LTC4099
I2C Controlled
USB Power Manager/Charger
with Overvoltage Protection
Description
Features
The LTC®4099 is an I2C controlled high efficiency USB
PowerPath™ controller and full-featured Li-Ion/Polymer
battery charger. It seamlessly manages power distribution
from multiple sources including USB, a wall adapter and
a Li-Ion/Polymer battery.
Switching Regulator with Bat-Track™ Adaptive Output
Control Makes Optimal Use of Limited Input Power
n I2C Port for Optimal System Performance and
Status Information
n Input Overvoltage Protection
n Bat-Track Control of External Step-Down Switching
Regulator Maximizes Efficiency from Automotive
and Other High Voltage Sources
n Instant-On Operation with Low Battery
n Optional Overtemperature Battery Conditioner
Improves High Temperature Battery Safety Margin
n Ideal Diode Seamlessly Connects Battery When Input
Power is Limited or Unavailable
n Full-Featured Li-Ion/Polymer Battery Charger
n 1.5A Maximum Charge Current with Thermal Limiting
n Slew Control Reduces Switching EMI
n 20-Lead 3mm × 4mm × 0.75mm QFN Package
n
The LTC4099 automatically limits its input current for
USB compatibility. For automotive and other high voltage applications, the LTC4099 interfaces with an external
switching regulator. Both the USB input and the auxiliary
input controller feature Bat-Track optimized charging to
provide maximum power to the application and reduced
heat in high power density applications.
The I2C port allows digital control of important application
parameters including input current limit, charge current
and float voltage. Several status bits can also be read back
via I2C.
An overvoltage protection circuit guards the LTC4099
from high voltage damage on the low voltage VBUS pin.The
LTC4099 is available in a 20-Lead 3mm × 4mm × 0.75mm
QFN Package.
Applications
n
n
n
n
n
Media Players
Portable Navigation Devices
Smart Phones
Industrial Handhelds
Portable Medical Instruments
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. PowerPath, Bat-Track and ThinSOT are trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6522118, 6570372, 6700364, 6819094. Other patents
pending.
Typical Application
I2C Controlled High Efficiency Battery Charger/
USB Power Manager
VBUS
VOUT
BAT
LTC4099
OVSENS
2
SYSTEM
LOAD
SW
OVGATE
6.2k
I2C
0.1µF
10µF
BATSENS
CLPROG PROG
3.01k
GND
1.02k
NTCBIAS
NTC
100k
100k
T
LINEAR BATTERY
CHARGER
1.6
3.3µH
10µF
TO µCONTROLLER
1.8
+
POWER DISSIPATION (W)
OVERVOLTAGE
USB PROTECTION
Reduced Power Dissipation
vs Linear Battery Charger
VIN = 5V
ICHARGE = 1A
1.4
1.2
1.0
ADDITIONAL POWER
AVAILABLE FOR CHARGING
0.8
0.6
0.4
SWITCHING BATTERY
CHARGER
0.2
Li-Ion
4099 TA01a
0
3.3
3.4
3.5
3.6
3.7
3.8
3.9
BATTERY VOLTAGE (V)
4
4.1
4099 TA01b
4099fd
LTC4099
pIN CONFIGURATION
VBUS, WALL (Transient) t < 1ms,
Duty Cycle < 1%....................................... –0.3V to 7V
VBUS, WALL (Static), BAT, BATSENS, IRQ,
NTC, DVCC................................................ –0.3V to 6V
SDA, SCL........... –0.3V to Max (VBUS, VOUT, BAT) + 0.3V
IOVSENS.................................................................±10mA
ICLPROG.....................................................................3mA
IPROG, INTCBIAS..........................................................2mA
IOUT, ISW, IBAT, IVBUS...............................................2.25A
Maximum Junction Temperature........................... 125°C
Operating Temperature Range.................. –40°C to 85°C
Storage Temperature Range....................–65°C to 125°C
IIRQ.........................................................................50mA
IACPR.......................................................................±5mA
SDA
ACPR
CLPROG
OVSENS
TOP VIEW
20 19 18 17
OVGATE 1
16 SCL
15 DVCC
NTC 2
NTCBIAS 3
14 SW
21
GND
VC 4
13 VBUS
12 VOUT
WALL 5
11 BAT
9 10
IDGATE
8
GND
7
IRQ
BATSENS 6
PROG
Absolute Maximum Ratings
(Notes 1, 2, 3)
UDC PACKAGE
20-LEAD (3mm s 4mm) PLASTIC QFN
TJMAX = 125°C, θJA = 38°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
order information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4099EPDC#PBF
LTC4099EPDC#TRPBF
DQKT
20-Lead (3mm × 4mm) Plastic UTQFN
–40°C to 85°C (OBSOLETE)
LTC4099EUDC#PBF
LTC4099EUDC#TRPBF
LFPY
20-Lead (3mm × 4mm) Plastic QFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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 l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, DVCC = 3.3V, RPROG = 1.02k, RCLPROG = 3.01k, unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Power Supply
VBUS
Input Supply Voltage
IBUS(LIM)
Total Input Current
IVBUSQ (Note 4) Input Quiescent Current
100mA Mode
500mA Mode
620mA Mode
790mA Mode
1A Mode
1.2A Mode
Low Power Suspend Mode
High Power Suspend Mode
100mA Mode
500mA, 620mA, 790mA, 1A, 1.2A Modes
Low Power Suspend Mode
High Power Suspend Mode
l
4.35
l
l
88
460
580
725
920
1150
0.30
1.6
l
l
93
485
620
790
965
1220
0.37
2.05
6
15
0.039
0.037
5.5
V
100
500
650
850
1000
1295
0.5
2.5
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
4099fd
LTC4099
Electrical
Characteristics
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, DVCC = 3.3V, RPROG = 1.02k, RCLPROG = 3.01k, unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
hCLPROG
(Note 4)
Ratio of Measured VBUS Current to
CLPROG Program Current
100mA Mode
500mA Mode
620mA Mode
790mA Mode
1A Mode
1.2A Mode
Low Power Suspend Mode
High Power Suspend Mode
IVOUT
VOUT Current Available Before Discharging 100mA Mode, BAT = 3.3V
Battery
500mA Mode, BAT = 3.3V
620mA Mode, BAT = 3.3V
790mA Mode, BAT = 3.3V
1A Mode, BAT = 3.3V
1.2A Mode, BAT = 3.3V
Low Power Suspend Mode
High Power Suspend Mode
VCLPROG
CLPROG Servo Voltage in Current Limit
Switching Modes
Suspend Modes
VUVLO
VBUS Undervoltage Lockout
Rising Threshold
Falling Threshold
VDUVLO
VBUS to BAT Differential Undervoltage
Lockout
VBUS–BAT Rising Threshold
VBUS–BAT Falling Threshold
VOUT
VOUT Voltage
Switching Modes, BAT = 4.2V,
IVOUT = 0mA, Battery Charger Off
4.3
4.5
4.7
V
Switching Modes, BAT < 3.0V,
IVOUT = 0mA, Battery Charger Off
3.5
3.6
3.75
V
USB Suspend Modes, IVOUT = 250µA
4.5
4.6
4.7
V
1.96
2.25
2.65
MHz
fOSC
Switching Frequency
MIN
TYP
MAX
mA/mA
mA/mA
mA/mA
mA/mA
mA/mA
mA/mA
mA/mA
mA/mA
220
1200
1540
1980
2420
3080
10.9
65
0.23
1.6
135
672
840
1080
1251
1550
0.30
2.16
0.41
2.46
1.18
102
3.90
4.30
4.00
UNITS
mA
mA
mA
mA
mA
mA
mA
mA
V
mV
4.35
200
50
V
V
mV
mV
RPMOS
PMOS On-Resistance
0.18
Ω
RNMOS
NMOS On-Resistance
0.30
Ω
IPEAK
Peak Inductor Current Clamp
3
A
RSUSP
Suspend LDO Output Resistance
16
Ω
500mA to 1.2A Input Limit Modes
