LTC4120_15 [Linear]
Wireless Power Receiver and 400mA Buck Battery Charger;型号: | LTC4120_15 |
厂家: | Linear |
描述: | Wireless Power Receiver and 400mA Buck Battery Charger 电池 无线 |
文件: | 总32页 (文件大小:786K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC4120/LTC4120-4.2
Wireless Power Receiver and
400mA Buck Battery Charger
FeaTures
DescripTion
The LTC®4120 is a constant-current/constant-voltage wire-
less receiver and battery charger. An external program-
ming resistor sets the charge current up to 400mA. The
LTC4120-4.2 is suitable for charging Li-Ion/Polymer bat-
teries,whiletheprogrammablefloatvoltageoftheLTC4120
accommodates several battery chemistries. The LTC4120
usesaDynamicHarmonizationControl(DHC)techniquethat
allowshighefficiencycontactlesschargingacrossanairgap.
n
Dynamic Harmonization Control Optimizes
Wireless Charging Over a Wide Coupling Range
n
Wide Input Voltage Range (12.5V to 40V)
n
Adjustable Float Voltage (3.5V to 11V)
n
n
Fixed 4.2V Float Voltage Option (LTC4120-4.2)
50mA to 400mA Charge Current Programmed with a
Single Resistor
n
n
n
n
n
1% Feedback Voltage Accuracy
Programmable 5% Accurate Charge Current
No Microprocessor Required
The LTC4120 regulates its input voltage via the DHC pin.
This technique modulates the resonant frequency of a
receiver tank to automatically adjust the power received
as well as the power transmitted to provide an efficient
solution for wirelessly charging battery-powered devices.
No Transformer Core
Thermally Enhanced, Low Profile 16-Lead
(3mm × 3mm × 0.75mm) QFN Package
Wireless charging with the LTC4120 provides a method
to power devices in harsh environments without requiring
expensive failure-prone connectors. This allows products
to be charged while locked within sealed enclosures, or
in moving or rotating equipment, or where cleanliness or
sanitation is critical.
applicaTions
n
Handheld Instruments
n
Industrial/Military Sensors and Devices
n
Harsh Environments
n
Portable Medical Devices
n
This full featured battery charger includes accurate RUN
pinthreshold,lowvoltagebatterypreconditioningandbad
battery fault detection, timer termination, auto-recharge,
and NTC temperature qualified charging. The FAULT pin
providesanindicationofbadbatteryortemperaturefaults.
Physically Small Devices
n
Electrically Isolated Devices
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
Once charging is terminated, the LTC4120 signals end-of-
charge via the CHRG pin, and enters a low current sleep
mode. An auto-restart feature starts a new charging cycle
if the battery voltage drops by 2.2%.
Typical applicaTion
Wireless Rx Voltage/Charge Current vs Spacing
26.7nF
400
333
267
200
133
67
40
35
30
25
IN
RUN
INTV
CC
FREQ
BOOST
I
CHARGE
MAX
2.2µF
22nF 33µH
10µF
V
IN
LTC4120
6.5nF
47µH
SW
NOT
Tx CIRCUITRY
5µH
DHC
CHGSNS
NTC
CHARGING
FAULT
CHRG
BAT
20
15
10
1.01M
1.35M
+
Li-Ion
4.2V
T
CHARGING
FB
GND PROG FBG
3.01k
22µF
0
0.4 0.6
0.8 1.0 1.2
SPACING (cm)
1.4
1.6 1.8
4120 TA01a
4120 TA01b
4120fe
1
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
absoluTe MaxiMuM raTings (Note 1)
IN, RUN, CHRG, FAULT, DHC...................... –0.3V to 43V
BOOST ................................... V – 0.3V to (V + 6V)
I
............................................................... 350mA
DHC RMS
I
I
, I
, I .................................................. 5mA
SW
SW
CHRG FAULT FBG
FB
SW (DC)........................................ –0.3V to (V + 0.3V)
......................................................................... 5mA
IN
SW (Pulsed <100ns) ......................–1.5V to (V + 1.5V)
I
.................................................................. –5mA
IN
INTVCC
CHGSNS, BAT, FBG, FB ...............................–0.3V to 12V
Operating Junction Temperature Range
(Note 2).................................................. –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
FREQ, NTC, PROG, INTV .......................... –0.3V to 6V
CC
I
, I ..................................................... 600mA
CHGSNS BAT
pin conFiguraTion
LTC4120
LTC4120-4.2
TOP VIEW
TOP VIEW
16 15 14 13
16 15 14 13
INTV
1
2
3
4
12 NTC
11 FBG
INTV
1
2
3
4
12 NTC
11 NC
CC
CC
BOOST
IN
BOOST
IN
17
GND
17
GND
FB
BATSNS
10
9
10
9
SW
BAT
SW
BAT
5
6
7
8
5
6
7
8
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
= 125°C, θ = 54°C/W
T
= 125°C, θ = 54°C/W
T
JMAX
JMAX
JA
JA
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB TO OBTAIN θ
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB TO OBTAIN θ
JA
JA
orDer inForMaTion
LEAD FREE FINISH
LTC4120EUD#PBF
LTC4120IUD#PBF
TAPE AND REEL
PART MARKING*
LGHB
PACKAGE DESCRIPTION
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
LTC4120EUD#TRPBF
LTC4120IUD#TRPBF
16-Lead (3mm × 3mm) Plastic QFN
16-Lead (3mm × 3mm) Plastic QFN
16-Lead (3mm × 3mm) Plastic QFN
16-Lead (3mm × 3mm) Plastic QFN
LGHB
LTC4120EUD-4.2#PBF
LTC4120IUD-4.2#PBF
LTC4120EUD-4.2#TRPBF LGMT
LTC4120IUD-4.2#TRPBF LGMT
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard 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/
LTC4120 OPTIONS
LTC4120
FLOAT VOLTAGE
Programmable
4.2V Fixed
LTC4120-4.2
4120fe
2
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
elecTrical characTerisTics The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k,
VFB = 2.29V (LTC4120), VBATSNS = 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative.
SYMBOL
PARAMETER
CONDITIONS
MIN
12.5
0
TYP
MAX
40
UNITS
V
l
Operating Input Supply Range
Battery Voltage Range
DC Supply Current
11
V
I
Switching, FREQ = GND
Standby Mode (Note 3)
Sleep Mode (Note 3)
3.5
mA
µA
IN
l
l
130
220
100
LTC4120: V = 2.51V (Note 5),
LTC4120-4.2: V
60
µA
FB
= 4.4V
BATSNS
l
l
l
Disabled Mode (Note 3)
Shutdown Mode (Note 3)
37
20
80
70
40
µA
µA
Differential Undervoltage Lockout
Hysteresis
V -V Falling, V = 5V (LTC4120),
20
160
mV
∆V
IN BAT
IN BATSNS
IN
DUVLO
V -V
Falling, V = 5V (LTC4120-4.2)
IN
V -V Rising, V = 5V (LTC4120),
115
mV
IN BAT
IN BATSNS
IN
V -V
Rising, V = 5V (LTC4120-4.2)
IN
l
l
UV
INTVCC
INTV Undervoltage Lockout
INTV Rising, V = INTV + 100mV, V = NC
4.00
4.14
4.15
220
4.24
1.7
4.26
4.29
V
mV
V
CC
CC
IN
CC
BAT
Hysteresis
INTV Falling
CC
INTV Regulated Voltage
CC
INTV Load Regulation
I
= 0mA to –5mA (Note 4)
%
CC
INTVCC
Battery Charger
l
l
I
BAT Standby Current
Standby Mode (LTC4120) (Notes 3, 7, 8)
Standby Mode (LTC4120-4.2) (Notes 3, 7, 8)
2.5
50
4.5
1000
µA
nA
BAT
l
l
BAT Shutdown Current
Shutdown Mode (LTC4120) (Notes 3, 7, 8)
Shutdown Mode (LTC4120-4.2) (Notes 3, 7, 8)
1100 2000
nA
nA
10
1000
l
l
l
l
l
I
BATSNS Standby Current (LTC4120-4.2)
BATSNS Shutdown Current (LTC4120-4.2)
Feedback Pin Bias Current (LTC4120)
Standby Mode (Notes 3, 7, 8)
Shutdown Mode (Notes 3, 7, 8)
5.4
10
µA
nA
nA
µA
Ω
BATSNS
1100 2000
I
I
V
= 2.5V (Notes 5, 7)
FB
25
60
1
FB
Feedback Ground Leakage Current (LTC4120) Shutdown Mode (Notes 3, 7)
Feedback Ground Return Resistance (LTC4120)
FBG(LEAK)
R
1000 2000
2.393 2.400 2.407
2.370 2.418
FBG
V
Feedback Regulation Voltage (LTC4120)
Regulated Float Voltage (LTC4120-4.2)
Battery Charge Current
(Note 5)
V
V
FB(REG)
l
V
4.188 4.200 4.212
V
V
FLOAT
CHG
l
4.148
4.227
l
l
I
R
PROG
R
PROG
= 3.01k
= 24.3k
383
45
402
50
421
55
mA
mA
V
V
V
Undervoltage Current Limit
V
V
V
Falling
12.0
–50
–92
988
V
mV
UVCL
IN
l
l
Battery Recharge Threshold
Battery Recharge Threshold
Ratio of BAT Current to PROG Current
Falling Relative to V (LTC4120) (Note 5)
FB_REG
–38
–70
–62
RCHG
FB
Falling Relative to V (LTC4120-4.2)
FLOAT
–114
mV
RCHG_4.2
PROG
BATSNS
h
V
V
< V < V (LTC4120) (Note 5)
FB(REG)
TRKL_4.2
mA/mA
TRKL
FB
< V
< V
(LTC4120-4.2)
BATSNS
FLOAT
l
V
PROG Pin Servo Voltage
1.206 1.227 1.248
300
V
PROG
R
CHGSNS-BAT Sense Resistor
I
= –100mA
BAT
mΩ
SNS
4120fe
3
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
elecTrical characTerisTics The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k,
VFB = 2.29V (LTC4120), VBATSNS = 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Low Battery Linear Charge Current
0V < V < V
BATSNS
, V = 2.6V (LTC4120),
6
9
16
mA
LOWBAT
FB
TRKL BAT
V
< V
, V = 2.6V (LTC4120-4.2)
TRKL_4.2 BAT
l
V
Low Battery Threshold Voltage
V
V
Rising (LTC4120),
BATSNS
2.15
2.21
2.28
V
LOWBAT
BAT
Rising (LTC4120-4.2)
Hysteresis
147
mV
mA
I
Switch Mode Trickle Charge Current
V
V
< V , V < V
< V
(LTC4120) (Note 5),
TRKL_4.2
I
/10
CHG
TRKL
LOWBAT
LOWBAT
BAT FB
BATSNS
TRKL
< V
(LTC4120-4.2)
PROG Pin Servo Voltage in Switch Mode
Trickle Charge
V
V
< V , V < V
(LTC4120) (Note 5),
122
mV
LOWBAT
LOWBAT
BAT FB
TRKL
< V
< V
(LTC4120-4.2)
BATSNS
TRKL_4.2
l
l
V
V
Trickle Charge Threshold
Hysteresis
V
V
V
V
Rising (LTC4120) (Note 5)
Falling (LTC4120) (Note 5)
1.64
2.86
1.68
50
1.71
2.98
V
mV
TRKL
FB
FB
Trickle Charge Threshold
Hysteresis
Rising (LTC4120-4.2)
Falling (LTC4120-4.2)
2.91
88
V
TRKL_4.2
BATSNS
BATSNS
mV
h
End of Charge Indication Current Ratio
Safety Timer Termination Period
Bad Battery Termination Timeout
(Note 6)
0.1
2.0
30
mA/mA
Hours
Minutes
C/10
1.3
19
2.8
42
Switcher
l
l
f
Switching Frequency
FREQ = INTV
FREQ = GND
1.0
0.5
1.5
0.75
2.0
1.0
MHz
MHz
OSC
CC
t
Minimum Controllable On-Time
Duty Cycle Maximum
(Note 9)
(Note 9)
120
ns
%
MIN(ON)
94
Top Switch R
I
I
= –100mA
0.8
0.5
750
Ω
DS(ON)
SW
SW
Bottom Switch R
= 100mA
Ω
DS(ON)
I
I
Peak Current Limit
Measured Across R
Series with R
with a 15µH Inductor in
SNS
(Note 9)
585
1250
mA
PEAK
SNS
l
l
Switch Pin Current (Note 8)
V
V
= Open-Circuit, V
= Open-Circuit, V
= 0V, V = 8.4V (LTC4120)
15
7
30
15
µA
µA
SW
IN
IN
RUN
RUN
SW
= 0V, V = 4.2V
SW
(LTC4120-4.2)
Status Pins FAULT, CHRG
Pin Output Voltage Low
Pin Leakage Current
I = 2mA
500
1
mV
µA
V = 43V, Pin High Impedance
0
NTC
l
l
l
Cold Temperature V /V
Fault
Fault
Rising V
Falling V
Threshold
Threshold
73
35.5
1
74
72
75
%INTV
%INTV
NTC INTVCC
NTC
NTC
CC
CC
Hot Temperature V /V
Falling V
Rising V
Threshold
Threshold
36.5
37.5
37.5 %INTV
%INTV
NTC INTVCC
NTC
NTC
CC
CC
NTC Disable Voltage
Falling V
Rising V
Threshold
Threshold
2
3
3
%INTV
%INTV
NTC
NTC
CC
CC
NTC Input Leakage Current
V
= V
–50
50
nA
NTC
INTVCC
4120fe
4
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
elecTrical characTerisTics The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k,
VFB = 2.29V (LTC4120), VBATSNS = 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative.
