LTC3577/LTC3577-1
Highly Integrated
6-Channel Portable PMIC
DESCRIPTION
FEATURES
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Full Featured Li-Ion/Polymer Charger/PowerPath™
Controller with Instant-On Operation
Triple Adjustable High Efficiency Step-Down
Switching Regulators (800mA, 500mA, 500mA IOUT)
6μA Battery Drain Current in Hard Reset
Bat-Track™ Control for External HV Buck DC/DCs
I2C Adjustable SW Slew Rates for EMI Reduction
High Temperature Battery Voltage Reduction
Improves Safety and Reliability
Overvoltage Protection for USB (VBUS)/Wall Inputs
Provides Protection to 30V
Integrated 40V Series LED Backlight Driver with 60dB
Brightness Control and Gradation via I2C
1.5A Maximum Charge Current with Thermal Limiting
Battery Float Voltage: 4.2V (LTC3577)
4.1V (LTC3577-1)
Pushbutton On/Off Control with System Reset
Dual 150mA Current Limited LDOs
Small 4mm × 7mm 44-Pin QFN Package
APPLICATIONS
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PNDs, DMB/DVB-H; Digital/Satellite Radio;
Media Players
Portable Industrial/Medical Products
Universal Remotes, Photo Viewers
Other USB-Based Handheld Products
The LTC®3577 is a highly integrated power management
IC for single cell Li-Ion/Polymer battery applications. It
includes a PowerPath manager with automatic load prioritization, a battery charger, an ideal diode, input overvoltage
protection and numerous other internal protection features.
The LTC3577 is designed to accurately charge from current
limited supplies such as USB by automatically reducing
charge current such that the sum of the load current and
the charge current does not exceed the programmed input
current limit (100mA or 500mA modes). The LTC3577
reduces the battery voltage at elevated temperatures to
improve safety and reliability. Efficient high current charging from supplies up to 38V is available using the on-chip
Bat-Track controller. The LTC3577 also includes a pushbutton input to control the three synchronous step-down
switching regulators and system reset. The onboard LED
backlight boost circuitry can drive up to 10 series LEDs
and includes versatile digital dimming via I2C input. The
I2C input also controls two 150mA LDOs as well as other
operating modes and status read back. The LTC3577 is
available in a low profile 4mm × 7mm × 0.75mm 44-pin
QFN package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
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,
6700364, 7511390, 5481178, 6580258. Other Patents Pending.
TYPICAL APPLICATION
HV SUPPLY
8V TO 38V
(TRANSIENTS TO 60V)
HIGH VOLTAGE
BUCK DC/DC
LED Driver Efficiency (10 LEDs)
OPTIONAL
90
100mA/500mA
1000mA
USB
80
70
CC/CV
CHARGER
LTC3577/LTC3577-1
CHARGE
2
I
2C PORT
+
NTC
0.8V to 3.6V/150mA
0.8V to 3.6V/150mA
DUAL LDO
REGULATORS
UP TO 10 LED
BOOST
LED BACKLIGHT WITH DIGITALLY
CONTROLLED DIMMING
PB
TRIPLE HIGH EFFICIENCY
STEP-DOWN SWITCHING
REGULATORS WITH
PUSHBUTTON CONTROL
SINGLE CELL
Li-Ion
0.8V to 3.6V/800mA
0.8V to 3.6V/500mA
0.8V to 3.6V/500mA
3577 TA01a
EFFICIENCY (%)
VOUT
0V
OVERVOLTAGE
PROTECTION
60
MAX PWM
50
CONSTANT
CURRENT
40
30
20
10
0
1.E-06
1.E-05
1.E-04 1.E-03 1.E-02
LED CURRENT (A)
1.E-01
3577 TA01b
3577fa
1
LTC3577/LTC3577-1
TABLE OF CONTENTS
Features ............................................................................................................................ 1
Applications ....................................................................................................................... 1
Typical Application ............................................................................................................... 1
Description......................................................................................................................... 1
Absolute Maximum Ratings ..................................................................................................... 3
Order Information ................................................................................................................. 3
Pin Configuration ................................................................................................................. 3
Electrical Characteristics ........................................................................................................ 4
Typical Performance Characteristics .........................................................................................10
Pin Functions .....................................................................................................................16
Block Diagram....................................................................................................................19