Battery Charger
VFLOAT
BAT Regulated Output Voltage
4.200V Setting Selected by I2C
l
4.179
4.165
4.200
4.200
4.221
4.235
V
V
l
4.079
4.065
4.100
4.100
4.121
4.135
V
V
4.100V Default Setting
ICHG_RANGE
Constant-Current Mode Charge Current
Range
ILIM2/1/0 = 101, Selectable by I2C
ICHG500mA
Zero-Scale Battery Charge Current
ILIM2/1/0 = 101, ICHARGE2/1/0 = 000
475
500
525
mA
ICHG1200mA
Full-Scale Battery Charge Current
ILIM2/1/0 = 101, ICHARGE2/1/0 = 111
1100
1200
1300
mA
ICHG_STEP
Charge Current I2C Step Size
ILIM2/1/0 = 101
100
IBATQ
Battery Drain Current
VBUS > VUVLO, Battery Charger Off,
IVOUT = 0µA
3.7
5
µA
VBUS = 0V, IVOUT = 0µA
(Ideal Diode Mode)
23
35
µA
500-1200
mA
mA
4099fd
LTC4099
Electrical
Characteristics
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, DVCC = 3.3V, RPROG = 1.02k, RCLPROG = 3.01k, unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VPROG,TRKL
PROG Pin Servo Voltage in Trickle Charge
BAT < VTRKL
hPROG
Ratio of IBAT to PROG Pin Current
VTRKL
Trickle Charge Threshold Voltage
MIN
TYP
MAX
UNITS
0.100
V
1030
mA/mA
BAT Rising
2.7
2.85
–75
–100
3
130
V
ΔVTRKL
Trickle Charge Hysteresis Voltage
VRECHRG
Recharge Battery Threshold Voltage
Threshold Voltage Relative to VFLOAT
tTERM_RANGE
Safety Timer Termination Period Range
Selectable by I2C, Timer Starts When
BAT = VFLOAT
tBADBAT
Bad Battery Termination Time
BAT < VTRKL
0.4
0.5
0.6
Hour
VC/x
Full Capacity Charge Indication PROG
Voltage (Note 5)
COVERX1/0 = 00
90
100
110
mV
COVERX1/0 = 01
40
50
60
mV
COVERX1/0 = 10
190
200
210
mV
COVERX1/0 = 11
490
500
510
mV
RON_CHG
Battery Charger Power FET
On-Resistance (Between VOUT and BAT)
IBAT = 200mA
TLIM
Junction Temperature in Constant
Temperature Mode
Selectable by I2C
mV
–125
1-8
mV
Hour
0.18
Ω
85, 105
°C
Bat-Track External Switching Regulator Control
VWALL
Absolute WALL Input Threshold
Rising Threshold
Falling Threshold
4.15
4.3
3.2
4.45
ΔVWALL
Differential WALL Input Threshold
WALL–BAT Rising Threshold
WALL–BAT Falling Threshold
VOUT
Regulation Target Under VC Control
IWALLQ
V
V
0
90
37
50
3.5
BAT + 0.3
V
WALL Quiescent Current
130
µA
RACPR
ACPR Pull-Down Strength
150
Ω
VHACPR
ACPR High Voltage
IACPR = 0mA
VOUT
V
VLACPR
ACPR Low Voltage
IACPR = 0mA
0
V
mV
mV
Overvoltage Protection
VOVCUTOFF
Overvoltage Protection Threshold
Rising Threshold, ROVSENS = 6.2k
VOVGATE
OVGATE Output Voltage
Input Below VOVCUTOFF
Input Above VOVCUTOFF
VOVGATELOAD
OVGATE Voltage with 1µA Load
5V Through 6.2k into OVSENS
IOVSENSQ
OVSENS Quiescent Current
tRISE
OVGATE Time to Reach Regulation
6.10
6.35
6.70
1.88 • VOVSENS 12
0
8
V
V
V
8.6
V
VOVSENS = 5V
40
µA
COVGATE = 1nF
2.5
ms
Overtemperature Battery Conditioner
IDISCHARGE
Overtemperature Battery Discharge
Current
Only When Enabled via I2C Control,
BAT = 4.2V
180
mA
VALLOW
Maximum Allowed Overtemperature
Battery Voltage
Only When Enabled via I2C Control
3.85
V
4099fd
LTC4099
Electrical
Characteristics
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, DVCC = 3.3V, RPROG = 1.02k, RCLPROG = 3.01k, unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
NTC
VTOO_COLD
Cold Temperature Fault Threshold Voltage Rising Threshold
Hysteresis
72.3
73.8
3.6
75.3 %NTCBIAS
%NTCBIAS
VTOO_WARM
Hot Temperature Fault Threshold Voltage
Falling Threshold
Hysteresis
31.3
32.6
3.3
33.9 %NTCBIAS
%NTCBIAS
VOVERTEMP
Critically High Temperature Fault
Threshold Voltage
Falling Threshold
Hysteresis
21.9
22.8
50
23.7 %NTCBIAS
mV
INTC
NTC Leakage Current
NTC = NTCBIAS
–50
VFWD
Forward Voltage
IVOUT = 10mA
RDROPOUT
Internal Diode On-Resistance, Dropout
IVOUT = 200mA
IMAX
Diode Current Limit
2
DVCC
I2C Logic Reference
1.6
IDVCCQ
DVCC Current
50
nA
Ideal Diode
15
mV
0.18
Ω
A
I2C Port
SCL/SDA = 0kHz
5.5
V
0.2
µA
1
V
VDVCC_UVLO
DVCC UVLO
ADDRESS
I2C Address
VIRQ
IRQ Pin Output Low Voltage
IIRQ = 5mA
65
100
mV
IIRQ
IRQ Pin Leakage Current
VIRQ = 5V
0
1
µA
VIH, SDA, SCL
Input High Threshold
VIL, SDA, SCL
Input Low Threshold
IIH, SDA, SCL
Input Leakage High
SDA, SCL = DVCC
IIL, SDA, SCL
Input Leakage Low
SDA, SCL = 0V
VOL
Digital Output Low (SDA)
ISDA = 3mA
fSCL
Clock Operating Frequency
tBUF
Bus Free Time Between Stop and Start
Condition
1.3
µs
tHD_SDA
Hold Time After (Repeated) Start
Condition
0.6
µs
tSU_SDA
Repeated Start Condition Set-Up Time
0.6
µs
tSU_STO
Stop Condition Time
0.6
µs
tHD_DAT(OUT)
Data Hold Time
0
tHD_DAT(IN)
Input Data Hold Time
0
ns
tSU_DAT
Data Set-Up Time
100
ns
tLOW
Clock Low Period
1.3
µs
tHIGH
Clock High Period
0.6
µs
tSP
Spike Suppression Time
R
0001001
W
0.7 •
DVCC
V
0.3 •
DVCC
V
–1
1
µA
–1
1
µA
0.4
V
400
kHz
900
50
ns
ns
4099fd
LTC4099
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 LTC4099 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.
Note 3: The LTC4099 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature 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, IVBUSQ, and
measured current given by:
VCLPROG /RCLPROG • (hCLPROG + 1)
Note 5: The PROG pin always represents actual charge current. See the
Full Capacity Charge Indication (C/x) section.
Typical Performance Characteristics
RCLPROG = 3.01k, unless otherwise noted.
Battery and VBUS Currents
vs Output Current
Battery and VBUS Currents
vs Output Current
VBUS CURRENT
VBUS CURRENT
0
BATTERY
CURRENT
(DISCHARGING)
–200
VBUS INPUT LIMIT SET
–400 FOR USB 500mA
BATTERY CHARGER SET
FOR 800mA
–600
200
600
800
0
400
OUTPUT CURRENT (mA)
400
–200
90
EFFICIENCY (%)
BATTERY CURRENT (µA)
100
15
10
0
VBUS = 5V
(SUSPEND MODES)
2.7
3.0
3.3
3.6
3.9
BATTERY VOLTAGE (V)
200
0
600
800
400
OUTPUT CURRENT (mA)
4.5
4.2
4099 G04
100
70
500mA TO 1.2A
VBUS INPUT LIMIT MODES
0.1
OUTPUT CURRENT (A)
200
600
800
400
OUTPUT CURRENT (mA)
1000
4099 G03
Battery Charging Efficiency
vs Battery Voltage with No
External Load (PBAT /PVBUS)
90
80
40
0.01
0
500mA USB SETTING
100mA VBUS INPUT
LIMIT MODE
50
VBUS INPUT LIMIT SET
FOR USB 500mA
BATTERY CHARGER DISABLED
4099 G02
VCLPROG = 0V
60
BAT = 3.4V
3.5
3.0
1000
BAT = 4V
4.0
PowerPath Switching Regulator
Efficiency vs Output Current
VBUS = 0V
5
BATTERY
CURRENT
(DISCHARGING)
4099 G01
IVOUT = 0µA
20
VBUS INPUT LIMIT SET
FOR 790mA
BATTERY CHARGER SET
FOR 500mA
200
Battery Drain Current
vs Battery Voltage
25
BATTERY
CURRENT
(CHARGING)
0
1000
OUTPUT VOLTAGE (V)
600
BATTERY
CURRENT
(CHARGING)
CURRENT (mA)
CURRENT (mA)
400
200
Output Voltage vs Output Current
5.0
800
EFFICIENCY (%)
600
TA = 25°C, VBUS = 5V, BAT = 3.8V, RPROG = 1.02k,
100mA USB SETTING
80
70
60
1
4099 G05
50
2.7
3.0
3.3
3.6
3.9
BATTERY VOLTAGE (V)
4.2
4099 G06
4099fd
LTC4099
Typical Performance Characteristics
RCLPROG = 3.01k, unless otherwise noted.