SYMBOL
RUN
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
V
V
Enable threshold
Hysteresis
V
V
V
V
Rising
Falling
= 40V
Falling
2.35
2.45
200
2.55
V
mV
µA
V
EN
RUN
RUN
RUN
RUN
Run Pin Input Current
Shutdown Threshold (Note 3)
Hysteresis
0.01
0.1
1.2
0.4
0.4
SD
220
mV
FREQ
l
l
FREQ Pin Input Low
FREQ Pin Input High
FREQ Pin Input Current
V
V
V
-V
0.6
1
INTVCC FREQ
0V < V
< V
µA
FREQ
INTVCC
Dynamic Harmonization Control
V
Input Regulation Voltage
DHC Pin Current
14
V
IN(DHC)
V
= 1V, V < V
330
mA
RMS
DHC
IN
IN(DHC)
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.
Note 4: The internal supply INTV should only be used for the NTC
CC
divider, it should not be used for any other loads.
Note 5: The FB pin is measured with a resistance of 588k in series with
the pin.
Note 2: The LTC4120 is tested under pulsed load conditions such that
Note 6: h
is expressed as a fraction of measured full charge current as
C/10
T ≈ T . The LTC4120E is guaranteed to meet performance specifications
J
A
measured at the PROG pin voltage when the CHRG pin de-asserts.
for junction temperatures from 0°C to 85°C. Specifications over the
–40°C to 125°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
The LTC4120I is guaranteed over the full –40°C to 125°C operating
junction temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance, and other environmental factors.
Note 7: In an application circuit with an inductor connected from SW to
CHGSNS, the total battery leakage current when disabled is the sum of
I
, I
and I (LTC4120), or I
and I and I (LTC4120-
BATSNS BAT SW
BAT FBG(LEAK)
4.2).
SW
Note 8: When no supply is present at IN, the SW powers IN through
the body diode of the topside switch. This may cause additional SW pin
current depending on the load present at IN.
Note 9: Guaranteed by design and/or correlation to static test.
Note 3: Standby mode occurs when the LTC4120 stops switching due
to an NTC fault condition, or when the charge current has dropped low
enough to enter Burst Mode operation. Disabled mode occurs when V
RUN
is between V and V . Shutdown mode occurs when V
is below V
SD
EN
RUN
SD
or when the differential undervoltage lockout is engaged. SLEEP mode
occurs after a timeout while the battery voltage remains above the V
RCHG
or V
threshold.
RCHG_42
4120fe
5
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
Typical perForMance characTerisTics
Typical VFB(REG) vs Temperature
TA = 25°C, unless otherwise noted.
Typical VFLOAT vs Temperature
LTC4120-4.2
2.43
4.25
4.24
4.23
4.22
4.21
4.20
4.19
4.18
4.17
4.16
4.15
4 UNITS TESTED
4 UNITS TESTED
2.42
2.41
HIGH LIMIT
DUT1 V
HIGH LIMIT
(V)
(V)
(V)
(V)
DUT1 V
FB(REG)
FLOAT
2.40
2.39
2.38
2.37
DUT2 V
DUT3 V
DUT4 V
DUT2 V
FLOAT
FB(REG)
FB(REG)
FB(REG)
DUT3 V
FLOAT
DUT4 V
FLOAT
LOW LIMIT
LOW LIMIT
DUT = DEVICE
UNDER TEST
2.36
–40
5
35 50 65 80 95 110 125
–25 –10
20
50 110 125
65 80 95
–40 –25 –10
5
20 35
TEMPERATURE (°C)
TEMPERATURE (°C)
4120 G01
4120 G20
IN Pin Standby/Sleep Current vs
Temperature
IN Pin Disabled/Shutdown Current
vs Temperature
60
50
40
30
180
160
2 UNITS TESTED
2 UNITS TESTED
V
= 15V
V
= 15V
IN
IN
140
120
100
80
I
IN
I
IN
I
IN
I
IN
I
IN
I
IN
STANDBY FREQ = INTV
STANDBY FREQ = INTV
STANDBY FREQ = GND
STANDBY FREQ = GND
SLEEP
CC
CC
IIN DISABLED
IIN DISABLED
SLEEP
20
10
0
IIN SD
IIN SD
60
40
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
4120 G03
4120 G02
BAT Pin Sleep/Shutdown Current
vs Temperature
Typical Battery Charge Current
vs Temperature
Typical RSNS Current Limit
vs Temperature
8
402
401
1120
1100
1080
1060
1040
1020
1000
980
DUT1
DUT2
DUT3
2 UNITS TESTED
V
R
R
= 4.2V
= 1.01M
= 1.35M
BAT
FB2
FB1
7
6
I
I
SLEEP
SLEEP
400
399
398
397
396
BAT
BAT
5
4
3
2
1
R
PROG
= 3.01k
2 UNITS TESTED
FREQ = GND
FREQ = GND
FREQ = INTV
FREQ = INTV
I
I
SHUTDOWN
SHUTDOWN
BAT
BAT
960
CC
CC
940
3 UNITS TESTED
0
395
920
–25
0
50
75 100 125
–50
25
50
TEMPERATURE (°C)
100 125
50
75
–50 –25
0
25
75
–50 –25
0
25
100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
4120 G06
4120 G04
4120 G05
4120fe
6
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
TA = 25°C, unless otherwise noted.
Typical perForMance characTerisTics
Switching Frequency
BAT Pin Leakage Current/VBAT-VIN
vs Temperature
vs Temperature
Buck Efficiency vs Battery Current
16
400
95
90
85
80
75
70
65
60
55
50
V
V
= OPEN-CIRCUIT
BAT
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
IN
= 4.2V
14
12
350
300
FREQ = INTV
FREQ = INTV
CC
CC
10
8
250
200
150
100
50
V
IN
V
IN
V
IN
V
IN
= 12.5V
= 14V
= 20V
= 30V
FREQ = GND
FREQ = GND
6
2 UNITS TESTED
4
I
BAT
BAT
BAT IN
I
L
= 68µH, SLF12555T-680M1R3
SW
2
V
V
-V
FREQ = GND
= 4.2V
-V
V
2 UNITS TESTED
BAT IN
BAT
0
0
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
–25
0
50
75 100 125
–50
25
200 250
0
50 100 150
I
300 350 400
TEMPERATURE (°C)
(mA)
BAT
4120 G07
4120 G09
4120 G08
Wireless Power Transfer Efficiency,
VIN_RX vs Battery Current
Typical tMIN(ON) vs Temperature
130
125
120
115
110
105
100
95
70
60
24
V
SW
R
= 8.3V
FLOAT
2 UNITS TESTED
L
= SLF6028-470MR59
22
= 4.64k
PROG
50
40
30
20
10
0
20
18
16
14
12
10
9mm EFFICIENCY
10mm EFFICIENCY
11mm EFFICIENCY
9mm V_RX
10mm V_RX
11mm V_RX
90
85
80
50
100
150
(mA)
250
0
200
–50
0
25
50
75 100 125
–22
TEMPERATURE (°C)
I
BAT
4120 G11
4120 G10
Typical Burst Mode Waveforms,
IBAT = 38mA
Typical Wireless Charging Cycle
Burst Mode Trigger Current
450
400
350
300
250
200
150
100
50
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
90
80
70
60
50
40
30
20
10
V
BAT
R
PROG
= 3k
V
SW
5V/DIV
V
CHRG
I
BAT
R
= 6.2k
PROG
0V
V
PROG
500mV/DIV
0V
I
LSW
BAT = 940mAhr
200mA/DIV
0mA
L
R
R
= TDK SLF4075 15µH
SW
FB1
= 732k, R = 976k
FB2
4120 G14
= 3.01k
PROG
4µs/DIV
APPLICATION CCT OF FIGURE 10
SPACING = 14mm
0
0
0
0
1
2
3
10
15
20
25
(V)
40
30
35
TIME (HOURS)
V
IN
4120 G12
4120 G13
4120fe
7
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
TA = 25°C, unless otherwise noted.
Typical perForMance characTerisTics
IN Pin Shutdown Current
IN Pin Standby Current vs VIN
vs Input Voltage
220
80
V
= 0.4V
V
= 4.21V
RUN
BAT
NTC = GND
70
60
50
40
30
20
10
0
200
180
I
IN
I
IN
I
IN
I
IN
I
IN
I
IN
STBY FREQ HIGH 130°C
STBY FREQ LOW 130°C
STBY FREQ HIGH 25°C
STBY FREQ LOW 25°C
STBY FREQ HIGH –45°C
STBY FREQ LOW –45°C
160
140
120
100
I
IN
I
IN
I
IN
SD TEMP = 125°C
SD TEMP = 35°C
SD TEMP = –40°C
80
5
10
40
0
15 20 25 30 35
(V)
20
(V)
0
10
30
40
V
V
IN
IN
4120 G15
4120 G16
IN Pin Disabled Current
vs Input Voltage
IN Pin Switching Current vs Input
Voltage
UVCL: ICHARGE vs Input Voltage
100
90
80
70
60
50
40
30
20
10
0
7
6
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
V
= 1.6V
RUN
I
I
I
TEMP=125°C
TEMP=35°C
TEMP=–40°C
130°C
25°C
–45°C
BAT
BAT
BAT
I
FREQ HIGH
CC
ICCQ(SWITCHING)
5
4
3
2
1
FREQ = INTV
I
FREQ LOW
ICCQ(SWITCHING)
FREQ = GND
I
I
I
SD TEMP = 125°C
SD TEMP = 35°C
SD TEMP = –40°C
IN
IN
IN
UVCL
15
I
= 0
BAT
0
0
10
20
(V)
30
40
12.00 12.05 12.10 12.15
12.20
25
(V)
35
40
11.90 11.95
10
20
30
V
V
(V)
V
IN
IN
IN
4120 G18
4120 G17
4120 G19
4120fe
8
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
pin FuncTions
linear charge current, I
, is sourced from this pin to
precondition the battery. Decouple the BAT pin with a low
ESR 22µF or greater ceramic capacitor to GND.
INTV (Pin 1): Internal Regulator Output Pin. This pin is
LOWBAT
CC
the output of an internal linear regulator that generates the
internal INTV supply from IN. It also supplies power to
CC
the switch gate drivers and the low battery linear charge
BATSNS (Pin 10, LTC4120-4.2 Only): Battery Voltage
Sense Pin. For proper operation, this pin must always be
connectedphysicallyclosetothepositivebatteryterminal.
current I
. Connect a 2.2µF low ESR capacitor from
LOWBAT
INTV to GND. Do not place any external load on INTV
CC
CC
other than the NTC bias network. When the RUN pin is
FB(Pin10, LTC4120Only):BatteryVoltageFeedbackPin.
