LTC4160/LTC4160-1
Switching Power Manager
with USB On-The-Go And
Overvoltage Protection
DESCRIPTION
FEATURES
Bidirectional Switching Regulator Makes Optimal
Use of Limited Power Available from USB Port and
also Provides a 5V Output for USB On-The-Go
n Overvoltage Protection Guards Against Damage
n 180mΩ Internal Ideal Diode Plus Optional External
Ideal Diode Controller Seamlessly Provides Low
Loss PowerPath When Input Power is Limited or
Unavailable
n Instant-On Operation with Discharged Battery
n Full Featured Li-Ion/Polymer Battery Charger
n Bat-Track™ Adaptive Output Control For Efficient
Charging
n 1.2A Max Input Current Limit
n 1.2A Max Charge Current with Thermal Limiting
n Battery Float Voltage: 4.2V (LTC4160), 4.1V
(LTC4160-1)
n Low Battery Powered Quiescent Current (8µA)
n 20-pin 3mm × 4mm × 0.75mm QFN Package
The LTC®4160/LTC4160-1 are high efficiency power management and Li-Ion/Polymer battery charger ICs. They each
include a bidirectional switching PowerPath™ controller
with automatic load prioritization, a battery charger, and
an ideal diode.
n
The LTC4160/LTC4160-1’s bidirectional switching regulator
transfers nearly all of the power available from the USB
port to the load with minimal loss and heat which eases
thermal constraints in small spaces. These devices feature
a precision input current limit for USB compatibility and
Bat-Track output control for efficient charging. In addition,
the ICs can also generate 5V at 500mA for USB On-TheGo applications.
An overvoltage circuit protects the LTC4160/LTC4160-1
from high voltage damage on the USB/wall adapter inputs
with an external N-channel MOSFET and a resistor.
The LTC4160/LTC4160-1 are available in a 3mm × 4mm
× 0.75mm QFN surface mount package.
APPLICATIONS
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
and PowerPath and Bat-Track are a trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
6522118, 6404251. Other patents pending.
Media Players and Personal Navigation Devices
Digital Cameras, PDAs, Smart Phones
n
n
TYPICAL APPLICATION
5.5
USB
ON-THE-GO
VOUT = BAT = 3.8V
3.3µH
VBUS
USB
5.0
VBUS = 4.75V
4.5
4.0
3.5
6.2k
OPTIONAL
OVERVOLTAGE
PROTECTION
SYSTEM
LOAD
750
VOUT
BAT
OVSENS
CLPROG
0.1µF
PROG
3.01k
VBUS CURRENT
500
10µF
OVGATE
USB 2.0 SPECIFICATIONS
REQUIRE THAT HIGH
POWER DEVICES NOT
OPERATE IN THIS REGION
Battery and VBUS Currents
vs Load Current
SW
LTC4160/
LTC4160-1
10µF
IVBUS = 500mA
VBUS (V)
High Efficiency Power Manager/Battery Charger with USB
On-The-Go and Overvoltage Protection
+
Li-Ion
CURRENT (mA)
USB OTG VBUS Voltage
vs VBUS Current
250
BATTERY CURRENT
(CHARGING)
0
VBUS = 5V
BAT = 3.8V
5x MODE
–250
1k
BATTERY CURRENT
(DISCHARGING)
41601 TA01a
3.0
0
100
200 300 400 500
VBUS CURRENT (mA)
600
700
41601 TA01b
–500
0
200
600
800
400
LOAD CURRENT (mA)
1000
41601 TA01c
41601fa
1
LTC4160/LTC4160-1
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2, 3)
CLPROG
LDO3V3
NTC
NTCBIAS
TOP VIEW
VBUS (Transient) t < 1ms, Duty Cycle < 1%... –0.3V to 7V
VBUS (Static), BAT, VOUT, NTC, ENOTG, ID,
ENCHARGER, VBUSGD, FAULT, CHRG......... –0.3V to 6V
ILIM0, IILIM1......... –0.3V to Max(VBUS, VOUT, BAT) + 0.3V
IOVSENS....................................................................10mA
ICLPROG.....................................................................3mA
ICHRG, IVBUSGD, IFAULT.............................................50mA
IPROG.........................................................................2mA
ILDO3V3....................................................................30mA
ISW, IBAT, IVOUT, IVBUS...................................................2A
Operating Temperature Range.................. –40°C to 85°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range.................... –65°C to 125°C
20 19 18 17
OVGATE 1
16 ILIM1
OVSENS 2
15 ILIM0
VBUSGD 3
14 SW
21
GND
FAULT 4
13 VBUS
12 VOUT
ID 5
9 10
IDGATE
8
CHRG
7
PROG
11 BAT
ENCHARGER
ENOTG 6
UDC PACKAGE
20-LEAD (3mm × 4mm) PLASTIC QFN
TJMAX = 125°C, θJA = 43°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
LTC4160EUDC#PBF
LTC4160EUDC#TRPBF
LFXY
20-Lead (3mm × 4mm) Plastic QFN
–40°C to 85°C
LTC4160EUDC-1#PBF
LTC4160EUDC-1#TRPBF
LFXZ
20-Lead (3mm × 4mm) Plastic QFN
–40°C to 85°C
LTC4160EPDC#PBF
LTC4160EPDC#TRPBF
FDRT
20-Lead (3mm × 4mm) Plastic UTQFN
–40°C to 85°C (OBSOLETE)
LTC4160EPDC-1#PBF
LTC4160EPDC-1#TRPBF
FDST
20-Lead (3mm × 4mm) Plastic UTQFN
–40°C to 85°C (OBSOLETE)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL
CHARACTERISTICS l denotes the specifications which apply over the full operating
The
temperature range, otherwise specifications are at TA = 25°C (Note 2). VBUS = 5V, BAT = 3.8V, RCLPROG = 3.01k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
90
480
955
0.43
100
500
1000
0.5
UNITS
PowerPath Switching Regulator – Step-Down Mode
VBUS
Input Supply Voltage
IBUS(LIM)
Total Input Current
1x Mode
5x Mode
10x Mode
Suspend Mode
IVBUSQ (Note 4)
Input Quiescent Current
1x Mode
5x, 10x Modes
Suspend Mode
7
20
0.050
mA
mA
mA
1x Mode
5x Mode
10x Mode
Suspend Mode
211
1170
2377
9.6
mA/mA
mA/mA
mA/mA
mA/mA
hCLPROG (Note 4) Ratio of Measured VBUS Current to
CLPROG Program Current
4.35
l
l
l
l
82
440
900
0.32
5.5
V
mA
mA
mA
mA
41601fa
2
LTC4160/LTC4160-1
ELECTRICAL
CHARACTERISTICS
The
l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C (Note 2). VBUS = 5V, BAT = 3.8V, RCLPROG = 3.01k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
IVOUT(POWERPATH) VOUT Current Available Before
Discharging Battery
1x Mode, BAT = 3.3V
5x Mode, BAT = 3.3V
10x Mode, BAT = 3.3V
Suspend Mode
VCLPROG
CLPROG Servo Voltage in Current Limit
Switching Modes
Suspend Mode
VUVLO
VBUS Undervoltage Lockout
Rising Threshold
Falling Threshold
VDUVLO
VBUS To BAT Differential Undervoltage
Lockout
Rising Threshold
Falling Threshold
VOUT
VOUT Voltage
1x, 5x, 10x Modes, 0V < BAT ≤ 4.2V,
IVOUT = 0mA, Battery Charger Off
USB Suspend Mode, IVOUT = 250µA
fOSC
Switching Frequency
MIN
TYP
0.26
121
667
1217
0.34
MAX
UNITS
0.43
mA
mA
mA
mA
1.183
100
3.95
4.3
4
V
mV
4.35
200
50
V
V
mV
mV
3.5
4.5
BAT + 0.3
4.6
4.7
4.7
V
V
1.8
2.25
2.7
MHz
RPMOS_POWERPATH PMOS On-Resistance
0.18
Ω
RNMOS_POWERPATH NMOS On-Resistance
0.3
Ω
IPEAK_POWERPATH Peak Inductor Current Clamp
1x Mode (Note 5)
5x Mode (Note 5)
10x Mode (Note 5)
1
1.6
3
A
A
A
RSUSP
Closed Loop