USB Compliant Output Current Available
Before Discharging Battery
USB Compliant Output Current Available
Before Discharging Battery
175
700
150
600
125
500
500
400
300
200
100
75
50
25
VBUS INPUT LIMIT SET FOR USB 500mA
2.7
3.0
3.3
3.6
3.9
BATTERY VOLTAGE (V)
0
4.2
400
VFLOAT VOLTAGE SET FOR 4.2V
VBUS INPUT LIMIT SET FOR USB 500mA
BATTERY CHARGER SET FOR 1200mA
300
200
100
2.7
3.0
0
4.2
3.3
3.6
3.9
BATTERY VOLTAGE (V)
2.7
USB Limited Battery Charge
Current vs Battery Voltage
1.0
140
120
Ideal Diode Resistance
vs Battery Voltage
0.8
CURRENT (A)
60
0.25
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
100
0.20
0.6
INTERNAL IDEAL
DIODE ONLY
0.4
INTERNAL IDEAL
DIODE
0.15
0.10
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
40
20
0
0.05
0.2
VFLOAT VOLTAGE SET FOR 4.2V
VBUS INPUT LIMIT SET FOR USB 100mA
2.7
3.0
3.3
3.6
3.9
BATTERY VOLTAGE (V)
0
4.2
0
0.04
0.12
0.16
0.08
FORWARD VOLTAGE (V)
Low Battery (Instant-On) Output
Voltage vs Temperature
3.64
3.62
3.60
–40
–15
35
10
TEMPERATURE (°C)
60
85
4099 G13
3.6
3.9
3.3
BATTERY VOLTAGE (V)
1.001
500
1.000
400
0.999
0.998
300
200
100
0.997
0.996
–40
4.2
Automatic Low Battery Charge
Current Reduction
CHARGE CURRENT (mA)
BAT = 2.7V
IVOUT = 100mA
VBUS INPUT LIMIT SET FOR USB 500mA
3.0
4099 G12
Normalized Battery Charger Float
Voltage vs Temperature
NORMALIZED FLOAT VOLTAGE
3.66
0
2.7
0.20
4099 G11
4099 G10
3.68
4.2
3.3
3.6
3.9
BATTERY VOLTAGE (V)
4099 G09
Ideal Diode V-I Characteristics
80
3.0
4099 G08
4099 G07
RESISTANCE (Ω)
0
CHARGE CURRENT (V)
700
VBUS INPUT LIMIT SET FOR USB 100mA
CHARGE CURRENT (V)
600
100
OUTPUT VOLTAGE (V)
USB Limited Battery Charge
Current vs Battery Voltage
800
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
TA = 25°C, VBUS = 5V, BAT = 3.8V, RPROG = 1.02k,
–15
35
10
TEMPERATURE (°C)
60
85
4099 G14
0
3.50
3.55
3.60
VOUT (V)
3.65
3.70
4099 G15
4099fd
LTC4099
Typical Performance Characteristics
RCLPROG = 3.01k, unless otherwise noted.
Oscillator Frequency
vs Temperature
Battery Charge Current
vs Temperature
CHARGE CURRENT (mA)
500
FREQUENCY (MHz)
105°C
SETTING
THERMAL
REGULATION
300
200
85°C
SETTING
100
0
–40 –20
0
20
40
60
80
2.35
50
2.30
40
VBUS CURRENT (µA)
600
400
2.25
2.20
2.15
2.10
–40
100 120
–15
35
10
TEMPERATURE (°C)
60
4099 G16
20
36
33
30
SUSPEND HIGH
500mA USB MODE
11
8
100mA USB MODE
4.0
3.5
SUSPEND LOW
3.0
2
–40
85
–15
–10
35
TEMPERATURE (°C)
2.5
85
60
BAT = 3.3V
0.5
0
1.5
2.0
1.0
OUTPUT CURRENT (mA)
2.5
4099 G21
4099 G20
CLPROG Voltage
vs Output Current
1.2
BAT = 3.3V
6
4.5
14
VBUS Current vs Output Current
in Suspend
0.8
Static DVCC Current vs Voltage
SDA = SCL = DVCC
1.5
1.0
0.5
CLPROG VOLTAGE (V)
SUSPEND HIGH
DVCC CURRENT (µA)
1.0
2.0
VBUS CURRENT (mA)
5
5.0
4099 G19
0.8
0.6
0.4
0.2
VBUS INPUT LIMIT SET FOR USB 500mA
BATTERY CHARGER DISABLED
SUSPEND LOW
0
4
3
VBUS VOLTAGE (V)
Output Voltage vs Output Current
in Suspend
5
60
2
1
4099 G18
OUTPUT VOLTAGE (V)
39
2.5
20
0
85
IVOUT = 0µA
17
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (µA)
42
10
35
TEMPERATURE (°C)
30
VBUS Quiescent Current
vs Temperature
IVOUT = 0µA
–15
IVOUT = 0mA
4099 G17
VBUS Quiescent Current in
Suspend vs Temperature
27
–40
VBUS Current
vs VBUS Voltage (Suspend)
10
TEMPERATURE (˚C)
45
TA = 25°C, VBUS = 5V, BAT = 3.8V, RPROG = 1.02k,
0
0.5
1.5
2.0
1.0
OUTPUT CURRENT (mA)
2.5
4099 G22
0
0
200
400
600
800
OUTPUT CURRENT (mA)
1000
4099 G23
0.6
0.4
0.2
0
1.5
2.5
3.5
4.5
DVCC VOLTAGE (V)
5.5
4099 G24
4099fd
LTC4099
Typical Performance Characteristics
TA = 25°C, VBUS = 5V, BAT = 3.8V, RPROG = 1.02k,
RCLPROG = 3.01k, unless otherwise noted.
OVSENS Quiescent Current
vs Temperature
6.280
37
6.275
35
6.270
6.265
6.260
6.255
–40
–15
35
10
TEMPERATURE (°C)
60
OVSENS CONNECTED
TO INPUT THROUGH
10 6.2k RESISTOR
VOVSENS = 5V
8
33
31
6
4
29
2
27
–40
85
OVGATE vs OVSENS
12
OVGATE (V)
QUIESCENT CURRENT (µA)
OVP THRESHOLD (V)
Rising Overvoltage Threshold
vs Temperature
–15
35
10
TEMPERATURE (°C)
60
0
85
4099 G25
0
2
4
6
INPUT VOLTAGE (V)
4099 G27
4099 G26
IRQ Pin Current vs Voltage
(Pull-Down State)
8
OVP Connection Waveform
OVP Disconnect Waveform
100
VBUS
5V/DIV
OVGATE
IRQ PIN CURRENT (mA)
80
2V/DIV
60
40
OVP INPUT
VOLTAGE
5V TO
10V STEP
5V/DIV
0V
20
0
OVGATE
5V/DIV
VBUS
4099 G29
250µs/DIV
1
0
3
2
IRQ PIN VOLTAGE (V)
4
500µs/DIV
4099 G30
5
4099 G28
150
500
500mA USB SETTING
120
300
BATTERY CURRENT (mA)
INPUT CURRENT (mA)
400
BATTERY CHARGER
SET FOR 1200mA
200
100mA USB SETTING
100
0
–40
–15
10
35
TEMPERATURE (°C)
Battery Safety Conditioner Discharge
Current vs Battery Voltage
100
BATTERY CONDITIONER ENABLED
VNTC / VNTCBIAS < 0.219
VBUS = 0V
85
90
60
0
3.6
60
CONVENTIONAL 5V BUCK
WITHOUT Bat-Track
40
20
BATTERY CHARGE SET FOR 700mA
INPUT VOLTAGE = 13.5V
3.7
3.8
3.9
4.0
4.1
4.2
BATTERY VOLTAGE (V)
4099 G31
USING THE LT3653
WITH Bat-Track
80
30
60
High Voltage Input Charging
Efficiency vs Battery Voltage
EFFICIENCY (%)
Input Current vs Temperature
0
3.0
3.3
3.6
3.9
BATTERY VOLTAGE (V)
4.2
4099 G33
4099 G32
4099fd
LTC4099
Typical Performance Characteristics
TA = 25°C, VBUS = 5V, BAT = 3.8V, RPROG = 1.02k,
RCLPROG = 3.01k, unless otherwise noted.
Battery Charge Current and
Voltage vs Time
Output Voltage vs Battery Voltage;
Battery Charger Overprogrammed
5
1.0
0.6
500mA
2
0.4
CHARGER TERMINATION
4-HOUR SETTING
1
0
5
6
3
4
TIME (HOURS)
VBUS INPUT LIMIT SET FOR 790mA
BATTERY CHARGER SET FOR 500mA
FLOAT VOLTAGE SET FOR 4.2V
0
1
2
7
0.2
8
4099 G34
0
OUTPUT VOLTAGE (V)
0.8
3
BATTERY CHARGER SET FOR 1200mA
4.2
BATTERY CURRENT (A)
BATTERY VOLTAGE (V)
4
4.4
Suspend LDO Transient Response
(500µA to 1.5mA)
IOUT
500µA/DIV
4.0
500mA USB
SETTING
3.8
0mA
VOUT
20mV/DIV
AC-COUPLED
3.6
3.4
100mA USB
SETTING
500µs/DIV
3.2
4099 G36
BATTERY VOLTAGE
3.0
2.4
2.7
3.0
3.3
3.6
3.9
4.2
BATTERY VOLTAGE (V)
4099 G35
Pin Functions
OVGATE (Pin 1): Overvoltage Protection Gate Output.
Connect OVGATE to the gate pin of an external N-channel
MOSFET pass transistor. The source of the transistor should
be connected to VBUS and the drain should be connected
to the product’s DC input connector. In the absence of an
overvoltage condition, this pin is driven from an internal
charge pump capable of creating sufficient overdrive to
fully enhance the pass transistor. If an overvoltage condition
is detected, OVGATE is brought rapidly to GND to prevent
damage to the LTC4099. OVGATE works in conjunction
with OVSENS to provide this protection.
NTC (Pin 2): Input to the Negative Temperature Coefficient
Thermistor Monitoring Circuit. The NTC pin connects to
a negative temperature coefficient thermistor which is
typically copackaged with the battery to determine if the
battery is too hot or too cold to charge. If the battery’s
temperature is out of range, charging is paused until the
battery temperature re-enters the valid range. A low drift
bias resistor is required from NTCBIAS to NTC and a
thermistor is required from NTC to ground.
