LTC3566 [Linear]
High Effi ciency USB Power Manager Plus 1A Buck-Boost Converter; 高艾菲效率USB电源管理器加上1A降压 - 升压型转换器型号: | LTC3566 |
厂家: | Linear |
描述: | High Effi ciency USB Power Manager Plus 1A Buck-Boost Converter |
文件: | 总28页 (文件大小:262K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC3566
High Efficiency USB
Power Manager Plus 1A
Buck-Boost Converter
FEATURES
DESCRIPTION
POWER MANAGER
The LTC®3566 is a highly integrated power management
and battery charger IC for Li-Ion/Polymer battery applica-
tions.Itincludesahighefficiencycurrentlimitedswitching
PowerPath manager with automatic load prioritization,
a battery charger, an ideal diode, and a high efficiency
synchronous buck-boost switching regulator. Designed
specifically for USB applications, the LTC3566’s switch-
ing power manager automatically limits input current to a
maximumofeither100mAor500mAforUSBapplications
or 1A for adapter-powered applications.
High Efficiency Switching PowerPathTM Controller
■
with Bat-TrackTM Adaptive Output Control
■
Programmable USB or Wall Input Current Limit
(100mA/500mA/1A)
■
Full Featured Li-Ion/Polymer Battery Charger
■
“Instant-On” Operation with Discharged Battery
■
1.5A Maximum Charge Current
■
Internal 180mΩ Ideal Diode Plus External Ideal Diode
Controller Powers Load in Battery Mode
■
Low No-Load I when Powered from BAT (<30μA)
Q
The LTC3566’s switching input stage transmits nearly all of
the 2.5W available from the USB port to the system load
with minimal power wasted as heat. This feature allows the
LTC3566toprovidemorepowertotheapplicationandeases
the constraint of thermal budgeting in small spaces.
1A BUCK-BOOST DC/DC
■
High Efficiency (1A I
)
OUT
■
■
■
■
2.25MHz Constant Frequency Operation
Low No-Load Quiescent Current (~13μA)
Zero Shutdown Current
The synchronous buck-boost DC/DC can provide up to 1A.
Pin Control of All Functions
The LTC3566 is available in a low profile 24-lead
4mm × 4mm QFN surface mount package.
APPLICATIONS
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
PowerPath and Bat-Track are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6522118, 6404251.
■
HDD Based MP3 Players, PDA, GPS, PMP Products
Other USB Based Handheld Products
■
TYPICAL APPLICATION
LTC3566 USB Power Manager with 3.3V/1A Buck-Boost
Switching Regulator Efficiency to
System Load (POUT/PBUS
)
FROM AC
ADAPTER
3.3μH
100
90
80
70
60
50
40
30
20
10
V
=
OUT
V
SW
V
OUT
FROM USB
BAT + 300mV
TO OTHER
DC/DCs
BUS
10μF
4.7μF
CLPROG
PROG
GATE
BAT
3.01k
100k
OPTIONAL
BAT = 4.2V
0.1μF
2k
+
Li-Ion
1μF
3.3V/25mA
ALWAYS
ON LDO
BAT = 3.3V
NTC
LDO3V3
V
IN1
CHRG
CHRGEN
ILIM0
ILIM1
MODE
EN1
100k
LTC3566
T
SWAB1
2.2μH
1.3nF
1μF
SWCD1
3.3V/1A
HDD
V
I
= 5V
V
OUT1
BUS
BAT
DIGITAL CONTROL
= 0mA
324k
10x MODE
10μF
FB1
VC1
0
105k
0.01
0.1
(A)
1
GND
EXPOSED PAD
I
3566 TA01
OUT
3566 TA01b
3566fa
1
LTC3566
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
(Note 1)
TOP VIEW
V
V
(Transient) t < 1ms,
BUS
Duty Cycle < 1% ...................................... –0.3V to 7V
(Static), V , BAT, NTC, CHRG, MODE, I
24 23 22 21 20 19
,
LIM0
BUS
I
IN1
LDO3V3
CLPROG
NTC
1
2
3
4
5
6
18 GATE
, EN1, CHRGEN ................................ –0.3V to 6V
LIM1
17
16
GND
CHRG
FB1, V ..............–0.3V to Lesser of 6V or (V + 0.3V)
C1
IN1
25
FB1
15 PROG
I
I
I
I
I
I
....................................................................3mA
CLPROG
CHRG
PROG
LDO3V3
SW BAT VOUT
VOUT1 SWAB1 SWCD1
V
C1
14
13
I
I
LIM1
LIM0
......................................................................50mA
GND
7
8
9 10 11 12
........................................................................2mA
...................................................................30mA
, I , I
............................................................2A
UF PACKAGE
24-LEAD (4mm × 4mm) PLASTIC QFN
, I
, I
.............................................2.5A
Operating Temperature Range (Note 2).... –40°C to 85°C
Junction Temperature (Note 3) ............................. 125°C
Storage Temperature Range................... –65°C to 125°C
T
= 125°C, θ = 37°C/W
JMAX JA
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
24-Lead (4mm × 4mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
LTC3566EUF#PBF
LTC3566EUF#TRPBF
3566
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/
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, DVCC = 3.3V, RCLPROG = 3.01k, RPROG = 1k,
V
IN1 = VOUT1 = 3.8V unless otherwise noted.
SYMBOL PARAMETER
Power Path Switching Regulator
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Supply Voltage
Total Input Current
4.35
5.5
V
BUS
●
●
●
●
I
1x Mode, V
5x Mode, V
= BAT
= BAT
OUT
87
95
100
500
1000
0.50
mA
mA
mA
mA
BUSLIM
OUT
OUT
436
800
0.31
460
860
0.38
10x Mode, V
= BAT
Suspend Mode, V
= BAT
OUT
I
V
Quiescent Current
1x Mode, I
5x Mode, I
= 0mA
= 0mA
7
15
mA
mA
mA
mA
BUSQ
BUS
OUT
OUT
10x Mode, I
= 0mA
15
OUT
Suspend Mode, I
= 0mA
0.044
OUT
h
Ratio of Measured V
Current to
1x Mode
224
1133
2140
11.3
mA/mA
mA/mA
mA/mA
mA/mA
CLPROG
BUS
(Note 4)
CLPROG Program Current
5x Mode
10x Mode
Suspend Mode
3566fa
2
LTC3566
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, DVCC = 3.3V, RCLPROG = 3.01k, RPROG = 1k,
VIN1 = VOUT1 = 3.8V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
V
Current Available Before
OUT
1x Mode, BAT = 3.3V
5x Mode, BAT = 3.3V
10x Mode, BAT = 3.3V
Suspend Mode
135
672
1251
0.32
mA
mA
mA
mA
OUT
(PowerPath)
Loading BAT
V
V
V
CLPROG Servo Voltage in Current
Limit
1x, 5x, 10x Modes
Suspend Mode
1.188
100
V
CLPROG
mV
V
Undervoltage Lockout
Rising Threshold
Falling Threshold
4.30
4.00
4.35
4.7
V
V
UVLO_VBUS
UVLO_VBUS
BUS
3.95
3.4
V
to BAT Differential
Rising Threshold
Falling Threshold
200
50
mV
mV
BUS
Undervoltage Lockout
Voltage
-VBAT
V
OUT
V
1x, 5x, 10x Modes, 0V < BAT < 4.2V,
BAT + 0.3
V
OUT
I
= 0mA, Battery Charger Off
OUT
USB Suspend Mode, I
= 250μA
4.5
1.8
4.6
4.7
2.7
V
MHz
Ω
OUT
●
f
Switching Frequency
PMOS On-Resistance
NMOS On-Resistance
Peak Switch Current Limit
2.25
0.18
0.30
OSC
R
R
PMOS_PowerPath
NMOS_PowerPath
PEAK_PowerPath
Ω
I
1x, 5x Modes
10x Mode
2
3
A
A
Battery Charger
V
FLOAT
BAT Regulated Output Voltage
4.179
4.165
4.200
4.200
4.221
4.235
V
V
●
I
I
Constant Current Mode Charge
Current
980
185
1022
204
1065
223
mA
mA
CHG
R
= 5k
PROG
Battery Drain Current
V
> V , Battery Charger Off,
UVLO
= 0μA
= 0V, I
2
3.5
5
μA
BAT
BUS
OUT
BUS
I
V
= 0μA (Ideal Diode
OUT
27
38
μA
Mode)
V
V
PROG Pin Servo Voltage
1.000
0.100
V
V
PROG
PROG Pin Servo Voltage in Trickle
Charge
V < V
BAT TRIKL
PROG_TRIKL
V
C/10 Threshold Voltage at PROG
100
1022
100
2.85
135
–100
4
mV
mA/mA
mA
C/10
PROG
TRKL
h
Ratio of I to PROG Pin Current
BAT
I
Trickle Charge Current
BAT < V
TRKL
V
TRIKL
Trickle Charge Threshold Voltage
Trickle Charge Hysteresis Voltage
BAT Rising
2.7
3.0
V
mV
ΔV
TRKL
RECHRG
TERM
V
Recharge Battery Threshold Voltage Threshold Voltage Relative to V
–75
3.3
–125
5
mV
FLOAT
t
t
Safety Timer Termination
Timer Starts When BAT = V
BAT < V
Hour
Hour
mA/mA
FLOAT
Bad Battery Termination Time
0.42
0.088
0.5
0.63
0.112
BADBAT
TRKL
h
C/10
End of Charge Indication Current
Ratio
(Note 5)
0.1
V
I
= 5mA
= 5V
65
100
1
mV
μA
CHRG
CHRG
CHRG Pin Output Low Voltage
CHRG Pin Leakage Current
I
V
CHRG
CHRG
3566fa
3
LTC3566
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, DVCC = 3.3V, RCLPROG = 3.01k, RPROG = 1k,
VIN1 = VOUT1 = 3.8V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
R
Battery Charger Power FET On
0.18
Ω
ON_CHG
Resistance (Between V
and BAT)
OUT
T
LIM
Junction Temperature in Constant
Temperature Mode
110
°C
NTC
V
V
V
Cold Temperature Fault Threshold
Voltage
Rising Threshold
Hysteresis
75.0
33.4
0.7
76.5
1.5
78.0
36.4
2.7
%V
%V
COLD
HOT
DIS
BUS
BUS
Hot Temperature Fault Threshold
Voltage
Falling Threshold
Hysteresis
34.9
1.5
%V
%V
BUS
BUS
NTC Disable Threshold Voltage
Falling Threshold
Hysteresis
1.7
50
%V
BUS
mV
I
NTC Leakage Current
V
NTC
= V = 5V
BUS
–50
50
nA
NTC
Ideal Diode
V
Forward Voltage
V
= 0V, I = 10mA
OUT
= 10mA
2
15
mV
mV
FWD
BUS
OUT
I
R
Internal Diode On-Resistance,
Dropout
V
BUS
= 0V
0.18
Ω
DROPOUT
I
Internal Diode Current Limit
1.6
3.1
A
MAX_DIODE
Always On 3.3V Supply
V
Regulated Output Voltage
Closed-Loop Output Resistance
Dropout Output Resistance
, EN1, CHRGEN, MODE)
Logic Low Input Voltage
Logic High Input Voltage
0mA < I
< 25mA
3.3
4
3.5
V
Ω
Ω
LDO3V3
LDO3V3
R
R
CL_LDO3V3
OL_LDO3V
23
Logic (I
, I
LIM0 LIM1
V
0.4
10
V
V
IL
IH
V
1.2
I
I
I
, I , EN1, MODE
LIM0 LIM1
1.6
1.6
μA
PD1
Pull-Down Currents
CHRGEN Pull-Down Current
μA
PD1_CHRGEN
Buck-Boost Regulator
V
Input Supply Voltage
2.7
2.5
5.5
2.9
2.7
V
IN1
V
V
OUT
V
OUT
UVLO -V
Falling
Rising
V
Connected to V Through
OUT
2.6
2.8
V
V
OUTUVLO
OUT
OUT
IN1
UVLO - V
Low Impedance. Switching Regulator
Disabled in UVLO
●
f
I
Oscillator Frequency
Input Current
PWM Mode
1.8
2.25
MHz
OSC
PWM Mode, I
= 0μA
220
13
0
400
20
1
μA
μA
μA
VIN1
OUT1
Burst Mode® Operation, I
Shutdown
= 0μA
OUT1
Burst Mode is a registered trademark of Linear Technology Corporation.