10
Ω
Suspend LDO Output Resistance
PowerPath Switching Regulator – Step-Up Mode (USB On-The-Go)
VBUS
Output Voltage
VOUT
Input Voltage
IVBUS
Output Current Limit
0 ≤ IVBUS ≤ 500mA, VOUT > 3.2V
l
4.75
5.25
V
2.9
4.2
V
550
680
mA
IPEAK
Peak Inductor Current Limit
(Note 5)
1.8
A
IOTGQ
VOUT Quiescent Current
VOUT = 3.8V, IVBUS = 0mA (Note 6)
1.6
mA
VCLPROG
Output Current Limit Servo Voltage
1.15
V
VOUTUVLO
VOUT UVLO – VOUT Falling
VOUT UVLO – VOUT Rising
tSCFAULT
Short Circuit Fault Delay
2.5
PMOS Switch Off
2.6
2.8
2.9
7.2
V
V
ms
Overvoltage Protection
VOVCUTOFF
Overvoltage Protection Threshold
With 6.2k Series Resistor
6.42
6.7
V
VOVGATE
OVGATE Output Voltage
VOVSENS < VOVCUTOFF
VOVSENS > VOVCUTOFF
6.1
1.88 • VOVSENS
0
12
V
V
tRISE
OVGATE Time To Reach Regulation
OVGATE CLOAD = 1nF
1.25
BAT Regulated Output Voltage
LTC4160
ms
Battery Charger
VFLOAT
l
4.179
4.165
4.2
4.2
4.221
4.235
V
V
l
4.079
4.065
4.1
4.1
4.121
4.135
V
V
1120
185
1219
206
1320
223
mA
mA
3.8
6
µA
8
12
µA
LTC4160-1
ICHG
Constant Current Mode Charger Current
RPROG = 845Ω, 10x Mode RCLPROG ≤ 2.49k
RPROG = 5k, 5x or 10x Mode
IBAT
Battery Drain Current
VBUS > VUVLO, Suspend Mode,
IVOUT = 0µA
VBUS = 0V, IVOUT = 0µA
(Ideal Diode Mode)
41601fa
3
LTC4160/LTC4160-1
ELECTRICAL
CHARACTERISTICS
The
l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C (Note 2). VBUS = 5V, BAT = 3.8V, RCLPROG = 3.01k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
VPROG
PROG Pin Servo Voltage
VPROG_TRKL
PROG Pin Servo Voltage in Trickle Charge BAT < VTRKL
0.1
V
VC/10
C/10 Threshold Voltage at PROG
100
mV
hPROG
Ratio of IBAT to PROG Pin Current
1030
mA/mA
1
ITRKL
Trickle Charge Current
BAT < VTRKL
VTRKL
Trickle Charge Threshold Voltage
BAT Rising
2.7
2.85
UNITS
V
100
mA
3
135
V
∆VTRKL
Trickle Charge Hysteresis Voltage
∆VRECHRG
Recharge Battery Threshold Voltage
Threshold Voltage Relative to VFLOAT
–75
–100
–125
mV
mV
tTERM
Safety Timer Termination Period
Timer Starts when VBAT = VFLOAT
3.9
4.3
5.4
Hour
tBADBAT
Bad Battery Termination Time
BAT < VTRKL
hC/10
End of Charge Current Ratio
(Note 7)
RON_CHG
Battery Charger Power FET
On-Resistance (Between VOUT and BAT)
0.18
Ω
TLIM
Junction Temperature in Constant
Temperature Mode
110
°C
0.4
0.5
0.6
0.085
0.1
0.115
Hour
mA/mA
NTC
VCOLD
Cold Temperature Fault Threshold
Voltage
VHOT
Rising Threshold
Hysteresis
75
76.5
1.5
78
%NTCBIAS
%NTCBIAS
Hot Temperature Fault Threshold Voltage Falling Threshold Hysteresis
33.4
34.9
1.8
36.4
%NTCBIAS
%NTCBIAS
VDIS
NTC Disable Threshold Voltage
Falling Threshold
Hysteresis
0.7
1.7
50
2.7
%NTCBIAS
mV
INTC
NTC Leakage Current
NTC = NTCBIAS = 5V
–50
50
nA
VFWD
Forward Voltage Detection
VBUS = 0V, IVOUT = 10mA
IVOUT = 10mA
RDROPOUT
Internal Diode On-Resistance, Dropout
IVOUT = 200mA
IMAX_DIODE
Diode Current Limit
Ideal Diode
2
15
mV
mV
0.18
Ω
2
A
Always On 3.3V LDO Supply
VLDO3V3
Regulated Output Voltage
0mA < ILDO3V3 < 20mA
3.1
3.3
3.5
V
RCL_LDO3V3
Closed-Loop Output Resistance
2.7
Ω
ROL_LDO3V3
Dropout Output Resistance
23
Ω
Logic (ILIM0, ILIM1, ID, ENOTG, ENCHARGER)
VIL
Logic Low Input Voltage
VIH
Logic High Input Voltage
0.4
IPD1
ILIM0, ILIM1, ENOTG, ENCHARGER
Pull-Down Current
1.8
µA
IPU1
ID Pull-Up Current
2.5
µA
1.2
V
V
Status Outputs (CHRG, VBUSGD, FAULT)
VVBUSGD
Output Low Voltage
IVBUSGD = 5mA, VBUS = 5V
65
100
mV
VCHRG, VFAULT
Output Low Voltage
ICHRG = IFAULT = 5mA, VOUT = 3.8V
100
150
mV
ICHRG, IVBUSGD,
IFAULT
Leakage Current
VCHRG = VVBUSGD = VFAULT = 5V
1
μA
41601fa
4
LTC4160/LTC4160-1
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 LTC4160E/LTC4160E-1 are guaranteed to meet 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 LTC4160E/LTC4160E-1 include 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 current limit features of this part are intended to protect the
IC from short term or intermittent fault conditions. Continuous operation
above the maximum specified pin current rating may result in device
degradation or failure.
Note 6: The bidirectional switcher’s supply current is bootstrapped to
VBUS and in the application will reflect back to VOUT by (VBUS/VOUT) •
1/efficiency. Total quiescent current is the sum of the current into the VOUT
pin plus the reflected current.
Note 7: hC/10 is expressed as a fraction of the measured full charge current
with indicated PROG resistor.
TYPICAL PERFORMANCE CHARACTERISTICS
USB Limited Load Current vs Battery
Voltage (Battery Charger Disabled)
USB Limited Load Current vs Battery
Voltage (Battery Charger Disabled)
160
VBUS = 5V
5x MODE
800
LOAD CURRENT (mA)
LOAD CURRENT (mA)
600
500
400
300
200
100
80
60
40
2.7
3.0
3.9
3.6
3.3
BATTERY VOLTAGE (V)
0
4.2
2.7
BATTERY CURRENT
(CHARGING)
0
VBUS = 5V
BAT = 3.8V
5x MODE
RCLPROG = 3.01k BATTERY CURRENT
RPROG = 1k
(DISCHARGING)
3.0
3.3
3.9
3.6
BATTERY VOLTAGE (V)
–500
4.2
USB Limited Battery Charge
Current vs Battery Voltage
1000
600
120
750
300
200
VBUS = 5V
5x MODE
RPROG = 1k
100
2.7
3.0
3.9
3.6
3.3
BATTERY VOLTAGE (V)
100
80
60
40
20
4.2
41601 G04
0
600
800
400
LOAD CURRENT (mA)
1000
41601 G03
VBUS CURRENT
CURRENT (mA)
CHARGE CURRENT (mA)
140
400
200
Battery and VBUS Currents
vs Load Current
700
500
0
41601 G02
USB Limited Battery Charge
Current vs Battery Voltage
CHARGE CURRENT (mA)
250
–250
41601 G01
0
VBUS CURRENT
500
120
20
100
0
750
VBUS = 5V
1x MODE
140
700
Battery and VBUS Currents vs
Load Current
CURRENT (mA)
900
TA = 25°C, unless otherwise noted.
VBUS = 5V
1x MODE
RPROG = 1k
2.7
3.0
3.9
3.6
3.3
BATTERY VOLTAGE (V)
BATTERY CURRENT
(CHARGING)
500
250
VBUS = 5V
BAT = 3.8V
10x MODE
RCLPROG = 3.01k
RPROG = 2k
0
–250
4.2
41601 G05
–500
0
250
BATTERY CURRENT
(DISCHARGING)
750 1000 1250
500
LOAD CURRENT (mA)
1500
41601 G06
41601fa
5
LTC4160/LTC4160-1
TYPICAL PERFORMANCE CHARACTERISTICS
INTERNAL IDEAL
DIODE ONLY
0.2
0
INTERNAL IDEAL
DIODE
0.15
0.10
VBUS = 5V
0.04
0
0.12
0.16
0.08
FORWARD VOLTAGE (V)
0
2.7
0.20
3.0
3.6
3.9
3.3
BATTERY VOLTAGE (V)
BAT = 3.4V
3.75
BAT = 2.8V
3.50
3.25
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
0.05
BAT = 4V
4.00
VOUT (V)
RESISTANCE (Ω)
CURRENT (A)
4.25
0.20
0.6
0.4
4.50
0.25
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
0.8
VOUT Voltage vs Load Current
(Battery Charger Disabled)
Ideal Diode Resistance
vs Battery Voltage
Ideal Diode V-I Characteristics
1.0
TA = 25°C, unless otherwise noted.