PowerPath Operation ............................................................................................................................................ 20
Low Dropout Linear Regulator Operation ............................................................................................................. 30
Step-Down Switching Regulator Operation........................................................................................................... 31
LED Backlight/Boost Operation ............................................................................................................................. 35
I2C Operation ........................................................................................................................................................ 38
Pushbutton Interface Operation ............................................................................................................................ 43
Layout and Thermal Considerations ..................................................................................................................... 48
Typical Applications .............................................................................................................50
Package Description ............................................................................................................52
Related Parts .....................................................................................................................53
Revision History .................................................................................................................54
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LTC3577/LTC3577-1
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2, 3)
44 CHRG
43 CLPROG
42 VC
41 ACPR
40 VBUS
39 VOUT
38 BAT
TOP VIEW
ILIM0 1
ILIM1 2
LED_FS 3
WALL 4
SW3 5
VIN3 6
FB3 7
OVSENS 8
LED_OV 9
DVCC 10
SDA 11
SCL 12
OVGATE 13
PWR_ON 14
ON 15
45
GND
37 IDGATE
36 PROG
35 NTC
34 NTCBIAS
33 SW1
32 VIN12
31 SW2
30 VINLD02
29 LDO2
28 LDO1
27 LDO1_FB
26 FB1
25 FB2
24 LDO2_FB
23 VINLDO1
PBSTAT 16
WAKE 17
SW 18
SW 19
SW 20
PG_DCDC 21
ILED 22
VSW ............................................................ –0.3V to 45V
VBUS, VOUT , VIN12, VIN3, VINLDO1, VINLDO2, WALL
t < 1ms and Duty Cycle < 1% ................... –0.3V to 7V
Steady State ............................................ –0.3V to 6V
CHRG, BAT, LED_FS, LED_OV, PWR_ON, WAKE,
PBSTAT, PG_DCDC, FB1, FB2, FB3, LDO1, LDO1_FB,
LDO2, LDO2_FB, DVCC, SCL, SDA ............... –0.3V to 6V
NTC, PROG, CLPROG, ON, ILIM0, ILIM1
(Note 4)........................................... –0.3V to VCC + 0.3V
IVBUS, IVOUT , IBAT, Continuous (Note 16) .....................2A
ISW3, Continuous (Note 16)................................. 850mA
ISW2, ISW1, Continuous (Note 16)........................ 600mA
ILDO1, ILDO2, Continuous (Note 16) ..................... 200mA
ICHRG , IACPR , IWAKE, IPBSTAT, IPG_DCDC ...................75mA
IOVSENS ..................................................................10mA
ICLPROG, IPROG, ILED_FS, ILED_OV ..............................2mA
Junction Temperature ............................................110°C
Operating Temperature Range .................–40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
UFF PACKAGE
44-LEAD (7mm s 4mm) PLASTIC QFN
TJMAX = 110°C, θJA = 45°C/W
EXPOSED PAD (PIN 45) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3577EUFF#PBF
LTC3577EUFF#TRPBF
3577
44-Lead (4mm × 7mm) Plastic QFN
–40°C to 85°C
LTC3577EUFF-1#PBF
LTC3577EUFF-1#TRPBF
35771
44-Lead (4mm × 7mm) Plastic QFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
3577fa
3
LTC3577/LTC3577-1
ELECTRICAL CHARACTERISTICS
Power Manager. The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, ILIM0 = ILIM1 = WALL = 0V,
VINLDO1 = VINLDO2 = VIN12 = VIN3 = VOUT, RPROG = 2k, RCLPROG = 2.1k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
90
475
950
100
500
1000
mA
mA
mA
0.42
0.042
0.1
mA
mA
Input Power Supply
VBUS
Input Supply Voltage
IBUS(LIM)
Total Input Current (Note 5)
ILIM0 = 0V, ILIM1 = 0V (1x Mode)
ILIM0 = 5V, ILIM1 = 5V (5x Mode)
ILIM0 = 5V, ILIM1 = 0V (10x Mode)
4.35
IBUSQ
Input Quiescent Current, POFF State
1x, 5x, 10x Modes
ILIM0 = 0V, ILIM1 = 5V (Suspend Mode)
hCLPROG
Ratio of Measured VBUS Current to
CLPROG Program Current
VCLPROG
CLPROG Servo Voltage in Current
Limit
1x Mode
5x Mode
10x Mode
VUVLO
VBUS Undervoltage Lockout
Rising Threshold
Falling Threshold
l
l
l
80
450
900
5.5
1000
mA/mA
0.2
1.0
2.0
3.5
V
V
V
V
3.8
3.7
3.9
V
V
100
mV
mV
VDUVLO
VBUS to VOUT Differential Undervoltage Rising Threshold
Lockout
Falling Threshold
50
–50
RON_ILIM