NTCBIAS (Pin 3): NTC Thermistor Bias Output. Connect a
bias resistor between NTCBIAS and NTC, and a thermistor
between NTC and GND.
10
VC (Pin 4): Bat-Track Auxiliary Switching Regulator Control
Output. This pin drives the VC pin of an external Linear
Technology step-down switching regulator. In conjunction
with WALL and ACPR, it will regulate VOUT to maximize
battery charger efficiency.
WALL (Pin 5): Auxiliary Power Source Sense Input. WALL
is used to determine when power is available from an
auxiliary power source. When power is detected, ACPR is
driven low and the USB input is automatically disabled.
BATSENS (Pin 6): Battery Voltage Sense Input. For proper
operation, this pin must always be connected to BAT. For
best operation, connect BATSENS to BAT physically close
to the Li-Ion cell.
PROG (Pin 7): Charge Current Program and Charge Current
Monitor Pin. Connecting a resistor from PROG to ground
programs the charge current. If sufficient input power
is available in constant-current mode, this pin servos
to one of eight possible I2C controllable voltages (see
Table 3). The voltage on this pin always represents the
actual charge current by using the following formula:
IBAT =
VPROG
• 1030
RPROG
4099fd
LTC4099
Pin Functions
IRQ (Pin 8): Open-Drain Interrupt Output. The IRQ pin
can be used to generate an interrupt due to a multitude
of maskable status change events within the LTC4099.
See Table 1.
DVCC (Pin 15): Logic Reference for the I2C Serial Port. A
0.01µF bypass capacitor is required.
GND (Pin 9, Exposed Pad Pin 21): Ground. The Exposed
Pad and pin must be soldered to the PCB to provide a low
electrical and thermal impedance connection to ground.
SDA (Pin 17): Data Input/Output for the I2C Serial Port.
The I2C input levels are scaled with respect to DVCC.
IDGATE (Pin 10): Ideal Diode Amplifier Output. This pin
controls the gate of an external P-channel MOSFET transistor used to supplement the internal ideal diode. The
source of the P-channel MOSFET should be connected to
VOUT and the drain should be connected to BAT.
BAT (Pin 11): Single-Cell Li-Ion Battery Pin. Depending
on available power and load, a Li-Ion battery on BAT will
either deliver system power to VOUT through the ideal
diode or be charged from the battery charger.
VOUT (Pin 12): Output Voltage of the Switching PowerPath
Controller and Input Voltage of the Battery Charger. The
majority of the portable product should be powered from
VOUT. The LTC4099 will partition the available power between the external load on VOUT and the internal battery
charger. Priority is given to the external load and any extra
power is used to charge the battery. An ideal diode from
BAT to VOUT ensures that VOUT is powered even if the load
exceeds the allotted power from VBUS or if the VBUS power
source is removed. VOUT should be bypassed with a low
impedance multilayer ceramic capacitor.
VBUS (Pin 13): Input Voltage for the Switching PowerPath
Controller. VBUS will usually be connected to the USB port
of a computer or a DC output wall adapter. VBUS should
be bypassed with a low impedance multilayer ceramic
capacitor.
SW (Pin 14): Switching Regulator Power Transmission
Pin. The SW pin delivers power from VBUS to VOUT via the
step-down switching regulator. An inductor should be connected from SW to VOUT. See the Applications Information
section for a discussion of inductance value.
SCL (Pin 16): Clock Input for the I2C Serial Port. The I2C
input levels are scaled with respect to DVCC.
ACPR (Pin 18): Auxiliary Power Source Present Output
(Active Low). ACPR indicates that the output of an external
high voltage step-down switching regulator connected to
WALL is suitable for use by the LTC4099. ACPR may be
connected to the gate of an external P-channel MOSFET
transistor whose source is connected to VOUT and whose
drain is connected to WALL. ACPR has a high level of VOUT
and a low level of GND.
CLPROG (Pin 19): USB Current Limit Program and Monitor
Pin. A 1% resistor from CLPROG to ground determines
the upper limit of the current drawn from the VBUS pin.
A precise fraction of the input current, hCLPROG, is sent
to the CLPROG pin when the high side switch is on. The
switching regulator delivers power until the CLPROG pin
reaches 1.18V. Therefore, the current drawn from VBUS
will be limited to an amount given by hCLPROG and
RCLPROG. There are a multitude of ratios for hCLPROG
available by I2C control, two of which correspond to the
100mA and 500mA USB specifications (see Table 2). A
multilayer ceramic averaging capacitor is also required at
CLPROG for filtering.
OVSENS (Pin 20): Overvoltage Protection Sense Input.
OVSENS should be connected through a 6.2k resistor to
the input power connector and the drain of an external
N‑channel MOSFET pass transistor. When the voltage
on this pin exceeds VOVCUTOFF, the OVGATE pin will be
pulled to GND to disable the pass transistor and protect
the LTC4099 from potentially damaging high voltage.
4099fd
11
LTC4099
Block Diagram
TO AUTOMOTIVE,
FIREWIRE, ETC.
VIN
SW
LT3480
VC
4
TO USB
OR WALL
ADPAPTER
13
6V
+
–
1
OVGATE
s2
5
VC
VOUT
3.6V
BAT + 0.3V
+
+
–
20
OVERVOLTAGE PROTECTION
OVSENS
FB
WALL
4.3V
ACPR
18
Bat-Track HV CONTROL
+–
VBUS
SW
TO
SYSTEM
LOAD
14
NONOVERLAP
AND DRIVE
LOGIC
ISWITCH/N ILDO/M
19
100mV
+
–
VOUT
CLPROG
4.6V
IDEAL
DIODE
Q
CONSTANT-CURRENT
CONSTANT-VOLTAGE
BATTERY CHARGER
R
0V
15mV
3
2
NTC
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
–
+
TOO COLD
–
+
TOO WARM
–
+
IDGATE
BATSENS
3.6V
BAT
+–
OSC
VOUT
–
+
+
–
0.3V
VC/x
+
–
1.18V
NTCBIAS
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
+
+
–
–
+
12
– +
SUSPEND
LDO
S
T NTC
–
+
+
–
OPTIONAL
EXTERNAL
IDEAL DIODE
PMOS
10
6
11
SINGLECELL
Li-Ion
C/x
+
VPROG
IBAT/1030
BATTERY CONDITIONER
3.85V
OVERTEMPERATURE
+
–
IRQ
I2C PORT
DVCC
15
SCL
16
8
INTERRUPT LOGIC
SDA
17
GND
9
GND
21
PROG
7
4099 BD
4099fd
12
LTC4099
TIMING Diagram
SDA
tSU, DAT
tLOW
tSU, STA
tHD, DAT
tBUF
tSU, STO
tHD, STA
4099 TD03
SCL
tHIGH
tHD, STA
START
CONDITION
tSP
REPEATED START
CONDITION
tf
tr
STOP
CONDITION
START
CONDITION
I2C Write Protocol
WRITE ADDRESS
SUB ADDRESS
R/ W
A7
0
0
0
1
0
0
1
0
SDA
0
0
0
1
0
0
1
0
ACK
SCL
1
2
3
4
5
6
7
8
9
A6
A5
A4
A3
INPUT DATA BYTE
A2
A1
A0
B7
B6
B5
B4
B3
B2
B1
B0
START
STOP
ACK
1
2
3
4
5
6
7
8
ACK
9
1
2
3
4
5
6
7
8
9
4099 TD01
I2C Read Protocol
READ ADDRESS
OUTPUT DATA BYTE
R/W
A7
0
0
0
1
0
0
1
1
SDA
0
0
0
1
0
0
1
1
ACK
SCL
1
2
3
4
5
6
7
8
9
A6
A5
A4
A3
A2
A1
A0
START
ACK
1
2
3
4
5
6
7
8
9
4099 TD02
4099fd
13
LTC4099
Operation
Introduction
The LTC4099 is an I2C controlled power manager and
Li‑Ion charger designed to make optimal use of the power
available from a variety of sources while minimizing power
dissipation and easing thermal budgeting constraints. The
innovative PowerPath architecture ensures that the application is powered immediately after external voltage is
applied, even with a completely dead battery, by prioritizing
power to the application.
The LTC4099 includes a Bat-Track monolithic step-down
switching regulator for USB, wall adapters and other 5V
sources. Designed specifically for USB applications, the
switching regulator incorporates a precision average input current limit for USB compatibility. Because power is
conserved, the LTC4099 allows the load current on VOUT to
exceed the current drawn by the USB port making maximum
use of the allowable USB power for battery charging. The
switching regulator and battery charger communicate to
ensure that the average input current never exceeds the
USB specifications.
For automotive and other high voltage applications, the
LTC4099 provides Bat-Track control of an external Linear
Technology step-down switching regulator to maximize battery charger efficiency and minimize heat production.
When power is available from both the USB and an auxiliary input, the auxiliary input is prioritized.
The LTC4099 contains both an internal 180mΩ ideal diode
as well as an ideal diode controller for use with an external
P-channel MOSFET. The ideal diodes from BAT to VOUT
guarantee that ample power is always available to VOUT even
if there is insufficient or absent power at VBUS or WALL.