3.00
VBUS = 5V
RCLPROG = 3.01k
RPROG = 2k
2.75
2.50
4.2
200
0
41601 G08
600
800
400
LOAD CURRENT (mA)
1000
41601 G09
41601 G07
600
4.7
RCLPROG = 3.01k
RPROG = 2k
5x MODE
4.3
4.1
400
300
200
3.9
3.7
3.5
4.25
BATTERY VOLTAGE
2.7
2.7
3.0
3.6
3.9
3.3
BATTERY VOLTAGE (V)
2.50
4.2
95
90
1x MODE
EFFICIENCY (%)
EFFICIENCY (%)
5x, 10x MODE
70
60
50
41601 G13
600
800
400
LOAD CURRENT (mA)
1000
41601 G12
RCLPROG = 3.01k
RPROG = 1k
1x MODE
80
75
70
65
5x MODE
60
40
30
200
0
85
80
20µs/DIV
VBUS = 5V
RCLPROG = 3.01k
RPROG = 2k
Battery Charging Efficiency vs
Battery Voltage with No External
Load (PBAT/PVBUS)
90
VBUS = 5V
VOUT = 3.65V
CHARGER OFF
10x MODE
BAT = 2.8V
41601 G11
PowerPath Switching Regulator
Efficiency vs Load Current
VOUT
50mV/DIV
AC-COUPLED
BAT = 3.4V
2.75
100
0mA
3.50
3.25
41601 G10
IVOUT
500mA/DIV
3.75
3.00
2.9
PowerPath Switching Regulator
Transient Response
BAT = 4V
4.00
1x MODE
3.1
0
3.40 3.45 3.50 3.55 3.60 3.65 3.70 3.75 3.80
VOUT (V)
4.50
5x MODE
3.3
100
VOUT Voltage vs Load Current
(Battery Charger Enabled)
VBUS = 5V
IVOUT = 0µA
RCLPROG = 3.01k
RPROG = 1k
4.5
VOUT (V)
BATTERY CURRENT (mA)
500
VOUT Voltage vs Battery Voltage
(Charger Overprogrammed)
VOUT (V)
Battery Charge Current vs VOUT
Voltage
55
10
100
LOAD CURRENT (mA)
1000
41601 G14
50
2.7
3.0
3.9
3.6
3.3
BATTERY VOLTAGE (V)
4.2
41601 G15
41601fa
6
LTC4160/LTC4160-1
TYPICAL PERFORMANCE CHARACTERISTICS
VOUT Voltage vs Load Current in
Suspend
BAT = 3.8V
40
VOUT (V)
30
5.0
0.5
4.5
0.4
4.0
3.5
20
3.0
10
0
0
1
2
3
4
BUS VOLTAGE (V)
5
2.5
6
0.1
0
0.3
0.4
0.2
LOAD CURRENT (mA)
41601 G16
Battery Drain Current vs
Battery Voltage
600
IVOUT = 0mA
VBUS = 0V
6
5
4
3
VBUS = 5V
(SUSPEND MODE)
2
0
2.7
3.0
3.3
3.6
3.9
400
THERMAL REGULATION
300
200
BATTERY VOLTAGE (V)
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (mA)
100 120
0.998
0.997
0.996
–40
5x MODE
15
10
1x MODE
5
35
10
TEMPERATURE (°C)
60
85
41601 G22
60
85
41601 G21
10
50
40
30
20
0
–40
35
10
TEMPERATURE (°C)
12
VBUS = 5V
8
6
4
2
10
–15
–15
Battery Drain Current vs
Temperature
60
20
41601 G18
0.999
VBUS Quiescent Current in
Suspend vs Temperature
70
0.5
1.000
41601 G20
VBUS = 5V
0
–40
20 40 60 80
TEMPERATURE (°C)
41601 G19
VBUS Quiescent Current vs
Temperature
25
0
0.3
0.4
0.2
LOAD CURRENT (mA)
1.001
RPROG = 2k
0
–40 –20
4.2
0.1
Normalized Battery Charger Float
Voltage vs Temperature
100
1
0
41601 G17
500
7
0.2
0
0.5
BATTERY CURRENT (µA)
BATTERY CURRENT (µA)
8
0.3
Battery Charge Current vs
Temperature
CHARGE CURRENT (mA)
9
VBUS = 5V
BAT = 3.3V
RCLPROG = 3.01k
0.1
VBUS = 5V
BAT = 3.3V
RCLPROG = 3.01k
NORMALIZED FLOAT VOLTAGE
QUIESCENT CURRENT (µA)
50
VBUS Current vs Load Current in
Suspend
VBUS CURRENT (mA)
60
VBUS Quiescent Current vs
VBUS Voltage (Suspend)
TA = 25°C, unless otherwise noted.
–15
10
35
TEMPERATURE (°C)
60
85
41601 G23
0
–40
BAT = 3.8V
VBUS = 0V
–15
10
35
TEMPERATURE (°C)
60
85
41601 G24
41601fa
7
LTC4160/LTC4160-1
TYPICAL PERFORMANCE CHARACTERISTICS
OTG Boost VBUS Voltage
vs Load Current
OTG Boost Quiescent Current
vs Battery Voltage
VOUT = BAT
QUIESCENT CURRENT (mA)
2.5
5.5
100
5.0
90
VBUS (V)
1.5
80
VBUS = 4.75V
4.5
2.0
OTG Boost Efficiency
vs Load Current
4.0
EFFICIENCY (%)
3.0
TA = 25°C, unless otherwise noted.
IVBUS = 500mA
3.5
1.0
2.5
4.2
3.9
3.6
3.3
BATTERY VOLTAGE (V)
50
0
200 300 400 500
LOAD CURRENT (mA)
100
600
41601 G25
500mA LOAD
80
100mA LOAD
90
2.0
3.9
3.6
3.3
BATTERY VOLTAGE (V)
22µF ON VBUS,
NO OVP
1.9
22µF ON VBUS,
LOAD THROUGH OVP
4.2
3.0
70
60
50
40
30
20
VOUT = BAT
ILOAD = 500mA
1.6
2.7
VOUT = BAT
80
2.1
1.7
3.0
22µF ON VBUS, 22µF AND
LOAD THROUGH OVP
1.8
75
70
2.7
100
2.2
TIME (ms)
EFFICIENCY (%)
95
10
4.2
3.9
3.6
3.3
BATTERY VOLTAGE (V)
0
2.7
3.0
3.9
3.6
3.3
BATTERY VOLTAGE (V)
41601 G29
41601 G28
OTG Boost Start-Up into Current
Source Load
OTG Boost Transient Response
1000
OTG Boost Burst Mode Current
Threshold vs Battery Voltage
2.4
2.3
85
10
100
LOAD CURRENT (mA)
1
41601 G27
OTG Boost Start-Up Time
into Current Source Load vs
Battery Voltage
VOUT = BAT
90
30
700
41601 G26
OTG Boost Efficiency
vs Battery Voltage
100
VOUT = BAT = 4.2V
VOUT = BAT = 3.8V
VOUT = BAT = 3.4V
VOUT = BAT = 3V
40
LOAD CURRENT (mA)
3.0
60
VOUT = BAT = 4.2V
VOUT = BAT = 3.8V
VOUT = BAT = 3.4V
VOUT = BAT = 3V
3.0
0.5
2.7
70
4.2
41601 G30
OTG Boost Burst Mode Operation
VBUS
50mV/DIV
AC COUPLED
VBUS
50mV/DIV
AC COUPLED
IVBUS
200mA/DIV
VSW
1V/DIV
0mA
IVBUS
200mA/DIV
VBUS
2V/DIV
0V
0mA
VOUT = 3.8V
20µs/DIV
41601 G31
VOUT = 3.8V
ILOAD = 500mA
200µs/DIV
41601 G32
0V
VOUT = 3.8V
ILOAD = 10mA
50µs/DIV
41601 G33
41601fa
8
LTC4160/LTC4160-1
TYPICAL PERFORMANCE CHARACTERISTICS
3.3V LDO Step Response
(5mA to 15mA)
3.3V LDO Output Voltage vs
Load Current, VBUS = 0V
BAT = 3.9V, 4.2V
BAT = 3.4V
2.30
BAT = 3.5V
ILDO3V3
5mA/DIV
BAT = 3.6V
3.2
Oscillator Frequency vs
Temperature
2.25
FREQUENCY (MHz)
OUTPUT VOLTAGE (V)
3.4
TA = 25°C, unless otherwise noted.
0mA
3.0
2.8 BAT = 3V
BAT = 3.1V
BAT = 3.2V
BAT = 3.3V
2.6
5
15
0
20
10
LOAD CURRENT (mA)
VLDO3V3
20mV/DIV
AC COUPLED
BAT = 3.8V
2.15
VOUT = 5V
VOUT = 4.2V
VOUT = 3.6V
VOUT = 3V
VOUT = 2.7V
2.10
41601 G35
20µs/DIV
2.20
2.05
–40
25
–15
35
10
TEMPERATURE (°C)
60
41601 G36
41601 G34
OVP Connect Waveform
85
Rising OVP Threshold vs
Temperature
OVP Disconnect Waveform
6.47
VBUS
5V/DIV
OVGATE
6.46
OVP THRESHOLD (V)
2V/DIV
OVGATE
5V/DIV
VBUS
OVP INPUT
VOLTAGE
5V TO 10V
STEP 5V/DIV
0V
250µs/DIV
41601 G37
41601 G38
500µs/DIV
6.45
6.44
6.43
6.42
–40
48
OVSENS CONNECTED
TO INPUT THROUGH
10 6.2k RESISTOR
QUIESCENT CURRENT (µA)
45
OVGATE (V)
8
6
4
2
0
VOVSENS = 5V
VBUSGD, CHRG, FAULT PIN CURRENT (mA)
OVGATE vs OVSENS
42
39
36
33
0
2
4
6
INPUT VOLTAGE (V)
8
41601 G40
30
–40
–15
35
10
TEMPERATURE (°C)
60
35
10
TEMPERATURE (°C)
60
85
41601 G39
VBUSGD, CHRG, FAULT Pin
Current vs Voltage (Pull-Down
State)
OVSENS Quiescent Current vs
Temperature
12
–15
85
41601 G41
120
VBUS = 5V
BAT = 3.8V
100
VBUSGD
80
60
FAULT, CHRG
40
20
0
0
1
3
4
5
2
VBUSGD, CHRG, FAULT PIN VOLTAGE (V)
41601 G42
41601fa
9
LTC4160/LTC4160-1
PIN FUNCTIONS
OVGATE (Pin 1): Overvoltage Protection Gate Output.
Connect OVGATE to the gate pin of an external N-channel
MOSFET. 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 connected to an internal charge pump
capable of creating sufficient overdrive to fully enhance
the MOSFET. If an overvoltage condition is detected, OVGATE is brought rapidly to GND to prevent damage to the
LTC4160/LTC4160-1. OVGATE works in conjunction with
OVSENS to provide this protection.
ENCHARGER (Pin 7): Logic Input. This pin enables the
battery charger. Active low. Has an internal 1.8µA pulldown current source.
OVSENS (Pin 2): 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. When the voltage on this pin exceeds
VOVCUTOFF, the OVGATE pin will be pulled to GND to disable the MOSFET and protect the LTC4160/LTC4160-1.
The OVSENS pin shunts current during an overvoltage
transient in order to keep the pin voltage at 6V.
VBUSGD (Pin 3): Logic Output. This is an open-drain
output which indicates that VBUS is above VUVLO and
VDUVLO. VBUSGD requires a pull-up resistor and/or LED
to provide indication.
FAULT (Pin 4): Logic Output. This in an open-drain output
which indicates a bad battery fault when the charger is
enabled or a short circuit condition on VBUS when the
bidirectional PowerPath switching regulator is in step-up
mode (On-The-Go). FAULT requires a pull-up resistor
and/or LED to provide indication.