3566fa
4
LTC3566
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, DVCC = 3.3V, RCLPROG = 3.01k, RPROG = 1k,
VIN1 = VOUT1 = 3.8V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Minimum Regulated Output Voltage For Burst Mode Operation or
Synchronous PWM Operation
2.65
2.75
V
OUT1(LOW)
V
Maximum Regulated Output Voltage
5.50
2
5.60
2.5
V
A
OUT1(HIGH)
LIMF1
●
●
I
I
Forward Current Limit (Switch A)
PWM Mode
3
Forward Burst Current Limit (Switch Burst Mode Operation
A)
200
275
350
mA
PEAK1(BURST)
●
I
I
Reverse Burst Current Limit (Switch Burst Mode Operation
D)
–30
50
0
30
mA
mA
ZERO1(BURST)
MAX1(BURST)
Maximum Deliverable Output Current 2.7V ≤ V ≤ 5.5V, 2.75V ≤ V
≤ 5.5V
IN1
OUT
in Burst Mode Operation
Feedback Servo Voltage
FB1 Input Current
(Note 6)
●
V
0.780
–50
0.800
0.820
50
V
nA
Ω
FB1
I
V
FB1
= 0.8V
FB1
R
R
PMOS R
NMOS R
Switches A, D
Switches B, C
Switches A, D
Switches B, C
0.22
0.17
DS(ON)P
DS(ON)N
LEAK(P)
LEAK(N)
DS(ON)
DS(ON)
Ω
I
I
PMOS Switch Leakage
NMOS Switch Leakage
–1
–1
1
1
μA
μA
kΩ
%
R
V
Pull-Down in Shutdown
OUT1
10
VOUT1
●
D
D
Maximum Buck Duty Cycle
Maximum Boost Duty Cycle
Soft-Start Time
PWM Mode
PWM Mode
100
BUCK(MAX)
75
%
BOOST(MAX)
t
0.5
ms
SS1
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.
temperatures will exceed 125°C when overtemperature protection is
active. Continuous operation above the specified maximum operating
junction temperature may impair device reliability.
Note 4: Total input current is the sum of quiescent current, I
,
VBUSQ
Note 2: The LTC3566E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
and measured current given by:
V
/R
• (h
+ 1)
CLPROG CLPROG
CLPROG
Note 5: h
is expressed as a fraction of measured full charge current
C/10
with indicated PROG resistor.
Note 3: The LTC3566 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
Note 6: Guaranteed by design.
3566fa
5
LTC3566
TA = 25°C unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Ideal Diode Resistance
vs Battery Voltage
Output Voltage vs Output Current
(Battery Charger Disabled)
Ideal Diode V-I Characteristics
1.0
0.8
0.6
0.4
0.2
0
0.25
0.20
0.15
0.10
0.05
0
4.50
4.25
4.00
3.75
3.50
3.25
V
= 5V
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
BUS
BAT = 4V
5x MODE
INTERNAL IDEAL
DIODE
INTERNAL IDEAL
DIODE ONLY
BAT = 3.4V
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
V
V
= 0V
= 5V
BUS
BUS
0
0.04
0.08
0.12
0.16
0.20
2.7
3.0
3.3
3.6
3.9
4.2
0
200
400
600
800
1000
FORWARD VOLTAGE (V)
BATTERY VOLTAGE (V)
OUTPUT CURRENT (mA)
3566 G01
3566 G02
3566 G03
USB Limited Battery Charge
Current vs Battery Voltage
USB Limited Battery Charge
Current vs Battery Voltage
Battery Drain Current
vs Battery Voltage
700
600
150
125
25
20
15
10
5
I
= 0μA
VOUT
V
= 0V
BUS
V
R
R
= 5V
BUS
500
400
300
200
100
0
V
R
R
= 5V
BUS
= 1k
PROG
CLPROG
100
75
= 1k
PROG
CLPROG
= 3.01k
= 3.01k
50
25
0
V
= 5V
BUS
(SUSPEND MODE)
1x USB SETTING,
BATTERY CHARGER SET FOR 1A
5x USB SETTING,
BATTERY CHARGER SET FOR 1A
0
3.0
3.3
3.6
4.2
2.7
3.9
2.7 3.0 3.3 3.6
BATTERY VOLTAGE (V)
3.9
4.2
2.7
3.0
3.3
3.6
3.9
4.2
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
3566 G04
3566 G05
3566 G06
Battery Charging Efficiency vs
Battery Voltage with No External
Load (PBAT/PBUS
PowerPath Switching Regulator
Efficiency vs Output Current
VBUS Quiescent Current vs VBUS
Voltage (Suspend)
)
100
90
80
70
60
50
40
100
90
80
70
60
50
40
30
20
10
0
BAT = 3.8V
R
R
VOUT
= 3.01k
BAT = 3.8V
CLPROG
PROG
5x, 10x MODE
= 1k
I
= 0mA
1x MODE
VOUT
5x CHARGING
EFFICIENCY
I
= 0mA
1x CHARGING
EFFICIENCY
0.01
0.1
1
2.7
3.0
3.3
3.6
3.9
4.2
0
1
2
3
4
5
OUTPUT CURRENT (A)
BATTERY VOLTAGE (V)
V
VOLTAGE (V)
BUS
3566 G07
3566 G08
3566 G09
3566fa
6
LTC3566
TA = 25°C unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage
vs Load Current in Suspend
VBUS Current
vs Load Current in Suspend
3.3V LDO Output Voltage vs Load
Current, VBUS = 0V
5.0
4.5
4.0
3.5
3.0
2.5
3.4
3.2
3.0
2.8
2.6
0.5
0.4
0.3
0.2
0.1
0
BAT = 3.5V
V
= 5V
BAT = 3.9V, 4.2V
BUS
BAT = 3.4V
BAT = 3.6V
BAT = 3.3V
= 3.01k
R
CLPROG
BAT = 3V
BAT = 3.1V
BAT = 3.2V
BAT = 3.3V
V
= 5V
BUS
BAT = 3.3V
= 3k
R
CLPROG
0
0.1
0.2
0.3
0.4
0.5
0
5
10
15
20
25
0
0.1
0.2
0.3
0.4
0.5
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
3566 G10
3566 G12
3566 G11
Battery Charge Current
vs Temperature
Battery Charger Float Voltage
vs Temperature
Low-Battery (Instant-On) Output
Voltage vs Temperature
4.21
4.20
4.19
4.18
4.17
3.68
3.66
3.64
3.62
3.60
600
500
400
300
200
100
0
BAT = 2.7V
I
= 100mA
VOUT
5x MODE
THERMAL REGULATION
R
= 2k
PROG
10x MODE
60 80
20 40
TEMPERATURE (°C)
–40 –20
0
100 120
–40
–15
10
35
60
85
–40
–15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
3566 G13
3566 G14
3566 G15
Oscillator Frequency
vs Temperature
VBUS Quiescent Current
vs Temperature
VBUS Quiescent Current in
Suspend vs Temperature
2.6
2.4
2.2
2.0
1.8
15
12
9
70
60
50
40
30
V
VOUT
= 5V
= 0μA
I
= 0μA
BUS
VOUT
I
5x MODE
BAT = 3.6V
= 0V
V
= 5V
BUS
V
BUS
BAT = 3V
= 0V
1x MODE
V
BUS
6
BAT = 2.7V
= 0V
V
BUS
3
–40
–15
10
35
60
85
–40
–15
35
TEMPERATURE (°C)
60
85
10
–40
–15
35
TEMPERATURE (°C)
60
85
10
TEMPERATURE (°C)
3566 G16
3566 G17
3566 G18
3566fa
7
LTC3566
TA = 25°C unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
CHRG Pin Current vs Voltage
(Pull-Down State)
3.3V LDO Step Response
(5mA to 15mA)
Battery Drain Current vs
Temperature
100
80
60
40
20
0
50
40
30
20
10
0
V
= 5V
BAT = 3.8V
BUS
BUCK REGULATORS OFF
BUS
BAT = 3.8V
V
= 0V
I
LDO3V3
5mA/DIV
0mA
V
LDO3V3
20mV/DIV
AC COUPLED
3566 G2
BAT = 3.8V
20μs/DIV
0
1
2
3
4
5
–40
–15
10
35
60
85
CHRG PIN VOLTAGE (V)
TEMPERATURE (°C)
3566 G19
3566 G21
RDS(ON) for Buck-Boost Regulator
Power Switches vs Temperature
Buck-Boost Regulator Current
Limit vs Temperature
Buck-Boost Regulator Burst Mode
Operation Quiescent Current
0.30
0.25
0.40
0.35
2600
2550
14.0
13.5
V
= 3.3V
V
= 3V
OUT1
IN1
PMOS V = 3V
IN1
PMOS V = 3.6V
IN1
V
= 4.5V
IN1
PMOS V = 4.5V
IN1
V
= 3.6V
= 4.5V
IN1
IN1
0.20
0.30
2500
13.0
V
= 3V
V
IN1
NMOS V = 3V
IN1
0.15
0.10
0.25
0.20
2450
2400
12.5
12.0
NMOS V = 3.6V
V
= 3.6V
IN1
IN1
NMOS V = 4.5V
IN1
0.05
0
0.15
0.10
2350
2300
11.5
11.0
–55 –35 –15
5
25 45 65 85 105 125
–55 –35 –15
5
25 45 65 85 105 125
–55 –35 –15
5
25 45 65 85 105 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3566 G22
3566 G23
3566 G24
Buck-Boost Regulator PWM Mode
Efficiency
Buck-Boost Regulator PWM
Efficiency vs VIN1
Buck-Boost Regulator vs ILOAD
Burst Mode OPERATION
CURVES
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
Burst Mode
OPERATION
CURVES
PWM MODE
CURVES
PWM MODE
CURVES
V
V
V
= 3V
= 3.6V
= 4.5V
I
I
I
= 50mA
IN1
IN1
IN1
LOAD
LOAD
LOAD
V
V
V
= 3V
= 3.6V
= 4.5V
IN1
IN1
IN1
= 200mA
V
V
V
= 3V
= 3.6V
= 4.5V
IN1
IN1
IN1
= 1000mA
V
V
V
= 3V
= 3.6V
= 4.5V
IN1
IN1
IN1
V
T
= 3.3V
V
= 3.3V
V
= 5V
OUT1
A
OUT1
OUT1
= 27°C
T
A
= 27°C
T = 27°C
A
TYPE 3 COMPENSATION
2.7
3.5
3.1 3.9
(V)
TYPE 3 COMPENSATION
TYPE 3 COMPENSATION
10 100 1000
(mA)
0.1
1
10
(mA)
100
1000
4.3
4.7
0.1
1
I
I
LOAD
V
LOAD
IN1
3566 G25
3566 G27
3566 G26
3566fa
8
LTC3566
TA = 25°C unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Buck-Boost Regulator Load
Regulation
Reduction in Current
Buck-Boost Regulator Load Step,
0mA to 300mA
Deliverability at Low VIN1
3.333
3.322
3.311
3.300
3.289
3.278
3.267
300
250
V
V
V
= 3V
= 3.6V
= 4.5V
STEADY STATE I
START-UP WITH A
RESISTIVE LOAD
START-UP WITH A
CURRENT SOURCE LOAD
IN1
IN1
IN1
LOAD
CH1 V
OUT1
AC 100mV/DIV
200
150
CH2 I
LOAD
100
50
0
DC 200mA/DIV
V
= 3.3V
T = 27°C
A
3566 G30
V
A
= 3.3V
OUT1
OUT1
V
V
= 4.2V
100μs/DIV
IN1
OUT1
T
= 27°C
= 3.3V
TYPE 3 COMPENSATION
3.9 4.3 4.7
(V)
TYPE 3 COMPENSATION
L = 2.2μH
= 47μF
C
OUT
1
10
100
1A
2.7
3.1
3.5
V
IN1
I
(mA)
LOAD
3566 G28
3566 G29
PIN FUNCTIONS
LDO3V3 (Pin 1): 3.3V LDO Output Pin. This pin provides
FB1(Pin4):FeedbackInputforthe(Buck-Boost)Switching
Regulator. When the regulator’s control loop is complete,
this pin servos to a fixed voltage of 0.8V.