Thechargefunctionoperatestoachieveafinalfloatvoltage
of 2.4V at this pin. Battery float voltage is programmed
using a resistive divider from BAT to FB to FBG, and can be
programmed up to 11V. The feedback pin input bias cur-
above V , and INTV rises above the UVLO threshold,
EN
CC
and IN rises above BAT by ∆V
and its hysteresis,
DUVLO
the charger is enabled.
BOOST(Pin2):BoostedSupplyPin.Connecta22nFboost
capacitor from this pin to the SW pin.
rent, I , is 25nA. Using a resistive divider with a Thevenin
FB
IN (Pin 3): Positive Input Power Supply. Decouple to GND
with a 10µF or larger low ESR capacitor.
equivalent resistance of 588k compensates for input bias
current error (see curve of FB Pin Bias Current versus
Temperature in the Typical Performance Characteristics).
SW (Pin 4): Switch Pin. The SW pin delivers power from
IN to BAT via the step-down switching regulator. An in-
ductor should be connected from SW to CHGSNS. See
the Applications Information section for a discussion of
inductor selection.
FBG (Pin 11, LTC4120 Only): Feedback Ground Pin. This
pindisconnectstheexternalFBdividerloadfromthebattery
when it is not needed. When sensing the battery voltage
this pin presents a low resistance, R , to GND. When in
FBG
disabled or shutdown modes this pin is high impedance.
GND (Pin 5, Exposed Pad Pin 17): Ground Pin. Connect
toexposedpad. TheexposedpadmustbesolderedtoPCB
GND to provide a low electrical and thermal impedance
connection to ground.
NTC(Pin12):InputtotheNegativeTemperatureCoefficient
Thermistor Monitoring Circuit. The NTC pin connects to
a negative temperature coefficient thermistor which is
typically co-packaged with the battery to determine if the
battery is too hot or too cold to charge. If the battery’s
temperature is out of range, the LTC4120 enters standby
mode and charging is paused until the battery tempera-
ture re-enters the valid range. A low drift bias resistor is
DHC(Pin6):DynamicHarmonizationControlPin.Connect
a Schottky diode from the DHC pin to the IN pin, and a
capacitor from the DHC pin as shown in the Typical Ap-
plication or the Block Diagram. When V is greater than
IN
V
V
, this pin is high impedance. When V is below
IN(DHC)
IN(DHC)
IN
this pin is low impedance allowing the LTC4120
required from INTV to NTC and a thermistor is required
CC
to modulate the resonance of the tuned receiver network.
See Applications Information for more information on the
tuned receiver network.
from NTC to GND. Tie the NTC pin to GND to disable NTC
qualified charging if NTC functionality is not required.
PROG(Pin13):ChargeCurrentProgramandChargeCurrent
MonitorPin.Connecta1%resistorbetween3.01k(400mA)
and 24.3k (50mA) from PROG to ground to program the
charge current. While in constant-current mode, this pin
regulates to 1.227V. The voltage at this pin represents the
averagebatterychargecurrentusingthefollowingformula:
FREQ (Pin 7): Buck Switching Frequency Select Input Pin.
ConnecttoINTV toselecta1.5MHzswitchingfrequency
CC
orGNDtoselecta750kHzswitchingfrequency.Donotfloat.
CHGSNS (Pin 8): Battery Charge Current Sense Pin. An
internal current sense resistor between CHGSNS and BAT
pins monitors battery charge current. An inductor should
be connected from SW to CHGSNS.
VPROG
IBAT = hPROG
•
RPROG
BAT (Pin 9): Battery Output Pin. Battery charge current
is delivered from this pin through the internal charge
current sense resistor. In low battery conditions a small
where h
is typically 988. Keep parasitic capacitance
PROG
on the PROG pin to a minimum.
4120fe
9
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
pin FuncTions
CHRG (Pin 14): Open-Drain Charge Status Output Pin.
Typically pulled up through a resistor to a reference
voltage, the CHRG pin indicates the status of the battery
charger. The pin can be pulled up to voltages as high as
IN when disabled, and can sink currents up to 5mA when
enabled. When the battery is being charged, the CHRG
pin is pulled low. When the termination timer expires or
the charge current drops below 10% of the programmed
value, the CHRG pin is forced to a high impedance state.
pulled low. A bad battery fault also causes this pin to
be pulled low. If no fault conditions exist, the FAULT pin
remains high impedance.
RUN (Pin 16): Run Pin. When RUN is pulled below V
EN
and its hysteresis, the device is disabled. In disabled
mode, battery charge current is zero and the CHRG and
FAULT pins assume high impedance states. If the voltage
at RUN is pulled below V , the device is in shutdown
SD
mode. When the voltage at the RUN pin rises above V ,
EN
FAULT (Pin 15): Open-Drain Fault Status Output Pin. Typi-
cally pulled up through a resistor to a reference voltage,
this status pin indicates fault conditions during a charge
cycle. The pin can be pulled up to voltages as high as IN
when disabled, and can sink currents up to 5mA when
enabled. An NTC temperature fault causes this pin to be
the INTV LDO turns on. When the INTV LDO rises
CC CC
above its UVLO threshold the charger is enabled. The
RUN pin should be tied to a resistive divider from V to
IN
program the input voltage at which charging is enabled.
Do not float the RUN pin.
block DiagraM
C2S
ENABLE
INTV
LTC4120
IN
CC
LDO
3
1
2
C
INTVCC
2.2µF
RUN
INTV
CC
+
–
16
ENABLE
BOOST
C
IN
2.45V
10µF
C
22nF
BST
+
–
C2P
SW
PWM
4
INTV
CC
0.9V
BAT
SHUTDOWN
•
+
–
L
L
R
SW
33µH
DUVLO
GND
CHGSNS
BAT
5
8
9
IN – 80mV
INTV
CC
+
–
V
IN(DHC)
DHC
DHC
6
R
SNS
IN
0.3Ω
IN
IN
I
C-EA
INTV
FREQ
TH
R
7
NOM
C
BAT
10k
IN
INTV
INTV
+
CC
CC
CC
FAULT
R
R
22µF
FB1
15
FB
1.2V
10
11
–
+
ENABLE
LOWBAT
+
588k
V
–
FB2
FB(REG)
T
10k
FBG
CNTRL
UVCL
V-EA
CHRG
14
12
ENABLE
Li-Ion
INTV
CC
PROG
13
NTC
NTC
D
R
Z
PROG
HOT
COLD
DISABLE
–
+
BAT
2.21V
LOWBAT
4120 F01
Figure 1. Block Diagram
4120fe
10
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
block DiagraM
LTC4120-4.2
INTV
C-EA
CC
+
–
CHGSNS
8
R
SNS
I
TH
0.3Ω
BAT
9
BATSNS
+
–
DUVLO
IN – 80mV
BATSNS
10
C
+
BAT
IN
INTV
+
INTV
CC
CC
Li-Ion
22µF
1.2V
–
+
588k
V
–
FB(REG)
UVCL
V-EA
ENABLE
–
+
BATSNS
2.21V
PROG
13
LOWBAT
D
R
Z
PROG
4120 F02
Figure 2. LTC4120-4.2 BATSNS Connections
TesT circuiT
20V
2k
680nF
665Ω
49.9Ω
IRLML5103TR
V
IN(DHC)
IN
NTC
LTC4120
RUN
INTV
CC
665Ω
10Ω
10µF
2.2µF
DHC
GND
4120 F03
Figure 3. VIN(DHC) Test Circuit
4120fe
11
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
operaTion
Wireless Power System Overview
application. The LTC4120 serves as a constant-current/
constant-voltagebatterychargerwiththefollowingbuilt-in
chargerfunctions:programmablechargecurrent,program-
mable float voltage (LTC4120), battery precondition with
half-hour timeout, precision shutdown/run control, NTC
thermal protection, a 2-hour safety termination timer, and
automatic recharge. The LTC4120 also provides output
pins to indicate state of charge and fault status.
The LTC4120 is one component in a complete wireless
power system. A complete system is composed of trans-
mit circuitry, a transmit coil, a receive coil and receive
circuitry—including the LTC4120. Please refer to the
Applications Information section for more information
on transmit circuitry and coils. In particular, the Resonant
Transmitter and Receiver and the Alternative Transmit-
ter Options sections include information necessary to
complete the design of a wireless power system. Further
information can be found in the Applications Information
section of this document under the heading Resonant
Transmitter and Receiver, as well as in AN138: Wireless
Power Users Guide, as well as the DC1969A: wireless
power transmit and receiver demo kit and manual. The
Gerber layout files for both the Transmitter and Receiver
boards are available at the following link:
The circuit in Figure 4 is a fully functional system using a
basic current-fed resonant converter for the transmitter
and a series resonant converter for the receiver with the
1
LTC4120.AdvancedtransmittersbyPower-By-Proxi may
also be used with the LTC4120. For more information on
transmitter design refer to Application Note 138: Wireless
Power Users Guide.
Wireless Power Transfer
A wireless coupled power transfer system consists of a
transmitter that generates an alternating magnetic field,
and a receiver that collects power from that field. The
ideal transmitter efficiently generates a large alternating
http://www.linear.com/product/LTC4120#demoboards
LTC4120 Overview
The LTC4120 is a synchronous step-down (buck) wire-
less battery charger with dynamic harmonization control
(DHC). DHC is a highly efficient method of regulating the
receivedinputvoltageinaresonantcoupledpowertransfer
current in the transmitter coil, L . The push-pull current-
X
fed resonant converter, shown in Figure 4, is an example
1
www.PowerByProxi.com
V
DC
5V
TRANSMITTER
C2S
D9
L1
C4
L2
D6
39V
C
IN
C
X
L
X
L
R
D8
D5
DFLZ39
C2P
IN
DHC BOOST
C5
C
BST
SW
LTC4120
R1
D2
R2
D3
L
SW
D5, D8, D9: DFLS240L
CHGSNS
BAT
M1
M2
+
Li-Ion
C
BAT
D1
D4
GND
4120 F04
Figure 4. DC-AC Converter, Transmit/Receive Coils, Tuned Series Resonant Receiver and AC-DC Rectifier
4120fe
12
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
operaTion
of a basic power transmitter that may be used with the
LTC4120.Thistransmittertypicallyoperatesatafrequency
of approximately 130kHz; though the operating frequency
varies depending on the load at the receiver and the cou-
pling to the receiver coil. For L = 5µH, and C = 300nF,
the transmitter frequency is:
power to appear at the receiver by tuning the receiver
resonance closer to the transmitter resonance. If the input
voltage exceeds V
, the LTC4120 tunes the receiver
IN(DHC)
resonance away from the transmitter, which reduces the
power available at the receiver. The amount that the input
powerincreasesordecreasesisafunctionofthecoupling,
X
X
the tuning capacitor, C2P, the receiver coil, L , and the
R
1
fO ≈
= 130kHz
operating frequency.
2 • π • LX •CX
Figure 5 illustrates the components that implement the
DHC function to automatically tune the resonance of the
This transmitter typically generates an AC coil current of
receiver. Capacitor C2S and inductor L serve as a series
about 2.5A . For more information on this transmitter,
R
RMS
resonator. Capacitor C2P and the DHC pin of the LTC4120
form a parallel resonance when the DHC pin is low imped-
ance,anddisconnectwhentheDHCpinishighimpedance.
C2P adjusts the receiver resonance to control the amount
of power available at the input of the LTC4120. C2P also
affects power dissipation in the LTC4120 due to the AC
current being shunted by the DHC pin. For this reason it
is not recommended to apply total capacitance in excess
of 30nF at this pin.
refer to AN138: Wireless Power Users Guide.