Input Current Limit Power FET OnResistance (Between VBUS and VOUT)
200
mΩ
Battery Charger
VFLOAT
VBAT Regulated Output Voltage
ICHG
Constant-Current Mode Charge Current RPROG = 1k, Input Current Limit = 2A
RPROG = 2k, Input Current Limit = 1A
RPROG = 5k, Input Current Limit = 0.4A
IBATQ_HR
Battery Drain Current, Hard Reset
VBUS = 0V, IOUT = 0μA
7
15
μA
IBATQ_OFF
Battery Drain Current, POFF State
VBAT = 4.3V, Charger Time Out
VBUS = 0V
6
40
27
100
μA
μA
IBATQ_ON
Battery Drain Current, PON State
LDOs, and LED Backlight Disabled
VBUS = 0V, IOUT = 0μA, No Load on
Supplies, Burst Mode Operation (Note 10)
90
160
μA
VPROG,CHG
PROG Pin Servo Voltage
VBAT > VTRKL
1.000
V
VBAT < VTRKL
0.100
V
1000
mA/mA
VPROG,TRKL PROG Pin Servo Voltage in Trickle
Charge
LTC3577
LTC3577, 0 ≤ TA ≤ 85°C
LTC3577-1
LTC3577-1, 0 ≤ TA ≤ 85°C
l
l
l
4.179
4.165
4.079
4.065
4.200
4.200
4.100
4.100
4.221
4.235
4.121
4.135
V
V
V
V
950
465
180
1000
500
200
1050
535
220
mA
mA
mA
hPROG
Ratio of IBAT to PROG Pin Current
ITRKL
Trickle Charge Current
VBAT < VTRKL
40
50
60
mA
VTRKL
Trickle Charge Rising Threshold
Trickle Charge Falling Threshold
VBAT Rising
VBAT Falling
3.0
2.5
2.85
2.75
V
V
ΔVRECHRG
Recharge Battery Threshold Voltage
Threshold Voltage Relative to VFLOAT
–75
–100
–125
mV
tTERM
Safety Timer Termination Period
Timer Starts When VBAT = VFLOAT – 50mV
3.2
4
4.8
Hour
tBADBAT
Bad Battery Termination Time
VBAT < VTRKL
0.4
0.5
0.6
Hour
hC/10
End-of-Charge Indication Current Ratio (Note 6)
0.085
0.1
0.11
mA/mA
RON_CHG
Battery Charger Power FET OnResistance (Between VOUT and BAT)
200
mΩ
TLIM
Junction Temperature in Constant
Temperature Mode
110
°C
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LTC3577/LTC3577-1
ELECTRICAL CHARACTERISTICS
Power Manager. The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, ILIM0 = ILIM1 = WALL = 0V,
VINLDO1 = VINLDO2 = VIN12 = VIN3 = VOUT, RPROG = 2k, RCLPROG = 2.1k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
NTC, Battery Discharge Protection
VCOLD
Cold Temperature Fault Threshold
Voltage
Rising NTC Voltage
Hysteresis
75
76
1.3
77
%VNTCBIAS
%VNTCBIAS
VHOT
Hot Temperature Fault Threshold
Voltage
Falling NTC Voltage
Hysteresis
34
35
1.3
36
%VNTCBIAS
%VNTCBIAS
V2HOT
NTC Discharge Threshold Voltage
Falling NTC Voltage
Hysteresis
24.5
25.5
50
26.5
%VNTCBIAS
mV
INTC
NTC Leakage Current
VNTC = VBUS = 5V
–50
IBAT2HOT
BAT Discharge Current
VBAT = 4.1V, NTC < VTOO_HOT
180
mA
VBAT2HOT
BAT Discharge Threshold
IBAT < 0.1mA, NTC < VTOO_HOT
3.9
V
VFWD
Forward Voltage Detection
IOUT = 10mA
RDROPOUT
Diode On-Resistance, Dropout
IOUT = 200mA
200
mΩ
IMAX
Diode Current Limit
(Note 7)
3.6
A
50
nA
Ideal Diode
5
15
25
mV
Overvoltage Protection
VOVCUTOFF
Overvoltage Protection Threshold
Rising Threshold, ROVSENS = 6.2k
6.10
6.35
6.70
V
VOVGATE
OVGATE Output Voltage
Input Below VOVCUTOFF
Input Above VOVCUTOFF
1.88 • VOVSENS
0
12
V
V
IOVSENSQ
OVSENS Quiescent Current
VOVSENS = 5V
40
μA
tRISE
OVGATE Time to Reach Regulation
COVGATE = 1nF
2.5
ms
ACPR Pin Output High Voltage
ACPR Pin Output Low Voltage
IACPR = 0.1mA
IACPR = 1mA
Absolute Wall Input Threshold Voltage
VWALL Rising
VWALL Falling
Wall Adapter
VACPR
VW
ΔVW
Differential Wall Input Threshold
Voltage
VWALL – VBAT Falling
VWALL – VBAT Rising
IQWALL
Wall Operating Quiescent Current
IWALL + IVOUT , IBAT = 0mA,
WALL = VOUT = 5V
VOUT – 0.3
3.1
0
VOUT
0
4.3
3.2
25
75
0.3
4.45
100
440
V
V
V
V
mV
mV
μA
Logic (ILIM0, ILIM1 and CHRG)
VIL
Input Low Voltage
ILIM0, ILIM1
VIH
Input High Voltage
ILIM0, ILIM1
IPD
Static Pull-Down Current
ILIM0, ILIM1; VPIN = 1V
VCHRG
CHRG Pin Output Low Voltage
ICHRG = 10mA
ICHRG
CHRG Pin Input Current
VBAT = 4.5V, VCHRG = 5V
0.4
1.2
V
V
2
μA
0.15
0.4
V
0
1
μA
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LTC3577/LTC3577-1
ELECTRICAL CHARACTERISTICS
I2C Interface. The l denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. DVCC = 3.3V, VOUT = 3.8V, unless otherwise noted.
SYMBOL
PARAMETER
DVCC
Input Supply Voltage
IDVCC
DVCC Supply Current
VDVCC,UVLO
DVCC UVLO
CONDITIONS
MIN
TYP
1.6
SCL = 400kHz
SCL = SDA = 0kHz
MAX
UNITS
5.5
V
1
0.4
μA
μA
1.0
V
VIH
Input HIGH Voltage
VIL
Input LOW Voltage
50
IIH
Input HIGH Leakage Current
SDA = SCL = DVCC = 5.5V
–1
1
μA
IIL
Input LOW Leakage Current
SDA = SCL = 0V, DVCC = 5.5V
–1
1
μA
VOL
SDA Output LOW Voltage
ISDA = 3mA
0.4
V
400
kHz
30
70
50
%DVCC
%DVCC
Timing Characteristics (Note 8) (All Values are Referenced to VIH and VIL)
fSCL
SCL Clock Frequency
tLOW
LOW Period of the SCL Clock
1.3
μs
tHIGH
HIGH Period of the SCL Clock
0.6
μs
tBUF
Bus Free Time Between Stop and Start Condition
1.3
μs
tHD,STA
Hold Time After (Repeated) Start Condition
0.6
μs
tSU,STA
