE
1760fa
46
LTC1760
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
04/11 I-Grade part added. Reflected throughout the data sheet
1-48
1760fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
47
LTC1760
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1571
1.5A Switching Regulator Battery Charger
Li-Ion Linear Charger with Thermal Regulation
ꢀA Switching Regulator Battery Charger
Dual Battery Charger/Selector with SPI
500kHz or ꢀ00kHz Switching Frequency for Small Design
Will Not Overheat, Standalone Charger, Complete Charger
Monolithic, ꢀ0-Lead TSSOP, ꢀ8-Lead SSOP Packages
LTC1733
LT1769
LTC1960
LTC4006
11-Bit V , 0.82 Voltage Accuracy, 10-Bit I
for 52 Current Accuracy
DAC
DAC
Small, High Efficiency, Fixed Voltage,
Lithium-Ion Battery Charger
Constant Current/ Constant Voltage Switching Regulator
with Termination Timer; AC Adapter Current Limit and
SafetySignal Sensor in a Small 16 Pin Package
LTC4007
LTC4008
High Efficiency, Programmable Voltage
Battery Charger with Termination
Complete Charger for 3- or 4-Cell Lithium-Ion Batteries,
AC Adapter Current Limit, SafetySignal Sensor and Indicator Outputs
High Efficiency, Programmable Voltage/
Current Battery Charger
Constant Current/ Constant Voltage Switching Regulator;
Resistor Voltage/Current Programming, AC Adapter Current
Limit and SafetySignal Sensor
LTC4100
Smart Battery Charger Controller
SMBus Rev 1.1 Compliant
1760fa
LT 0411 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
48
●
●
© LINEAR TECHNOLOGY CORPORATION 2010
(408) 43ꢀ-1900 FAX: (408) 434-0507 www.linear.com
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