Thereceiverconsistsofacoil,L ,configuredinaresonant
R
circuitfollowedbyarectifierandtheLTC4120.Thereceiver
coilpresentsaloadreflectedbacktothetransmitterthrough
the mutual inductance between L and L . The reflected
R
X
impedance of the receiver may influence the operating
frequency of the transmitter. Likewise, the power output
by the transmitter depends on the load at the receiver. The
resonant coupled charging system, consisting of both the
transmitter and LTC4120 charger, provides an efficient
method for wireless battery charging as the power output
bythetransmittervariesautomaticallybasedonthepower
used to charge a battery.
Using DHC, the LTC4120 automatically adjusts the power
received depending on load requirements; typically the
load is battery charge current. This technique results in
significant power savings, as the power required by the
C2S
D9
Dynamic Harmonization Control
1:n
C
IN
D5
C
L
L
R
D8
X
X
Dynamic harmonization control (DHC) is a technique for
regulating the received input power in a wireless power
transfer system. DHC modulates the impedance of the
resonant receiver to regulate the voltage at the input to
the LTC4120. When the input voltage to the LTC4120 is
C2P
IN
LTC4120
DHC
4120 F05
Figure 5. Resonant Receiver Tank
below the V
set point, the LTC4120 allows more
IN(DHC)
4120fe
13
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
operaTion
transmitter automatically adjusts to the requirements
at the receiver. Furthermore, DHC reduces the rectified
voltage seen at the input of the LTC4120 under light load
conditions when the battery is fully charged.
Programming The Battery Float Voltage
For the LTC4120, the battery float voltage is programmed
by placing a resistive divider from the battery to FB and
FBG as shown in Figure 6. The programmable battery float
The design of the resonant receiver circuit (L , C2S and
voltage,V
,isthengovernedbythefollowingequation:
FLOAT
R
C2P), the transmitter circuit, and the mutual inductance
R
FB1 + RFB2
RFB2
(
•
FB(REG)
)
betweenL andL determinesboththemaximumunloaded
X
R
V
= V
FLOAT
voltageattheinputtotheLTC4120aswellasthemaximum
power available at the input to the LTC4120. The value and
tolerancesofthesecomponentsmustbeselectedwithcare
for stable operation, for this reason it is recommended to
only use components with tight tolerances.
where V
is typically 2.4V.
FB(REG)
Due to the input bias current (I ) of the voltage error amp
FB
(V-EA), care must also be taken to select the Thevenin
equivalent resistance of R ||R close to 588k. Start by
FB1 FB2
To understand the operating principle behind dynamic
harmonization control (DHC), consider the following sim-
plification.Here,afixed-frequencytransmitterisoperating
calculating R to satisfy the following relations:
FB1
VFLOAT • 588k
RFB1
=
at a frequency f = 130kHz. DHC automatically adjusts the
O
VFB(REG)
impedanceofthereceivertunednetworksoastomodulate
the resonant frequency of the receiver between f and f .
T
D
Find the closest 0.1% or 1% resistor to the calculated
value. With R calculate:
1
FB1
fT ≅
fD ≅
2 • π • L • C2P + C2S
(
)
VFB(REG) •RFB1
R
RFB2
=
– 1000Ω
1
V
– VFB(REG)
FLOAT
2 • π • LR •C2S
where 1000Ω represent the typical value of R . This is
the resistance of the FBG pin which serves as the ground
return for the battery float voltage divider.
FBG
When the input voltage is above V
(typically 14V),
IN(DHC)
the LTC4120 opens the DHC pin, detuning the receiver
resonance away from the transmitter frequency f , so that
O
less power is received. When the input voltage is below
V
FLOAT
V
, the LTC4120 shunts the DHC pin to ground,
IN(DHC)
BAT
FB
LTC4120
I
tuning the receiver resonance closer to the transmitter
frequency so that more power is available.
Li-Ion
R
R
22µF
FB1
4120 F06
FB
FB2
FBG
FortheresonantconvertershowninFigure4,theoperating
frequencyofthetransmitterisnotfixed,butvariesdepend-
ing on the load impedance. However the basic operating
principle of DHC remains valid. For more information on
the design of the wireless power receiver resonant circuit
refer to the applications section.
ENABLE
Figure 6. Programming the Float Voltage with the LTC4120
4120fe
14
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
operaTion
Once R and R are selected, recalculate the value of
where h
is typically 988, V
is either 1.227V or
PROG
FB1
FB2
PROG
V
obtained with the resistors available. If the error
122mV during trickle charge, and R
is the resistance
FLOAT
PROG
is too large substitute another standard resistor value for
of the grounded resistor applied to the PROG pin. The
PROG resistor sets the maximum charge current, or the
currentdeliveredwhilethechargerisoperatinginconstant-
current (CC) mode.
R
and recalculate R . Repeat until the float voltage
FB1
FB2
error is acceptable.
Table 1 and Table 2 list recommended standard 0.1% and
1% resistor values for common battery float voltages.
Analog Charge Current Monitor
Table 1: Recommended 0.1% Resistors for Common VFLOAT
The PROG pin provides a voltage signal proportional to
the actual charge current. Care must be exercised in mea-
suring this voltage as any capacitance at the PROG pin
forms a pole that may cause loop instability. If observing
the PROG pin voltage, add a series resistor of at least 2k
and limit stray capacitance at this node to less than 50pF.
V
R
R
FB2
TYPICAL ERROR
–0.13%
0.15%
FLOAT
FB1
3.6V
4.1V
4.2V
7.2V
8.2V
8.4V
887k
1.01M
1.01M
1.8M
1780k
1.42M
1.35M
898k
–0.13%
0.08%
2.00M
2.05M
825k
0.14%
816k
0.27%
In the event that the input voltage cannot support the
demanded charge current, the PROG pin voltage may not
represent the actual charge current. In cases such as this,
the PWM switch frequency drops as the charger enters
drop-out operation where the top switch remains on for
morethanoneclockcycleastheinductorcurrentattempts
torampuptothedesiredcurrent. Ifthetopswitchremains
on in drop-out for 8 clock cycles a dropout detector forces
the bottom switch on for the remainder of the 8th cycle.
In such a case, the PROG pin voltage remains at 1.227V,
but the charge current may not reach the desired level.
Table 2: Recommended 1% Resistors for Common VFLOAT
V
R
R
FB2
TYPICAL ERROR
–0.13%
0.26%
FLOAT
FB1
3.6V
4.1V
4.2V
7.2V
8.2V
8.4V
887k
1.02M
1.02M
1.78M
2.00M
2.1M
1780k
1.43M
1.37M
887k
–0.34%
0.16%
825k
0.14%
845k
–0.50%
Programming the Charge Current
The current-error amp (C-EA) measures the current
through an internal 0.3Ω current sense resistor between
the CHGSNS and BAT pins. The C-EA outputs a fraction
Undervoltage Current Limit
The undervoltage current limit (UVCL) feature reduces
charge current as the input voltage drops below V
UVCL
of the charge current, 1/h
, to the PROG pin. The
PROG
(typically 12V). This low gain amplifier typically keeps V
IN
voltage-error amp (V-EA) and PWM control circuitry can
limit the PROG pin voltage to control charge current. An
within 100mV of V
, but if insufficient power is avail-
UVCL
able the input voltage may drop below this value; and the
charge current will be reduced to zero.
internal clamp (D ) limits the PROG pin voltage to V
,
Z
PROG
which in turn limits the charge current to:
hPROG • V
1212V
RPROG
PROG
ICHG
=
=
RPROG
PROG • V
h
120V
RPROG
PROG_ TRKL
ICHG_ TRKL
=
=
RPROG
4120fe
15
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
operaTion
NTC Thermal Battery Protection
of the R
resistor. For the same Vishay Curve 2 therm-
BIAS
istor, this corresponds to approximately 40°C. With a
Vishay Curve 2 thermistor, the hot and cold comparators
both have about 2°C of hysteresis to prevent oscillations
about the trip points.
TheLTC4120monitorsbatterytemperatureusingatherm-
istor during the charging cycle. If the battery temperature
moves outside a safe charging range, the IC suspends
charging and signals a fault condition until the tempera-
ture returns to the safe charging range. The safe charging
range is determined by two comparators that monitor the
voltage at the NTC pin. NTC qualified charging is disabled
Thehotandcoldtrippointsmaybeadjustedusingadiffer-
ent type of thermistor, or a different R
resistor, or by
BIAS
adding a desensitizing resistor, R , or by a combination
ADJ
if the NTC pin is pulled below about 85mV (V ).
of these measures as shown in Figure 7. For example, by
DIS
increasing R
to 12.4k, with the same thermistor as
BIAS
Thermistor manufacturers usually include either a tem-
perature lookup table identified with a characteristic curve
number, or a formula relating temperature to the resistor
value. Each thermistor is also typically designated by a
before, the cold trip point moves down to –5°C, and the
hot trip point moves down to 34°C. If a Vishay Curve 1
thermistor with B
= 3950 and resistance of 100k at
25/85
25°C is used, a 1% R
resistor of 118k and a 1% R
BIAS
ADJ
thermistor gain value B
.
25/85
resistor of 12.1k results in a cold trip point of 0°C, and a
hot trip point of 39°C.
The NTC pin should be connected to a voltage divider
from INTV to GND as shown in Figure 7. In the simple
CC
application (R
= 0) a 1% resistor, R
, with a value
End-Of-Charge Indication and Safety Timeout
ADJ
BIAS
equal to the resistance of the thermistor at 25°C is
The LTC4120 uses a safety timer to terminate charging.
Whenever the LTC4120 is in constant current mode the
connected from INTV to NTC, and a thermistor is con-
CC
nected from NTC to GND. With this setup, the LTC4120
timer is paused, and if FB transitions through the V
RCHG
pauses charging when the resistance of the thermistor
threshold the timer is reset. When the battery voltage
reaches the float voltage, a safety timer begins count-
ing down a 2-hour timeout. If charge current falls below
one-tenth of the programmed maximum charge current
increases to 285% of the R
resistor as the tempera-
BIAS
ture drops. For a Vishay Curve 2 thermistor with B
25/85
= 3490 and 25°C resistance of 10k, this corresponds to
a temperature of about 0°C. The LTC4120 also pauses
charging if the thermistor resistance decreases to 57.5%
(h ), the CHRG status pin rises, but top-off charge
C/10
current continues to flow until the timer finishes. After
the timeout, the LTC4120 enters a low power sleep mode.
BAT
LTC4120
INTV
CC
Automatic Recharge
R
BIAS
NTC
+
–
In sleep mode, the IC continues to monitor battery volt-
TOO COLD
TOO HOT
R
ADJ
74% INTV
age. If the battery falls 2.2% (V
or V
) from
CC
OPT
RCHG
RCHG_42
the full-charge float voltage, the LTC4120 engages an
automatic recharge cycle. Automatic recharge has a
built-in filter of about 0.5ms to prevent triggering a new
charge cycle if a load transient causes the battery voltage
to drop temporarily.
+
+ 36.5% INTV
–
R
NTC
T
CC
Li-Ion
4120 F07
+
–
IGNORE NTC
2% INTV
CC
Figure 7. NTC Connections
4120fe
16
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
operaTion
State of Charge and Fault Status Pins
Precision Run/Shutdown Control
The LTC4120 contains two open-drain outputs which
provide charge status and signal fault indications. The
binary-coded CHRG pin pulls low to indicate charging at a
rate higher than C/10. The FAULT pin pulls low to indicate
a bad battery timeout, or to indicate an NTC thermal fault
condition. During NTC faults the CHRG pin remains low,
but when a bad battery timeout occurs the CHRG pin de-
asserts. When the open-drain outputs are pulled up with
a resistor, Table 3 summarizes the charger state that is
indicated by the pin voltages.
The LTC4120 remains in a low power disabled mode until
the RUN pin is driven above V (typically 2.45V). While
EN
the LTC4120 is in disabled mode, current drain from the
batteryisreducedtoextendbatterylifetime,thestatuspins
are both de-asserted, and the FBG pin is high impedance.
Charging can be stopped at any time by pulling the RUN
pin below 2.25V. The LTC4120 also offers an extremely
low operating current shutdown mode when the RUN pin
is pulled below V (typically 0.7V). In this condition less
SD
than 20µA is drawn from the supply at IN.