ID (Pin 5): Logic Input. This pin independently enables
the bidirectional switching regulator to step-up the voltage on VOUT and provide a 5V output on the VBUS pin for
USB On-The-Go applications. If the host does not power
down VBUS then connect this pin directly to the ID pin of
a USB micro-AB receptacle. Active low. Has an internal
2.5µA pull-up current source.
ENOTG (Pin 6): Logic Input. This pin independently enables
the bidirectional switching regulator to step-up the voltage
on VOUT and provide a 5V output on the VBUS pin for USB
On-The-Go applications. Active high. Has an internal 1.8µA
pull-down current source.
PROG (Pin 8): Charge Current Program and Charge Current Monitor Pin. Connecting a 1% resistor from PROG to
ground, programs the charge current. If sufficient input
power is available in constant-current mode, this pin servos
to 1V. The voltage on this pin always represents the actual
charge current by using the following formula:
IBAT =
VPROG
• 1030
RPROG
CHRG (Pin 9): Logic Output. This is an open-drain output that indicates whether the battery is charging or not
charging. CHRG requires a pull-up resistor and/or LED to
provide indication.
IDGATE (Pin 10): Ideal Diode Amplifier Output. This pin
controls the gate of an optional external P-channel MOSFET
used as an ideal diode between VOUT and BAT. The external
ideal diode operates in parallel with the internal ideal diode.
The source of the P-channel MOSFET should be connected
to VOUT and the drain should be connected to BAT. If the
external ideal diode MOSFET is not used, IDGATE should
be left floating.
BAT (Pin 11): Single Cell Li-Ion Battery Pin. Depending on
available VBUS power, a Li-Ion battery on BAT will either
deliver power to VOUT through the ideal diode or be charged
from VOUT via the battery charger.
VOUT (Pin 12): Output Voltage of the Bidirectional PowerPath Switching Regulator in Step-Down Mode and Input
Voltage of the Battery Charger. The majority of the portable
product should be powered from VOUT. The LTC4160/
LTC4160-1 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. In On-The-Go mode, this pin delivers power
to VBUS via the SW pin. VOUT should be bypassed with a
low impedance multilayer ceramic capacitor.
41601fa
10
LTC4160/LTC4160-1
PIN FUNCTIONS
VBUS (Pin 13): Power Pin. This pin delivers power to VOUT
via the SW pin by drawing controlled current from a DC
source such as a USB port or DC output wall adapter.
In On-The-Go mode this pin provides power to external
loads. Bypass VBUS with a low impedance multilayer
ceramic capacitor.
SW (Pin 14): The SW pin transfers power between VBUS
to VOUT via the bidirectional switching regulator. See
the Applications Information section for a discussion of
inductance value and current rating.
ILIM0, ILIM1 (Pins 15, 16): ILIM0 and ILIM1 control the VBUS
input current limit of the bidirectional PowerPath switching
regulator in step-down mode. See Table 1. Each has an
internal 1.8µA pull-down current source.
CLPROG (Pin 17): USB Current Limit Program and Monitor
Pin. A 1% resistor from CLPROG to ground determines
the upper limit of the current drawn or sourced from the
VBUS pin. A precise fraction, hCLPROG, of the VBUS current
is sent to the CLPROG pin when the PMOS switch of the
bidirectional PowerPath switching regulator is on. The
switching regulator delivers power until the CLPROG pin
reaches 1.18V in step-down mode and 1.15V in step-up
mode. When the switching regulator is in step-down mode,
CLPROG is used to regulate the average input current.
Several VBUS current limit settings are available via user
input which will typically correspond to the 500mA and
100mA USB specifications. When the switching regulator
is in step-up mode (USB On-The-Go), CLPROG is used to
limit the average output current to 680mA. A multilayer
ceramic averaging capacitor or R-C network is required
at CLPROG for filtering.
LDO3V3 (Pin 18): 3.3V LDO Output Pin. This pin provides
a regulated always-on 3.3V supply voltage. LDO3V3
gets its power from VOUT. It may be used for light loads
such as a watch dog microprocessor or real time clock.
A 1µF capacitor is required from LDO3V3 to ground. If
the LDO3V3 output is not used it should be disabled by
connecting it to VOUT.
NTCBIAS (Pin 19): NTC Thermistor Bias Output. If NTC
operation is desired, connect a bias resistor between
NTCBIAS and NTC, and an NTC thermistor between NTC
and GND. To disable NTC operation, connect NTC to GND
and leave NTCBIAS open.
NTC (Pin 20): Input to the Thermistor Monitoring Circuits.
The NTC pin connects to a negative temperature coefficient
thermistor, which is typically co-packaged with the battery,
to determine if the battery is too hot or too cold to charge.
If the battery’s temperature is out of range, charging is
paused until it 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. To disable NTC operation,
connect NTC to GND and leave NTCBIAS open.
GND (Exposed Pad Pin 21): Ground. The Exposed Pad
should be connected to a continuous ground plane on the
second layer of the printed circuit board by several vias
directly under the LTC4160/LTC4160-1.
41601fa
11
2
1
4
3
OVSENS
OVGATE
FAULT
VBUSGD
CLPROG
17
VCLPROG
6V
FAULT
BAD CELL
OTG SHORT CIRCUIT
+
–
BAT
5.1V
16
ILIM1
VBUS VOLTAGE
CONTROLLER
VBUSGD
0.2V
4.6V
– +
AVERAGE VBUS
CURRENT LIMIT
CONTROLLER
4.3V
SUSPEND
LDO
+
–
OVERVOLTAGE PROTECTION
×2
ILDO/M
100mV
–+
ISWITCH/N
–
+
OPTIONAL
EXTERNAL
OVERVOLTAGE
PROTECTION
RESISTOR
–+
+
–
VBUS
15
ILIM0
6
ENOTG
CONTROL LOGIC
PWM AND
GATE DRIVE
5
ID
VOUT VOLTAGE
CONTROLLER
7
+–
0.3V
ENCHARGER
NTC FAULT
RECHRG
LOW BAT
3.6V
VRECHRG
21
GND
2.9V
100mV
VOUT
4HRS
–
+
15mV
OmV
IDEAL
DIODE
3.3V
– +
NTC ENABLE
OVERTEMP
+
–
3V3 LDO
UNDERTEMP
VFLOAT
IBAT/1000
1V
BATTERY CHARGER
–
+
+
–
13
–
+
+
+
–
+
–
OPTIONAL EXTERNAL
OVERVOLTAGE PROTECTION
N-CHANNEL MOSFET
+
–
+
–
+
–
+
–
+
–
12
+
–
TO USB
OR WALL
ADAPTER
0.1V
20
19
9
8
41601 BD
NTC
NTCBIAS
CHRG
PROG
BAT
11
IDGATE
10
12
VOUT
LDO3V3
18
14
SW
NTC T
+
SINGLE CELL
Li-Ion
OPTIONAL
EXTERNAL
IDEAL DIODE
P-CHANNEL
MOSFET
TO SYSTEM LOAD
LTC4160/LTC4160-1
BLOCK DIAGRAM
41601fa
LTC4160/LTC4160-1
OPERATION
Introduction
The LTC4160/LTC4160-1 are high efficiency bidirectional
switching power managers and Li-Ion/Polymer battery
chargers designed to make optimal use of the power
available while minimizing power dissipation and easing
thermal budgeting constraints. The innovative PowerPath
architecture ensures that the end product application is
powered immediately after external voltage is applied,
even with a completely dead battery, by prioritizing power
to the end product.
When acting as a step-down converter, the LTC4160/
LTC4160-1’s bidirectional switching regulator takes power
from USB, wall adapters, or other 5V sources and provides
power to the end product application and efficiently charges
the battery using Bat-Track. Because power is conserved,
the LTC4160/LTC4160-1 allow 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.
For USB compatibility, the switching regulator includes
a precision average input current limit. The bidirectional
switching regulator and battery charger communicate to
ensure that the average input current never exceeds the
USB specifications.
In addition, the bidirectional switching regulator can also
operate as a 5V synchronous step-up converter, taking
power from VOUT and delivering up to 500mA to VBUS
without the need for any additional external components.
This enables systems with USB dual-role transceivers to
function as USB On-The-Go dual-role devices. True output
disconnect and average output current limit features are
included for short circuit protection.
The LTC4160/LTC4160-1 contain 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.
An always-on LDO provides a regulated 3.3V from available power at VOUT. Drawing very little quiescent current,
this LDO will be on at all times and can be used to supply
up to 20mA.
The LTC4160/LTC4160-1 also feature an overvoltage protection circuit which is designed to work with an external
N-channel MOSFET to prevent damage to their inputs
caused by accidental application of high voltage.
Finally, to prevent battery drain when a device is connected to a suspended USB port, an LDO from VBUS to
VOUT provides low power USB suspend current to the end
product application.
Bidirectional PowerPath Switching Regulator –
Step-Down Mode
The power delivered from VBUS to VOUT is controlled by
a 2.25MHz constant frequency bidirectional switching
regulator in step-down mode. VOUT drives the combination
of the external load and the battery charger. To meet the
maximum USB load specification, the switching regulator
contains a measurement and control system that ensures
that the average input current remains below the level
programmed at CLPROG.
If the combined load does not cause the switching regulator 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 flow in step-down mode.
If the combined external load plus battery charge current
is large enough to cause the switching regulator 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 current, 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,
load current will be drawn from the battery via the ideal
diode(s) 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
41601fa
13
LTC4160/LTC4160-1
OPERATION
the programmed limit, CLPROG reaches 1.18V and power
delivered by the switching regulator is held constant.
The input current limit is programmed by the ILIM0 and
ILIM1 pins. The input current limit has four possible settings ranging from the USB suspend limit of 500μA up
to 1A for wall adapter applications. Two of these settings
are specifically intended for use in the 100mA and 500mA
USB application. Refer to Table 1 for current limit settings
using ILIM0 and ILIM1.