a regulated, always-on, 3.3V supply voltage. LDO3V3
gets its power from V . It may be used for light loads
OUT
such as a watchdog microprocessor or real time clock.
A 1μF capacitor is required from LDO3V3 to ground. If
the LDO3V3 output is not used it should be disabled by
V (Pin5):OutputoftheErrorAmplifierandVoltageCom-
C1
pensationNodeforthe(Buck-Boost)SwitchingRegulator.
ExternalTypeIorTypeIIIcompensation(toFB1)connects
tothispin.SeeApplicationsInformationsectionforselect-
ing buck-boost loop compensation components.
connecting it to V
.
OUT
CLPROG (Pin 2): USB Current Limit Program and Moni-
tor Pin. A resistor from CLPROG to ground determines
GND (Pins 6, 12): Power GND pins for the buck-boost.
the upper limit of the current drawn from the V
pin.
BUS
SWAB1(Pin7):SwitchNodeforthe(Buck-Boost)Switch-
ing Regulator. Connected to internal power switches A
and B. External inductor connects between this node and
SWCD1.
A fraction of the V
current is sent to the CLPROG pin
BUS
when the synchronous switch of the PowerPath switching
regulator is on. The switching regulator delivers power
until the CLPROG pin reaches 1.188V. Several V
cur-
BUS
rent limit settings are available via user input which will
typically correspond to the 500mA and the 100mA USB
specifications. A multilayer ceramic averaging capacitor
or R-C network is required at CLPROG for filtering.
MODE (Pin 8): Logic Input. Mode enables Burst Mode
functionality for the buck-boost switching regulator when
pin is set high. Has a 1.6μA internal pull-down current
source.
NTC (Pin 3): Input to the Thermistor Monitoring Circuits.
The NTC pin connects to a battery’s thermistor to deter-
mine if the battery is too hot or too cold to charge. If the
battery’s temperature is out of range, charging is paused
until it re-enters the valid range. A low drift bias resistor
V
(Pin 9): Power Input for the (Buck-Boost) Switching
IN1
Regulator. This pin will generally be connected to V
OUT
(Pin 20). A 1μF(min) MLCC capacitor is recommended
on this pin.
V
(Pin 10): Regulated Output Voltage for the (Buck-
OUT1
is required from V
to NTC and a thermistor is required
BUS
Boost) Switching Regulator.
from NTC to ground. If the NTC function is not desired,
the NTC pin should be grounded.
3566fa
9
LTC3566
PIN FUNCTIONS
SWCD1 (Pin 11): Switch Node for the (Buck-Boost)
SwitchingRegulator.Connectedtointernalpowerswitches
C and D. External inductor connects between this node
and SWAB1.
BAT (Pin 19): Single-Cell Li-Ion Battery Pin. Depending on
available V power, a Li-Ion battery on BAT will either
BUS
deliverpowertoV throughtheidealdiodeorbecharged
OUT
from V
via the battery charger.
OUT
ILIM0 (Pin 13): Logic Input. Control pin for ILIM0 bit of
the current limit of the PowerPath switching regulator.
See Table 2. Active high. Has a 1.6μA internal pull-down
current source.
V
(Pin 20): Output Voltage of the Switching Power-
OUT
Path Controller and Input Voltage of the Battery Charger.
The majority of the portable product should be powered
from V . The LTC3566 will partition the available power
OUT
between the external load on V
and the internal battery
OUT
ILIM1 (Pin 14): Logic Input. Control pin for ILIM1 bit of
the current limit of the PowerPath switching regulator.
See Table 2. Active high. Has a 1.6μA internal pull-down
current source.
charger. Priority is given to the external load and any extra
power is used to charge the battery. An ideal diode from
BAT to V
ensures that V
is powered even if the load
OUT
OUT
exceeds the allotted power from V
or if the V
power
BUS
BUS
PROG (Pin 15): Charge Current Program and Charge
Current Monitor Pin. Connecting a resistor from PROG
to ground programs the charge current. If sufficient in-
put power is available in constant-current mode, this pin
servos to 1V. The voltage on this pin always represents
the actual charge current.
source is removed. V
should be bypassed with a low
OUT
impedance ceramic capacitor.
V
(Pin 21): Primary Input Power Pin. This pin delivers
BUS
powertoV viatheSWpinbydrawingcontrolledcurrent
OUT
from a DC source such as a USB port or wall adapter.
SW (Pin 22): Power Transmission Pin for the USB Pow-
CHRG (Pin 16): Open-Drain Charge Status Output. The
CHRG pin indicates the status of the battery charger. Four
possible states are represented by CHRG: charging, not
charging, unresponsive battery and battery temperature
out of range. CHRG is modulated at 35kHz and switches
between a low and high duty cycle for easy recognition
by either humans or microprocessors. See Table 1. CHRG
requires a pull-up resistor and/or LED to provide indica-
tion.
erPath. The SW pin delivers power from V
to V
BUS
OUT
via the step-down switching regulator. A 3.3μH inductor
should be connected from SW to V
.
OUT
CHRGEN (Pin 23): Logic Input. This logic input pin inde-
pendently enables the battery charger. Active low. Has a
1.6μA internal pull-down current source.
EN1(Pin24):LogicInput.Thislogicinputpinindependently
enables the buck-boost switching regulator. Active high.
Has a 1.6μA internal pull-down current source.
GND (Pin 17): GND pin for USB Power Manager.
GATE (Pin 18): Analog Output. This pin controls the gate
ExposedPad(Pin25):Ground. Buck-boostlogicandUSB
Power Manager ground connections. The Exposed Pad
should be connected to a continuous ground plane on the
printed circuit board directly under the LTC3566.
of an optional external P-channel MOSFET transistor used
to supplement the ideal diode between V
and BAT. The
OUT
external ideal diode operates in parallel with the internal
ideal diode. The source of the P-channel MOSFET should
be connected to V
and the drain should be connected
OUT
to BAT. If the external ideal diode FET is not used, GATE
should be left floating.
3566fa
10
LTC3566
BLOCK DIAGRAM
V
BUS
21
SW
2.25MHz PowerPath
BUCK REGULATOR
22
1
LDO3V3
3.3V LDO
V
OUT
SUSPEND LDO
500μA/2.5mA
20
18
+
CLPROG
NTC
–
+
–
GATE
2
3
IDEAL
+
+
BATTERY
TEMPERATURE
MONITOR
–
–
CC/CV
CHARGER
+
15mV
CHRG
BAT
16
1.2V
19
15
3.6V
+–
CHARGE
STATUS
PROG
0.3V
CHRGEN
V
IN1
9
7
ENABLE
MODE
SWAB1
ILIM
DECODE
LOGIC
V
OUT1
10
11
CHRGEN
EN1
1A, 2.25MHz
BUCK-BOOST
REGULATOR
23
24
13
14
8
SWCD1
ILIM0
ILIM1
MODE
FB1
4
5
V
C1
GND
6, 12, 17, 25
3566 BD
3566fa
11
LTC3566
OPERATION
Introduction
If the combined load does not exceed the PowerPath
switchingregulator’sprogrammedinputcurrentlimit,V
will track 0.3V above the battery (Bat-Track). By keeping
the voltage across the battery charger low, efficiency is
optimized because power lost to the linear battery char-
ger is minimized. Power available to the external load is
therefore optimized.
OUT
The LTC3566 is a highly integrated power management IC
which includes a high efficiency switch mode PowerPath
controller, a battery charger, an ideal diode, an always-on
LDO, and a 1A buck-boost switching regulator. The entire
chip is controlled via direct digital inputs.