Table 3. LTC4120 Open-Drain Indicator Outputs with Resistor
Pull-Ups
Differential Undervoltage Lockout
The LTC4120 monitors the difference between the battery
voltage, V , and the input supply, V . If the difference
FAULT CHRG CHARGER STATE
High
High
Low
Low
High Off or Topping Off Charging at a Rate Less Than C/10
Low Charging at Rate Higher Than C/10
High Bad Battery Fault
BAT
IN
(V -V ) falls to V
, all functions are disabled and
IN BAT
DUVLO
thepartisforcedintoshutdownmodeuntil(V -V )rises
IN BAT
above the V
hysteresis. The LTC4120-4.2 monitors
theBATSNSandINpinvoltagestosenseDUVLOcondition.
Low NTC Thermal Fault Charging Paused
DUVLO
Low Battery Voltage Operation
User Selectable Buck Operating Frequency
The LTC4120 automatically preconditions heavily dis-
charged batteries. If the battery voltage is below V
The LTC4120 uses a constant-frequency synchronous
step-down buck architecture to produce high operating
efficiency. The nominal operating frequency of the buck,
LOWBAT
minus its hysteresis (typically 2.05V—e.g., battery pack
protection has been engaged) a DC current, I
, is
LOWBAT
applied to the BAT pin from the INTV supply. When the
f
, is programmed by connecting the FREQ pin to
CC
OSC
batteryvoltagerisesaboveV
,theswitchingregula-
LOWBAT
either INTV or to GND to obtain a switching frequency
CC
tor is enabled and charges the battery at a trickle charge
level of 10% of the full-scale charge current (in addition
of 1.5MHz or 750kHz, respectively. The high operating
frequency allows the use of smaller external components.
to the DC I
current). Trickle charging of the battery
LOWBAT
Selectionoftheoperatingfrequencyisatrade-offbetween
efficiency,componentsize,andmarginfromtheminimum
on-time of the switcher. Operation at lower frequency
improves efficiency by reducing internal gate charge and
switching losses, but requires larger inductance values to
maintain low output ripple. Operation at higher frequency
allows the use of smaller components, but may require
sufficient margin from the minimum on-time at the lowest
duty cycle if fixed-frequency switching is required.
continues until the sensed battery voltage (sensed via
the feedback pin for the LTC4120) rises above the trickle
charge threshold, V
. When the battery rises above
TRKL
the trickle charge threshold, the full-scale charge current
is applied and the DC trickle charge current is turned off.
If the battery remains below the trickle charge threshold
for more than 30 minutes, charging terminates and the
fault status pin is asserted to indicate a bad battery.
Afterabadbatteryfault,theLTC4120automaticallyrestarts
a new charge cycle once the failed battery is removed and
replaced with another battery. The LTC4120-4.2 monitors
the BATSNS pin voltage to sense LOWBAT and TRKL
conditions.
4120fe
17
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
operaTion
PWM Dropout Detector
between bursts, as shown in G14. If the PROG pin voltage
falls below 120mV for longer than 350µs this causes the
CHRGpintode-assert,indicatingC/10.Burstcurrentripple
If the input voltage approaches the battery voltage, the
LTC4120mayrequiredutycyclesapproaching100%.This
mode of operation is known as dropout. In dropout, the
operating frequency may fall well below the programmed
depends on the selected switch inductor, and V /V
.
IN BAT
BOOST Supply Refresh
f
value. If the top switch remains on for eight clock
OSC
The BOOST supply for the top gate drive in the LTC4120
switching regulator is generated by bootstrapping the
cycles, the dropout detector activates and forces the
bottom switch on for the remainder of that clock cycle
or until the inductor current decays to zero. This avoids
a potential source of audible noise when using ceramic
input or output capacitors and prevents the boost sup-
ply capacitor for the top gate drive from discharging. In
dropout operation, the actual charge current may not be
able to reach the full-scale programmed value. In such a
scenario the analog charge current monitor function does
not represent actual charge current being delivered.
BOOST flying capacitor to INTV whenever the bottom
CC
switch is turned on. This technique provides a voltage of
INTV from the BOOST pin to the SW pin. In the event
CC
that the bottom switch remains off for a prolonged period
of time, e.g., during Burst Mode operation, the BOOST
supply may require a refresh. Similar to the PWM dropout
timer, the LTC4120 counts the number of clock cycles
since the last BOOST refresh. When this count reaches
32, the next PWM cycle begins by turning on the bottom
side switch first. This pulse refreshes the BOOST flying
Burst Mode Operation
capacitor to INTV and ensures that the topside gate
CC
Atlowchargecurrents,forexampleduringconstant-voltage
mode,theLTC4120automaticallyentersBurstModeopera-
tion. In Burst Mode operation the switcher is periodically
forced into standby mode in order to improve efficiency.
The LTC4120 automatically enters Burst Mode operation
afteritexitsconstant-current(CC)modeandasthecharge
current drops below about 80mA. Burst Mode operation
is triggered at lower currents for larger PROG resistors,
and depends on the input supply voltage. Refer to graph
Burst Mode Trigger Current and graph Typical Burst Mode
Waveform, intheTypicalPerformanceCharacteristics, for
more information on Burst Mode operation. Burst Mode
operation has some hysteresis and remains engaged for
battery currents up to about 150mA.
driver has sufficient voltage to turn on the topside switch
at the beginning of the next cycle.
Operation Without an Input Supply or Wireless Power
When a battery is the only available power source, care
should be taken to eliminate loading of the IN pin. Load
current on IN drains the battery through the body diode
of the top side power switch as V falls below V . To
IN
SW
prevent this possibility, place a diode between the input
supply and the IN capacitor, C . The rectification diode
IN
(D9 in Figure 5 and Figure 11) in the wireless power ap-
plications also eliminates this discharge path. Alternately,
a P-channel MOSFET may be placed in series with the BAT
pin provided care is taken to directly sense the positive
battery terminal voltage with FB via the battery resistive
divider. This is illustrated in Figure 15.
While in Burst Mode operation, the PROG pin voltage to
average charge current relationship is not well defined.
This is due to the PROG pin voltage falling to 0V in
4120fe
18
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
0.50
0.45
+
I
NO MISALIGNMENT
R
I
AC
X
X
5mm MISALIGNMENT
L
L
V
R
X
R
0.40 X
+
+
X
X
10mm MISALIGNMENT
0.35 X
0.30
0.25
0.20
0.15
1:n
+
X
4120 F08
+
X
X
Figure 8. Wireless Power Transfer
X
X
+
X
+
X
X
Wireless Power Transfer
0.10
0
1
2
3
4
5
6
7
8
9
10
4120 F09
In a wireless power transfer system, power is transmitted
using alternating magnetic fields. Power is transferred
based on the principle that an AC current in a transmit-
ter coil produces an AC current in a receiver coil that is
placed in the magnetic field generated by the transmitter
coil. The magnetic field coupling is described by the mu-
tual inductance, M. This term does not have a physical
representation but is referred to using the unit-less terms
k and n. Where k is the coupling coefficient:
COIL DISTANCE (mm)
Figure 9. Coupling Coefficient k vs Distance
(L ||C ).Withapeak-to-peakamplitudethatisproportional
to the applied input voltage:
X
X
V
≅ 2 • π • V
AC
DC
This generates a sinusoidal current in the transmit coil
with peak-to-peak amplitude:
M
k =
VAC
VDC
LX •LR
IAC
=
≅
2 • π • fO •LX fO •LX
Andnistheturnsratio—thenumberofturnsinthereceiver
coil divided by the number of turns in the transmitter coil:
The AC voltage induced at the receive coil is a function
of both the applied voltage, the coupling, as well as the
impedance at the receiver. With no load at the receiver,
nR
nX
LR
LX
n =
=
the open-circuit voltage, V
, is approximately:
IN(OC)
V
≅ k • n • 2 • π • V
DC
IN(OC)
Theturnsratioisproportionaltothesquarerootoftheratio
of receiver coil inductance to transmitter coil inductance.
The receiver (shown in Figures 5 and 10) uses a resonant
tuned circuit followed by a rectifier to convert the induced
AC voltage into a DC voltage to power the LTC4120 and
chargeabattery.PowerdeliveredtotheLTC4120depends
on the impedance of the LTC4120 and the impedance of
the tuned circuit at the resonant frequency of the trans-
mitter. The LTC4120 employs a proprietary circuit, called
dynamic harmonization control (DHC) that modulates the
impedance of the receiver depending on the voltage at the
input to the LTC4120. This technique ensures that over a
wide range of coupling coefficients the induced rectified
voltage does not exceed voltage compliance ratings when
theloadgoesaway(e.g, whenthebatteryisfullycharged).
DHC efficiently adjusts the receiver impedance depending
on the load without compromising available power.
In the wireless power transfer system an AC current, I ,
AC
applied to the transmit coil L , produces an AC current in
X
the receive coil, L of:
R
I
= 2 • π • M • I = 2 • π • k • √L • L • I
AC X R AC
R(AC)
The coupling coefficient is a variable that depends on the
orientation and proximity of the transmitter coil relative
to the receiver coil. If the two coils are in a transformer,
then k = 1. If the two coils are completely isolated from
each other then k = 0. In a typical LTC4120-based wireless
power design, k varies from around 0.18 at 10mm spac-
ing, to about 0.37 with the coils at 3mm spacing. This is
illustrated in Figure 9.
With low resistance in the L and L coils, the efficiency is
X
R
inherentlyhigh,evenatlowcouplingratios.Thetransmitter
In the event that the coupling may become too large (e.g.
receiver coil is placed too close to the transmitter coil)
then it is recommended to place a Zener diode across the
in Figures 4 and 10 generates a sine wave at the resonant
frequency, f , across the transmitter coil and capacitor
O
4120fe
19
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
input to the LTC4120 to prevent exceeding the absolute
maximum rating of the LTC4120. Diode D6 (in Figure 4
and Figure 10) illustrates this connection.
tion of a 39V Zener diode (D6 in Figures 4 and 10) at the
input to the LTC4120 will prevent overvoltage conditions
from damaging the LTC4120.
The RMS voltage at the rectifier output depends on the
load of the LTC4120, i.e., the charge current, as well as the
Resonant Transmitter and Receiver
An example DC/AC transmitter is shown in Figure 10.
A 5V 5% supply to the transmitter efficiently produces a
circulating AC current in L , which is coupled to L . For
applied AC current, I . The applied AC current depends
AC
both on the components of the tuned network as well as
the applied DC voltage. The load at the receiver depends
on the state of charge of the battery. If the coupling and/
or the applied AC current is not well controlled, the addi-
X
R
higher voltage inputs, a pre-regulator DC/DC converter
can be used to generate 5V (see Figure 11). Power is
transmitted from transmitter to receiver at the resonant
V
CC
4.75V TO 5.25V
TRANSMITTER
RECEIVER
C2S2
L
L
B2
68µH
B1
68µH
D1
D4
C5
C
L
X
X
39V
OPT
C2S1
C2P1
D2
D3
DHC
L
R
10µF
0.3µF 5µH
IN
C4
0.01µF
C5
0.01µF
BOOST
SW
C3
U1
LTC4120
C2P2
R1
100Ω
R2
100Ω
L1
CHGSNS
D2
D3
BAT
INTV
CC
+
C4
2.2µF
C1
10µF
C2
47µF
M1
M2
FB
D1
D4
FBG
GND
4120 F10
Figure 10. DC/AC Converter, Transmit/Receive Coils, Tuned Series Resonant Receiver and AC/DC Rectifier
HV
IN
8V TO 38V
C6
4.7µF
GND
V
IN
BD
BOOST
R3
L3
C9
150k
4.7µF
0.47µF
RUN/SS
SW
D5
DFLS240L
C7
0.068µF
C10
22µF
R8
M3
U1
LT3480
150k
Si2333DS
M4
2N7002L
SYNC
PG
VC
V
CC
RT
FB
5V
R10
100k
R5
20k
C8
R4
40.2k
CONNECT
TO Tx V
GND
CC
R7
536k
330pF
R6
100k
4120 F11
Figure 11. High Voltage Pre-Regulator for Transmitter
4120fe
20
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
Resonant Converter Component Selection
frequency, f ; which depends on both component values
O
as well as the load at the receiver. The tolerance of the
components selected in both the transmitter and receiver
circuits is critical to achieving maximum power transfer.