Table 1. USB Current Limit Settings Using ILIM0 and ILIM1
ILIM1
ILIM0
USB SETTING
0
0
1x Mode (USB 100mA Limit)
0
1
10x Mode (Wall 1A Limit)
1
0
Low Power Suspend (USB 500μA Limit)
1
1
5x Mode (USB 500mA Limit)
When the switching regulator is activated, the average
input current will be limited by the CLPROG programming
resistor according to the following expression:
IVBUS = IVBUSQ +
VCLPROG
• hCLPROG + 1
RCLPROG
(
)
where IVBUSQ is the quiescent current of the LTC4160/
LTC4160-1, 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.
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 operation will allow a portable product to run
immediately when power is applied without waiting for the
battery to charge. If the load does exceed the current limit
at VBUS, VOUT will range between the no-load voltage and
slightly below the battery voltage, indicated by the shaded
region of Figure 2.
TO USB
OR WALL
ADAPTER
13
3.5V TO
(BAT + 0.3V)
TO SYSTEM LOAD
14
SW
VBUS
PWM AND
GATE DRIVE
VBUS
VOLTAGE
CONTROLLER
CLPROG
17
1.18V
–
+
BATTERY CHARGER
AVERAGE VBUS INPUT
CURRENT LIMIT
CONTROLLER
1V
+
–
5V
12
–
+
+
–
ISWITCH/N
VOUT
VFLOAT
IDEAL
DIODE
OmV
15mV
–
+
+
–
10
IDGATE
IBAT/1000
OVGATE
–
+ +
–
2
OVSENS
OVERVOLTAGE PROTECTION
6V
+
+
–
×2
1
0.3V
3.6V
+–
11
BAT
VOUT VOLTAGE
CONTROLLER
8
PROG
USB INPUT
BATTERY POWER
+
SINGLE CELL
Li-Ion
41601 F01
Figure 1. Power Path Block Diagram – Power Available from USB/Wall Adapter
41601f
14
LTC4160/LTC4160-1
OPERATION
For very low-battery voltages, the battery charger acts like
a load and, due to limited input power, 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
Over Programming the Battery Charger in the Applications
Information section.
The voltage regulation loop compensation is controlled by
the capacitance on VOUT. A multilayer ceramic 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
4.30V and is about 200mV above the battery voltage.
When both conditions are met, VBUSGD goes low and
the switching regulator turns on. Hysteresis on the UVLO
forces VBUSGD high and turns off the switching regulator
if VBUS falls below 4.00V or to within 50mV of the battery
voltage. When this happens, system power at VOUT will
be drawn from the battery via the ideal diode(s).
4.5
4.2
VOUT (V)
3.9
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)
3.9
4.2
41601 F02
Figure 2. VOUT vs BAT
Bidirectional PowerPath Switching Regulator –
Step-Up Mode
For USB On-The-Go applications, the bidirectional
PowerPath switching regulator acts as a step-up converter
to deliver power from VOUT to VBUS. The power from VOUT
comes from the battery via the ideal diode(s). As a step-up
converter, the bidirectional switching regulator produces
5V on VBUS and is capable of delivering at least 500mA.
USB On-The-Go can be enabled by either of the external
control pins, ENOTG or ID. Figure 3 shows the power flow
in step-up mode.
An undervoltage lockout circuit monitors VOUT and prevents
step-up conversion until VOUT rises above 2.8V. To prevent
backdriving of VBUS when input power is available, the VBUS
undervoltage lockout circuit prevents step-up conversion
if VBUS is already greater than 4.3V at the time step-up
mode is enabled. The switching regulator is also designed
to allow true output disconnect by eliminating body diode
conduction of the internal PMOS switch. This allows VBUS
to go to zero volts during a short-circuit condition or while
shutdown, drawing zero current from VOUT.
The voltage regulation loop is compensated by the capacitance on VBUS. A 4.7µF multilayer ceramic capacitor is
required for loop stability. Additional capacitance beyond
this value will improve transient response. The VBUS voltage has approximately 3% load regulation up to an output
current of 500mA. At light loads, the switching regulator
goes into Burst Mode® operation. The regulator will deliver
power to VBUS until it reaches 5.1V after which the NMOS
and PMOS switches shut off. The regulator delivers power
again to VBUS once it falls below 5.1V.
The switching regulator features both peak inductor and
average output current limit. The peak current-mode
architecture limits peak inductor current on a cycle-bycycle basis. The peak current limit is equal to VBUS/2Ω to
a maximum of 1.8A so that in the event of a sudden short
circuit, the current limit will fold back to a lower value.
In step-up mode, the voltage on CLPROG represents the
average output current of the switching regulator when
a programming resistor and an averaging capacitor are
connected from CLPROG to GND. With a 3.01k resistor
on CLPROG, the bidirectional switching regulator has an
output current limit of 680mA. As the output current approaches this limit, CLPROG servos to 1.15V and VBUS falls
rapidly to VOUT. When VBUS is close to VOUT there may not
be sufficient negative slope on the inductor current when
the PMOS switch is on to balance the rise in the inductor
41601f
15
LTC4160/LTC4160-1
OPERATION
TO USB
OR WALL
ADAPTER
13
3.5V TO
(BAT + 0.3V)
TO SYSTEM LOAD
14
SW
VBUS
PWM AND
GATE DRIVE
VBUS
VOLTAGE
CONTROLLER
CLPROG
17
1.18V
BATTERY CHARGER
AVERAGE VBUS OUTPUT
– CURRENT LIMIT
CONTROLLER
1V
+
–
5.1V
12
–
+
+
–
ISWITCH/N
VOUT
VFLOAT
IDEAL
DIODE
OmV
15mV
–
+
+
–
10
IDGATE
+
IBAT/1000
OVGATE
–
+ +
–
2
OVSENS
OVERVOLTAGE PROTECTION
6V
+
+
–
×2
1
0.3V
3.6V
+–
11
BAT
VOUT VOLTAGE
CONTROLLER
8
PROG
+
SINGLE CELL
Li-Ion
BATTERY POWER
41601 F03
Figure 3. PowerPath Block Diagram – USB On-The-Go
The PMOS switch is enabled when VBUS rises above
VOUT + 180mV and is disabled when it falls below
VOUT + 70mV to prevent the inductor current from running away when not in current limit. If the PMOS switch is
disabled for more than 7.2ms then the switcher will shut
off, the FAULT pin will go low and a short circuit fault will be
declared. To re-enable step-up mode, the ENOTG pin, with
ID high, must be cycled low and then high or the ID pin, with
ENOTG grounded, must be cycled high and then low.
If the load current increases beyond the power allowed
from the bidirectional switching regulator, additional
power will be pulled from the battery via the ideal diode(s).
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 diode(s). The ideal diode(s) will
prevent VOUT from drooping with only the storage capacitance required for the bidirectional switching regulator. The
internal ideal diode consists of a precision amplifier that
activates a large on-chip P-channel MOSFET whenever
2200
VISHAY Si2333
OPTIONAL EXTERNAL
IDEAL DIODE
2000
1800
1600
CURRENT (mA)
current when the NMOS switch is on. This will cause the
inductor current to run away and the voltage on CLPROG
to rise. When CLPROG reaches 1.2V the switching of the
synchronous PMOS is terminated and VOUT is applied
statically to its gate. This ensures that the inductor current
will have sufficient negative slope during the time current
is flowing out of the VBUS pin. The PMOS will resume
switching when CLPROG drops down to 1.15V.
LTC4160/
LTC4160-1
IDEAL DIODE
1400
1200
1000
800
Ideal Diode(s) from BAT to VOUT
600
The LTC4160/LTC4160-1 each have 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.
200
ON
SEMICONDUCTOR
MBRM120LT3
400
0
0
60 120 180 240 300 360 420 480
FORWARD VOLTAGE (mV) (BAT – VOUT)
41601 F04
Figure 4. Ideal Diode V-I Characteristics
41601fa
16
LTC4160/LTC4160-1
OPERATION
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.
To supplement the internal ideal diode, an external Pchannel MOSFET may be added from BAT to VOUT. The
IDGATE pin of the LTC4160/LTC4160-1 drives the gate of
the external P-channel MOSFET 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 having an
on-resistance of 30mΩ or lower.
Suspend LDO
If the LTC4160/LTC4160-1 is configured for USB suspend
mode, the bidirectional switching regulator is disabled and
the suspend LDO provides power to the VOUT pin (presuming there is power available at VBUS). 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 bidirectional
switching regulator is disabled (suspended). The suspend LDO sends a scaled copy of the VBUS current to the
CLPROG pin, which will servo to approximately 100mV in
this mode. In accordance with the USB specification, the
input to the LDO is current limited so that it will not exceed
the low power suspend specification. If the load on VOUT
exceeds the suspend current limit, the additional current
will come from the battery via the ideal diode(s).
3.3V Always-On LDO Supply
The LTC4160/LTC4160-1 include a low quiescent current
low dropout regulator that is always powered. This LDO
can be used to provide power to a system pushbutton
controller, standby microcontroller or real time clock.
Designed to deliver up to 20mA, the always-on LDO requires at least a 1μF multilayer ceramic bypass capacitor
for compensation. The LDO is powered from VOUT, and
therefore will enter dropout at loads less than 20mA as
VOUT falls near 3.3V. If the LDO3V3 output is not used, it
should be disabled by connecting it to VOUT.
Battery Charger
The LTC4160/LTC4160-1 include a constant-current/constant-voltage battery charger with automatic recharge,
automatic termination by safety timer, low voltage trickle
charging, bad cell detection, and thermistor sensor input
for out-of-temperature charge pausing. The charger can
be disabled using the ENCHARGER pin.
Battery Preconditioning
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
10% of the programmed value. If the low voltage persists
for more than a 1/2 hour, the battery charger automatically
terminates and indicates via the CHRG and FAULT pins that
the battery was unresponsive.