DesignedspecificallyforUSBapplications,thePowerPath
controller incorporates a precision average input current
step-down switching regulator to make maximum use of
the allowable USB power. Because power is conserved,
the LTC3566 allows the load current on V
the current drawn by the USB port without exceeding the
USB load specifications.
If the combined load at V
is large enough to cause the
OUT
switching power supply to reach the programmed input
current limit, the battery charger will reduce its charge
current by the amount necessary to enable the external
load to be satisfied. Even if the battery charge current is
settoexceedtheallowableUSBcurrent,theUSBspecifica-
tion will not be violated. The switching regulator will limit
the average input current so that the USB specification
to exceed
OUT
The PowerPath switching regulator and battery charger
communicatetoensurethattheinputcurrentneverviolates
the USB specifications.
is never violated. Furthermore, load current at V
will
OUT
always be prioritized and only remaining available power
will be used to charge the battery.
The ideal diode from BAT to V
guarantees that ample
even if there is insuf-
OUT
OUT
power is always available to V
If the voltage at BAT is below 3.3V, or the battery is not
presentandtheloadrequirementdoesnotcausetheswitch-
ficient or absent power at V
.
BUS
ing regulator to exceed the USB specification, V
will
OUT
An “always-on” LDO provides a regulated 3.3V from avail-
regulateat3.6V,therebyproviding“Instant-On”operation.
If the load exceeds the available power, V will drop to
able power at V . Drawing very little quiescent current,
OUT
OUT
this LDO will be on at all times and can be used to supply
a voltage between 3.6V and the battery voltage. If there
up to 25mA.
is no battery present when the load exceeds the available
The LTC3566 also has a general purpose buck-boost
switching regulator, which can be independently enabled
via direct digital control. Along with constant frequency
PWM mode, the buck-boost regulator has a low power
burst-onlymodesettingforsignificantlyreducedquiescent
current under light load conditions.
USB power, V
can drop toward ground.
OUT
The power delivered from V
to V
is controlled
OUT
BUS
by a 2.25MHz constant-frequency step-down switching
regulator. To meet the USB maximum load specification,
the switching regulator includes a control loop which
ensures that the average input current is below the level
programmed at CLPROG.
High Efficiency Switching PowerPath Controller
–1
ThecurrentatCLPROGisafraction(h
)oftheV
BUS
Whenever V
is available and the PowerPath switching
CLPROG
BUS
current. When a programming resistor and an averaging
capacitorareconnectedfromCLPROGtoGND,thevoltage
regulator is enabled, power is delivered from V
to V
BUS
OUT
via SW. V
drives both the external load (including the
OUT
buck-boost regulator) and the battery charger.
3566fa
12
LTC3566
OPERATION
on CLPROG represents the average input current of the
switching regulator. When the input current approaches
the programmed limit, CLPROG reaches V
and power out is held constant.
2200
2000
1800
1600
1400
1200
1000
800
VISHAY Si2333
OPTIONAL EXTERNAL
IDEAL DIODE
, 1.188V
CLPROG
LTC3566
IDEAL DIODE
The input current is programmed by the ILIM0 and ILIM1
pins. It can be configured to limit average input current to
one of several possible settings as well as be deactivated
(USB Suspend). The input current limit will be set by the
600
ON
SEMICONDUCTOR
MBRM120LT3
400
200
V
servo voltage and the resistor on CLPROG ac-
CLPROG
0
cording to the following expression:
0
120 180 240 300 360 420 480
FORWARD VOLTAGE (mV) (BAT – V
60
)
OUT
3566 F02
V
IVBUS =IBUSQ
+
CLPROG •(hCLPROG +1)
RCLPROG
Figure 2. Ideal Diode Operation
consists of a precision amplifier that enables a large on-
chipP-channelMOSFETtransistorwheneverthevoltageat
Figure 1 shows the range of possible voltages at V
as
OUT
a function of battery voltage.
V
is approximately 15mV (V ) below the voltage at
4.5
OUT
FWD
BAT. The resistance of the internal ideal diode is approxi-
mately180mΩ. Ifthisissufficientfortheapplication, then
no external components are necessary. However, if more
conductance is needed, an external P-channel MOSFET
4.2
3.9
NO LOAD
3.6
300mV
transistor can be added from BAT to V
.
OUT
3.3
WhenanexternalP-channelMOSFETtransistorispresent,
the GATE pin of the LTC3566 drives its gate for automatic
ideal diode control. The source of the external P-chan-
3.0
2.7
2.4
nel MOSFET should be connected to V
and the drain
OUT
3.6
4.2
2.4
2.7
3.0
3.3
3.9
should be connected to BAT. Capable of driving a 1nF load,
the GATE pin can control an external P-channel MOSFET
transistor having an on-resistance of 40mΩ or lower.
BAT (V)
3566 F01
Figure 1. VOUT vs BAT
Suspend LDO
Ideal Diode from BAT to V
OUT
If the LTC3566 is configured for USB suspend mode, the
switching regulator is disabled and the suspend LDO
The LTC3566 has an internal ideal diode as well as a con-
troller for an optional external ideal diode. The ideal diode
controller is always on and will respond quickly whenever
provides power to the V
pin (presuming there is power
OUT
available to V ). This LDO will prevent the battery from
BUS
V
drops below BAT.
OUT
running down when the portable product has access to
a suspended USB port. Regulating at 4.6V, this LDO only
becomes active when the switching converter is disabled
(suspended). ToremaincompliantwiththeUSBspecifica-
tion, the input to the LDO is current limited so that it will
not exceed the 500μA low power suspend specification.
If the load current increases beyond the power allowed
from the switching regulator, additional power will be
pulled from the battery via the ideal diode. Furthermore,
if power to V
(USB or wall power) is removed, then all
BUS
of the application power will be provided by the battery via
If the load on V
exceeds the suspend current limit,
the ideal diode. The transition from input power to battery
OUT
the additional current will come from the battery via the
power at V
will be quick enough to allow only a 10μF
OUT
ideal diode.
capacitor to keep V
from drooping. The ideal diode
OUT
3566fa
13
LTC3566
OPERATION
SYSTEM LOAD
3.5V TO
(BAT + 0.3V)
TO USB
OR WALL
ADAPTER
V
BUS
SW
OUT
21
22
20
I
/N
SWITCH
V
PWM AND
GATE DRIVE
IDEAL
DIODE
OPTIONAL
CONSTANT CURRENT
CONSTANT VOLTAGE
BATTERY CHARGER
EXTERNAL
IDEAL DIODE
PMOS
+
–
GATE
BAT
OV
18
19
–
+
15mV
–
+
–
+
+
0.3V
CLPROG
1.188V
2
+
–
3.6V
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
+
SINGLE CELL
Li-Ion
3566 F03
Figure 3. PowerPath Block Diagram
3.3V Always-On Supply
termination by safety timer, low voltage trickle charging,
bad cell detection and thermistor sensor input for out-of-
temperature charge pausing.
TheLTC3566includesalowquiescentcurrentlowdropout
regulator that is always powered. This LDO can be used to
provide power to a system pushbutton controller, standby
microcontroller or real time clock. Designed to deliver up
to 25mA, the always-on LDO requires at least a 1μF low
impedance ceramic bypass capacitor for compensation.
Battery Preconditioning
When a battery charge cycle begins, the battery charger
first determines if the battery is deeply discharged. If the
batteryvoltageisbelowV ,typically2.85V,anautomatic
TRKL
The LDO is powered from V , and therefore will enter
OUT
trickle charge feature sets the battery charge current to
10% of the programmed value. If the low voltage persists
for more than 1/2 hour, the battery charger automatically
terminates and indicates via the CHRG pin that the battery
was unresponsive.
dropout at loads less than 25mA as V
falls near 3.3V.
OUT
If the LDO3V3 output is not used, it should be disabled
by connecting it to V
.
OUT
V
Undervoltage Lockout (UVLO)
BUS
AninternalundervoltagelockoutcircuitmonitorsV and
Oncethebatteryvoltageisabove2.85V,thebatterycharger
begins charging in full power constant-current mode. The
current delivered to the battery will try to reach 1022V/
BUS
keeps the PowerPath switching regulator off until V
BUS
rises above 4.30V and is about 200mV above the battery
voltage. Hysteresis on the UVLO turns off the regulator if
R
. Depending on available input power and external
PROG
V
drops below 4.00V or to within 50mV of BAT. When
load conditions, the battery charger may or may not be
able to charge at the full programmed rate. The external
load will always be prioritized over the battery charge
current. The USB current limit programming will always
be observed and only additional power will be available to
charge the battery. When system loads are light, battery
charge current will be maximized.
BUS
this happens, system power at V
the battery via the ideal diode.
will be drawn from
OUT
Battery Charger
The LTC3566 includes a constant-current/constant-volt-
age battery charger with automatic recharge, automatic
3566fa
14
LTC3566
OPERATION
Charge Termination
Ineithertheconstant-currentorconstant-voltagecharging
modes, the voltage at the PROG pin will be proportional to
the actual charge current delivered to the battery. There-
fore, the actual charge current can be determined at any
time by monitoring the PROG pin voltage and using the
following equation:
The battery charger has a built-in safety timer. When
the voltage on the battery reaches the pre-programmed
float voltage of 4.200V, the battery charger will regulate
the battery voltage and the charge current will decrease
naturally. Once the battery charger detects that the battery
has reached 4.200V, the four hour safety timer is started.
After the safety timer expires, charging of the battery will
discontinue and no more current will be delivered.
V
IBAT
=
PROG •1022
RPROG
In many cases, the actual battery charge current, I , will
BAT
Automatic Recharge
belowerthanI
duetolimitedinputpoweravailableand
CHG
After the battery charger terminates, it will remain off
drawing only microamperes of current from the battery.
If the portable product remains in this state long enough,
the battery will eventually self discharge. To ensure that
the battery is always topped off, a charge cycle will au-
tomatically begin when the battery voltage falls below
4.1V. In the event that the safety timer is running when
the battery voltage falls below 4.1V, it will reset back to
zero. To prevent brief excursions below 4.1V from reset-
ting the safety timer, the battery voltage must be below
4.1V for more than 1.3ms. The charge cycle and safety
prioritization with the system load drawn from V
.
OUT
Charge Status Indication
The CHRG pin indicates the status of the battery charger.
Four possible states are represented by CHRG which
include charging, not charging, unresponsive battery and
battery temperature out of range.
The signal at the CHRG pin can be easily recognized as
one of the above four states by either a human or a mi-
croprocessor. An open drain output, the CHRG pin can
drive an indicator LED through a current limiting resistor
for human interfacing or simply a pull-up resistor for
microprocessor interfacing.
timer will also restart if the V
UVLO cycles low and
BUS
then high (e.g. V , is removed and then replaced) or if
BUS
the battery charger is cycled on and off by the CHRGEN
digital I/O pin.