Setup Time for a Repeated Start Condition
0.6
μs
tSU,STO
Stop Condition Setup Time
0.6
μs
tHD,DATO
Output Data Hold Time
0
tHD,DATI
Input Data Hold Time
0
tSU,DAT
Data Setup Time
tSP
Input Spike Suppression Pulse Width
900
ns
ns
100
ns
50
ns
Step-Down Switching Regulators. The l denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at TA = 25°C. VOUT = VIN12 = VIN3 = 3.8V, all regulators enabled unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Step-Down Switching Regulators (Buck1, Buck2 and Buck3)
VIN12, VIN3
Input Supply Voltage
(Note 9)
VOUT UVLO
VOUT Falling
VOUT Rising
VIN12 and VIN3 Connected to VOUT Through
Low Impedance. Switching Regulators are
Disabled Below VOUT UVLO
fOSC
l
2.7
2.5
Oscillator Frequency
1.91
5.5
2.7
V
V
2.8
2.9
V
2.25
2.59
MHz
800mA Step-Down Switching Regulator 3 (Buck3 – Pushbutton Enabled, Third in Sequence)
IVIN3Q
Pulse-Skipping Mode Input Current
(Note 10)
Burst Mode Operation Input Current
(Note 10)
100
Shutdown Input Current
μA
17
μA
0.01
μA
ILIM3
Peak PMOS Current Limit
(Note 7)
VFB3
Feedback Voltage
Pulse-Skipping Mode
Burst Mode Operation
IFB3
FB3 Input Current
(Note 10)
–0.05
D3
Max Duty Cycle
FB3 = 0V
100
RP3
RDS(ON) of PMOS
0.3
Ω
RN3
RDS(ON) of NMOS
0.4
Ω
l
l
1000
1400
1700
mA
0.78
0.78
0.8
0.8
0.82
0.824
V
V
0.05
μA
%
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LTC3577/LTC3577-1
ELECTRICAL CHARACTERISTICS
Step-Down Switching Regulators. The l denotes the specifications
which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VOUT = VIN12 = VIN3 = 3.8V,
all regulators enabled unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
RSW3_PD
SW3 Pull-Down in Shutdown
POFF State
MIN
TYP
MAX
UNITS
10
kΩ
100
μA
500mA Step-Down Switching Regulator 2 (Buck2 – Pushbutton Enabled, Second in Sequence)
IVIN12Q
Pulse-Skipping Mode Input Current
(Note 10)
Burst Mode Operation Input Current
(Note 10)
Shutdown Input Current
ILIM2
Peak PMOS Current Limit
(Note 7)
Pulse-Skipping Mode
Burst Mode Operation
l
l
17
μA
0.01
μA
650
900
1200
mA
0.78
0.78
0.8
0.8
0.82
0.824
V
V
0.05
μA
VFB2
Feedback Voltage
IFB2
FB2 Input Current
(Note 10)
–0.05
D2
Max Duty Cycle
FB2 = 0V
100
RP2
RDS(ON) of PMOS
ISW2 = 100mA
0.6
RN2
RDS(ON) of NMOS
ISW2 = –100mA
0.6
Ω
RSW2_PD
SW2 Pull-Down in Shutdown
POFF State
10
kΩ
%
Ω
500mA Step-Down Switching Regulator 1 (Buck1 – Pushbutton Enabled, First in Sequence)
IVIN12Q
Pulse-Skipping Mode Input Current
(Note 10)
100
μA
Burst Mode Operation Input Current
(Note 10)
17
μA
Shutdown Input Current
0.01
μA
ILIM1
Peak PMOS Current Limit
(Note 7)
VFB1
Feedback Voltage
Pulse-Skipping Mode
Burst Mode Operation
IFB1
FB1 Input Current
(Note 10)
–0.05
D1
Max Duty Cycle
FB1 = 0V
100
RP1
RDS(ON) of PMOS
ISW1 = 100mA
0.6
RN1
RDS(ON) of NMOS
ISW1 = –100mA
0.6
Ω
RSW1_PD
SW1 Pull-Down in Shutdown
POFF State
10
kΩ
l
l
650
900
1200
mA
0.78
0.78
0.8
0.8
0.82
0.824
V
V
0.05
μA
%
Ω
LDO Regulators. The l denotes the specifications which apply over the full operating temperature range, otherwise specifications
are at TA = 25°C. VINLDO1 = VINLDO2 = VOUT = VBAT = 3.8V, LDO1 and LDO2 enabled unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
LDO Regulator 1 (LDO1 – Enabled via I2C)
VINLDO1
Input Voltage Range
VINLDO1 ≤ VOUT + 0.3V
VOUT_UVLO
VOUT Falling
VOUT Rising
LDO1 is Disabled Below VOUT UVLO
IQLDO1_VO
IQLDO1_VI
LD01 VOUT Quiescent Current
LD01 VINLDO1 Quiescent Current
LDO1 Enabled, PON State, ILDO1 = 0mA
LDO1 Enabled, PON State, ILDO1 = 0mA
IVINLDO1
Shutdown Current
LDO1 Disabled, PON or POFF State
VLDO1_FB
LDO1_FB Regulated Feedback Voltage
ILDO1 = 1mA
LDO1_FB Line Regulation (Note 11)
ILDO1 = 1mA, VIN = 1.65V to 5.5V
LDO1_FB Load Regulation (Note 11)
ILDO1 = 1mA to 150mA
ILDO1_FB
LDO1_FB Input Current
LDO1_FB = 0.8V
ILDO1_OC
Available Output Current
l
1.65
2.5
l
0.78
5.5
V
2.7
2.8
2.9
V
V
18
0.1
30
2
μA
μA
0.01
1
μA
0.8
0.82
V
0.4
mV/V
5
–50
l
150
μV/mA
50
nA
mA
3577fa
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LTC3577/LTC3577-1
ELECTRICAL CHARACTERISTICS
LDO Regulators. The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. VINLDO1 = VINLDO2 = VOUT = VBAT = 3.8V, LDO1 and LDO2
enabled unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
ILDO1_SC
Short-Circuit Output Current
VDROP1
Dropout Voltage (Note 12)
ILDO1 = 150mA, VINLDO1 = 3.6V
ILDO1 = 150mA, VINLDO1 = 2.5V
ILDO1 = 75mA, VINLDO1 = 1.8V
160
200
170
RLDO1_PD
Output Pull-Down Resistance in Shutdown
LDO1 Disabled
10
MAX
270
UNITS
mA
260
320
280
mV
mV
mV
kΩ
LDO Regulator 2 (LDO2 – Enabled via I2C)
VINLDO2
Input Voltage Range
VINLDO2 ≤ VOUT + 0.3V
VOUT_UVLO
VOUT Falling
VOUT Rising
LDO2 is Disabled Below VOUT UVLO
IQLDO2_VO
IQLDO2_VI
LDO2 VOUT Quiescent Current
LDO2 VINLDO2 Quiescent Current