Once the battery voltage is above 2.85V, the charger begins
charging in full power constant-current mode. The current delivered to the battery will try to reach 1030/RPROG.
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.
Charge Termination
The battery charger has a built-in safety timer. When the
voltage on the battery reaches the pre-programmed float
voltage, the battery charger will regulate the battery voltage and the charge current will decrease naturally. Once
the battery charger detects that the battery has reached
the float voltage, the four hour safety timer is started.
After the safety timer expires, charging of the battery will
discontinue and no more current will be delivered.
Automatic Recharge
After the battery charger terminates, it will remain off
drawing only microamperes of current from the battery.
If the portable product remains in this state long enough,
41601fa
17
LTC4160/LTC4160-1
OPERATION
the battery will eventually self discharge. To ensure that
the battery is always topped off, a charge cycle will automatically begin when the battery voltage falls below the
recharge threshold which is typically 100mV less than
the charger’s float voltage. In the event that the safety
timer is running when the battery voltage falls below the
recharge threshold, it will reset back to zero. To prevent
brief excursions below the recharge threshold from resetting the safety timer, the battery voltage must be below
the recharge threshold for more than 1ms. The charge
cycle and safety timer will also restart if the VBUS UVLO
cycles low and then high (e.g., VBUS is removed and then
replaced), or if the battery charger is cycled on and off by
the ENCHARGER pin.
Charge Current
The charge current is programmed using a single resistor from PROG to ground. 1/1030th of the battery charge
current is sent to PROG, which will attempt to servo to
1.000V. Thus, the battery charge current will try to reach
1030 times the current in the PROG pin. The program
resistor and the charge current are calculated using the
following equation:
V
ICHG = PROG • 1030
RPROG
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. Therefore, the actual charge current can be determined at any
time by monitoring the PROG pin voltage and using the
following equation:
IBAT =
VPROG
•1030
RPROG
In many cases, the actual battery charge current, IBAT, will
be lower than ICHG due to limited input power available and
prioritization with the system load drawn from VOUT.
The Battery Charger Flow Chart on the next page illustrates
the battery charger’s algorithm.
Charge Status Indication
The CHRG and FAULT pins can be used to indicate the status
of the battery charger. Two possible states are represented
by CHRG: charging and not charging. An open-drain output,
the CHRG pin can drive an indicator LED through a current
limiting resistor for human interfacing or simply a pull-up
resistor for microprocessor interfacing.
When charging begins, CHRG is pulled low and remains
low for the duration of a normal charge cycle. When charging is complete, i.e., the BAT pin reaches the float and the
charge current has dropped to one tenth of the programmed
value, the CHRG pin goes high. The CHRG pin does not
respond to the C/10 threshold if the LTC4160/LTC4160-1
is in VBUS input current limit. This prevents false end-ofcharge indications due to insufficient power available to
the battery charger.
Table 2 illustrates the possible states of the CHRG and
FAULT pins when the battery charger is active.
Table 2. Charge Status Readings Using the CHRG and FAULT Pins
STATUS
CHRG
FAULT
Charging/NTC Fault
Low
High
Not Charging
High
High
Bad Battery
High
Low
An NTC fault pauses charging while the battery temperature is out of range but is not indicated using the CHRG
or FAULT pins.
If a battery is found to be unresponsive to charging (i.e.,
its voltage remains below 2.85V for 1/2 hour) the CHRG
pin goes high and the FAULT pin goes low to indicate a
bad battery fault.
Note that the LTC4160/LTC4160-1 are 3-terminal
PowerPath products where system load is always prioritized over battery charging. Due to excessive system load,
there may not be sufficient power to charge the battery
beyond the trickle charge threshold voltage within the bad
battery timeout period. In this case, the battery charger
will falsely indicate a bad battery. System software may
then reduce the load and reset the battery charger to try
again.
The FAULT pin is also used to indicate whether there is
a short circuit condition on VBUS when the bidirectional
41601fa
18
LTC4160/LTC4160-1
OPERATION
Battery Charger Flow Chart
POWER ON/
ENABLE CHARGER
CLEAR EVENT TIMER
ASSERT CHRG LOW
NTC OUT OF RANGE
YES
NO
BAT < 2.85V
BATTERY STATE
BAT > VFLOAT – ε
2.85V < BAT < VFLOAT – ε
NO
CHARGE AT
100V/RPROG (C/10 RATE)
CHARGE AT
1030V/RPROG RATE
CHARGE WITH
FIXED VOLTAGE
(VFLOAT)
INHIBIT CHARGING
RUN EVENT TIMER
PAUSE EVENT TIMER
RUN EVENT TIMER
PAUSE EVENT TIMER
TIMER > 30 MINUTES
TIMER > 4 HOURS
YES
NO
YES
INHIBIT CHARGING
STOP CHARGING
IBAT < C/10
NO
YES
BAT RISING
THROUGH
VRECHRG
INDICATE BATTERY
FAULT AT FAULT
YES
CHRG Hi-Z
CHRG Hi-Z
NO
BAT > 2.85V
YES
NO
BAT FALLING
THROUGH
VRECHRG
NO
YES
BAT < VRECHRG
NO
YES
41601 FLOW
41601fa
19
LTC4160/LTC4160-1
OPERATION
switching regulator is in On-The-Go mode. When a short
circuit condition is detected, FAULT will go low-Z. The
ENOTG or VBUSGD pins can be used to determine which
fault has occurred. If ENOTG or VBUSGD is low when FAULT
went low, then a bad battery fault has occurred. If either
pin is high, then a short circuit on VBUS has occurred.
a given circuit board design. The benefit of the LTC4160/
LTC4160-1 thermal regulation loop is that charge current
can be set according to actual conditions rather than
worst-case conditions for a given application with the
assurance that the charger will automatically reduce the
current in worst-case conditions.
NTC Thermistor
Overvoltage Protection
The battery temperature is measured by placing a negative temperature coefficient (NTC) thermistor close to the
battery pack.
The LTC4160/LTC4160-1 can protect themselves from the
inadvertent application of excessive voltage to VBUS 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 MOSFET
and its associated drain breakdown voltage.
To use this feature connect the NTC thermistor, RNTC, between the NTC pin and ground and a bias resistor, RNOM,
from NTCBIAS to NTC. RNOM should be a 1% 200ppm
resistor with a value equal to the value of the chosen NTC
thermistor at 25°C (R25).
The LTC4160/LTC4160-1 will pause charging when the
resistance of the NTC thermistor drops to 0.54 times the
value of R25 or approximately 54k for a 100k thermistor. For a Vishay Curve 1 thermistor, this corresponds to
approximately 40°C. If the battery charger is in constantvoltage (float) mode, the safety timer also pauses until the
thermistor indicates a return to a valid temperature. As the
temperature drops, the resistance of the NTC thermistor
rises. The LTC4160/LTC4160-1 are also designed to pause
charging when the value of the NTC thermistor increases
to 3.25 times the value of R25. For a Vishay Curve 1
100k thermistor, this resistance, 325k, corresponds to
approximately 0°C. The hot and cold comparators each
have approximately 3°C of hysteresis to prevent oscillation about the trip point. Grounding the NTC pin disables
all NTC functionality.
Thermal Regulation
To prevent thermal damage to the LTC4160/LTC4160-1 or
surrounding components, 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 LTC4160/LTC4160-1
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
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 MOSFET. When OVSENS is below 6V, an internal charge pump will drive OVGATE to approximately
1.88 • OVSENS. This will enhance the N-channel MOSFET
and provide a low impedance connection to VBUS which
will, in turn, power the LTC4160/LTC4160-1. If OVSENS
should rise above 6V due to a fault or the use of an incorrect wall adapter, OVGATE will be pulled to GND. This
disables the external MOSFET and protects downstream
circuitry. When the voltage drops below 6V again, the
external MOSFET will be re-enabled.
The charge pump output on OVGATE has limited output
drive capability. Care must be taken to avoid leakage on
this pin as it may adversely affect operation.
See the Applications Information section for resistor power
dissipation rating calculations, a table of recommended
components, and reverse-voltage protection.
Shutdown Mode
The USB switching regulator is enabled whenever VBUS is
above VUVLO and the LTC4160/LTC4160-1 are not in USB
suspend mode.
The ideal diode(s) are enabled at all times and cannot be
disabled.
41601fa
20
LTC4160/LTC4160-1
APPLICATIONS INFORMATION
Bidirectional PowerPath Switching Regulator CLPROG
Resistor and Capacitor Selection
Bidirectional PowerPath Switching Regulator VBUS
and VOUT Bypass Capacitor Selection
As described in the Bidirectional PowerPath Switching
Regulator – Step-Down Mode section, the resistor on the
CLPROG pin determines the average VBUS input current
limit. In step-down mode the switching regulator’s VBUS
input current limit can be set to either the 1x mode (USB
100mA), the 5x mode (USB 500mA) or the 10x mode. The
VBUS input current will be comprised of two components,
the current that is used to drive VOUT and the quiescent
current of the switching regulator. To ensure that the total
average input current remains below the USB specification,
both components of input current should be considered.
The Electrical Characteristics table gives the typical values
for quiescent currents in all settings as well as current limit
programming accuracy. To get as close to the 500mA or
100mA specifications as possible, a precision resistor
should be used. Recall that:
The type and value of capacitors used with the LTC4160/
LTC4160-1 determine several important parameters such
as regulator control-loop stability and input voltage ripple.
Because the LTC4160/LTC4160-1 use a bidirectional
switching regulator between VBUS and VOUT, the VBUS
current waveform contains high frequency components.
It is strongly recommended that a low equivalent series
resistance (ESR) multilayer ceramic capacitor (MLCC) be
used to bypass VBUS. Tantalum and aluminum capacitors
are not recommended because of their high ESR. The value
of the capacitor on VBUS directly controls the amount of
input ripple for a given load current. Increasing the size
of this capacitor will reduce the input ripple.