To make the CHRG pin easily recognized by both humans
and microprocessors, the pin is either low for charging,
high for not charging, or it is switched at high frequency
(35kHz) to indicate the two possible faults, unresponsive
battery and battery temperature out of range.
Charge Current
The charge current is programmed using a single resis-
tor from PROG to ground. 1/1022 of the battery charge
th
current is sent to PROG which will attempt to servo to
1.000V. Thus, the battery charge current will try to reach
1022 times the current in the PROG pin. The program
resistor and the charge current are calculated using the
following equations:
When charging begins, CHRG is pulled low and remains
lowforthedurationofanormalchargecycle.Whencharg-
ing is complete, i.e., the BAT pin reaches 4.200V and the
chargecurrenthasdroppedtoonetenthoftheprogrammed
value, the CHRG pin is released (Hi-Z). If a fault occurs,
the pin is switched at 35kHz. While switching, its duty
cycle is modulated between a high and low value at a very
low frequency. The low and high duty cycles are disparate
1022V
ICHG
1022V
RPROG
RPROG
=
,ICHG =
3566fa
15
LTC3566
OPERATION
enough to make an LED appear to be on or off thus giving
the appearance of “blinking”. Each of the two faults has
its own unique “blink” rate for human recognition as well
as two unique duty cycles for machine recognition.
charge threshold voltage within the bad battery timeout
period. Inthiscase, thebatterychargerwillfalselyindicate
a bad battery. System software may then reduce the load
and reset the battery charger to try again.
The CHRG pin does not respond to the C/10 threshold if
Although very improbable, it is possible that a duty cycle
reading could be taken at the bright-dim transition (low
duty cycle to high duty cycle). When this happens the
duty cycle reading will be precisely 50%. If the duty cycle
reading is 50%, system software should disqualify it and
take a new duty cycle reading.
the LTC3566 is in V
current limit. This prevents false
BUS
end of charge indications due to insufficient power avail-
able to the battery charger.
Table 1 illustrates the four possible states of the CHRG
pin when the battery charger is active.
NTC Thermistor
Table 1. CHRG Output Pin
The battery temperature is measured by placing a nega-
tive temperature coefficient (NTC) thermistor close to the
battery pack.
MODULATION (BLINK)
STATUS
Charging
FREQUENCY
0Hz
FREQUENCY
DUTY CYCLE
100%
0Hz (Lo-Z)
To use this feature connect the NTC thermistor, R , be-
Not Charging
NTC Fault
0Hz
0Hz (Hi-Z)
0%
NTC
, from
tween the NTC pin and ground and a resistor, R
NOM
35kHz
35kHz
1.5Hz at 50%
6.1Hz at 50%
6.25%, 93.75%
12.5%, 87.5%
V
to the NTC pin. R
should be a 1% resistor with
BUS
NOM
Bad Battery
a value equal to the value of the chosen NTC thermistor
at 25°C (R25). A 100k thermistor is recommended since
thermistor current is not measured by the LTC3566 and
will have to be budgeted for USB compliance.
An NTC fault is represented by a 35kHz pulse train whose
duty cycle alternates between 6.25% and 93.75% at a
1.5Hz rate. A human will easily recognize the 1.5Hz rate
as a “slow” blinking which indicates the out-of-range
battery temperature while a microprocessor will be able
to decode either the 6.25% or 93.75% duty cycles as an
NTC fault.
The LTC3566 will pause charging when the resistance of
the NTC thermistor drops to 0.54 times the value of R25
or approximately 54k. For Vishay “Curve 1” thermistor,
this corresponds to approximately 40°C. If the battery
charger is in constant-voltage (float) mode, the safety
timer also pauses until the thermistor indicates a return
to a valid temperature. As the temperature drops, the
resistance of the NTC thermistor rises. The LTC3566 is
also designed to pause charging when the value of the
NTC thermistor increases to 3.25 times the value of R25.
For Vishay “Curve 1” this resistance, 325k, corresponds
to approximately 0°C. The hot and cold comparators each
haveapproximately3°Cofhysteresistopreventoscillation
about the trip point. Grounding the NTC pin disables the
NTC charge pausing function.
If a battery is found to be unresponsive to charging (i.e.,
its voltage remains below 2.85V, for 1/2 hour), the CHRG
pingivesthebatteryfaultindication.Forthisfault,ahuman
would easily recognize the frantic 6.1Hz “fast” blink of the
LEDwhileamicroprocessorwouldbeabletodecodeeither
the 12.5% or 87.5% duty cycles as a bad battery fault.
Note that the LTC3566 is a 3-terminal PowerPath prod-
uct where system load is always prioritized over battery
charging. Due to excessive system load, there may not be
sufficient power to charge the battery beyond the trickle
3566fa
16
LTC3566
OPERATION
Thermal Regulation
Input Current Limit
To optimize charging time, an internal thermal feedback
loop may automatically decrease the programmed charge
current. This will occur if the die temperature rises to
approximately 110°C. Thermal regulation protects the
LTC3566 from excessive temperature due to high power
operation or high ambient thermal conditions and allows
the user to push the limits of the power handling capability
with a given circuit board design without risk of damag-
ing the LTC3566 or external components. The benefit
of the LTC3566 thermal regulation loop is that charge
current can be set according to actual conditions rather
than worst-case conditions with the assurance that the
battery charger will automatically reduce the current in
worst-case conditions.
The input current limit comparator will shut the input
PMOS switch off once current exceeds 2.5A (typical). The
2.5A input current limit also protects against a grounded
V
node.
OUT1
Output Overvoltage Protection
If the FB1 node were inadvertently shorted to ground, then
the output would increase indefinitely with the maximum
current that could be sourced from V . The LTC3566
IN1
protects against this by shutting off the input PMOS if
the output voltage exceeds a 5.6V (typical).
Low Output Voltage Operation
When the output voltage is below 2.65V (typical) during
start-up, Burst Mode operation is disabled and switch D
is turned off (allowing forward current through the well
diode and limiting reverse current to 0mA).
Buck-Boost DC/DC Switching Regulator
TheLTC3566containsa2.25MHzconstant-frequencyvolt-
age mode buck-boost switching regulator. The regulator
provides up to 1A of output load current. The buck-boost
canbeprogrammedtoaminimumoutputvoltageof2.75V
and can be used to power a microcontroller core, micro-
controller I/O, memory, disk drive, or other logic circuitry.
Tosuitavarietyofapplications,aselectablemodefunction
allows the user to trade off noise for efficiency. Two modes
are available to control the operation of the LTC3566’s
buck-boost regulator. At moderate to heavy loads, the
constant frequency PWM mode provides the least noise
switching solution. At lighter loads Burst Mode operation
may be selected. The output voltage is programmed by
a user supplied resistive divider returned to the FB1 pin.
An error amplifier compares the divided output voltage
with a reference and adjusts the compensation voltage
accordingly until the FB1 has stabilized at 0.8V. The buck-
boost regulator also includes a soft-start to limit inrush
current and voltage overshoot when powering on, short
circuit current protection, and switch node slew limiting
circuitry for reduced radiated EMI.
Buck-Boost Regulator PWM Operating Mode
In PWM mode the voltage seen at FB1 is compared to a
0.8V reference. From the FB1 voltage an error amplifier
generates an error signal seen at V . This error signal
C1
commands PWM waveforms that modulate switches A,
B, C and D. Switches A and B operate synchronously as
do switches C and D. If V is significantly greater than
IN1
the programmed V
, then the converter will operate
OUT1
in buck mode. In this mode switches A and B will be
modulated, with switch D always on (and switch C always
off), to step-down the input voltage to the programmed
output. If V is significantly less than the programmed
IN1
V
OUT1
, then the converter will operate in boost mode. In
this mode switches C and D are modulated, with switch A
always on (and switch B always off), to step-up the input
voltage to the programmed output. If V is close to the
IN1
programmed V
, then the converter will operate in
OUT1
4-switchmode.Inthismodetheswitchessequencethrough
the pattern of AD, AC, BD to either step the input voltage
up or down to the programmed output.
3566fa
17
LTC3566
OPERATION
Buck-Boost Regulator Burst Mode Operation
Buck-Boost Regulator Soft-Start Operation
In Burst Mode operation, the buck-boost regulator uses
a hysteretic FB1 voltage algorithm to control the output
voltage. By limiting FET switching and using a hysteretic
control loop, switching losses are greatly reduced. In this
mode output current is limited to 50mA typical. While
operating in Burst Mode operation, the output capacitor
is charged to a voltage slightly higher than the regulation
point. The buck-boost converter then goes into a sleep
state, during which the output capacitor provides the
load current. The output capacitor is charged by charg-
ing the inductor until the input current reaches 275mA
typical and then discharging the inductor until the reverse
current reaches 0mA typical. This process is repeated
until the feedback voltage has charged to 6mV above the
regulation point. In the sleep state, most of the regulator’s
circuitry is powered down, helping to conserve battery
power. When the feedback voltage drops 6mV below the
regulation point, the switching regulator circuitry is pow-
ered on and another burst cycle begins. The duration for
which the regulator sleeps depends on the load current
and output capacitor value. The sleep time decreases as
the load current increases. The maximum load current in
Burst Mode operation is 50mA. The buck-boost regulator
will not go to sleep if the current is greater than 50mA
and if the load current increases beyond this point while
in Burst Mode operation the output will lose regulation.
Burst Mode operation provides a significant improve-
ment in efficiency at light loads at the expense of higher
output ripple when compared to PWM mode. For many
noise-sensitive systems, Burst Mode operation might
be undesirable at certain times (i.e. during a transmit or
receive cycle of a wireless device), but highly desirable
at others (i.e. when the device is in low power standby
mode). The MODE pin is used to enable or disable Burst
Mode operation at any time, offering both low noise and
low power operation when they are needed.
Soft-start is accomplished by gradually increasing the
reference voltage input to the error amplifier over a 0.5ms
(typical)period.Thislimitstransientinrushcurrentsduring
start-up because the output voltage is always “in regula-
tion”. Ramping the reference voltage input also limits the
rate of increase in the V voltage which helps minimize
C1
output overshoot during start-up. A soft-start cycle oc-
curs whenever the buck-boost is enabled, or after a fault
condition has occurred (thermal shutdown or UVLO). A
soft-start cycle is not triggered by changing operating
modes.Thisallowsseamlessoperationwhentransitioning
between Burst Mode operation and PWM mode.
Low Supply Operation
TheLTC3566incorporatesanundervoltagelockoutcircuit
on V
(connected to V ) which shuts down the buck-
OUT
IN1
boost regulator when V
drops below 2.6V. This UVLO
OUT
prevents unstable operation.