IVINLDO2
VLDO2_FB
l
1.65
5.5
V
2.7
2.8
2.9
V
V
LDO2 Enabled, PON State, ILDO2 = 0mA
LDO2 Enabled, PON State, ILDO2 = 0mA
18
0.1
30
2
μA
μA
Shutdown Current
LDO2 Disabled, PON or POFF State
0.01
1
μA
LDO2_FB Regulated Output Voltage
ILDO2 = 1mA
0.8
0.82
LDO2_FB Line Regulation (Note 11)
ILDO2 = 1mA, VIN = 1.65V to 5.5V
LDO2_FB Load Regulation (Note 11)
ILDO2 = 1mA to 150mA
LDO2_FB = 0.8V
2.5
l
0.78
mV/V
5
μV/mA
ILDO2_FB
LDO2_FB Input Current
ILDO2_OC
Available Output Current
–50
ILDO2_SC
Short-Circuit Output Current
VDROP2
Dropout Voltage (Note 12)
ILDO2 = 150mA, VINLDO2 = 3.6V
ILDO2 = 150mA, VINLDO2 = 2.5V
ILDO1 = 75mA, VINLDO1 = 1.8V
160
200
170
RLDO2_PD
Output Pull-Down Resistance in Shutdown
LDO2 Disabled
14
l
V
0.4
50
150
nA
mA
270
mA
260
320
280
mV
mV
mV
kΩ
LED Boost Switching Regulator. The l denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at TA = 25°C. VIN3 = VOUT = 3.8V, ROV = 10M, RLED_FS = 20k, boost regulator disabled unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VIN3, VOUT
Operating Supply Range
(Note 9)
IVOUT_LED
Operating Quiescent Current
Shutdown Quiescent Current
(Notes 10, 14)
VLED_OV
LED_OV Overvoltage Threshold
LED_OV Rising
LED_OV Falling
MIN
l
TYP
2.7
MAX
5.5
560
0.01
UNITS
V
μA
μA
1.0
0.85
1.25
0.6
V
V
ILIM
Peak NMOS Switch Current
800
1000
1200
mA
ILED_FS
ILED Pin Full-Scale Operating Current
18
20
22
mA
ILED_DIM
ILED Pin Full-Scale Dimming Range
RNSWON
RDS(ON) of NMOS Switch
INSWOFF
NMOS Switch-Off Leakage Current
fOSC
Oscillator Frequency
64 Steps
60
dB
240
VSW = 5.5V
VLED_FS
LED_FS Pin Voltage
ILED_OV
LED_OV Pin Current
RLED_FS = 20k
DBOOST
Maximum Duty Cycle
ILED = 0
VBOOSTFB
Boost Mode ILED Feedback Voltage
mΩ
0.01
1
μA
0.95
1.125
1.3
MHz
l
780
800
820
mV
l
3.8
4
4.2
μA
l
775
800
825
mV
97
%
3577fa
8
LTC3577/LTC3577-1
ELECTRICAL CHARACTERISTICS
Pushbutton Controller. The l denotes the specifications which apply
over the full operating temperature range, otherwise specifications are at TA = 25°C. VOUT = 3.8V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Pushbutton Pin (ON)
VOUT
Pushbutton Operating Supply Range
(Note 9)
VOUT UVLO
VOUT Falling
VOUT Rising
Pushbutton is Disabled Below VOUT UVLO
VON_TH
ON Threshold Rising
ON Threshold Falling
ION
ON Input Current
VON = VOUT
VON = 0V
l
2.7
2.5
2.7
2.8
0.4
0.8
0.7
–1
–4
–9
0.4
0.8
0.7
5.5
V
2.9
V
V
1.2
V
V
1
–14
μA
μA
1.2
V
V
Power-On Input Pin (PWR_ON)
VPWR_ON
IPWR_ON
PWR_ON Threshold Rising
PWR_ON Threshold Falling
PWR_ON Input Current
VPWR_ON = 3V
–1
1
μA
–1
1
μA
0.1
0.4
V
1
μA
0.1
0.4
V
1
μA
Status Output Pins (PBSTAT, WAKE, PG_DCDC)
IPBSTAT
PBSTAT Output High Leakage Current
VPBSTAT = 3V
VPBSTAT
PBSTAT Output Low Voltage
IPBSTAT = 3mA
IWAKE
Wake Output High Leakage Current
VWAKE = 3V
VWAKE
Wake Low Output Voltage
IWAKE = 3mA
IPG_DCDC
PG_DCDC Output High Leakage Current
VPG_DCDC = 3V
VPG_DCDC
PG_DCDC Output Low Voltage
IPG_DCDC = 3mA
0.1
VTHPG_DCDC
PG_DCDC Threshold Voltage
(Note 13)
–8
%
–1
–1
0.4
V
Pushbutton Timing Parameters
tON_PBSTAT1
ON Low Time to PBSTAT Low
WAKE High
50
ms
tON_PBSTAT2
ON High to PBSTAT High
PBSTAT Low > tPBSTAT_PW
900
μs
tON_WAKE
ON Low Time to WAKE High
WAKE Low > tPWR_ONBK2
tON_HR
ON Low to Hard Reset
Hard Reset = All Supplies Disabled
400
4.2
40
ms
5
5.8
50
60
Seconds
tPBSTAT_PW
PBSTAT Minimum Pulse Width
tWAKE_EXTP
WAKE High from USB or Wall Present
WAKE Low > tPWR_ONBK2
100
ms
ms
tWAKE_DCDC
WAKE High to Buck1 Enable
WAKE Low > tPWR_ONBK2
5
μs
tPWR_ONH
PWR_ON High to WAKE High
WAKE Low > tPWR_ONBK2
50
ms
tPWR_ONL
PWR_ON Low to WAKE Low
WAKE High > tPWR_ONBK1
50
ms
tPWR_ONBK1
PWR_ON Power-Up Blanking
WAKE Rising Until PWR_ON Low Recognized
5
Seconds
tPWR_ONBK2
PWR_ON Power-Down Blanking
WAKE Falling Until PWR_ON High Recognized
1
Seconds
tPG_DCDCH
Bucks in Regulation to PG_DCDC High
All Bucks Within PG_DCDC Threshold Voltage
230
ms
tPG_DCDCL
Bucks Disabled to PG_DCDC Low
All Bucks Disabled
44
μs
3577fa
9
LTC3577/LTC3577-1
ELECTRICAL CHARACTERISTICS
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 2: The LTC3577E/LTC3577E-1 are 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.
Note 3: This IC includes over temperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperatures will exceed 110°C when over temperature protection is
active. Continuous operation above the specified maximum operating
junction temperature may result in device degradation or failure.
Note 4: VCC is the greater of VBUS, VOUT or BAT.
Note 5: Total input current is the sum of quiescent current, IBUSQ, and
measured current given by VCLPROG/RCLPROG • (hCLPROG + 1).
Note 6: hC/10 is expressed as a fraction of measured full charge current
with indicated PROG resistor.