IVBUS = IVBUSQ + VCLPROG/RCLPPROG • (hCLPROG +1).
An averaging capacitor is required in parallel with the
resistor so that the switching regulator can determine the
average input current. This capacitor also provides the
dominant pole for the feedback loop when current limit
is reached. To ensure stability, the capacitor on CLPROG
should be 0.1µF or larger.
Bidirectional PowerPath Switching Regulator Inductor
Selection
Because the VBUS voltage range and VOUT voltage range
of the PowerPath switching regulator are both fairly narrow, the LTC4160/LTC4160-1 were designed for a specific
inductance value of 3.3μH. Some inductors which may be
suitable for this application are listed in Table 3.
Table 3. Recommended PowerPath Inductors for the
LTC4160/LTC4160-1
INDUCTOR L MAX IDC MAX DCR SIZE IN mm
TYPE
(μH)
(A)
(Ω)
(L x W x H) MANUFACTURER
LPS4018 3.3
2.2
0.08 3.9 x 3.9 x 1.7 Coilcraft
www.coilcraft.com
D53LC
3.3
2.26
0.034
5 x 5 x 3 Toko
DB318C
3.3
1.55
0.070 3.8 x 3.8 x 1.8 www.toko.com
WE-TPC
3.3
1.95
0.065 4.8 x 4.8 x 1.8 Wurth Electronik
Type M1
www.we-online.com
CDRH6D12 3.3
2.2
0.063 6.7 x 6.7 x 1.5 Sumida
CDRH6D38 3.3
3.5
0.020
7 x 7 x 4 www.sumida.com
The inrush current limit specification for USB devices is
calculated in terms of the total number of Coulombs needed
to charge the VBUS bypass capacitor to 5V. The maximum
inrush charge for USB On-The-Go devices is 33μC. This
places a limit of 6.5μF of capacitance on VBUS assuming
a linear capacitor. However, most ceramic capacitors have
a capacitance that varies with bias voltage. The average
capacitance needs to be less than 6.5μF over a 0V to 5V bias
voltage range to meet the inrush current-limit specification.
A 10μF capacitor in a 0805 package, such as the Murata
GRM21BR71A106KE51L would be a suitable VBUS bypass
capacitor. If more capacitance is required for better noise
performance and stability, it should be connected directly
to the VBUS pin when using the overvoltage protection
circuit. This extra capacitance will be soft-connected over
a couple of milliseconds to limit inrush current and avoid
excessive transient voltage drops on VBUS.
To prevent large VOUT voltage steps during transient load
conditions, it is also recommended that an MLCC be used
to bypass VOUT. The output capacitor is used in the compensation of the switching regulator. At least 10µF with
low ESR are required on VOUT. Additional capacitance will
improve load transient performance and stability.
MLCCs typically have exceptional ESR performance.
MLCCs combined with a tight board layout and an unbroken
ground plane will yield very good performance and low
EMI emissions.
41601fa
21
LTC4160/LTC4160-1
APPLICATIONS INFORMATION
There are MLCCs available with several types of dielectrics
each having considerably different characteristics. For
example, X7R MLCCs have the best voltage and temperature stability. X5R MLCCs have apparently higher packing
density but poorer performance over their rated voltage
and temperature ranges. Y5V MLCCs have the highest
packing density, but must be used with caution, because
of their extreme nonlinear characteristic of capacitance
versus voltage. The actual in-circuit capacitance of a
ceramic capacitor should be measured with a small AC
signal and DC bias as is expected in-circuit. Many vendors
specify the capacitance versus voltage with a 1VRMS AC
test signal and, as a result, over state the capacitance that
the capacitor will present in the application. Using similar
operating conditions as the application, the user must
measure or request from the vendor the actual capacitance
to determine if the selected capacitor meets the minimum
capacitance that the application requires.
Overvoltage Protection
VBUS can be protected from overvoltage damage with two
additional components, a resistor R1 and an N-channel
MOSFET MN1, as shown in Figure 5. Suitable choices for
MN1 are listed in Table 4.
Table 4. Recommended N-Channel MOSFETs for the Overvoltage
Protection Circuit
PART #
BVDSS
RON
PACKAGE
Si1472DH
30V
57mΩ
SC70-6
Si2302ADS
20V
60mΩ
SOT-23
Si2306BDS
30V
47mΩ
SOT-23
Si2316DS
30V
50mΩ
SOT-23
IRLML2502
20V
50mΩ
SOT-23
FDN372S
30V
50mΩ
SOT-23
NTLJS4114N
30V
35mΩ
WDFN6
USB/WALL
ADAPTER
MN1
VBUS
C1
R1
LTC4160/
LTC4160-1
OVGATE
OVSENS
41601 F05
Figure 5. Overvoltage Protection
R1 is a 6.2k resistor and must be rated for the power dissipated during maximum overvoltage. In an overvoltage
condition the OVSENS pin will be clamped at 6V. R1 must
be sized appropriately to dissipate the resultant power.
For example, a 1/10W 6.2k resistor can have at most
√(PMAX • 6.2kΩ) = 25V applied across its terminals. With
the 6V at OVSENS, the maximum overvoltage magnitude
that this resistor can withstand is 31V. A 1/4W 6.2k resistor raises this value to 45V. OVSENS’s absolute maximum
current rating of 10mA imposes an upper limit of 68V
protection.
Reverse Voltage Protection
The LTC4160/LTC4160-1 can also be easily protected
against the application of reverse voltages, as shown in
Figure 6. D1 and R1 are necessary to limit the maximum
VGS seen by MP1 during positive overvoltage events. D1’s
breakdown voltage must be safely below MP1’s BVGS. The
circuit shown in Figure 6 offers forward voltage protection
up to MN1’s BVDSS and reverse voltage protection up to
MP1’s BVDSS.
USB/WALL
ADAPTER
MP1
MN1
D1
VBUS
C1
LTC4160/
LTC4160-1
R1
R2
OVGATE
OVSENS
VBUS POSITIVE PROTECTION UP TO BVDSS OF MN1
VBUS NEGATIVE PROTECTION UP TO BVDSS OF MP1
41601 F06
Figure 6. Dual Polarity Voltage Protection
Battery Charger Over Programming
The USB high power specification allows for up to 2.5W
to be drawn from the USB port. The LTC4160/LTC4160‑1’s
bidirectional switching regulator in step-down mode converts the voltage at VBUS to a voltage just above BAT on
VOUT, while limiting power to less than the amount programmed at CLPROG. The charger should be programmed
(with the PROG pin) to deliver the maximum safe charging
current without regard to the USB specifications. If there
is insufficient current available to charge the battery at the
programmed rate, the charge current will be reduced until
the system load on VOUT is satisfied and the VBUS current limit is satisfied. Programming the charger for more
41601fa
22
LTC4160/LTC4160-1
APPLICATIONS INFORMATION
current than is available will not cause the average input
current limit to be violated. It will merely allow the battery
charger to make use of all available power to charge the
battery as quickly as possible, and with minimal dissipation within the charger.
are connected to NTC. By using a bias resistor whose
value is equal to the room temperature resistance of the
thermistor (R25) the upper and lower temperatures are
pre-programmed to approximately 40°C and 0°C respectively assuming a Vishay Curve 1 thermistor.
Battery Charger Stability Considerations
The upper and lower temperature thresholds can be adjusted by either a modification of the bias resistor value
or by adding a second adjustment resistor to the circuit.
If only the bias resistor is adjusted, then either the upper
or the lower threshold can be modified but not both. The
other trip point will be determined by the characteristics
of the thermistor. Using the bias resistor in addition to an
adjustment resistor, both the upper and the lower temperature trip points can be independently programmed with
the constraint that the difference between the upper and
lower temperature thresholds cannot decrease. Examples
of each technique are given below.
The LTC4160/LTC4160-1’s battery charger contains both a
constant-voltage and a constant-current control loop. The
constant-voltage loop is stable without any compensation
when a battery is connected with low impedance leads.
Excessive lead length, however, may add enough series
inductance to require a bypass capacitor of at least 1µF
from BAT to GND.
High value, low ESR MLCCs reduce the constant-voltage
loop phase margin, possibly resulting in instability. Up
to 22µF may be used in parallel with a battery, but larger
capacitors should be decoupled with 0.2Ω to 1Ω of series
resistance.
Furthermore, a 100µF capacitor in series with a 0.3Ω resistor from BAT to GND is required to prevent oscillation
when the battery is disconnected.
In constant-current mode, the PROG pin is in the feedback loop rather than the battery voltage. Because of the
additional pole created by any PROG pin capacitance,
capacitance on this pin must be kept to a minimum. With
no additional capacitance on the PROG pin, the charger
is stable with program resistor values as high as 25k.
However, additional capacitance on this node reduces the
maximum allowed program resistor. The pole frequency at
the PROG pin should be kept above 100kHz. Therefore, if
the PROG pin has a parasitic capacitance, CPROG, the following equation should be used to calculate the maximum
resistance value for RPROG:
RPROG ≤
1
2π • 100kHz • CPROG
Alternate NTC Thermistors and Biasing
The LTC4160/LTC4160-1 provide temperature qualified
charging if a grounded thermistor and a bias resistor
NTC thermistors have temperature characteristics which
are indicated on resistance-temperature conversion tables.
The Vishay-Dale thermistor NTHS0603N011-N1003F, used
in the following examples, has a nominal value of 100k
and follows the Vishay Curve 1 resistance-temperature
characteristic.
In the explanation below, the following notation is used.
R25 = Value of the thermistor at 25°C
RNTC|COLD = Value of the thermistor at the cold
trip point
RNTC|HOT = Value of the thermistor at the hot
trip point
rCOLD = Ratio of RNTC|COLD to R25
rHOT = Ratio of RNTC|HOT to R25
RNOM – Primary thermistor bias resistor
(see Figure 7)
R1 = Optional temperature range adjustment resistor
(see Figure 8)
The trip points for the LTC4160/LTC4160-1’s temperature
qualification are internally programmed at 0.349 • NTCBIAS
for the hot threshold and 0.765 • NTCBIAS for the cold
threshold.