Table 2. USB Current Limit Settings
ILIM1
ILIM0
USB SETTING
0
0
1
1
0
1
0
1
1x Mode (USB 100mA Limit)
10x Mode (Wall 1A Limit)
Suspend
5x Mode (USB 500mA Limit)
Table 3. Switching Regulator Modes
MODE
SWITCHING REGULATOR MODE
PWM Mode
0
1
Burst Mode Operation
3566fa
18
LTC3566
APPLICATIONS INFORMATION
CLPROG Resistor and Capacitor
Choosing the PowerPath Inductor
As described in the High Efficiency Switching PowerPath
Controller section, the resistor on the CLPROG pin deter-
mines the average input current limit when the switching
regulator is set to either the 1x mode (USB 100mA), the
5x mode (USB 500mA) or the 10x mode. The input cur-
rent will be comprised of two components, the current
Because the input voltage range and output voltage range
of the PowerPath switching regulator are both fairly nar-
row, the LTC3566 was designed for a specific inductance
value of 3.3μH. Some inductors which may be suitable
for this application are listed in Table 4.
Table 4. Recommended Inductors for PowerPath Controller
that is used to drive V
and the quiescent current of the
OUT
INDUCTOR
TYPE
L
MAX MAX
SIZE IN mm MANUFACTURER
(L × W × H)
switching regulator. To ensure that the USB specification
is strictly met, both components of input current should
be considered. The Electrical Characteristics table gives
values for quiescent currents in either setting as well as
current limit programming accuracy. To get as close to
the 500mA or 100mA specifications as possible, a 1%
(μH) IDC
(A)
DCR
(Ω)
LPS4018
3.3
2.2
0.08
CoilCraft
www.coilcraft.
com
3.9 × 3.9 × 1.7
D53LC
DB318C
3.3 2.26 0.034
3.3 1.55 0.070
Toko
www.toko.com
5.0 × 5.0 × 3.0
3.8 × 3.8 × 1.8
resistor should be used. Recall that I
= I
+
VBUS
VBUSQ
WE-TPC
Type M1
3.3 1.95 0.065
Würth Elektronik
www.we-online.
com
4.8 × 4.8 × 1.8
V
/R
• (h
+ 1).
CLPROG CLPROG
CLPROG
An averaging capacitor or an R-C combination is required
in parallel with the CLPROG resistor so that the switching
regulator can determine the average input current. This
network also provides the dominant pole for the feedback
loop when current limit is reached. To ensure stability, the
capacitor on CLPROG should be 0.1μF or larger.
CDRH6D12 3.3
CDRH6D38 3.3
2.2 0.0625
3.5 0.020
Sumida
www.sumida.com
6.7 × 6.7 × 1.5
7.0 × 7.0 × 4.0
3566fa
19
LTC3566
APPLICATIONS INFORMATION
Buck-Boost Regulator Inductor Selection
Different core materials and shapes will change the
size/current and price/current relationship of an induc-
tor. Toroid or shielded pot cores in ferrite or Permalloy
materials are small and do not radiate much energy, but
generally cost more than powdered iron core inductors
with similar electrical characteristics. Inductors that are
very thin or have a very small volume typically have much
higher core and DCR losses, and will not give the best ef-
ficiency. The choice of which style inductor to use often
depends more on the price vs size, performance and any
radiated EMI requirements than on what the LTC3566
requires to operate.
Many different sizes and shapes of inductors are avail-
able from numerous manufacturers. Choosing the right
inductor from such a large selection of devices can be
overwhelming, but following a few basic guidelines will
make the selection process much simpler.
The buck-boost converter is designed to work with induc-
tors in the range of 1μH to 5μH. For most applications a
2.2μH inductor will suffice. Larger value inductors reduce
ripplecurrentwhichimprovesoutputripplevoltage.Lower
valueinductorsresultinhigherripplecurrentandimproved
transient response time. To maximize efficiency, choose
an inductor with a low DC resistance. For a 3.3V output,
efficiency is reduced about 3% for a 100mΩ series resis-
tance at 1A load current, and about 2% for 300mΩ series
resistance at 200mA load current. Choose an inductor
with a DC current rating at least 2 times larger than the
maximum load current to ensure that the inductor does
notsaturateduringnormaloperation.Ifoutputshortcircuit
is a possible condition, the inductor should be rated to
handle the 2.5A maximum peak current specified for the
buck-boost converter.
The inductor value also has an effect on Burst Mode op-
eration. Lower inductor values will cause the Burst Mode
operation switching frequencies to increase.
Table 5 shows several inductors that work well with the
LTC3566’s buck-boost regulator. These inductors offer a
good compromise in current rating, DCR and physical
size. Consult each manufacturer for detailed information
on their entire selection of inductors.
Table 5. Recommended Inductors for Buck-Boost Regulator
INDUCTOR TYPE
L (μH)
MAX I (A)
MAX DCR (ꢀ)
MANUFACTURER
SIZE IN mm (L × W × H)
DC
LPS4018
3.3
2.2
2.2
2.5
0.08
0.07
Coilcraft
www.coilcraft.com
3.9 × 3.9 × 1.7
3.9 × 3.9 × 1.7
D53LC
2.0
2.2
2.2
2.0
3.25
0.02
0.028
0.044
0.045
Toko
5.0 × 5.0 × 3.0
4.8 × 4.8 × 2.8
4.7 × 4.7 × 2.4
5.2 × 5.2 × 1.45
www.toko.com
7440430022
CDRH4D22/HP
SD14
2.5
Würth Elektronik
www.we-online.com
2.4
Sumida
www.sumida.com
2.56
Cooper
www.cooperet.com
3566fa
20
LTC3566
APPLICATIONS INFORMATION
V
and V
Bypass Capacitors
from the vendor the actual capacitance to determine if the
selected capacitor meets the minimum capacitance that
the application requires.
BUS
OUT
The style and value of capacitors used with the LTC3566
determineseveralimportantparameterssuchasregulator
control-loop stability and input voltage ripple. Because
the LTC3566 uses a step-down switching power supply
Buck-Boost Regulator Input/Output Capacitor
Selection
from V
to V , its input current waveform contains
BUS
OUT
Low ESR MLCC capacitors should be used at both the
high frequency components. It is strongly recommended
buck-boost regulator output (V
) and the buck-boost
that a low equivalent series resistance (ESR) multilayer
OUT1
regulator input supply (V ). Only X5R or X7R ceramic
ceramic capacitor be used to bypass V . Tantalum and
IN1
BUS
capacitors should be used because they retain their ca-
pacitance over wider voltage and temperature ranges than
other ceramic types. A 22μF output capacitor is sufficient
formostapplications.Thebuck-boostregulatorinputsup-
ply should be bypassed with a 2.2μF capacitor. Consult
with capacitor manufacturers for detailed information on
their selection and specifications of ceramic capacitors.
Many manufacturers now offer very thin (<1mm tall)
ceramic capacitors ideal for use in height restricted de-
signs. Table 6 shows a list of several ceramic capacitor
manufacturers.
aluminum capacitors are not recommended because of
their high ESR. The value of the capacitor on V
directly
BUS
controls the amount of input voltage ripple for a given load
current. Increasing the size of this capacitor will reduce
the input voltage ripple.
To prevent large V
voltage steps during transient load
OUT
conditions, it is also recommended that a ceramic capaci-
tor be used to bypass V . The output capacitor is used
OUT
in the compensation of the switching regulator. At least
4μF of actual capacitance with low ESR are required on
V
. Additional capacitance will improve load transient
OUT
performance and stability.
Table 6. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER
AVX
WEBSITE
Multilayer ceramic chip capacitors typically have excep-
tional ESR performance. MLCCs combined with a tight
board layout and an unbroken ground plane will yield very
good performance and low EMI emissions.
www.avxcorp.com
www.murata.com
www.t-yuden.com
www.vishay.com
www.tdk.com
Murata
Taiyo Yuden
Vishay Siliconix
TDK
There are several types of ceramic capacitors available,
each having considerably different characteristics. For
example, X7R ceramic capacitors have the best voltage
and temperature stability. X5R ceramic capacitors have
apparentlyhigherpackingdensitybutpoorerperformance
over their rated voltage and temperature ranges. Y5V
ceramic capacitors have the highest packing density,
but must be used with caution, because of their extreme
nonlinear characteristic of capacitance vs voltage. The
actual in-circuit capacitance of a ceramic capacitor should
be measured with a small AC signal (ideally less than
200mV) as is expected in-circuit. Many vendors specify
Over-Programming the Battery Charger
The USB high power specification allows for up to 2.5W to
bedrawnfromtheUSBport(5Vx500mA).ThePowerPath
switching regulator transforms the voltage at V
to just
BUS
abovethevoltageatBATwithhighefficiency,whilelimiting
power to less than the amount programmed at CLPROG.
In some cases the battery charger may be programmed
(withthePROGpin)todeliverthemaximumsafecharging
current without regard to the USB specifications. If there
is insufficient current available to charge the battery at the
programmed rate, the PowerPath regulator will reduce
the capacitance vs voltage with a 1V
AC test signal and
RMS
as a result overstate the capacitance that the capacitor will
present in the application. Using similar operating condi-
tions as the application, the user must measure or request
charge current until the system load on V
is satisfied
OUT
3566fa
21
LTC3566
APPLICATIONS INFORMATION
and the V
current limit is satisfied. Programming the
R
NOM
= Primary thermistor bias resistor (see Figure 4a)
BUS
battery charger for more current than is available will
not cause the average input current limit to be violated.
It will merely allow the battery charger to make use of
all available power to charge the battery as quickly as
possible, and with minimal power dissipation within the
battery charger.
R1 = Optional temperature range adjustment resistor
(see Figure 4b)
The trip points for the LTC3566’s temperature qualifica-
tion are internally programmed at 0.349 • V
for the hot
BUS
threshold and 0.765 • V
for the cold threshold.
BUS
Therefore, the hot trip point is set when:
Alternate NTC Thermistors and Biasing
RNTC|HOT
The LTC3566 provides temperature qualified charging if
a grounded thermistor and a bias resistor are connected
to NTC. By using a bias resistor whose value is equal to
the room temperature resistance of the thermistor (R25)
the upper and lower temperatures are pre-programmed
to approximately 40°C and 0°C, respectively (assuming
a Vishay “Curve 1” thermistor).
• VBUS = 0.349• VBUS
RNOM +RNTC|HOT
and the cold trip point is set when:
RNTC|COLD
• VBUS = 0.765• VBUS
RNOM +RNTC|COLD
The upper and lower temperature thresholds can be ad-
justed by either a modification of the bias resistor value
or by adding a second adjustment resistor to the circuit.
If only the bias resistor is adjusted, then either the upper
or the lower threshold can be modified but not both. The
other trip point will be determined by the characteristics
of the thermistor. Using the bias resistor in addition to an
adjustmentresistor,boththeupperandthelowertempera-
ture trip points can be independently programmed with
the constraint that the difference between the upper and
lower temperature thresholds cannot decrease. Examples
of each technique follow.