The voltages across the receiver components may reach
40V, so adequate voltage ratings must also be observed.
It is recommended tousethe components listedinTable 4
and Table 5 for the resonant transmitter and receiver
respectively. Figure 12 illustrates the PCB layout of the
embedded receiver coil. Figures 13 and 14 show the
finished transmitter and receiver. The 25mm ferrite bead
Table 4. Recommended Transmitter and High Voltage Pre-Regulator Components
Transmitter Components
ITEM
DESCRIPTION
MANUFACTURER/PART NUMBER
ON SEMI NSR10F40NXT5G
DIODES BZX84C16
D2, D3
D1, D4
M1, M2
DIODE, SCHOTTKY, 40V, 2A
DIODE, ZENER, 16V, 350mW, SOT23
MOSFET, SMT, N-CHANNEL, 60V, 11mΩ, S08
IND, SMT, 68µH, 0.41A, 0.4Ω, 20%
CAP, CHIP, X7R, 0.01µF, 10%, 50V, 0402
RES, CHIP, 100Ω, 5%, 1/16W, 0402
CAP, CHIP, PPS, 0.15µF, 2%, 50V
CAP, CHIP, PPS, 0.1µF, 2%, 50V
CAP, CHIP, PPS, 0.033µF, 2%, 50V
CAP, PPS, 0.15µF, 2.5%, 63VAC, MKS02
CAP, PPS, 0.10µF, 2.5%, 63VAC, MKS02
CAP, PPS, 0.033µF, 2.5%, 63VAC, MKS02
5.0µH TRANSMIT COIL
VISHAY Si4470EY-T1GE3
TDK VLCF5028T-680MR40-2
MURATA GRM155R71H103KA88D
VISHAY CRCW0402100RJNED
PANASONIC ECHU1H154GX9
PANASONIC ECHU1H104GX9
PANASONIC ECHU1H333GX9
WIMA MKS0D031500D00JSSD
WIMA MKS0D03100
L
, L
B1 B2
C4, C5
R1, R2
C
X1, 2
C (Opt)
X
WIMA MKS0D03033
L
TDK WT-505060-8K2-LT
X
or 6.3µH TRANSMIT COIL
TDK WT-505090-10K2-A11-G
WÜRTH 760308111
or 6.3µH TRANSMIT COIL
or 5.0µH TRANSMIT COIL
INTER-TECHNICAL L41200T02
High Voltage Pre-Regulator Components
U1
LT3480EDD, PMIC 38V, 2A, 2.4MHz Step-Down Switching
LINEAR TECH LT3480EDD
Regulator with 70µA Quiescent Current
MOSFET, SMT, P-CHANNEL, –12V, 32mΩ, SOT23
MOSFET, SMT, N-CHANNEL, 60V, 7.5Ω, 115mA, SOT23
DIODE, SCHOTTKY, 40V, 2A, POWERDI123
IND, SMT, 4.7µH, 1.6A, 0.125Ω, 20%
CAP, CHIP, X5R, 4.7µF, 10%, 50V, 1206
CAP, CHIP, X5R, 4.7µF, 10%, 50V, 0603
CAP, CHIP, COG, 330pF, 5%, 50V, 0402
CAP, CHIP, X7R, 0.47µF, 10%, 25V, 0603
CAP, CHIP, X5R, 22µF, 20%, 6.3V, 0805
RES, CHIP, 150k, 5%, 1/16W, 0402
M3
VISHAY Si2333DS
M4
ON SEMI 2N7002L
D5
DIODES DFLS240L
L3
COILCRAFT LPS4018-472M
MURATA GRM155R71H4755KA12L
MURATA GRM188R71H683K
TDK C1005COG1H331J
C6
C7
C8
C9
MURATA GRM188R71E474K
TAIYO-YUDEN JMK212BJ226MG
VISHAY CRCW0402150JNED
VISHAY CRCW040240K2FKED
VISHAY CRCW040220K0FKED
VISHAY CRCW0402100KFKED
VISHAY CRCW0402536KFKED
C10
R3, R8
R4
RES, CHIP, 40.2k, 1%, 1/16W, 0402
R5
RES, CHIP, 20k, 1%, 1/16W, 0402
R6, R10
RES, CHIP, 100k, 1%, 1/16W, 0402
R7
RES, CHIP, 536k, 1%, 1/16W, 0402
1
C = 300nF with 5µH L coil, or C = 233nF with 6.3µH L coil.
X
X
X
X
2
Pay careful attention to assembly guidelines when using ECHU capacitors, as the capacitance value may shift if the capacitor is over heated while
soldering. Plastic film capacitors such as Panasonic ECHU series or Metallized Polypropylene capacitors such as WIMA MKP as suitable for the
transmitter
4120fe
21
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
Table 5. Recommended Receiver Components
ITEM
DESCRIPTION
MANUFACTURER/PART NUMBER
DIODES DFLS240L
D1, D2, D3
D4 (Opt)
DIODE, SCHOTTKY, 40V, 2A, POWERDI123
DIODE, ZENER, 39V, 5%, 1W, POWERDI123
DIODES DFLZ39
L
IND, EMBEDDED, 47µH, 43 TURNS WITH 25mm FERRITE BEAD EMBEDDED 4-LAYER PCB (see Figure 12)
ADAMS MAGNETICS B67410-A0223-X195
R
or 47µH RECEIVER COIL
TDK WR282840-37K2-LR3
WÜRTH 760308101303
or 47µH RECEIVER COIL
or 48µH RECEIVER COIL
INTER-TECHNICAL L41200R02
COILCRAFT LPS4018-153ML
MURATA GRM21B5C1H472JA01L
KEMET C0603C182J5GAC7533
MURATA GRM21B5C1H223JA01L
MURATA GRM21B5C1H472JA01L
TDK C2012X5R1C106K
L1
IND, SMT, 15µH, 260mΩ, 20%, 0.86A, 4mm × 4mm
CAP, CHIP, COG, 0.0047µF, 5%, 50V, 0805
CAP, CHIP, COG, 0.00018µF, 5%, 50V, 0603
CAP, CHIP, COG, 0.022µF, 5%, 50V, 0805
CAP, CHIP, COG, 0.0047µF, 5%, 50V, 0805
CAP, CHIP, X5R, 10µF, 20%, 16V, 0805
CAP, CHIP, X5R, 47µF, 10%, 16V, 1210
CAP, CHIP, X7R, 0.01µF, 20%, 6.3V. 0402
CAP, CHIP, X5R, 10µF, 20%, 16V, 0805
C2P1
C2P2
C2S1
C2S2
C1
C2
MURATA GRM32ER61C476KE15L
TDK C1608X7R1H103K
C3
C4
TDK C2012X5R1C106K
U1
400mA WIRELESS SYNCHRONOUS BUCK BATTERY CHARGER LINEAR TECH LTC4120
LAYER STRUCTURE
L1 – TOP SIDE
L2
L3
L4 – BOTTOM SIDE
FINISHED THICKNESS TO BE 0.031" 0.00ꢀ"
TOTAL OF 4 LAYERS WITH 2oz CU ON THE
OUTER LAYERS AND 2oz CU ON THE INNER
LAYERS
TOP METAL
2nd METAL
3rd METAL
BOTTOM METAL
4120 F12
Figure 12. 4-Layer PCB Layout of Rx Coil
4120fe
22
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
Figure 13. Tx Layout: Demo Circuit 1968A
in Figure 14 covers the embedded receiver coil described
in Figure 12. Gerber layout files for both the transmitter
and receiver boards are available at the following link:
Figure 14. Rx Layout with Ferrite Shield: Demo Circuit 1967A-B
http://www.linear.com/product/LTC4120#demoboards
Alternative component values can be chosen by following
the design procedure outlined below.
Resonant Receiver Tuning: L , C2S, C2P
R
Thetunedcircuitresonanceofthereceiver,f ,isdetermined
T
by the selection of L and C2S + C2P. Select the capaci-
R
Resonant Transmitter Tuning: L , C
X
X
tors to obtain a resonant frequency 1% to 3% below f :
O
The basic transmitter (shown in Figure 4) has a resonant
frequency, f , that is determined by components L , and
1
fT ≅
O
X
2 • π • L • C2P + C2S
(
)
R
C . The selection of L and C are coupled so as to obtain
X
X
X
the correct operating frequency. The selection of L and
X
Asinthecaseofthetransmitter,multipleparallelcapacitors
may need to be used to obtain the optimum value. Finally,
L is also coupled to ideally obtain a turns ratio of 1:3.
R
Having selected a transmitter inductor, L , the transmitter
X
select the detuned resonance, f to be about 5% to 15%
D
capacitorshouldbeselectedtoobtainaresonantfrequency
of 130kHz. Due to limited selection of standard values,
several standard value capacitors may need to be used
higher than the tuned resonance, keeping the value of
C2P below 30nF to limit power dissipation in the DHC pin:
1
in parallel to obtain the correct value for f :
fD ≅
O
2 • π • LR •C2S
1
fO ≅
= 130kHz
2 • π • LX •CX
Alternative Transmitter Options
Thetransmitterinductorandcapacitor,L andC ,support
The resonant DC/AC transmitter discussed in the previous
section is a basic and inexpensive to build transmitter.
However, this basic transmitter requires a relatively pre-
cise DC input voltage to meet a given set of receive power
requirements. It is unable to prevent power transmission
to foreign metal objects—and can therefore cause these
objects to heat up. Furthermore, the operating frequency
ofthebasictransmittercanvarywithcomponentselection.
4120fe
X
X
alargecirculatingcurrent.Seriesresistanceintheinductor
is a source of loss and should be kept to a minimum for
optimal efficiency. Likewise the transmitter capacitor(s),
C ,mustsupportlargeripplecurrentsandmustbeselected
X
with adequate voltage rating and low dissipation factors.
23
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
LTC4120 customers can also choose more advanced
transmitter options. With additional features such as:
foreign metal detection; operation over a wide input
voltage range; and fixed operating frequency. For more
information on advanced transmitter options refer to the
Wireless Power Users Guide.
When operating from a high input voltage with a low bat-
tery voltage, the PWM control algorithm may attempt to
enforce a duty cycle which requires an on-time lower than
theLTC4120minimum,t
.Thisminimumdutycycle
MIN(ON)
is approximately 18% for 1.5MHz operation or 9% for
750kHz operation. Typical minimum on-time is illustrated
in graph G11 in the Typical Performance Characteristics
Maximum Battery Power Considerations
section. If the on-time is driven below t
, the charge
MIN(ON)
current and battery voltage remain in regulation, but the
switching duty cycle may not remain fixed, and/or the
switching frequency may decrease to an integer fraction
of its programmed value.
Using one of the approved transmitter options with this
wireless power design provides a maximum of 2W at the
input to the LTC4120. It is optimized for supplying 400mA
of charge current to a 4.2V Li-Ion battery. If a higher bat-
tery voltage is selected, then a lower charge current must
be used as the maximum power available is limited. The
The maximum input voltage allowed to maintain constant
frequency operation is:
maximum battery charge current, I
, that may
, can be
CHG(MAX)
V
LOWBAT
be programmed for a given float voltage, V
V
=
FLOAT
IN(MAX)
fOSC • tMIN(ON)
calculated based on the charger efficiency, η , as:
EFF
where V
, is the lowest battery voltage where the
ηEFF • 2W
LOWBAT
switcher is enabled.
ICHG(MAX)
≤
V
FLOAT
Exceedingtheminimumon-timeconstraintdoesnotaffect
charge current or battery float voltage, so it may not be
of critical importance in most cases and high switching
frequencies may be used in the design without any fear of
severeconsequences.AsthesectionsonInductorSelection
and Capacitor Selection show, high switching frequencies
allowtheuseofsmallerboardcomponents, thusreducing
the footprint of the applications circuit.