41601fa
23
LTC4160/LTC4160-1
APPLICATIONS INFORMATION
Therefore, the hot trip point is set when:
RNTCHOT
RNOM + RNTCHOT
• NTCBIAS = 0.349 • NTCBIAS
And the cold trip point is set when:
RNTC COLD
RNOM + RNTC COLD
• NTCBIAS = 0.765 • NTCBIAS
Solving these equations for RNTC|COLD and RNTC|HOT results
in the following:
RNTC|HOT = 0.536 • RNOM
and
RNTC|COLD = 3.25 • RNOM
By setting RNOM equal to R25, the above equations result
in rHOT = 0.536 and rCOLD = 3.25. Referencing these ratios
to the Vishay Resistance-Temperature Curve 1 chart gives
a hot trip point of about 40°C and a cold trip point of about
0°C. The difference between the hot and cold trip points
is approximately 40°C.
By using a bias resistor, RNOM, different in value from
R25, the hot and cold trip points can be moved in either
direction. The temperature span will change somewhat
due to the non-linear behavior of the thermistor. The following equations can be used to calculate a new value for
the bias resistor:
r
RNOM = HOT • R25
0.536
r
RNOM = COLD • R25
3.25
where rHOT and rCOLD are the resistance ratios at the desired hot and cold trip points. Note that these equations
are linked. Therefore, only one of the two trip points can
be chosen, the other is determined by the default ratios
designed in the IC. Consider an example where a 60°C
hot trip point is desired.
From the Vishay Curve 1 R-T characteristics, rHOT is
0.2488 at 60°C. Using the above equation, RNOM should
be set to 46.4k. With this value of RNOM, rCOLD is 1.436
and the cold trip point is about 16°C. Notice that the span
is now 44°C rather than the previous 40°C. This is due to
the decrease in “temperature gain” of the thermistor as
absolute temperature increases.
The upper and lower temperature trip points can be independently programmed by using an additional bias resistor,
R1, as shown in Figure 8. The following formulas can be
used to compute the values of RNOM and R1:
rCOLD – rHOT
• R25
2.714
R1 = 0.536 • RNOM – rHOT • R25
RNOM =
For example, to set the trip points to 0°C and 45°C with
a Vishay Curve 1 thermistor choose:
RNOM =
3.266 – 0.4368
• 100k = 104.2k
2.714
the nearest 1% value is 105k:
R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k
the nearest 1% value is 12.7k. The final solution is shown
in Figure 8 and results in an upper trip point of 45°C and
a lower trip point of 0°C.
NTCBIAS
0.765 • NTCBIAS
RNOM
100k
NTC
T
LTC4160/LTC4160-1
NTC BLOCK
3
–
TOO_COLD
+
4
RNTC
100k
–
0.349 • NTCBIAS
TOO_HOT
+
+
NTC_ENABLE
0.1V
–
41601 F07
Figure 7. Standard NTC Configuration
41601fa
24
LTC4160/LTC4160-1
APPLICATIONS INFORMATION
NTCBIAS
0.765 • NTCBIAS
RNOM
105k
NTC
LTC4160/LTC4160-1
NTC BLOCK
3
–
TOO_COLD
+
4
R1
12.7k
T
RNTC
100k
–
0.349 • NTCBIAS
TOO_HOT
+
+
NTC_ENABLE
0.1V
–
switching and VBUS will be held at the regulation voltage
of the external supply. If the external supply has a lower
regulation voltage and is capable of only sourcing current,
then VBUS will be regulated to 5.1V. The external supply
will not source current to VBUS.
For a supply that can also sink current and has a regulation
voltage less than 5.1V, the bidirectional switching regulator
will source current into the external supply in an attempt
to bring VBUS up to 5.1V. As long as the external supply
holds VBUS to more than VOUT + 70mV, the bidirectional
switching regulator will source up to 680mA into the supply. If VBUS is held to a voltage that is less than VOUT +
70mV then the short circuit timer will shut off the switching
regulator after 7.2ms. The FAULT pin will then go low to
indicate a short circuit current fault.
41601 F08
Figure 8. Modified NTC Configuration
Hot Plugging and USB Inrush Current Limiting
The overvoltage protection circuit provides inrush current
limiting due to the long time it takes for OVGATE to fully
enhance the N-channel MOSFET. This prevents the current
from building up in the cable too quickly and dampens
out any resonant overshoot on VBUS. It is possible to
observe voltage overshoot on VBUS when connecting the
LTC4160/LTC4160-1 to a lab supply if the overvoltage
protection circuit is not used. This overshoot is caused by
the inductance of the long leads from the supply to VBUS.
Twisting the wires together from the supply to VBUS can
greatly reduce the parasitic inductance of these long leads
and keep VBUS at a safe level. USB cables are generally
manufactured with the power leads in close proximity and
thus have fairly low parasitic inductance.
Hot Plugging and USB On-The-Go
If there is more than 4.3V on VBUS when On-The-Go is
enabled, the bidirectional switching regulator will not try
to drive VBUS. If USB On-The-Go is enabled and an external
supply is then connected to VBUS, one of three things will
happen depending on the properties of the external supply. If the external supply has a regulation voltage higher
than 5.1V, the bidirectional switching regulator will stop
VBUS Bypass Capacitance and USB On-The-Go
Session Request Protocol
When two On-The-Go devices are connected, one will be
the A device and the other will be the B device depending
on whether the device is connected to a micro-A or microB plug. The A device provides power to the B device and
starts as the host. To prolong battery life, the A device
can power down VBUS when the BUS is not being used.
If the A device has powered down VBUS, the B device can
request the A device to power up VBUS and start a new
session using the session request protocol (SRP). The
SRP consists of data-line pulsing and VBUS pulsing. The
B device must first pulse the D+ or D– data lines. The B
device must then pulse VBUS only if the A device does not
respond to the data-line pulse. The A device is required
to respond to only one of the pulsing methods. USB A
devices that never power down VBUS are not required to
respond to the SRP.
For VBUS pulsing, the limit on the VBUS capacitance on
the A device allows a B device to differentiate between a
powered down On-The-Go device and a powered down
standard host. The B device will send out a pulse of current
that will raise VBUS to a voltage between 2.1 and 5.25V if
connected to an On-The-Go A device which must have no
more than 6.5μF. An On-The-Go A device must drive VBUS
as soon as the current pulse raises VBUS above 2.1V if the
device is capable of responding to VBUS pulsing.
41601fa
25
LTC4160/LTC4160-1
APPLICATIONS INFORMATION
down On-The-Go A device and a powered down standard
host. A suitable pulse can be generated because of the
disparity in the bypass capacitances of an On-The-Go A
device and a standard host even if there is somewhat more
than 6.5μF capacitance connected to the VBUS pin of the
LTC4160/LTC4160-1.
This same current pulse must not raise VBUS any higher
than 2V when connected to a standard host which must
have at least 96μF. The 96μF for a standard host represents
the minimum capacitance with VBUS between 4.75V and
5.25V. Since the SRP pulse must not drive VBUS greater
than 2V, the capacitance seen at these voltage levels can be
greater than 96μF, especially if MLCCs are used. Therefore,
the 96μF represents a lower bound on the standard host
bypass capacitance for determining the amplitude and
duration of the current pulse. More capacitance will only
decrease the maximum level that VBUS will rise to for a
given current pulse.
Board Layout Considerations
The Exposed Pad on the backside of the LTC4160/
LTC4160‑1 package must be securely soldered to the PC
board ground. This is the primary ground pin in the package, and it serves as the return path for both the control
circuitry and N-channel MOSFET switch.
Figure 9 shows an On-The-Go device using the LTC4160/
LTC4160-1 acting as the A device. Additional capacitance
can be placed on the VBUS pin of the LTC4160/LTC41601 when using the overvoltage protection circuit. The B
device may not be able to distinguish between a powered
down LTC4160/LTC4160-1 with overvoltage protection
and a powered down standard host because of this extra
capacitance. In addition, if the SRP pulse raises VBUS
above its UVLO threshold of 4.3V the LTC4160/LTC4160-1
will assume input power is available and will not attempt
to drive VBUS. Therefore, it is recommended that an OnThe-Go device using the LTC4160/LTC4160-1 respond to
data-line pulsing.
Furthermore, due to its high frequency switching circuitry,
it is imperative that the input capacitor, inductor, and output
capacitor be as close to the LTC4160/LTC4160-1 as possible and that there be an unbroken ground plane under the
LTC4160/LTC4160-1 and all of its external high frequency
components. High frequency current, such as the VBUS
current tends to find its way on the ground plane along a
mirror path directly beneath the incident path on the top
of the board. If there are slits or cuts in the ground plane
due to other traces on that layer, the current will be forced
to go around the slits. If high frequency currents are not
allowed to flow back through their natural least-area path,
excessive voltage will build up and radiated emissions will
occur (see Figure 11). There should be a group of vias
directly under the grounded backside leading directly
down to an internal ground plane. To minimize parasitic
inductance, the ground plane should be as close as possible to the top plane of the PC board (layer 2).
When an On-The-Go device using the LTC4160/LTC4160-1
becomes the B device, as in Figure 10, it must send out
a data line pulse followed by a VBUS pulse to request a
session from the A device. The On-The-Go device designer
can choose how much capacitance will be placed on the
VBUS pin of the LTC4160/LTC4160-1 and then generate
a VBUS pulse that can distinguish between a powered
OVP
(OPTIONAL)
OVSENS
ON-THE-GO
POWER
MANAGER
OVGATE
LTC4160/
LTC4160-1
VBUS
ENOTG
CA
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湘ICP备2023018690号