The LTC4099 features an overvoltage protection circuit
which is designed to work with an external N-channel
MOSFET to prevent damage to its input caused by accidental application of high voltage.
To prevent battery drain when a device is connected to a
suspended USB port, an LDO from VBUS to VOUT provides
either a low power or high power USB suspend current
to the application.
Finally, the LTC4099 has considerable adjustability built
in so that power levels and status information can be
controlled and monitored via a simple two wire I2C port.
14
Bat-Track Input Current Limited Step-Down Switching
Regulator
The power delivered from VBUS to VOUT is controlled by a
2.25MHz constant-frequency step-down switching regulator. To meet the maximum USB load specification, the
switching regulator contains a measurement and control
system which ensures that the average input current remains below the level programmed at the CLPROG pin
and I2C port. VOUT drives the combination of the external
load and the battery charger.
If the combined load does not cause the switching power
supply to reach the programmed input current limit, VOUT
will track approximately 0.3V above the battery voltage.
By keeping the voltage across the battery charger at this
low level, power lost to the battery charger is minimized.
Figure 1 shows the power path components.
If the combined external load plus battery charge current
is large enough to cause the switching power supply to
reach the programmed input current limit, the battery
charger will reduce its charge current by precisely the
amount necessary to enable the external load to be satisfied. Even if the battery charge current is programmed to
exceed the allowable USB power, the USB specification
for average input current will not be violated; the battery
charger will reduce its current as needed. Furthermore, if
the load current at VOUT exceeds the programmed power
from VBUS, the extra load current will be drawn from the
battery via the ideal diodes even when the battery charger
is enabled.
The current out of CLPROG is a precise fraction of the
VBUS current. When a programming resistor and an averaging capacitor are connected from CLPROG to GND,
the voltage on CLPROG represents the average input
current of the switching regulator. As the input current
approaches the programmed limit, CLPROG reaches
1.18V and power delivered by the switching regulator
is held constant.
The input current limit has eight possible settings ranging from the USB suspend limit of 500µA up to 1.2A
for wall adapter applications. Two of these settings are
specifically intended for use in the 100mA and 500mA
USB applications.
4099fd
LTC4099
Operation
TO AUTOMOTIVE,
FIREWIRE, ETC.
HVIN HIGH VOLTAGE
STEP-DOWN
SWITCHING
VC
REGULATOR
4
OVGATE
s2
5
VC
OVERVOLTAGE PROTECTION
+
–
1
OVSENS
6V
+–
VOUT
3.6V
BAT + 0.3V
4.3V
–
+
VBUS
ACPR
SW
ISWITCH/N
VOUT
PWM AND
GATE DRIVE
IDEAL
DIODE
CONSTANT-CURRENT
CONSTANT-VOLTAGE
BATTERY CHARGER
OmV
15mV
CLPROG
1.18V
–
+
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
+
+
–
19
WALL
18
Bat-Track HV CONTROL
FROM USB
OR WALL
ADAPTER
13
FB
+
+
–
20
SW
–
+
+
–
IDGATE
0.3V
3.6V
BAT
+–
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
BATSENS
3.5V TO
(BAT + 0.3V)
TO SYSTEM
LOAD
14
12
OPTIONAL
EXTERNAL
IDEAL DIODE
PMOS
10
11
6
+
4099 F01
SINGLE-CELL
Li-Ion
Figure 1. PowerPath Block Diagram
IVBUS =IVBUSQ +
VCLPROG
• (hCLPROG + 1)
RCLPROG
where IVBUSQ is the quiescent current of the LTC4099,
VCLPROG is the CLPROG servo voltage in current limit,
RCLPROG is the value of the programming resistor and
hCLPROG is the ratio of the measured current at VBUS to the
sample current delivered to CLPROG. Refer to the Electrical Characteristics table for values of hCLPROG, VCLPROG
and IVBUSQ. Given worst-case circuit tolerances, the USB
specification for the average input current in 100mA or
500mA mode will not be violated, provided that RCLPROG
is 3.01k or greater. See Table 2 for other available settings
of input current limit.
While not in current limit, the switching regulator’s
Bat-Track feature will set VOUT to approximately 300mV
above the voltage at BAT. However, if the voltage at BAT is
below 3.3V, and the load requirement does not cause
the switching regulator to exceed its current limit, VOUT
will regulate at a fixed 3.6V, as shown in Figure 2. This
instant-on feature will allow a portable product to run
immediately when power is applied without waiting for
4.5
4.2
3.9
VOUT (V)
When the switching regulator is activated, the average
input current will be limited by the CLPROG programming
resistor according to the following expression:
3.6
NO LOAD
300mV
3.3
3.0
2.7
2.4
2.4
2.7
3.0
3.6
3.3
BAT (V)
Figure 2. VOUT vs BAT
3.9
4.2
4099 F02
4099fd
15
LTC4099
Operation
the battery to charge. If the input-referred load current
exceeds the input current limit at VBUS, VOUT will range
between the no-load voltage and slightly below the battery
voltage as indicated by the shaded region of Figure 2. If
there is no battery present when this happens, VOUT may
collapse to ground. In such cases the input-referred load
current should be maintained below the programmed input
current level in order to keep the VOUT and BAT voltages
within specified limits.
For very low battery voltages, the battery charger acts
like a load and, due to the input current limit circuit, its
current will tend to pull VOUT below the 3.6V instant-on
voltage. To prevent VOUT from falling below this level, an
undervoltage circuit automatically detects that VOUT is
falling and reduces the battery charge current as needed.
This reduction ensures that load current and voltage are
always prioritized while allowing as much battery charge
current as possible. See Overprogramming the Battery
Charger in the Applications Information section.
The voltage regulation loop compensation is controlled by
the capacitance on VOUT. An MLCC capacitor of 10µF is
required for loop stability. Additional capacitance beyond
this value will improve transient response.
An internal undervoltage lockout circuit monitors VBUS and
keeps the switching regulator off until VBUS rises above
the rising VUVLO threshold (4.3V). If VBUS falls below the
falling VUVLO threshold (4V), system power at VOUT will
be drawn from the battery via the ideal diodes. The voltage at VBUS must also be higher than the voltage at BAT
by VDUVLO, or approximately 200mV, for the switching
regulator to operate.
Bat-Track Auxiliary High Voltage Switching Regulator
Control
As shown in the Block Diagram, the WALL, ACPR and
VC pins can be used in conjunction with an external high
voltage Linear Technology step-down switching regulator, such as the LT3480 or LT3653, to minimize heat
production when operating from higher voltage sources.
Bat-Track control circuitry regulates the external switching
regulator’s output voltage to the larger of BAT + 300mV
or 3.6V in much the same way as the internal switching
regulator. This maximizes battery charger efficiency while
still allowing instant-on operation when the battery is
deeply discharged.
The feedback network of the high voltage regulator should
be set to program an output voltage between 4.5V and
5.5V. When high voltage is applied to the external regulator,
WALL will rise toward this programmed output voltage.
When WALL exceeds approximately 4.3V, ACPR is brought
low, and the Bat-Track control of the LTC4099 overdrives
the local VC control of the external high voltage step-down
switching regulator. Once the Bat-Track control is enabled,
the output voltage is independent of the switching regulator feedback network.
Bat-Track control provides a significant efficiency advantage
over the use of a simple 5V switching regulator output to
drive the battery charger. With a 5V output driving VOUT,
battery charger efficiency is approximately:
hTOTAL = hBUCK •
VBAT
5V
where hBUCK is the efficiency of the high voltage switching
regulator and 5V is the output voltage of the switching
regulator. With a typical switching regulator efficiency of
87% and a typical battery voltage of 3.8V, the total battery
charger efficiency is approximately 66%. Assuming a 1A
charge current, nearly 2W of power is dissipated just to
charge the battery!
With Bat-Track, battery charger efficiency is approximately:
hTOTAL = hBUCK •
VBAT
VBAT + 0.3V
With the same assumptions as above, the total battery
charger efficiency is approximately 81%. This example
works out to less than 1W of power dissipation, or almost
60% less heat.
See the Typical Applications section for complete circuits
using the LT3480 and LT3653 with Bat-Track control.
Ideal Diode from BAT to VOUT
The LTC4099 has an internal ideal diode as well as a controller for an external ideal diode. Both the internal and
the external ideal diodes are always on and will respond
quickly whenever VOUT drops below BAT.
4099fd
16
LTC4099
Operation
If the load current increases beyond the power allowed
from the switching regulator, additional power will be pulled
from the battery via the ideal diodes. Furthermore, if power
to VBUS (USB or wall adapter) is removed, then all of the
application power will be provided by the battery via the
ideal diodes. The ideal diodes will be fast enough to keep
VOUT from drooping with only the storage capacitance
required for the switching regulator. The internal ideal
diode consists of a precision amplifier that activates a
large on-chip MOSFET transistor whenever the voltage at
VOUT is approximately 15mV (VFWD) below the voltage at
BAT. Within the amplifier’s linear range, the small-signal
resistance of the ideal diode will be quite low, keeping
the forward drop near 15mV. At higher current levels, the
MOSFET will be in full conduction.