Note 7: The current limit features of this part are intended to protect the
IC from short term or intermittent fault conditions. Continuous operation
above the specified maximum pin current rating may result in device
degradation or failure.
Note 8: The serial port is tested at rated operating frequency. Timing
parameters are tested and/or guaranteed by design.
Note 9: VOUT not in UVLO.
Note 10: FB high, not switching.
Note 11: Measured with the LDO running unity gain with output tied to
feedback pin.
Note 12: Dropout voltage is the minimum input to output voltage
differential needed for an LDO to maintain regulation at a specified output
current. When an LDO is in dropout, its output voltage will be equal to
VIN – VDROP .
Note 13: PG_DCDC threshold is expressed as a percentage difference from
the Buck1-3 regulation voltages. The threshold is measured from Buck1-3
output rising.
Note 14: IVOUT_LED is the sum of VOUT and VIN3 current due to LED driver.
Note 15: The IBATQ specifications represent the total battery load assuming
VINLDO1, VINLDO2, VIN12 and VIN3 are tied directly to VOUT.
Note 16: Long-term current density rating for the part.
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise specified
Input Supply Current
vs Temperature
0.7
0.10
VBUS = 5V
1x MODE
400
NO LOAD ON SUPPLIES, LDOS AND LED
350 BOOST DISABLED. VBAT = 3.8V,
VBUS = 0V
PON STATE
300
PULSE-SKIPPING MODE
VBUS = 5V
0.08
0.6
0.5
IVBUS (mA)
IVBUS (mA)
Battery Drain Current
vs Temperature
0.4
0.3
0.06
IBAT (μA)
0.8
Input Supply Current
vs Temperature (Suspend Mode)
0.04
250
200
150
PON STATE
Burst Mode OPERATION
100
0.2
0.02
POFF STATE
50
0.1
HARD RESET STATE
0
–50 –25
0
50
75
25
TEMPERATURE (°C)
100
125
3577 G01
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3577 G02
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3577 G03
3577fa
10
LTC3577/LTC3577-1
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise specified
Input Current Limit
vs Temperature
1000
300
VBUS = 5V
RCLPROG = 2.1k
10x MODE
500
260
900
800
240
700
220
600
RON (mΩ)
IVBUS (mA)
600
IOUT = 400mA
280
5x MODE
500
VBUS = 4.5V
180
VBUS = 5.5V
160
400
120
200
1x MODE
100
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
0
–50
125
–25
50
25
0
75
TEMPERATURE (°C)
6
5
200
SAFETY
TIMER
2
TERMINATION
RCLPROG = 2.1k
RPROG = 2k
500 VBUS = 5V
10x MODE
IBAT = 2mA
LTC3577
400
4.16
IBAT (mA)
3
4.14
4.12
LTC3577-1
4.10
FALLING VBAT
100
4.06
IBAT
5
6
4.04
–50 –25
0
75
50
25
TEMPERATURE (°C)
0
100
3577 G07
0
2.0
125
0.25
RCLPROG = 2.1k
RPROG = 2k
500 VBUS = 5V
10x MODE
40
VBUS = 0V
TA = 25°C
4.0
4.4
VBAT = 3.8V
VBUS = 0V
TA = 25°C
35
VBAT = 3.2V
30
VBAT = 3.6V
400
VBAT = 4.2V
VFWD (V)
0.15
FALLING VBAT
3.2
3.6
VBAT (V)
Forward Voltage vs Ideal Diode
Current (with Si2333DS External FET)
0.20
300
2.8
3577 G09
Forward Voltage vs Ideal Diode
Current (No External FET)
600
2.4
3577 G08
LTC3577-1 IBAT vs VBAT
IBAT (mA)
RISING VBAT
300
200
4.08
1
125
LTC3577 IBAT vs VBAT
4.18
VBAT (V)
300
C/10
100
3577 G06
4.20
VBAT AND VCHRG (V)
4
400
50
25
75
0
TEMPERATURE (°C)
600
4.24
4.22
CHRG
VBAT
0.10
200
RISING VBAT
25
20
15
10
0.05
100
0
0
–50 –25
125
Battery Regulation (Float) Voltage
vs Temperature
600
3
4
TIME (HOUR)
100
3577 G05
Battery Current and Voltage
vs Time
1450mAhr
CELL
100 VBUS = 5V
RPROG = 2k
RCLPROG = 2k
0
0
2
1
VBUS = 5V
10x MODE
RPROG = 2k
100
100
3577 G04
500
300
200
140
300
IBAT (mA)
400
VBUS = 5V
IBAT (mA)
1100
VFWD (mV)
1200
Charge Current vs Temperature
(Thermal Regulation)
Input RON vs Temperature
5
2.0
2.4
2.8
3.2
3.6
VBAT (V)
4.0
4.4
3577 G10
0
0
0
0.2
0.4
0.6
IBAT (A)
0.8
1.0
1.2
3577 G11
0
0.2
0.4
0.6
IBAT (A)
0.8
1.0
3577 G12
3577fa
11
LTC3577/LTC3577-1
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise specified
Input Connect Waveform
Input Disconnect Waveform
Switching from 1x to 5x Mode
VBUS
5V/DIV
VBUS
5V/DIV
VOUT
5V/DIV
VOUT
5V/DIV
IBUS
0.5A/DIV
IBUS
0.5A/DIV
IBUS
0.5A/DIV
IBAT
0.5A/DIV
IBAT
0.5A/DIV
IBAT
0.5A/DIV
VBAT = 3.75V