SolvingtheseequationsforR
in the following:
andR
results
NTC|COLD
NTC|HOT
R
= 0.536 • R
NTC|HOT
NOM
and
R
= 3.25 • R
NTC|COLD
NOM
By setting R
equal to R25, the above equations result
NOM
= 0.536 and r
in r
= 3.25. Referencing these ratios
HOT
COLD
to the Vishay Resistance-Temperature Curve 1 chart gives
a hot trip point of about 40°C and a cold trip point of about
0°C. The difference between the hot and cold trip points
is approximately 40°C.
NTC thermistors have temperature characteristics which
areindicatedonresistance-temperatureconversiontables.
TheVishay-DalethermistorNTHS0603N011-N1003F,used
in the following examples, has a nominal value of 100k
and follows the Vishay “Curve 1” resistance-temperature
characteristic.
By using a bias resistor, R
, different in value from
NOM
R25, the hot and cold trip points can be moved in either
direction.Thetemperaturespanwillchangesomewhatdue
to the nonlinear behavior of the thermistor. The following
equations can be used to easily calculate a new value for
the bias resistor:
In the explanation below, the following notation is used.
R25 = Value of the thermistor at 25°C
rHOT
RNOM
=
=
•R25
0.536
r
R
R
= Value of thermistor at the cold trip point
NTC|COLD
RNOM
COLD •R25
3.25
= Value of thermistor at the hot trip point
NTC|HOT
r
r
= Ratio of R
to R25
COLD
NTC|COLD
= Ratio of R
to R25
HOT
NTC|HOT
3566fa
22
LTC3566
APPLICATIONS INFORMATION
where r
and r
are the resistance ratios at the de-
HOT
COLD
3.266−0.4368
RNOM
=
•100k =104.2k
sired hot and cold trip points. Note that these equations
are linked. Therefore, only one of the two trip points can
be chosen, the other is determined by the default ratios
designed in the IC. Consider an example where a 60°C
hot trip point is desired.
2.714
The nearest 1% value is 105k
R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k
The nearest 1% value is 12.7k. The final solution is shown
in Figure 4b and results in an upper trip point of 45°C and
a lower trip point of 0°C.
FromtheVishayCurve1R-Tcharacteristics,r is0.2488
HOT
should be set
at 60°C. Using the above equation, R
NOM
to 46.4k. With this value of R
, the cold trip point is
NOM
about 16°C. Notice that the span is now 44°C rather than
the previous 40°C. This is due to the decrease in “tem-
perature gain” of the thermistor as absolute temperature
increases.
USB Inrush Limiting
When a USB cable is plugged into a portable product,
the inductance of the cable and the high-Q ceramic input
capacitor form an L-C resonant circuit. If the cable does
not have adequate mutual coupling or if there is not much
impedance in the cable, it is possible for the voltage at
the input of the product to reach as high as twice the USB
voltage (~10V) before it settles out. To prevent excessive
voltagefromdamagingtheLTC3566duringahotinsertion,
it is best to have a low voltage coefficient capacitor at the
The upper and lower temperature trip points can be in-
dependently programmed by using an additional bias
resistor as shown in Figure 4b. The following formulas
can be used to compute the values of R
and R1:
NOM
rCOLD −r
RNOM
=
HOT •R25
2.714
R1 = 0.536 • R
V
BUS
pintotheLTC3566. Thisisachievablebyselectingan
MLCC capacitor that has a higher voltage rating than that
requiredfortheapplication. Forexample, a16V, X5R, 10μF
capacitor in a 1206 case would be a more conservative
choice than a 6.3V, X5R, 10μF capacitor in a smaller 0805
– r
• R25
HOT
NOM
For example, to set the trip points to 0°C and 45°C with
a Vishay Curve 1 thermistor choose:
LTC3566
NTC BLOCK
V
V
BUS
LTC3566
NTC BLOCK
V
V
BUS
BUS
BUS
0.765 • V
0.765 • V
BUS
BUS
R
R
NOM
105k
NTC
NOM
–
+
–
+
100k
TOO_COLD
TOO_HOT
TOO_COLD
TOO_HOT
NTC
3
3
R
R1
12.7k
NTC
100k
–
+
–
+
0.349 • V
0.349 • V
BUS
BUS
R
NTC
100k
+
–
+
–
NTC_ENABLE
NTC_ENABLE
0.017 • V
0.017 • V
BUS
BUS
3566 F04a
3566 F04b
(b)
(a)
Figure 4. NTC Circuits
3566fa
23
LTC3566
APPLICATIONS INFORMATION
case. The size of the input overshoot will be determined
Where C
is the output filter capacitor.
OUT
by the “Q” of the resonant tank circuit formed by C and
IN
The output filter zero is given by:
the input lead inductance. It is recommended to measure
the input ringing with the selected components to verify
compliance with the Absolute Maximum specifications.
1
f FILTER _ ZERO
=
Hz
2• π •RESR •COUT
Alternatively, the following soft connect circuit (Figure 5)
can be employed. In this circuit, capacitor C1 holds MP1
off when the cable is first connected. Eventually C1 begins
to charge up to the USB input voltage applying increasing
gate support to MP1. The long time constant of R1 and
C1 prevent the current from building up in the cable too
fast thus dampening out any resonant overshoot.
where R
tance.
is the capacitor equivalent series resis-
ESR
Atroublesomefeatureinboostmodeistheright-halfplane
zero (RHP), and is given by:
2
VIN1
f RHPZ
=
Hz
2•π •IOUT •L • VOUT1
Buck-Boost Regulator Output Voltage Programming
The loop gain is typically rolled off before the RHP zero
frequency.
The buck-boost regulator can be programmed for output
voltages greater than 2.75V and less than 5.5V. The output
voltage is programmed using a resistor divider from the
A simple Type I compensation network (as shown in
Figure 6), can be incorporated to stabilize the loop but
at the cost of reduced bandwidth and slower transient
response. To ensure proper phase margin, the loop must
cross unity-gain a decade before the LC double pole.
V
pin connected to the FB1 pin such that:
OUT1
⎛
⎞
R1
VOUT1= VFB1
+1
⎜
⎟
R
⎝
⎠
FB
The unity-gain frequency of the error amplifier with the
Type I compensation is given by:
where V is fixed at 0.8V (see Figure 6).
FB1
Closing the Feedback Loop
1
f UG
=
Hz
TheLTC3566incorporatesvoltagemodePWMcontrol.The
control to output gain varies with operation region (buck,
boost, buck-boost), but is usually no greater than 20. The
output filter exhibits a double pole response given by:
2• π •R1•CP1
Mostapplicationsdemandanimprovedtransientresponse
toallowasmalleroutputfiltercapacitor.Toachieveahigher
bandwidth, Type III compensation is required. Two zeros
are required to compensate for the double-pole response.
Type III compensation also reduces any V
seen at start-up.
1
f FILTER _POLE
=
Hz
2• π • L •COUT
overshoot
OUT1
The compensation network depicted in Figure 7 yields the
transfer function:
MP1
Si2333
V
BUS
C1
VC1
1
5V USB
INPUT
100nF
=
•
C2
10μF
USB CABLE
LTC3566
VOUT1 R1• C1+C2
(
)
R1
40k
1+sR2C2 • 1+s(R1+R3)C3
(
) (
)
)
GND
sR2C1C2
C1+C2
⎛
⎞
3566 F05
s• 1+
• 1+sR3C3
(
⎜
⎟
⎠
⎝
Figure 5. USB Soft Connect Circuit
3566fa
24
LTC3566
APPLICATIONS INFORMATION
A Type III compensation network attempts to introduce
a phase bump at a higher frequency than the LC double
pole. This allows the system to cross unity gain after the
LC double pole, and achieve a higher bandwidth. While
attempting to cross over after the LC double pole, the
system must still cross over before the boost right-half
plane zero. If unity gain is not reached sufficiently before
the right-half plane zero, then the –180° of phase lag from
the LC double pole combined with the –90° of phase lag
from the right-half plane zero will result in negating the
phase bump of the compensator.
Recommended Type III compensation components for a
3.3V output:
R1: 324kΩ
R : 105kΩ
FB
C1: 10pF
R2: 15kΩ
C2: 330pF
R3: 121kΩ
C3: 33pF
The compensator zeros should be placed either before
or only slightly after the LC double pole such that their
positive phase contributions offset the –180° that occurs
at the filter double pole. If they are placed at too low of a
frequency, theywillintroducetoomuchgaintothesystem
and the crossover frequency will be too high. The two high
frequency poles should be placed such that the system
crosses unity gain during the phase bump introduced by
the zeros and before the boost right-half plane zero and
such that the compensator bandwidth is less than the
bandwidth of the error amp (typically 900 kHz). If the gain
of the compensation network is ever greater than the gain
of the error amplifier, then the error amplifier no longer
acts as an ideal op-amp, another pole will be introduced
and at the same point.
C
: 22μF
OUT
L
: 2.2μH
OUT
Printed Circuit Board Layout Considerations
In order to be able to deliver maximum current under
all conditions, it is critical that the Exposed Pad on the
backside of the LTC3566 package be soldered to the PC
board ground. Failure to make thermal contact between
the Exposed Pad on the backside of the package and the
copper board will result in higher thermal resistances.
Furthermore, duetoitshighfrequencyswitchingcircuitry,
it is imperative that the input capacitors, inductors, and
output capacitors be as close to the LTC3566 as possible
V
OUT1
0.8V
FB1
+
–
V
OUT1
R3
C3
R1
ERROR
AMP
0.8V
FB1
+
–
R1
ERROR
AMP
C2
R
FB
V
C1
R2
C
R
P1
V
FB
C1
3566 F07
C1
3566 F06
Figure 6. Error Amplifier with Type I Compensation
Figure 7. Error Amplifier with Type III Compensation
3566fa
25
LTC3566
APPLICATIONS INFORMATION
1. Are the capacitors at V , V , and V
as close
OUT1
BUS IN1
as possible to the LTC3566? These capacitors provide
the AC current to the internal power MOSFETs and their
drivers. Minimizing inductance from these capacitors to
the LTC3566 is a top priority.
2.AreC andL1closelyconnected?The(-)plateofC
OUT
OUT
returns current to the GND plane, and then back to C .
IN
3566 F08
3. Keep sensitive components away from the SW pins.
Battery Charger Stability Considerations
Figure 8. Higher Frequency Ground Currents Follow Their Incident
Path. Slices in the Ground Plane Cause High Voltage and Increased
Emissions.