2200
VISHAY Si2333
EXTERNAL
IDEAL DIODE
2000
1800
CURRENT (mA)
1600
1400
LTC4099
IDEAL DIODE
1200
1000
800
600
ON
SEMICONDUCTOR
MBRM120LT3
400
200
0
0
60 120 180 240 300 360 420 480
FORWARD VOLTAGE (mV) (BAT – VOUT) 4099 F03
Figure 3. Ideal Diode V-I Characteristics
To supplement the internal ideal diode, an external
P‑channel MOSFET transistor may be added from BAT to
VOUT. The IDGATE pin of the LTC4099 drives the gate of
the external P-channel MOSFET transistor for automatic
ideal diode control. The source of the external P-channel
MOSFET should be connected to VOUT and the drain should
be connected to BAT. Capable of driving a 1nF load, the
IDGATE pin can control an external P-channel MOSFET
transistor having an on-resistance of 30mΩ or lower.
Battery Charger
The LTC4099 includes a battery charger with low voltage
precharge, constant-current/constant-voltage charging, C/x
state-of-charge detection, automatic termination by safety
timer, automatic recharge, bad cell detection and thermistor
sensor input for out-of-temperature charge pausing.
Precharge
When a battery charge cycle begins, the battery charger
first determines if the battery is deeply discharged. If the
battery voltage is below VTRKL, typically 2.85V, an automatic
trickle charge feature sets the battery charge current to
one-fifth of the default charge current. If the low voltage
persists for more than one-half hour, the battery charger
automatically terminates and indicates via the I2C port
that the battery was unresponsive.
Constant-Current
Once the battery voltage is above VTRKL, the charger begins
charging in full power constant-current mode. The current
delivered to the battery will try to reach VPROG/RPROG •
1030 where VPROG can be set by the I2C port and ranges
from 500mV to 1.2V in 100mV steps. The default value
of VPROG is 500mV. Depending on available input power
and external 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. Likewise, 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.
As mentioned above, the upper limit of charge current is
programmed by the combination of a resistor from PROG
to ground and the PROG servo voltage value set in the
I2C port. The charge current will be given by the following
expression:
V
ICHG = PROG • 1030
RPROG
Eight values of VPROG may be selected by the ICHARGE2,
ICHARGE1 and ICHARGE0 bits in the I2C port. See Table 3.
In either the constant-current or constant-voltage charging
modes, the voltage at the PROG pin will be proportional to
the actual charge current delivered to the battery. The charge
current can be determined at any time by monitoring the
PROG pin voltage and using the following relationship:
V
IBAT = PROG • 1030
RPROG
4099fd
17
LTC4099
Operation
Recall, however, that in many cases the actual battery
charge current, IBAT, will be lower than the programmed
current, ICHG, due to limited input power available and
prioritization of the system load drawn from VOUT.
Constant-Voltage
Once the battery terminal voltage reaches the preset float
voltage, the battery charger will hold the voltage steady
and the charge current will decrease naturally toward
zero. Two voltage settings, 4.100V and 4.200V, are available for final float voltage selection via the I2C port. For
applications that require as much run time as possible,
the 4.200V setting can be selected. For applications that
seek to extend battery life, the LTC4099’s default setting
of 4.100V should be used.
Full Capacity Charge Indication (C/x)
Since the PROG pin always represents the actual charge
current flowing, even in the constant-voltage phase of
charging, the PROG pin voltage represents the battery’s
state-of-charge during that phase. The LTC4099 has a full
capacity charge indication comparator on the PROG pin
which reports its results via the I2C port. Selection levels
for the C/x comparator of 50mV, 100mV, 200mV and 500mV
are available by I2C control. Recall that the PROG pin servo
voltage can be programmed from 500mV to 1.2V. If the 1V
servo setting represents the full charge rate of the battery
(1C), then the 100mV C/x setting would be equivalent to
C/10. Likewise the 200mV C/x setting would represent
C/5 and the 500mV setting C/2.
Charge Termination
The battery charger has a built-in termination safety
timer. When the voltage on the battery reaches the userprogrammed float voltage of 4.100V or 4.200V, the safety
timer is started. After the safety timer expires, charging of
the battery will discontinue and no more current will be
delivered. The safety timer’s default ending time of four
hours may be altered from one to eight hours in one-hour
increments by accessing the I2C port.
Automatic Recharge
After the battery charger terminates, it will remain off,
drawing only microamperes of current from the battery.
18
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 new charge cycle will
automatically begin when the battery voltage falls below
VRECHRG (typically 4.100V for the 4.200V float voltage
setting and 4.000V for the 4.100V float voltage setting). In
the event that the safety timer is running when the battery
voltage falls below VRECHRG, it will reset back to zero. To
prevent brief excursions below VRECHRG from resetting the
safety timer, the battery voltage must be below VRECHRG for
more than 2.5ms. The charge cycle and safety timer will
also restart if the VBUS UVLO cycles LOW and then HIGH
(e.g., VBUS or WALL is removed and then replaced) or if
the charger is momentarily disabled using the I2C port.
The flow chart in Figure 4 represents the battery charger’s
algorithm.
Thermistor Measurement
The battery temperature is measured by placing a negative temperature coefficient (NTC) thermistor close to
the battery pack. The thermistor circuitry is shown in the
Block Diagram.
To use this feature, connect the thermistor between the NTC
pin and ground and a bias resistor from NTCBIAS to NTC.
The bias resistor should be a 1% resistor with a value equal
to the value of the chosen thermistor at 25°C (R25).
The LTC4099 will pause charging when the resistance of
the thermistor drops to 0.484 times the value of R25 or
4.84k for a 10k thermistor. For a Vishay curve 2 thermistor, this corresponds to approximately 45°C. If the battery
charger is in constant-voltage (float) mode, the safety
timer also pauses until the thermistor indicates a return
to valid temperature. The LTC4099 is also designed to
pause charging when the value of the thermistor increases
to 2.816 times the value of R25. For a Vishay curve 2
10k thermistor, this resistance, 28.16k, corresponds to
approximately 0°C. The hot and cold comparators each
have approximately 4°C of hysteresis to prevent oscillation
about the trip point.
If the curve 2 thermistor’s temperature rises above 60°C,
its value will drop to 0.2954 times R25. When this happens,
the LTC4099 detects this critically high temperature and
indicates it via the I2C port (see Table 7). If this condition
4099fd
LTC4099
Operation
occurs, it may be desirable to have application software
enforce an emergency reduction of power in the portable
product. It is possible to enable the battery conditioner
circuit at this temperature to reduce stress caused by
simultaneous high temperature and high voltage via the
I2C port. See the Overtemperature Battery Conditioner
section.
The thermistor detection circuit samples the thermistor’s
value continuously whenever charging is enabled and
periodically when it is not. When the charger is not enabled, the thermistor is sampled for 150µs approximately
every 150ms. The thermistor data available to the I2C port
is updated at the end of each sample period.
POWER AVAILABLE
CLEAR EVENT TIMER
INDICATE CHARGING
NTC OUT-OF-RANGE
YES
INHIBIT CHARGING
NO
PAUSE EVENT TIMER
BAT < 2.85V
BATTERY STATE
BAT > VFLOAT – E
INDICATE NTC FAULT
2.85V < BAT < VFLOAT – E
NO
CHARGE WITH
103V/RPROG
CHARGE WITH
CONSTANT-CURRENT
CHARGE WITH
FIXED VOLTAGE
RUN EVENT TIMER
PAUSE EVENT TIMER
RUN EVENT TIMER
SAFETY TIMER
EXPIRED
TIMER > 30 MINUTES
YES
NO
YES
INHIBIT CHARGING
IBAT < C/x
NO
STOP CHARGING
YES
BAT RISING
THROUGH VRECHRG
YES
INDICATE CHARGING
STOPPED
INDICATE BATTERY FAULT
INDICATE C/x REACHED
NO
BAT > 2.85V
YES
NO
BAT FALLING
THROUGH VRECHRG
NO
YES
BAT < VRECHRG
NO
YES
4099 F04
Figure 4. Battery Charger Flow Chart
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19
LTC4099
Operation
Overtemperature Battery Conditioner
Overvoltage Protection
Since Li-Ion batteries deteriorate with full voltage and
high temperature, the LTC4099 contains an automatic
battery conditioner circuit that reduces the battery voltage if both high temperature and high voltage are present
simultaneously.
The LTC4099 can protect itself from the inadvertent application of excessive voltage to VBUS or WALL with just
two external components: an N-channel MOSFET and a
6.2k resistor. The maximum safe overvoltage magnitude
will be determined by the choice of the external FET and
its associated drain breakdown voltage.
Recall that battery charging is inhibited if the thermistor
temperature reaches 45°C. If the thermistor temperature
climbs above 60°C, and the battery conditioner circuit is
enabled, an internal load of approximately 180mA is applied to BAT. Once the battery voltage drops to 3.9V, or the
thermistor reading drops below 58°C, the internal load is
disabled. Battery charging resumes once the thermistor
temperature drops below 42°C.
When activated via the I2C port, the battery conditioner
operates whether or not external power is available,
charging has terminated or charging has been disabled
by I2C control.
Note that this circuit can dissipate significant power inside
the LTC4099. To prevent an excessive temperature rise
of the LTC4099, the LTC4099 reduces discharge current
as needed to prevent a junction temperature rise above
120°C.