IOUT = 100mA
RCLPROG = 2k
RPROG = 2k
1ms/DIV
3577 G13
ILIM0/ILIM1
5V/DIV
VBAT = 3.75V
IOUT = 100mA
RCLPROG = 2k
RPROG = 2k
Switching from Suspend Mode to
5x Mode
3577 G14
1ms/DIV
VBAT = 3.75V
IOUT = 50mA
RCLPROG = 2k
RPROG = 2k
WALL Connect Waveform
WALL Disconnect Waveform
ILIM0
5V/DIV
WALL
5V/DIV
WALL
5V/DIV
VOUT
5V/DIV
IBUS
0.5A/DIV
VOUT
5V/DIV
IWALL
0.5A/DIV
VOUT
5V/DIV
IWALL
0.5A/DIV
IBAT
0.5A/DIV
IBAT
0.5A/DIV
IBAT
0.5A/DIV
VBAT = 3.75V
IOUT = 100mA
RCLPROG = 2k
RPROG = 2k
ILIM1 = 5V
100μs/DIV
3577 G16
VBAT = 3.75V
IOUT = 100mA
RPROG = 2k
Oscillator Frequency
vs Temperature
VBAT = 3.75V
IOUT = 100mA
RPROG = 2k
100
Burst Mode
90 OPERATION
80
2.2
VIN = 5V
70
2.1
2.0
1.9
VIN = 2.9V
1.8
VIN = 2.7V
90
80
PULSE-SKIPPING MODE
60
50
40
30
EFFICIENCY (%)
VIN = 3.8V
EFFICIENCY (%)
2.3
3577 G18
1ms/DIV
Step-Down Switching Regulator 2
1.8V Output Efficiency vs IOUT2
100
2.4
fOSC (MHz)
3577 G17
1ms/DIV
Step-Down Switching Regulator 1
3.3V Output Efficiency vs IOUT1
2.5
3577 G15
1ms/DIV
Burst Mode
OPERATION
70
60
PULSE-SKIPPING MODE
50
40
30
1.7
20
VOUT1 = 3.3V
20
VOUT2 = 1.8V
1.6
10
VIN12 = 3.8V
VIN12 = 5V
10
VIN12 = 3.8V
VIN12 = 5V
1.5
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3577 G19
0
0.01
0.1
1
10
IOUT (mA)
100
1000
3577 G20
0
0.01
0.1
1
10
IOUT (mA)
100
1000
3577 G21
3577fa
12
LTC3577/LTC3577-1
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise specified
100
100
90
90
Burst Mode
OPERATION
EFFICIENCY (%)
70
60
PULSE-SKIPPING MODE
50
1500
Burst Mode
OPERATION
1400
80
40
70
EFFICIENCY (%)
80
PULSE-SKIPPING MODE
60
50
40
30
30
20
0
0.01
20
VOUT3 = 1.2V
VIN3 = 3.8V
VIN3 = 5V
10
0.1
1
10
IOUT (mA)
100
VOUT3 = 2.5V
VIN3 = 3.8V
VIN3 = 5V
10
0
0.01
1000
0.1
1
10
IOUT (mA)
100
1100
1000
900
500mA BUCK
800
700
VINx = 3.8V
VINx = 5V
600
500
–50 –25
1000
0
50
75
25
TEMPERATURE (°C)
100
VOUT1
50mV/DIV
(AC)
VOUT2
50mV/DIV
(AC)
VOUT3
100mV/DIV
(AC)
500mA
500mA
IOUT3
3577 G25
125
3577 G24
Step-Down Switching Regulator
Switch Impedance vs Temperature
0.9
VINX = 3.2V
0.8
SWITCH IMPEDANCE (Ω)
VOUT1
50mV/DIV
(AC)
VOUT2
50mV/DIV
(AC)
VOUT3
100mV/DIV
(AC)
VOUT1 = 3.3V
50μs/DIV
IOUT1 = 10mA
VOUT2 = 1.8V
IOUT2 = 20mA
VOUT3 = 1.2V
VOUT = VBAT = 3.8V
800mA BUCK
1200
Step-Down Switching Regulator
Output Transient (Pulse-Skipping
Mode)
Step-Down Switching Regulator
Output Transient (Burst Mode
Operation)
5mA
1300
3577 G23
3577 G22
IOUT3
Step-Down Switching Regulator
Short-Circuit Current vs Temperature
Step-Down Switching Regulator 3
2.5V Output Efficiency vs IOUT3
SHORT-CIRCUIT CURRENT (mA)
Step-Down Switching Regulator 3
1.2V Output Efficiency vs IOUT3
5mA
50μs/DIV
VOUT1 = 3.3V
IOUT1 = 30mA
VOUT2 = 1.8V
IOUT2 = 20mA
VOUT3 = 1.2V
VOUT = VBAT = 3.8V
0.7
500mA
NMOS
0.6
500mA
PMOS
0.5
0.4
800mA PMOS
0.3
800mA NMOS
0.2
3577 G26
0.1
0
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
3577 G27
500mA Step-Down Switching
Regulator Feedback Voltage
vs Output Current
800mA Step-Down Switching
Regulator Feedback Voltage
vs Output Current
0.85
0.85
0.84
0.84
0.83
0.83
0.81
Burst Mode
OPERATION
0.82
FEEDBACK (V)
FEEDBACK (V)
0.82
0.80
0.79
PULSE-SKIPPING MODE
0.78
LDO1
50mV/DIV
(AC)
Burst Mode
OPERATION
0.81
LDO2
20mV/DIV
(AC)
0.80
0.79
PULSE-SKIPPING MODE
0.78
0.77
IOUT1
0.77
3.8V
5V
0.76
0.75
0.1
LDO Load Step
1
10
100
OUTPUT CURRENT (mA)
1000
3577 G28
3.8V
5V
0.76
0.75
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
100mA
5mA
LDO1 = 1.2V
20μs/DIV
LDO2 = 2.5V
ILDO2 = 40mA
VOUT = VBAT = 3.8V
3577 G30
3577 G29
3577fa
13
LTC3577/LTC3577-1
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise specified
OVP Connection Waveform
OVP Protection Waveform
OVP Reconnection Waveform
VBUS
5V/DIV
VBUS
5V/DIV
VBUS
5V/DIV
OVGATE
5V/DIV
OVGATE
5V/DIV
OVP
INPUT
VOLTAGE
5V TO 10V
STEP 5V/DIV
OVP
INPUT
VOLTAGE
0V TO 5V
STEP 5V/DIV
3577 G31
500μs/DIV
Rising Overvoltage Threshold
vs Temperature
OVSENS Quiescent Current
vs Temperature
OVSENS CONNECTED
TO INPUT THROUGH
10 6.2k RESISTOR
31
8
OVGATE (V)
33
6.270
6.265
27
–40
–15
