LINER LTC4076

LTC4076
Dual Input Standalone
Li-Ion Battery Charger
FEATURES
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DESCRIPTIO
Charges Single-Cell Li-Ion Batteries from Wall
Adapter and USB Inputs
Automatic Input Power Detection and Selection
Charge Current Programmable up to 950mA from
Wall Adapter Input
C/X Charge Current Termination
Thermal Regulation Maximizes Charge Rate
Without Risk of Overheating*
Preset Charge Voltage with ±0.6% Accuracy
18µA USB Suspend Current in Shutdown
Power Present Status Output
Charge Status Output
Automatic Recharge
Available in a Thermally Enhanced, Low Profile
(0.75mm) 10-Lead (3mm × 3mm) DFN Package
U
APPLICATIO S
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Cellular Telephones
Handheld Computers
Portable MP3 Players
Digital Cameras
The LTC®4076 is a standalone linear charger that is capable
of charging a single-cell Li-Ion battery from both wall
adapter and USB inputs. The charger can detect power at
the inputs and automatically select the appropriate power
source for charging.
No external sense resistor or blocking diode is required
for charging due to the internal MOSFET architecture.
Internal thermal feedback regulates the battery charge
current to maintain a constant die temperature during high
power operation or high ambient temperature conditions.
The float voltage is fixed at 4.2V and the charge current
is programmed with an external resistor. The LTC4076
terminates the charge cycle when the charge current drops
below the user programmed termination threshold after
the final float voltage is reached. The LTC4076 can be put
into shutdown mode reducing the DCIN supply current to
20µA, the USBIN supply current to 10µA, and the battery
drain current to less than 2µA even with power applied
to both inputs.
Other features include automatic recharge, undervoltage
lockout, charge status output, power present status output
to indicate the presence of wall adapter or USB power and
high power/low power mode (C/5) for USB compatible
applications.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. patents, including 6522118
TYPICAL APPLICATIO
U
USB
PORT
1 F
800mA (WALL)
500mA (USB)
LTC4076
WALL
ADAPTER
DCIN
1 F
BAT
USBIN
HPWR
+
IUSB
2k
IDC
1% 1.24k
1%
ITERM
GND
4.2V
SINGLE CELL
Li-Ion BATTERY
1k
1%
4076 TA01
DCIN
VOLTAGE (V)
Dual Input Battery Charger for Single-Cell Li-Ion
BATTERY
CHARGE
VOLTAGE (V) CURRENT (mA)
Complete Charge Cycle (1100mAh Battery)
1000
800
600
400
200
0
4.2
4.0
3.8
3.6
3.4
CONSTANT VOLTAGE
USBIN = 5V
TA = 25°C
RIDC = 1.24k
RIUSB = 2k
HPWR = 5V
5.0
2.5
0
0
0.5
1.0
1.5
2.0
TIME (HR)
2.5
3.0
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LTC4076
AXI U RATI GS
U
W W
W
ABSOLUTE
U
W
U
PACKAGE/ORDER I FOR ATIO
(Notes 1, 7)
Input Supply Voltage (DCIN, USBIN) ......... –0.3V to 10V
EN, CHRG, PWR, HPWR ............................ –0.3V to 10V
BAT, IDC, IUSB, ITERM ................................ –0.3V to 7V
DCIN Pin Current (Note 6) ..........................................1A
USBIN Pin Current (Note 6) .................................700mA
BAT Pin Current (Note 6) ............................................1A
BAT Short-Circuit Duration............................ Continuous
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range (Note 2) .. –40°C to 85°C
Storage Temperature Range.................. –65°C to 125°C
TOP VIEW
10 DCIN
USBIN
1
IUSB
2
ITERM
3
PWR
4
7 HPWR
CHRG
5
6 EN
9 BAT
8 IDC
11
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 40°C/W (NOTE 3)
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
DD PART MARKING
LBWC
ORDER PART NUMBER
LTC4076EDD
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VDCIN = 5V, VUSBIN = 5V, HPWR = 5V unless otherwise noted.