Thermal Regulation
To prevent thermal damage to the LTC4099 or surrounding
components during normal charging, an internal thermal
feedback loop will automatically decrease the programmed
charge current if the die temperature rises to 105°C. This
thermal regulation technique protects the LTC4099 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. The benefit of the LTC4099 thermal
regulation loop is that charge current can be set according
to actual, rather than worst-case, conditions for a given
application with the assurance that the charger will automatically reduce the current in worst-case conditions.
The thermal regulation set-point can be adjusted down to
85°C from the default 105°C setting using the I2C port, as
explained in the Input Data section.
The overvoltage protection circuit consists of two pins. The
first, OVSENS, is used to measure the externally applied
voltage through an external resistor. The second, OVGATE,
is an output used to drive the gate pin of the external FET.
When OVSENS is below 6V, an internal charge pump will
drive OVGATE to approximately 1.88 • OVSENS. This will
enhance the N-channel FET and provide a low impedance
connection to VBUS or WALL which will, in turn, power
the LTC4099. If OVSENS should rise above 6V due to a
fault or use of an incorrect wall adapter, OVGATE will be
pulled to GND, disabling the external FET and, therefore,
protecting the LTC4099. When the voltage drops below
6V again, the external FET will be re-enabled.
See the Applications Information section for examples of
multiple input protections, reverse input protection and
recommended components.
Suspend LDO
The LTC4099 provides a small amount of power to VOUT
in suspend mode by including an LDO from VBUS to VOUT.
This LDO will prevent the battery from running down when
the portable product has access to a suspended USB port.
Regulating at 4.6V, this LDO only becomes active when
the internal switching converter is disabled. To remain
compliant with the USB specification, the input to the LDO
is current-limited so that it will not exceed the low power
or high power suspend specification. If the load on VOUT
exceeds the suspend current limit, the additional current
will come from the battery via the ideal diodes. The suspend LDO sends a scaled copy of the VBUS current to the
CLPROG pin, which will servo to a maximum voltage of
approximately 100mV. Thus, the high power and low power
suspend settings are related to the levels programmed by
the same CLPROG resistor for the 100mA, 500mA and
other switching power path settings. Command bits, ILIM2
4099fd
20
LTC4099
Operation
through ILIM0 in the I2C port determine whether the suspend LDO will limit input current to the low power setting
of 500µA or the high power setting of 2.5mA.
Interrupt Generation
The IRQ pin on the LTC4099 is an open-drain output that
can be used to generate an interrupt based on one or more
of a multitude of maskable PowerPath/battery charger
change events. The interrupt mask register column in
Table 1 indicates the categories of events that can generate an interrupt. If a 1 is written to a given location in the
mask register, then any change in the status data of that
category will cause an interrupt to occur. For example, if
a 1 is written to bit 6 of the mask register, then an interrupt will be generated when the WALL UVLO detects that
either power has become available at WALL, or that power
was available and is no longer available from WALL. If a
1 is written to bit 2 of the mask register, then an interrupt
will be triggered by any change in the status bits of the
battery charger, as given by Table 8. Likewise, a 1 at bit 3
will allow an interrupt due to any change in the thermistor
status bits of Table 7.
The IRQ pin is cleared when the bus master acknowledges
receipt of status data from a read operation. If the master
does not acknowledge the status byte, the interrupt will
not be cleared and the IRQ pin will not be released.
Upon generation of an interrupt, the current state of the
LTC4099 is recorded in the I2C port for retrieval (see
Output Data).
I2C Interface
The LTC4099 may communicate with a bus master using
the standard I2C 2-wire interface. The Timing Diagram
shows the relationship of the signals on the bus. The two
bus lines, SDA and SCL, must be HIGH when the bus is
not in use. External pull-up resistors or current sources,
such as the LTC1694 SMBus accelerator, are required
on these lines. The LTC4099 is both a slave receiver and
slave transmitter. The I2C control signals, SDA and SCL,
are scaled internally to the DVCC supply. DVCC should be
connected to the same power supply as the bus pull-up
resistors.
The I2C port has an undervoltage lockout on the DVCC pin.
When DVCC is below approximately 1V, the I2C serial port
is cleared, the LTC4099 is set to its default configuration
of all zeros and interrupts will be locked out.
Bus Speed
The I2C port is designed to be operated at speeds of up
to 400kHz. It has built-in timing delays to ensure correct
operation when addressed from an I2C compliant master
device. It also contains input filters designed to suppress
glitches should the bus become corrupted.
START and STOP Conditions
A bus master signals the beginning of communications
by transmitting a START condition. A START condition is
generated by transitioning SDA from HIGH to LOW while
SCL is HIGH. The master may transmit either the slave
write or the slave read address. Once data is written to the
LTC4099, the master may transmit a STOP condition which
commands the LTC4099 to act upon its new command set.
A STOP condition is sent by the master by transitioning
SDA from LOW to HIGH while SCL is HIGH.
Byte Format
Each byte sent to, or received from, the LTC4099 must
be eight bits long followed by an extra clock cycle for the
acknowledge bit. The data should be sent to the LTC4099
most significant bit (MSB) first.
Acknowledge
The acknowledge signal is used for handshaking between
the master and the slave. When the LTC4099 is written
to (write address), it acknowledges its write address as
well as the subsequent two data bytes. When it is read
from (read address), the LTC4099 acknowledges its read
address only. The bus master should acknowledge receipt
of information from the LTC4099.
An acknowledge (active LOW) generated by the LTC4099
lets the master know that the latest byte of information was
received. The acknowledge related clock pulse is generated
by the master. The master releases the SDA line (HIGH)
during the acknowledge clock cycle. The LTC4099 pulls
4099fd
21
LTC4099
Operation
down the SDA line during the write acknowledge clock
pulse so that it is a stable LOW during the HIGH period
of this clock pulse.
When the LTC4099 is read from, it releases the SDA line
so that the master may acknowledge receipt of the data.
Since the LTC4099 only transmits one byte of data, a master
not acknowledging the data sent by the LTC4099 has no
specific consequence on the operation of the I2C port.
However, without a read acknowledge from the master, a
pending interrupt from the LTC4099 will not be cleared
and the IRQ pin will not be released.
Slave Address
The LTC4099 responds to a 7-bit address which has been
factory programmed to 0b0001001[R/W]. The LSB of
the address byte, known as the read/write bit, should be
0 when writing data to the LTC4099, and 1 when reading
data from it. Considering the address an 8-bit word, then
the write address is 0x12, and the read address is 0x13.
The LTC4099 will acknowledge both its read and write
addresses.
Sub-Addressed Writing
The LTC4099 has three command registers for control
input. They are accessed by the I2C port via a sub-
addressed writing system.
Each write cycle of the LTC4099 consists of exactly three
bytes. The first byte is always the LTC4099’s write address.
The second byte represents the LTC4099’s sub address.
The sub address is a pointer which directs the subsequent
data byte within the LTC4099. The third bye consists of
the data to be written to the location pointed to by the
sub address. The LTC4099 contains control registers at
only three sub address locations: 0x00, 0x01 and 0x02.
Only the two LSBs of the sub address byte are decoded,
the remaining bits are don’t-cares. Therefore, a write to
sub address 0x06 for example, is effectively a write to
sub address 0x02.
Bus Write Operation
The master initiates communication with the LTC4099
with a START condition and the LTC4099’s write address.
If the address matches that of the LTC4099, the LTC4099
returns an acknowledge. The master should then deliver
the sub address. Again, the LTC4099 acknowledges and
the cycle is repeated for the data byte. The data byte is
transferred to an internal holding latch upon the return of
its acknowledge by the LTC4099. This procedure must be
repeated for each sub address that requires new data. After
one or more cycles of [ADDRESS][SUB-ADDRESS][DATA],
the master may terminate the communication with a STOP
condition. Alternatively, a repeat START condition can be
initiated by the master and another chip on the I2C bus can
be addressed. This cycle can continue indefinitely, and the
LTC4099 will remember the last input of valid data that it
received. Once all chips on the bus have been addressed
and sent valid data, a global STOP can be sent and the
LTC4099 will update its command latches with the data
that it had received.
Bus Read Operation
The bus master reads the status of the LTC4099 with a
START condition followed by the LTC4099 read address. If
the read address matches that of the LTC4099, the LTC4099
returns an acknowledge. Following the acknowledgement
of its read address, the LTC4099 returns one bit of status
information for each of the next eight clock cycles. A STOP
command is not required for the bus read operation.
Input Data
Table 1 illustrates the three data bytes that may be written to the LTC4099. The first byte at sub address 0x00
controls the three input current limit bits ILIM2 -ILIM0, the
three battery charge current control bits ICHARGE2 -ICHARGE0
and the two C/x state-of-charge indication control bits
COVERX1 and COVERX0.
The input current limit settings are decoded according to
Table 2. This table indicates the maximum current that will
be drawn from the VBUS pin in the event that the load at
VOUT (battery charger plus system load) exceeds the power
available. Any additional power will be drawn from the battery. The default state for the input current limit setting is
000, representing the low power 100mA USB setting.
4099fd
22
LTC4099
Operation
The battery charger current settings are decoded in
Table 3. The battery charger current settings are adjusted
by selecting one of the eight servo voltages for the PROG
pin. Recall that the programmed charge current is given
by the expression:
V
ICHG = PROG • 1030
RPROG
The default state for the battery charger current settings is
000, giving the lowest available servo voltage of 500mV.
The COVERX1 and COVERX0 bits are decoded in Table 4.