The charger efficiency, η , depends on the operating
EFF
conditionsandmaybeestimatedusingtheBuckEfficiency
curve in the Typical Performance Characteristics. Do
not select a charge current greater than this limit when
selecting R
.
PROG
Input Voltage and Minimum On-Time
TheLTC4120canoperatefrominputvoltagesupto40V.The
LTC4120 maintains constant frequency operation under
most operating conditions. Under certain situations with
high input voltage and high switching frequency selected
and a low battery voltage, the LTC4120 may not be able
to maintain constant frequency operation. These factors,
combined with the minimum on-time of the LTC4120,
impose a minimum limit on the duty cycle to maintain
fixed-frequency operation. The on-time of the top switch
Fixed-frequency operation may also be influenced by
dropoutandBurstModeoperationasdiscussedpreviously.
Switching Inductor Selection: L
SW
Theprimarycriterionforswitchinginductorvalueselection
in an LTC4120 charger is the ripple current created in that
inductor. Once the inductance value is determined, the
saturation current rating for that inductor must be equal
to or exceed the maximum peak current in the inductor,
is related to the duty cycle (V /V ) and the switching
BAT IN
I
. The peak value of the inductor current is the sum
L(PEAK)
frequency, f
in Hz:
OSC
of the programmed charge current, I , plus one-half of
CHG
V
BAT
the ripple current, ∆I . The peak inductor current must
also remain below the current limit of the LTC4120, I
L
tON
=
fOSC • V
:
IN
PEAK
∆IL
2
IL(PEAK) = ICHG
+
< IPEAK
4120fe
24
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
The current limit of the LTC4120, I
, is at least 585mA
capacitanceisafunctionofthedesiredinputripplevoltage
PEAK
(and at most 1250mA). The typical value of I
is
(∆V ), and follows the relation:
PEAK
IN
illustrated in graph R
Current Limit vs Temperature,
SNS
V
V
BAT
ICHG
in the Typical Performance Characteristics.
IN
CIN(BULK)
=
µF
( )
For a given input and battery voltage, the inductor value
and switching frequency determines the peak-to-peak
ripplecurrentamplitudeaccordingtothefollowingformula:
∆V
IN
Input ripple voltages (∆V ) above 10mV are not recom-
IN
mended. 10µF is typically adequate for most charger
V – V
fOSC • V •L
• V
BAT
(
)
IN
BAT
applications, with a voltage rating of 40V.
∆IL =
IN
SW
Reverse Blocking
Ripple current is typically set to be within a range of 20%
When a fully charged battery is suddenly applied to the BAT
to40%oftheprogrammedchargecurrent, I . Toobtain
CHG
pin,alargein-rushcurrentchargestheC capacitorthrough
IN
a ripple current in this range, select an inductor value us-
ing the nearest standard inductance value available that
obeys the following formula:
thebodydiodeoftheLTC4120topsidepowerswitch.While
the amplitude of this current can exceed several Amps, the
LTC4120 will survive provided the battery voltage is below
the maximum value of 11V. To completely eliminate this
current, a blocking P-channel MOSFET can be placed in
series with the BAT pin. When the battery is the only source
of power, this PFET also serves to decrease battery drain
V
IN(MAX) – V
• V
(
)
FLOAT
FLOAT
LSW
≥
fOSC • V
• 30% •I
(
)
IN(MAX)
CHG
Then select an inductor with a saturation current rating at
a value greater than I
.
current due to any load placed at V . As shown in Figure
L(PEAK)
IN
15, the PFET body diode serves as the blocking component
since CHRG is high impedance when the battery voltage
is greater than the input voltage. When CHRG pulls low,
i.e. during most of a normal charge cycle, the PFET is on
to reduce power dissipation. This PFET requires a forward
current rating equal to the programmed charge current and
areversebreakdownvoltageequaltotheprogrammedfloat
voltage. Figure 15 illustrates how to add a blocking PFET
connected with the LTC4120.
Input Capacitor: C
IN
The LTC4120 charger is biased directly from the input
supply at the V pin. This supply provides large switched
IN
currents, so a high quality, low ESR decoupling capacitor
is recommended to minimize voltage glitches at V . Bulk
IN
4.99k
V
V
IN
CHRG
IN
BST
10µF
22nF
L
SW
RUN
SW
CHGSNS
BAT
49.9k
LTC4120
4.7µF
22µF
+
470k
Li-Ion
SI2343DS
INTV
CC
2.2µF
R
R
FB1
PROG
FB
R
FB2
PROG
FBG
GND
4120 F15
Figure 15. Reverse Blocking with a P-Channel MOSFET in Series with the BAT Pin
4120fe
25
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
BAT Capacitor and Output Ripple: C
INTV supply is enabled, and when INTV rises above
BAT
CC
CC
UV
the charger is enabled.
INTVCC
The LTC4120 charger output requires bypass capacitance
connected from BAT to GND (C ). A 22µF ceramic
BAT
Calculating Power Dissipation
capacitor is required for all applications. In systems
where the battery can be disconnected from the charger
output, additional bypass capacitance may be desired.
In this type of application, excessive ripple and/or low
amplitudeoscillationscanoccurwithoutadditionaloutput
bulkcapacitance.Foroptimumstability,theadditionalbulk
capacitance should also have a small amount of ESR. For
these applications, place a 100µF low ESR non-ceramic
capacitor(chiptantalumororganicsemiconductorcapaci-
tors such as Sanyo OS-CONs or POSCAPs) from BAT to
GND, in parallel with the 22µF ceramic bypass capacitor,
or use large ceramic capacitors with an additional series
ESR resistor of less than 1Ω. This additional bypass
capacitance may also be required in systems where the
battery is connected to the charger with long wires. The
The user should ensure that the maximum rated junction
temperatureisnotexceededunderalloperatingconditions.
The thermal resistance of the LTC4120 package (θ ) is
JA
54°C/W; provided that the exposed pad is soldered to suf-
ficient PCB copper area. The actual thermal resistance in
the application may depend on forced air cooling or other
heat sinking means, and especially the amount of copper
on the PCB to which the LTC4120 is attached. The actual
power dissipation while charging is approximated by the
following formula:
P ≅ V – V
•I
TRKL
(
)
D
IN
BAT
+V •I
IN
IN(SWITCHING)
2
+RSNS •ICHG
voltage rating of all capacitors applied to C must meet
BAT
V
V
BAT
or exceed the battery float voltage.
2
+RDS(ON)(TOP)
•
•ICHG
IN
Boost Supply Capacitor: C
BST
BAT
V
2
+RDS(ON)(BOT) • 1–
•ICHG
The BOOST pin provides a bootstrapped supply rail that
provides power to the top gate drivers. The operating volt-
V
IN
age of the BOOST pin is internally generated from INTV
Duringtricklecharge(V <V
)thepowerdissipation
TRKL
CC
BAT
whenever the SW pin pulls low. This provides a floating
may be significant as I
is typically 10mA, however
TRKL
voltage of INTV above SW that is held by a capacitor tied
during normal charging the I
term is zero.
CC
TRKL
from BOOST to SW. A low ESR ceramic capacitor of 10nF
The junction temperature can be estimated using the fol-
lowing formula:
to 22nF is sufficient for C , with a voltage rating of 6V.
BST
INTV Supply and Capacitor: C
T = T + P • θ
JA
CC
INTVCC
J
A
D
Power for the top and bottom gate drivers and most other
internal circuitry is derived from the INTV pin. A low
where T is the ambient operating temperature.
A
CC
Significant power is also consumed in the transmitter
ESR ceramic capacitor of 2.2µF is required on the INTV
CC
electronics. The large AC voltage generated across the L
X
pin. The INTV supply has a relatively low current limit
CC
and C tank results in power being dissipated in the DC
X
(about 20mA) that is dialed back when INTV is low to
CC
resistance of the L coil and the ESR of the C capacitor.
X
X
reduce power dissipation. Do not use the INTV voltage
CC
The large induced magnetic field in the L coil may also
X
to supply power for any external circuitry apart from the
induce heating in nearby metallic objects.
NTCBIAS network. When the RUN pin is above V the
EN
4120fe
26
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
PCB Layout
7. Route the DHC trace with sufficient copper and vias
to support 350mA of RMS current, and ensure that
the spacing from the DHC node to other copper traces
be maximized to reduce capacitance and radiated EMI
from the DHC node to other sensitive nodes.
To prevent magnetic and electrical field radiation and
high frequency resonant problems, proper layout of the
components connected to the LTC4120 is essential. For
maximum efficiency, the switch node rise and fall times
should be minimized. The following PCB design priority
list will help insure proper topology. Layout the PCB using
the guidelines listed below in this specific order.
8. It is important to minimize parasitic capacitance on
the PROG pin. The trace connecting to this pin should
be as short as possible with extra wide spacing from
adjacent copper traces.
1. Keep foreign metallic objects away from the transmit-
ter coil. Metallic objects in proximity to the transmit
coil will suffer from induction heating and will be a
source of power loss. With the exception of a ferrite
shield that can be used to improve the coupling from
transmitter coil to receiver coil when placed behind
the transmitter coil.
9. Minimize capacitive coupling to GND from the FB pin.
10. Maximize the copper area connected to the exposed
pad. Place via connections directly under the exposed
pad to connect a large copper ground plane to the
LTC4120 to improve heat transfer.
Design Examples
Advanced transmitters from PowerByProxi include
features to detect the presence of foreign metallic
objects that mitigates this issue.
The design example illustrated in Figure 16, reviews the
design of the resonant coupled power transfer charger
application. First the design of the wireless power receiver
circuitisdescribed.Thenconsiderthedesignforthecharger
function given the maximum input voltage, a battery float
voltage of 8.2V, and a charge current of 200mA for the
LTC4120. This example also demonstrates how to select
the switching inductance value to avoid discontinuous
conduction; where switching noise increases.
2. V input capacitor should be placed as close as pos-
IN
sible to the IN and GND pins, with the shortest copper
traces possible and a via connection to the GND plane
3. Place the switching inductor as close as possible to
the SW pin. Minimize the surface area of the SW pin
node. Make the trace width the minimum needed to
support the programmed charge current, and ensure
that the spacing to other copper traces be maximized
to reduce capacitance from the SW node to any other
node.
The wireless power receiver is formed by the tuned net-
work LR and C2P, C2S. This tuned network automatically
modulates the resonance of the tank with the DHC pin of
the LTC4120 to optimize power transfer. The resonant
frequency of the tank should match the oscillation fre-
quency of the transmitter. Given the transmitter shown
in Figure 4 this frequency is 130kHz. The tuned receiver
resonant frequency is:
4. Place the BAT capacitor adjacent to the BAT pin and
ensure that the ground return feeds to the same cop-
per that connects to the input capacitor ground before
connecting back to system ground.
5. Routeanalogground(RUNgroundandINTV capaci-
CC
1
fT =
= 127kHz
tor ground) as a separate trace back to the LTC4120
2 • π • LR •(C2P + C2S)
GND pin before connecting to any other ground.
6. Place the INTV capacitor as close as possible to the
Inthisdesignexample,thede-tunedresonantfrequencyis:
1
CC
INTV pin with a via connection to the GND plane.
CC
fD =
= 142kHz
2 • π • LR •C2S
4120fe
27
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
f should be set between 5% and 15% higher than f . A
this voltage depends primarily on the amount of coupling
between the transmitter and the receiver, typically this
voltage is about 17V.
D
T
higher level gives more control range but results in more
power dissipation.
A 47µH coil is selected for L to obtain a turns ratio of 3:1
The maximum loaded input voltage is used to select the
operatingfrequencyandinfluencesthevalueoftheswitch-
inginductor.Thesaturationcurrentratingoftheswitching
inductor is selected based on the worst case conditions
at the maximum open-circuit voltage.
R
from the transmitter coil, L = 5µH.