35
10
TEMPERATURE (°C)
60
85
2
0
6.255
–40
–15
35
10
TEMPERATURE (°C)
60
Input and Battery Current
vs Load Current
LED Driver Efficiency 10 LEDs
IIN
EFFICIENCY (%)
CURRENT (mA)
400
ILOAD
300
IBAT
(CHARGING)
200
100
90
85
85
80
80
75
70
65
3V
3.6V
4.2V
4.8V
5.5V
–100
0
100
55
IBAT
(DISCHARGING)
WALL = 0V
200
400
300
ILOAD (mA)
500
50
600
3577 G37
4
6
INPUT VOLTAGE (V)
0
2
4
6
8
LED Driver Efficiency 8 LEDs
90
60
0
2
3577 G36
EFFICIENCY (%)
RPROG = 2k
RCLPROG = 2k
500
0
85
3577 G35
3577 G34
600
6
4
6.260
29
3577 G33
OVGATE vs OVSENS
6.275
35
500μs/DIV
12
6.280
VOVSENS = 5V
OPV THRESHOLD (V)
QUIESCENT CURRENT (μA)
37
3577 G32
500μs/DIV
OVGATE
5V/DIV
OVP
INPUT
VOLTAGE
10V TO 5V
STEP 5V/DIV
8 10 12 14 16 18 20
ILED (mA)
3577 G38
75
70
65
3V
3.6V
4.2V
4.8V
5.5V
60
55
50
0
2
4
6
8 10 12 14 16 18 20
ILED (mA)
35773 G39
3577fa
14
LTC3577/LTC3577-1
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise specified
LED Driver Efficiency 6 LEDs
LED Boost Current Limit
vs Temperature
LED Driver Efficiency 4 LEDs
90
90
85
85
80
80
1200
1100
75
70
65
3V
3.6V
4.2V
4.8V
5.5V
60
55
50
0
2
4
6
75
70
65
3V
3.6V
4.2V
4.8V
5.5V
60
55
50
8 10 12 14 16 18 20
ILED (mA)
0
2
4
CURRENT LIMIT (mA)
EFFICIENCY (%)
EFFICIENCY (%)
1000
3577 G40
600
500
400
200
100
0
–40 –20
3577 G42
LED Boost Maximum Duty Cycle
vs Temperature
LED Boost Start-Up Transient
70
96.6
60dB = 20mA
0dB = 20μA
60
RLED_FS = 20k
96.5
ILED
10mA/DIV
40
96.4
MAX DUTY CYCLE (%)
50
VBOOST
20V/DIV
30
IL
200mA/DIV
20
96.3
96.2
96.1
96.0
3V
3.6V
4.2V
5.5V
95.9
10
95.8
0
0
10
20
20 40 60 80 100 120
TEMPERATURE (°C)
0
3577 G41
DAC Code vs LED Current
CURRENT (dB)
800
700
300
8 10 12 14 16 18 20
ILED (mA)
6
900
40
30
DAC CODE
50
60
2ms/DIV
70
3577 G44
95.7
–50
–25
0
25
50
75
TEMPERATURE (°C)
3577 G43
Battery Discharge
vs Temperature
90
MAX PWM
50
CONSTANT
CURRENT
40
30
20
10
180
175
VBUS = 5V
140
125
VBUS = 0V
100
75
1.E-04 1.E-03 1.E-02
LED CURRENT (A)
1.E-01
3577 G46
120
100
80
60
50
VBAT = 4.1V
VNTC < VTOO_HOT
5x MODE
IVOUT = 0mA
25
0
1.E-05
VNTC < VTOO_HOT
VBUS = 0V
160
150
IBAT (mA)
BATTERY DISCHARGE CURRENT (mA)
EFFICIENCY (%)
60
0
1.E-06
Too Hot BAT Discharge
200
200
70
125
3577 G45
LED PWM
vs Constant Current Efficiency
80
100
50
60
70
90 100
80
TEMPERATURE (°C)
40
20
110
120
3577 G47
0
3.8
3.9
4.0
VBAT (V)
4.1
4.2
3577 G48
3577fa
15
LTC3577/LTC3577-1
PIN FUNCTIONS
ILIM0, ILIM1 (Pins 1, 2): Input Current Control Pins. ILIM0
and ILIM1 control the input current limit. See Table 1 in the
“USB PowerPath Controller” section. Both pins are pulled
low by a weak current sink.
LED_FS (Pin 3): A resistor between this pin and ground
sets the full-scale output current of the ILED pin.
WALL (Pin 4): Wall Adapter Present Input. Pulling this
pin above 4.3V will disconnect the power path from VBUS
to VOUT . The ACPR pin will also be pulled low to indicate
that a wall adapter has been detected.
SW3 (Pin 5): Power Transmission (Switch) Pin for StepDown Switching Regulator 3 (buck3).
VIN3 (Pin 6): Power Input for Step-Down Switching Regulator 3. This pin should be connected to VOUT .
FB3 (Pin 7): Feedback Input for Step-Down Switching
Regulator 3 (buck3). This pin servos to a fixed voltage of
0.8V when the control loop is complete.
OVSENSE (Pin 8): Overvoltage Protection Sense Input.
OVSENSE should be connected through a 6.2k resistor
to the input power connector and the drain of an external
N-channel MOS pass transistor. When the voltage on
this pin exceeds a preset level, the OVGATE pin will be
pulled to GND to disable the pass transistor and protect
downstream circuitry.
LED_OV (Pin 9): A resistor between this pin and the boosted
LED backlight voltage sets the overvoltage limit on the
boost output. If the boost voltage exceeds the programmed
limit the LED boost converter will be disabled.
DVCC (Pin 10): Supply Voltage for I2C Lines. This pin sets
the logic reference level of the LTC3577. A UVLO circuit on
the DVCC pin forces all registers to all 0s whenever DVCC
is