The LTC3566’s battery charger contains both a constant-
voltageandaconstant-currentcontrolloop.Theconstant-
voltage loop is stable without any compensation when a
battery is connected with low impedance leads. Excessive
lead length, however, may add enough series inductance
to require a bypass capacitor of at least 1μF from BAT to
GND. Furthermore, when the battery is disconnected, a
4.7μF capacitor in series with a 0.2Ω to 1Ω resistor from
BAT to GND is required to keep ripple voltage low.
and that there be an unbroken ground plane under the
LTC3566andallofitsexternalhighfrequencycomponents.
Highfrequencycurrents,suchastheV ,V ,andV
BUS IN1
OUT1
currents on the LTC3566, tend to find their way along the
ground plane in a myriad of paths ranging from directly
back to a mirror path beneath the incident path on the
top of the board. If there are slits or cuts in the ground
plane due to other traces on that layer, the current will be
forcedtogoaroundtheslits.Ifhighfrequencycurrentsare
not allowed to flow back through their natural least-area
path, excessive voltage will build up and radiated emis-
sions will occur. There should be a group of vias under
the grounded backside of the package leading directly
down to an internal ground plane. To minimize parasitic
inductance, the ground plane should be on the second
layer of the PC board.
High value, low ESR multilayer ceramic chip capacitors
reduce the constant-voltage loop phase margin, possibly
resulting in instability. Ceramic capacitors up to 22μF may
beusedinparallelwithabattery,butlargerceramicsshould
be decoupled with 0.2Ω to 1Ω of series resistance.
In constant-current mode, the PROG pin is in the feed-
back loop rather than the battery voltage. Because of the
additional pole created by any PROG pin capacitance,
capacitance on this pin must be kept to a minimum. With
no additional capacitance on the PROG pin, the battery
charger is stable with program resistor values as high
as 25k. However, additional capacitance on this node
reduces the maximum allowed program resistor. The pole
frequency at the PROG pin should be kept above 100kHz.
Therefore, if the PROG pin has a parasitic capacitance,
The GATE pin for the external ideal diode controller has
extremely limited drive current. Care must be taken to
minimize leakage to adjacent PC board traces. 100nA of
leakage from this pin will introduce an offset to the 15mV
ideal diode of approximately 10mV. To minimize leakage,
the trace can be guarded on the PC board by surrounding
C
, the following equation should be used to calculate
it with V
connected metal, which should generally be
PROG
OUT
the maximum resistance value for R
:
less than one volt higher than GATE.
PROG
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3566.
1
RPROG
≤
2π •100kHz •CPROG
3566fa
26
LTC3566
TYPICAL APPLICATIONS
Direct Pin Controlled LTC3566 USB Power Manager with 3.3V/1A Buck-Boost
L1
3.3μH
TO
OTHER
LOADS
USB
4.5V TO 5.5V
V
SW
OUT
BUS
C1
10μF
C2
22μF
100k
V
LTC3566
NTC
GATE
BAT
OPTIONAL
Li-Ion
1k
+
100k
T
PROG
GND
CLPROG
CHRG
2k
0.1μF 3.01k
V
IN1
2.2μF
33pF
SWAB1
L2
2.2μH
PARTS LIST
C1: MURATA GRM21BR61A/06KE19
C2,C3: TAIYO-YUDEN JMK212BJ226MG
L1: COILCRAFT LPS4018-332MLC
L2: COILCRAFT LPS4018-222MLC
LDO3V3
3.3V/1A
DISK DRIVE
SWCD1
1μF
121k
324k
C3
22μF
V
OUT1
FB1
CHRGEN
330pF
10pF
15k
MODE
EN1
V
C1
TO DIGITAL
CONTROLLER
GND
ILIM
105k
2
3566 TA02
PACKAGE DESCRIPTION
UF Package
24-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1697 Rev B)
BOTTOM VIEW—EXPOSED PAD
R = 0.115
PIN 1 NOTCH
R = 0.20 TYP OR
0.35 s 45o CHAMFER
0.75 p 0.05
4.00 p 0.10
(4 SIDES)
TYP
23 24
0.70 p 0.05
PIN 1
TOP MARK
(NOTE 6)
0.40 p 0.10
1
2
4.50 p 0.05
3.10 p 0.05
2.45 p 0.05
(4 SIDES)
2.45 p 0.10
(4-SIDES)
PACKAGE
OUTLINE
(UF24) QFN 0105
0.25 p 0.05
0.50 BSC
0.200 REF
0.25 p 0.05
0.00 – 0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGD-X)—TO BE APPROVED
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, IF PRESENT
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
3566fa
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.
27
LTC3566
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
V : 2.5V to 5.5V, V : 2.5V to 5.5V
LTC3440
600mA (I ), 2MHz Synchronous Buck-
OUT
IN
OUT
Boost DC/DC Converter
I = 25μA, ISD < 1μA, MS, DFN Package
Q
LTC3441/
LTC3442
1.2A (I ), Synchronous Buck-Boost DC/DC V : 2.5V to 5.5V, V : 2.4V to 5.25V
OUT IN OUT
Converters, LTC3441 (1MHz), LTC3443
I = 25μA, ISD < 1μA, MS, DFN Package
Q
(600kHz)
LTC3442
LTC3455
LTC3538
LTC3550
1.2A (I ), 2MHz Synchronous Buck-Boost V : 2.4V to 5.5V, V : 2.4V to 5.25V
OUT IN OUT
DC/DC Converter
I = 28μA, ISD < 1μA, MS Package
Q
Dual DC/DC Converter with USB Power
Management and Li-Ion Battery Charger
Efficiency >96%, Accurate USB Current Limiting (500mA/100mA),
4mm × 4mm QFN-24 Package
800mA, 2MHz Synchronous Buck-Boost
DC/DC Converter
V : 2.4V to 5.5V, V : 1.8V to 5.25V
IN OUT
Q
I = 35μA, 2mm × 3mm DFN-8 Package
Dual Input USB/AC Adapter Li-Ion Battery
Charger with adjustable output 600mA Buck
Converter
Synchronous Buck Converter, Efficiency: 93%, Adjustable Output at 600mA; Charge
Current: 950mA Programmable, USB Compatible, Automatic Input Power Detection and
Selection, 3mm × 5mm DFN-16 Package
LTC3550-1
LTC3552
Dual Input USB/AC Adapter Li-Ion Battery
Charger with 600mA Buck Converter
Synchronous Buck Converter, Efficiency: 93%, Output: 1.875V at 600mA; Charge
Current: 950mA Programmable, USB Compatible, Automatic Input Power Detection and
Selection, 3mm × 5mm DFN-16 Package
Standalone Linear Li-Ion Battery Charger
with Adjustable Output Dual Synchronous
Buck Converter
Synchronous Buck Converter, Efficiency: >90%, Adjustable Outputs at 800mA and
400mA; Charge Current Programmable Up to 950mA, USB Compatible,
3mm × 5mm DFN-16 Package
LTC3552-1
LTC3555
Standalone Linear Li-Ion Battery Charger
with Dual Synchronous Buck Converter
Synchronous Buck Converter, Efficiency: >90%, Output: 1.8V at 800mA, 1.575V at
400mA; Charge Current Programmable Up to 950mA, USB Compatible,
3mm × 5mm DFN-16 Package
Switching USB Power Manager with Li-Ion/
Polymer Charger, Triple Synchronous Buck
Converter Plus LDO
Complete Multi-Function PMIC: Switchmode Power Manager and Three Buck
Regulators Plus LDO; Charge Current Programmable Up to 1.5A from Wall Adapter
Input, Thermal Regulation, Synchronous Buck Converters Efficiency: >95%, ADJ
Outputs: 0.8V to 3.6V at 400mA/400mA/1A Bat-Track Adaptive Output Control, 200mΩ
Ideal Diode, 4mm × 5mm QFN-28 Package
LTC3556
Switching USB Power Manager with Li-Ion/
Complete Multi-Function PMIC: Switching Power Manager, 1A Buck-Boost + 2 Buck
Polymer Charger, 1A Buck-Boost + Dual Sync Regulators + LDO, ADJ Out Down to 0.8V at 400mA/400mA/1A, Synchronous Buck/
Buck Converter + LDO
Buck-Boost Converter Efficiency: >95%; Charge Current Programmable up to 1.5A from
Wall Adapter Input, Thermal Regulation, Bat-Track Adaptive Output Control, 180mΩ
Ideal Diode, 4mm × 5mm QFN-28 Package
LTC3557/
LTC3557-1
USB Power Manager with Li-Ion/Polymer
Charger, Triple Synchronous Buck Converter
Plus LDO
Complete Multi-Function PMIC: Linear Power Manager and Three Buck Regulators,
Charge Current Programmable Up to 1.5A from Wall Adapter Input, Thermal Regulation,
Synchronous Buck Converters Efficiency: >95%, ADJ Output: 0.8V to 3.6V at 400mA/
400mA/600mA, Bat-Track Adaptive Output Control, 200mΩ Ideal Diode, 4mm × 4mm
QFN-28 Package
LTC3559
Linear USB Li-Ion/Polymer Battery Charger
with Dual Synchronous Buck Converters
Adjustable Synchronous Buck Converters, Efficiency: >90%, Outputs: Down to 0.8V at
400mA for Each, Charge Current Programmable Up to 950mA, USB Compatible,
3mm × 3mm QFN-16 Package
LTC4055
LTC4067
LTC4085
USB Power Controller and Battery Charger
Charges Single-Cell Li-Ion Batteries Directly From USB Port,
Thermal Regulation, 4mm × 4mm QFN-16 Package
Linear USB Power Manager with OVP,
Ideal Diode Controller and Li-Ion Charger
13V Overvoltage Transient Protection, Thermal Regulation 200mΩ Ideal Diode with
<50mΩ Option, 3mm × 4mm QFN-14 Package
Linear USB Power Manager with Ideal Diode Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation,
Controller and Li-Ion Charger
200mΩ Ideal Diode with <50mΩ Option,
3mm × 4mm QFN-14 Package
LTC4088/
LTC4088-1/
LTC4088-2
High Efficiency USB Power Manager and
Battery Charger
Maximizes Available Power from USB Port, Bat-Track, “Instant-On” Operation, 1.5A
Maximum Charge Current, 180mΩ Ideal Diode with <50mΩ Option, 3.3V/25mA Always-
On LDO, 3mm × 4mm DFN-14 Package
LTC4090
High Voltage USB Power Manager with Ideal High Efficiency 1.2A Charger from 6V to 38V (60V Maximum) Input Charges Single Cell
Diode Controller and High Efficiency Li-Ion
Battery Charger
Li-Ion Batteries Directly from a USB Port, Thermal Regulation; 200mΩ Ideal Diode with
<50mΩ option, 3mm × 6mm DFN-22 Package Bat-Track Adaptive Output Control
3566fa
LT 0508 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
28
●
●
© LINEAR TECHNOLOGY CORPORATION 2008
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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