X
Now C2S can be calculated to be 26.7nF. Two standard
parallel 50V rated capacitors, 22nF and 4.7nF, provide a
value within 1% of the calculated C2S. Now C2P can be
calculated to be 6.5nF which can be obtained with 4.7nF
and1.8nFcapacitorsinparallel.Allofthecapacitorsshould
be selected with 5% or better tolerance.
Atypical2-cellLi-Ionbatterypackengagespackprotection
for V less than 5V, this is the lowest voltage considered
BAT
for determining the on-time and selecting the 1.5MHz
operating frequency.
The rectifier, D8, D9 and D5 are selected as 50V rated
Schottky diodes.
5V
tON
=
= 476ns > tMIN(ON)
1.5MHz •17V
Now consider the design circuit for the LTC4120 charger
function. First, the external feedback divider, R /R
,
FB1 FB2
Nowthe switching inductorvalueis calculated. Theinduc-
tor value is calculated based on achieving a 30% ripple
current. The ripple current is calculated at the typical input
operating voltage of 17V:
is found using standard 1% values:
8.2V • 588k
2.4V
2.00M• 588k
RFB1
RFB2
=
=
≅ 2.00M
17V – 8.2V • 8.2V
(
)
≅ 825k
L3 >
= 48µH
2.00M– 588k
1.5MHz •17V • 30% • 200mA
(
)
With these resistors, and including the resistance of the
FBG pin, the battery float voltage is 8.212V.
56µHisthenextstandardinductorvaluethatisgreaterthan
this minimum. This inductor value results in a worst-case
ripple current at the input open-circuit voltage, V
.
With an 8.2V float voltage the maximum charge current
available is limited by the maximum power available from
IN(OC)
V
is estimated based on the transmitter design in
IN(OC)
Figure 4, at the largest coupling coefficient k = 0.37 as:
the RCPT at η = 85% charger efficiency:
EFF
V
IN(OC)
V
IN(OC)
= k • n • π • V
IN(TX)
85% • 2W
ICHG(MAX)
≤
= 207mA
8.2V
= 0.37 • 3 • 3.14 • 5V = 34.9V
A charge current of 200mA is achieved by selecting a
34.9V – 8.2V • 8.2V
1.5MHz • 56µH• 34.9V
(
)
∆IL =
= 75mA
standard 1% R resistor of:
PROG
hPROG • V
PROG
RPROG
=
= 6.04k
This results in a worst-case peak inductor current of:
ICHG
∆IL
2
IL(PEAK) = ICHG
+
= 237mA
While charging a battery, the resonant receiver is loaded
by the charge current, this load reduces the input voltage
from the open-circuit value to a typical voltage in a range
from 12V (at UVCL) up to about 26V. The amplitude of
Select an inductor with a saturation current rating greater
than the worst-case peak inductor current of 237mA.
4120fe
28
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
applicaTions inForMaTion
Select a 50V rated capacitor for C = 10µF to achieve an
This dissipated power results in a junction temperature
rise of:
IN
input voltage ripple of 10mV at the typical operating input
voltage of 17V:
P • θ = 0.27W • 54°C/W = 15°C
D
JA
8.2V
During regular charging with V
dissipation reduces to:
> V , the power
TRKL
200mA •
BAT
17V
10µF
∆V =
= 10mV
IN
P = 20V • 5mA
D
And select 6V rated capacitors for C
= 2.2µF,
INTVCC
+0.3Ω • 0.2A2
C
=22nF,andC =22µF.OptionallyadddiodeD6,
BOOST
BAT
a 1W, 39V Zener diode if the coupling from transmitter to
8.2V
20V
+0.8Ω •
• 0.2A2
receiver coils is not well enough controlled to ensure that
V remains below 39V when the battery is fully charged.
IN
8.2V
20V
+0.5Ω • 1–
• 0.2A2
Finally the RUN pin divider is selected to turn on the char-
ger once the input voltage reaches 11.2V. With R3 = 374k
= 0.14mW
and R4 = 102k the RUN pin reaches 2.4V at V = 11.2V.
IN
With this RUN pin divider, the LTC4120 is disabled once
This dissipated power results in a junction temperature
rise of 6°C over ambient.
V falls below 10.5V.
IN
For this design example, power dissipation during trickle
charge,wheretheswitchingchargecurrentis20mAatV
BAT
= 3V and I switching = 5mA, is calculated as follows:
IN
P = 20V – 3V •10mA
(
)
D
+20V • 5mA
+0.3Ω • 0.02A2
3V
20V
+0.8Ω •
• 0.02A2
3V
20V
+0.5Ω • 1–
• 0.02A2
= 0.27W
4120fe
29
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
package DescripTion
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691 Rev Ø)
0.70 ±0.05
3.50 ±0.05
2.10 ±0.05
1.45 ±0.05
(4 SIDES)
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
R = 0.115
TYP
0.75 ±0.05
3.00 ±0.10
(4 SIDES)
15 16
PIN 1
TOP MARK
(NOTE 6)
0.40 ±0.10
1
2
1.45 ± 0.10
(4-SIDES)
(UD16) QFN 0904
0.200 REF
0.25 ±0.05
0.00 – 0.05
0.50 BSC
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
4120fe
30
For more information www.linear.com/LTC4120
LTC4120/LTC4120-4.2
revision hisTory
REV
DATE
12/13
03/14
DESCRIPTION
PAGE
A
Updated Table 4 component values and brands.
20
B
Removed word “battery” from float voltage range bullet.
Modified various specification limits and removed some temp dots.
Modified frequency range, resistor values and Note 3.
1
3
4
Amended I curves.
7
IN
Modified text to reflect typical f
values.
8
OSC
Updated text for V
servo.
9
PROG
Amended equation for f .
14
15
16
17
20
20
D
Modified I
equation.
CHG
Changed description of End-Of-Charge indication.
Modified typical f values.
OSC
Modified Resonant Converter Selection.
Added high voltage pre-regulator schematic.
Added Table 4: Recommended Transmitter and High Voltage Pre-Regulator Components.
Added Table 5: Recommended Receiver Components.
Added Figure 11, PCB Layout of Rx Coil.
Added Figure 12, Tx layout: photo of Demo Circuit 1968A.
Added Figure 13, Rx layout: photo of Demo Circuit 1967A-B
20
20
20
20
20
23
28
29
Modified text of f
and f .
T
OSC
Modified f equation.
T
Modified equation for t , L3, ∆I , and I and changed power dissipation calculations.
L(PEAK)
ON
L
C
05/14
Increased minimum V to 12.5V
1, 3
IN
Added fixed 4.2V float version, throughout document, also added electrical parameters for –4.2
1 to 32
Increased I specification to TYP 25nA
3
FB
Reduced min RECHG threshold to –38mV
3
Modified V
servo voltage spec by +3mV and –3mV
3
PROG
Loosened V
threshold voltage spec by –20mV and +10mV
4
TRKL
Increased TYP V
hysteresis spec to 50mV
4
TRKL
Changed conditions on I specification to IN = Open-Circuit from IN = Float
4
SW
Revised R
current limit typical performance characteristics curve
5
SNS
Added typical V
performance characteristics curve
6
FLOAT
Corrected error in I
Added Block Diagram of –4.2 BATSNS connections
Current curve (x-axis)
8
11
IN(SWITCHING)
Changed V labels to IN in Figure 4, 5, and 10
Remove SW inductor selection Tables 6, 7, 8, and 9
12, 13, 20
N/A
IN
Changed location of BAT decoupling cap in Figure 15 with reverse blocking diode
Corrected error in L3 equation and substituted correct 56µH inductor
25
28
D
E
01/15
05/15
Change CBAT from 10µF to 22µF
1, 9, 10, 11, 14, 25,
26, 29 and 32
Add Würth P/N for RX coil
Add INTER-TECH P/N for TX and RX coils
Remove dos on 68µ bias inductor in basic TX schematic for clarity
22
21, 22
12, 20
Clarified Battery Charge Current vs Temperature curve
Clarified End-of-Charge and Battery Recharge sections
Modified Operation without an Input Supply section
Enhanced Reverse Blocking section
6
16
18
25,26
26
Modified INTV Supply and Capacitor section
CC
4120fe
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.
31
LTC4120/LTC4120-4.2
Typical applicaTion
C2S
26.7nF
D9
IN
INTV
CC
FREQ
BOOST
C
INTVCC
C
IN
D8
D5
2.2µF
10µF
D6
OPT
L
SW
C
BST
2k
2k
56µH
LTC4120
22nF
CHRG
FAULT
RUN
SW
374k
102k
CHGSNS
BAT
V
FLOAT
C2P
6.5nF
8.2V
R
C
22µF
FB1
2.00M
BAT
Tx CIRCUITRY
FB
DHC
10k
R
FB2
825k
L
5µH
L
R
47µH
X
FBG
NTC
GND PROG
+
T
Li-Ion
R
6.04k
PROG
D5, D8, D9: DFLS240L
D6: MMSZ5259BT1G OR DFLZ39 (OPT)
: SLF6028-470MR59
4120 F16
L
SW
T: NTHS0402N02N1002F
Figure 16. Resonant Coupled Power Transfer Charger Application
relaTeD parTs
PART NUMBER DESCRIPTION
COMMENTS
AN138
Wireless Power Users Guide
LT3650-8.2/
LT3650-8.4
Monolithic 2A Switch Mode
Standalone 9V ≤ V ≤ 32V (40V Absolute Maximum), 1MHz, 2A Programmable Charge Current, Timer
IN
Non-Synchronous 2-Cell Li-Ion or C/10 Termination, Small and Few External Components, 3mm × 3mm DFN-12 Package “-8.2” for 2×
Battery Charger
4.1V Float Voltage Batteries, “-8.4” for 2× 4.2V Float Voltage Batteries
LT3650-4.1/
LT3650-4.2
Monolithic 2A Switch Mode
Standalone 4.75V ≤ V ≤ 32V (40V Absolute Maximum), 1MHz, 2A Programmable Charge Current,
IN
Non-Synchronous 1-Cell Li-Ion Timer or C/10 Termination, Small and Few External Components, 3mm × 3mm DFN-12 Package “-4.1”
Battery Charger
for 4.1V Float Voltage Batteries, “-4.2” for 4.2V Float Voltage Batteries
LT3652HV
LTC4070
Power Tracking 2A Battery
Charger
Input Supply Voltage Regulation Loop for Peak Power Tracking in (MPPT) Solar Applications Standalone,
4.95V ≤ V ≤ 34V (40V Absolute Maximum), 1MHz, 2A Charge Current, 3.3V ≤ V
≤ 18V. Timer or
IN
OUT
C/10 Termination, 3mm × 3mm DFN-12 Package and MSOP-12 Packages
Li-Ion/Polymer Shunt Battery Low Operating Current (450nA), 1% Float Voltage Accuracy Over Full Temperature and Shunt Current
Charger System
Range, 50mA Maximum Internal Shunt Current (500mA with External PFET), Pin Selectable Float
Voltages: 4.0V, 4.1V, 4.2V. Ultralow Power Pulsed NTC Float Conditioning for Li-Ion/Polymer Protection,
8-Lead (2mm × 3mm) DFN and MSOP
LTC4071
Li-Ion/Polymer Shunt Battery Integrated Pack Protection, <10nA Low Battery Disconnect Protects Battery From Over-Discharge. Low
Charger System with Low
Battery Disconnect
Operating Current (550nA), 1% Float Voltage Accuracy Over Full Temperature and Shunt Current Range,
50mA Maximum Internal Shunt Current, Pin Selectable Float Voltages: 4.0V, 4.1V, 4.2V. Ultralow Power
Pulsed NTC Float Conditioning for Li-Ion/Polymer Protection, 8-Lead (2mm × 3mm) DFN and MSOP
LTC4065/
LTC4065A
Standalone Li-Ion Battery
Charger in 2mm × 2mm DFN
4.2V 0.6% Float Voltage, Up to 750mA Charge Current ; “A” Version Has /ACPR Function. 2mm × 2mm
DFN Package
4120fe
LT 0515 REV E • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
32
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC4120
●
●
LINEAR TECHNOLOGY CORPORATION 2013
相关型号:
©2020 ICPDF网 联系我们和版权申明