The C/x setting controls the PROG pin level that the
LTC4099’s C/x comparator uses to report full capacity
charge. For example, if the 100mV setting is chosen, then
the LTC4099 reports that its PROG pin voltage has fallen
Table 1. LTC4099 Input Data Bytes
SUB ADDRESS 1
SUB ADDRESS 2
COMMAND
REGISTER 0
COMMAND
REGISTER 1
IRQ MASK
REGISTER
ILIM2
TIMER2
USBGOOD
Bit 6
ILIM1
TIMER1
WALLGOOD
Bit 5
ILIM0
TIMER0
BADCELL
Bit 4
ICHARGE2
DISABLE_CHARGER
THERMAL_ REG
Bit 3
ICHARGE1
ENABLE_ BATTERY_
CONDITIONER
THERMISTOR_
STATUS
Bit 2
ICHARGE0
VFLOAT = 4.2V
CHARGER_STATUS
Bit 1
COVERX1
TREG = 85°C
Not Used
Bit 0
COVERX0
Not Used
Not Used
Table 2. ILIM2 – ILIM0 Decode
ILIM2
0
0
0
0
1
1
1
1
*Default Setting
USB INPUT CURRENT LIMIT SETTINGS
ILIM1
ILIM0
IUSB
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
The second byte of data at sub address 0x01 controls the
three battery charger safety timer bits, TIMER2-TIMER0,
the DISABLE_CHARGER bit, the ENABLE_BATTERY_
CONDITIONER bit, the VFLOAT = 4.2V control bit and the
TREG = 85°C control bit.
The TIMER2–TIMER0 bits control the duration of the battery charger safety timer. The safety timer starts once the
LTC4099 reaches the 4.100V or the 4.200V float voltage.
As long as input power is available, charging will continue in float voltage mode until the safety timer expires.
Table 3. ICHARGE2 – ICHARGE0 Decode
SUB ADDRESS 0
Bit 7
below 100mV. For the 50mV setting, LTC4099 reports
that its PROG pin voltage has fallen below 50mV. The C/x
settings are adjusted by comparing the PROG pin voltage
with the values shows in Table 4. The default value for the
C/x setting is 00, giving 100mV detection.
100mA*
500mA
620mA
790mA
1000mA
1200mA
Suspend Low (500µA)
Suspend High (2.5mA)
BATTERY CHARGER CURRENT LIMIT SETTINGS
CHARGE CURRENT
ICHARGE1
ICHARGE0
VPROG
RPROG = 1.02k
ICHARGE2
0
0
0
500mV*
500mA
0
0
1
600mV
600mA
0
1
0
700mV
700mA
0
1
1
800mV
800mA
1
0
0
900mV
900mA
1
0
1
1000mV
1000mA
1
1
0
1100mV
1100mA
1
1
1
1200mV
1200mA
*Default Setting
Table 4. C/x Decode
C/x INDICATION SETTINGS
FULL CAPACITY CHARGE
INDICATION
RPROG = 1.02k
COVERX1 COVERX0
VPROG
0
0
100mV*
100mA*
0
1
50mV
50mA
1
0
200mV
200mA
1
1
500mV
500mA
*Default Setting
4099fd
23
LTC4099
Operation
Table 5 lists the possible safety timer settings from 1 to 8
hours, and how to decode them. The default state for the
LTC4099 safety timer is 4 hours.
Table 5. Safety Timer Decode
TIMER2
0
0
0
0
1
1
1
1
*Default Setting
SAFETY TIMER SETTINGS
TIMER1
TIMER0
0
0
0
1
1
0
1
1
0
0
0
1
1
0
1
1
TIMEOUT
4 Hours*
5 Hours
6 Hours
7 Hours
8 Hours
1 Hour
2 Hours
3 Hours
The DISABLE_CHARGER bit can be used to prevent battery
charging if needed. This bit should be used with caution
as it can prevent the battery charger from bringing up
the battery voltage. Without the ability to address the I2C
port, only a low voltage on DVCC will clear the I2C port to
its default state and re-enable charging.
The ENABLE_BATTERY_CONDITIONER bit enables the
automatic battery load circuit in the event of simultaneously
high battery voltage and temperature. See the Overtemperature Battery Conditioner section.
The VFLOAT = 4.2V bit controls the final float voltage of the
LTC4099’s battery charger. A 1 in this bit position changes
the charger from the default float voltage value of 4.100V
to the higher 4.200V level.
The TREG = 85°C control bit changes the LTC4099’s battery
charger junction thermal regulation temperature from its
default value of 105°C to a lower setting of 85°C. This may
be used to reduce heat in highly thermally compromised
systems. In general, the high efficiency charging system
of the LTC4099 will keep the junction temperature low
enough to avoid junction thermal regulation.
The third and final byte of input data at sub address 0x02
is the mask register. The mask register determines which
status change events or categories will be allowed to generate an interrupt. A 1 written to a given position in the mask
register allows status change in that category to generate
an interrupt. A zero in a given position in the mask register
prohibits the generation of an interrupt. The start-up state
of the LTC4099 is all zeros for this register indicating that
no interrupts will be generated without explicit request via
the I2C port. See the Interrupt Generation section.
Output Data
One status byte may be read from the LTC4099. Table 6
represents the status byte information. A 1 read back in
any of the bit positions indicates that the condition is true.
For example, 1s read back from bits 7 and 2 indicate that
power is available at VBUS, and that the battery charger’s
thermistor has halted charging due to an undertemperature
condition at the battery.
Table 6. LTC4099 Status Data Bytes
READ BYTE
Bit 7 (MSB)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
STATUS REGISTER
USBGOOD
WALLGOOD
BADCELL
THERMAL REG
NTC1
See Table 7
NTC0
CHRGR1
See Table 8
CHRGR0
Bit 7 in the status byte indicates the presence of power
at VBUS. Criteria for determining this status bit is derived
from the undervoltage lockout circuit on VBUS and is given
by the electrical parameters VUVLO and VDUVLO.
Bit 6 indicates the presence of voltage available at the WALL
pin and is derived from the WALL undervoltage lockout
circuit. Like the VBUS pin, this pin has both an absolute
voltage detection level given by the electrical parameter
VWALL, as well as a level relative to BAT given by ∆VWALL.
Both of the conditions must be met for bit 6 to indicate
the presence of power at WALL.
Bit 5 indicates that the battery has been below the precharge threshold level of approximately 2.85V for more
than one-half hour while the charger was attempting to
charge. When this occurs, it is usually the result of a defective cell. However, in some cases a bad cell indication
may be caused by system load prioritization over battery
charging. System software can test for this by forcing a
reduction of system load and restarting the battery charger
4099fd
24
LTC4099
Operation
via I2C (a disable followed by an enable). If the bad cell
indication returns, then the cell is definitively bad.
Bit 4 indicates that the battery charger is in thermal regulation due to excessive LTC4099 junction temperature. Recall
that there are two I2C programmable junction temperature
settings available at which to regulate, 85°C and 105°C.
Bit 4 indicates thermal regulation at whichever setting is
chosen.
Bits 3 and 2 indicate the status of the thermistor measurement circuit and are decoded in Table 7. The BATTERY
TOO COLD and BATTERY TOO HOT states indicate that
the thermistor temperature is out of range (either below
0°C or above 45°C for a curve 2 thermistor) and that
charging has paused until a return to valid temperature.
The BATTERY OVERTEMPERATURE state indicates that
the battery’s thermistor has reached a critical temperature
(above 60°C for a curve 2 thermistor) and that long term
battery capacity may be seriously compromised if the
condition persists.
Table 7. NTC1, NTC0 Decode
NTC1
0
0
1
1
THERMISTOR STATUS BIT DECODE
NTC0
THERMISTOR STATUS
0
NO NTC FAULT
1
BATTERY TOO COLD
0
BATTERY TOO HOT
1
BATTERY OVERTEMPERATURE
Table 8. CHRGR1, CHRGR0 Decode
CHRGR1
0
0
1
1
BATTERY CHARGER STATUS BIT DECODE
CHRGR0
CHARGER STATUS
0
CHARGER OFF
1
CONSTANT-CURRENT
0
CONSTANT V, IBAT > C/x
1
CONSTANT V, IBAT < C/x
Bits 1 and 0 indicate the status of the battery charger, and
are decoded into one of four possible battery charger states
in Table 8. The constant-current state indicates that the
battery charger is attempting to charge with all available
current up to the constant-current level programmed,
and that the battery has not yet reached the float voltage.
The CONSTANT V, IBAT > C/x bit indicates that the battery
charger has entered the float voltage phase of charging
(BAT at 4.1V or 4.2V), but that the charge current is still
above the C/x detection level programmed. The CONSTANT
V, IBAT 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
LTC3576/
LTC3576-1
Switching Power Manager
with USB On-The-Go + Triple
Step-Down DC/DCs
Complete Multifunction PMIC: Bidirectional Switching Power Manager and Three Buck
Regulators + LDO, ADJ Output Down to 0.8V at 400mA/400mA/1A, Overvoltage Protection,
USB On-The-Go, Charge Current Programmable Up to 1.5A from Wall Adapter Input, Thermal
Regulation, I2C, High Voltage Bat-Track Buck Interface, 180mΩ Ideal Diode; 4mm × 6mm
QFN-38 Package
LTC4088
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
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