SYMBOL
PARAMETER
VDCIN
VUSBIN
IDCIN
Supply Voltage
Supply Voltage
DCIN Supply Current
IUSBIN
USBIN Supply Current
VFLOAT
Regulated Output (Float) Voltage
IBAT
BAT Pin Current
VIDC
VIUSB
ITERMINATE
IDC Pin Regulated Voltage
IUSB Pin Regulated Voltage
Charge Current Termination Threshold
CONDITIONS
MIN
●
●
Charge Mode (Note 4), RIDC = 10k
Standby Mode; Charge Terminated
Shutdown Mode (EN = 5V)
Charge Mode (Note 5), RIUSB = 10k, VDCIN = 0V
Standby Mode; Charge Terminated, VDCIN = 0V
Shutdown (VDCIN = 0V, EN = 5V)
VDCIN > VUSBIN
IBAT = 1mA (Note 7)
IBAT = 1mA, 0°C < TA < 85°C, 4.3V < VCC < 8V
RIDC = 1.25k, Constant-Current Mode
RIUSB = 2.1k, Constant-Current Mode
RIUSB = 2.1k, HPWR = 0V
RIDC = 10k or RIUSB = 10k
Standby Mode, Charge Terminated
Shutdown Mode (Charger Disabled)
Sleep Mode (VDCIN = 0V, VUSBIN = 0V)
Constant-Current Mode
Constant-Current Mode
RITERM = 1k
RITERM = 2k
RITERM = 10k
RITERM = 20k
TYP
MAX
UNITS
250
50
20
250
50
18
10
4.2
4.2
800
476
95
100
–3
–1
±1
1
1
100
50
10
5
8
8
800
100
40
800
100
36
20
4.225
4.242
840
500
105
108
–6
–2
±2
1.05
1.05
110
55
12
6.5
V
V
µA
µA
µA
µA
µA
µA
µA
V
V
mA
mA
mA
mA
µA
µA
µA
V
V
mA
mA
mA
mA
4.3
4.3
●
●
●
●
●
●
●
●
4.175
4.158
760
450
84
92
●
●
●
●
0.95
0.95
90
45
8
3.5
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LTC4076
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VDCIN = 5V, VUSBIN = 5V, HPWR = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ITRIKL
Trickle Charge Current
VTRIKL
Trickle Charge Threshold Voltage
60
30
2.8
DCIN Undervoltage Lockout Voltage
VUVUSB
USBIN Undervoltage Lockout Voltage
VASD-DC
VDCIN – VBAT Lockout Threshold
VASD-USB
VUSBIN – VBAT Lockout Threshold
80
47.5
2.9
100
4.15
200
3.95
200
180
50
180
50
100
65
3
VUVDC
VBAT < VTRIKL; RIDC = 1.25k
VBAT < VTRIKL; RIUSB = 2.1k
VBAT Rising
Hysteresis
From Low to High
Hysteresis
From Low to High
Hysteresis
VDCIN from Low to High, VBAT = 4.2V
VDCIN from High to Low, VBAT = 4.2V
VUSBIN from Low to High
VUSBIN from High to Low
mA
mA
V
mV
V
mV
V
mV
mV
mV
mV
mV
VEN
REN
VHPWR
RHPWR
VCHRG
VPWR
ΔVRECHRG
tRECHRG
tTERMINATE
tSS
RON-DC
EN Input Threshold Voltage
EN
 Pulldown Resistance
RON-USB
TLIM
HPWR Input Threshold Voltage
HPWR Pulldown Resistance
CHRG Output Low Voltage
PWR Output Low Voltage
Recharge Battery Threshold Voltage
Recharge Comparator Filter Time
Termination Comparator Filter Time
Soft-Start Time
Power FET “ON” Resistance
(Between DCIN and BAT)
Power FET “ON” Resistance
(Between USBIN and BAT)
Junction Temperature in
Constant-Temperature Mode
4
3.8
140
20
140
20
●
●
ICHRG = 5mA
IPWR = 5mA
VFLOAT – VRECHRG, 0°C < TA < 85°C
VBAT from High to Low
IBAT Drops Below Termination Threshold
IBAT = 10% to 90% Full-Scale
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 LTC4076E is guaranteed to meet the 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: Failure to correctly solder the exposed backside of the package to
the PC board will result in a thermal resistance much higher than 40°C/W.
See Thermal Considerations.
0.4
1
0.4
1
65
3
0.8
175
0.7
2
0.7
2
0.35
0.35
100
6
1.5
250
400
4.3
4.1
220
80
220
80
1
5
1
5
0.6
0.6
135
10
2.2
325
V
MΩ
V
MΩ
V
V
mV
ms
ms
µs
mΩ
550
mΩ
105
°C
Note 4: Supply current includes IDC and ITERM pin current (approximately
100µA each) but does not include any current delivered to the battery
through the BAT pin.
Note 5: Supply current includes IUSB and ITERM pin current
(approximately 100µA each) but does not include any current delivered to
the battery through the BAT pin.
Note 6: Guaranteed by long term current density limitations.
Note 7: VCC is greater of DCIN or USBIN
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LTC4076
TYPICAL PERFOR A CE CHARACTERISTICS
U W
Regulated Output (Float) Voltage
vs Charge Current
4.26
4.220
VDCIN = VUSBIN = 5V
4.24
1.008
VDCIN = VUSBIN = 5V
4.22
4.210
1.004
4.20
4.205
1.002
4.18
4.16
VIDC (V)
1.006
4.200
0.998
4.14
4.190
0.996
4.12
4.185
0.994
RIDC = 1.25k
4.180
–50
100 200 300 400 500 600 700 800
CHARGE CURRENT (mA)
0
–25
75
0
25
50
TEMPERATURE (°C)
4076 G01
0.206
1.004
0.204
1.002
0.202
VUSBIN = 4.3V
0.998
0.994
0.194
75
0
25
50
TEMPERATURE (°C)
100
900
VUSBIN = 4.3V
800
600
200
–25
0
50
25
TEMPERATURE (°C)
75
IBAT (mA)
300
200
0
0
0.2
0.4
0.6
0.8
VIUSB (V)
1.0
1.2
4076 G06
0
0.4
0.2
0.6
0.8
VIDC (V)
PWR Pin I-V Curve
RIUSB = 1kΩ
TA = – 40°C
TA = 25°C
25
150
0
VDCIN = VUSBIN = 5V
30
RIUSB = 2kΩ
100
1.2
1.0
4076 G05
35
TA = 90°C
20
15
10
RIUSB = 4kΩ
50
RIUSB = 10k
100
0
100
VUSBIN = 5V
HPWR = 0V
200
400
RIDC = 10k
100
Charge Current vs IUSB Pin
Voltage
RIUSB = 2k
500
400
4076 G24
RIUSB = 1.25k
700
RIDC = 2k
500
300
250
VUSBIN = 5V
HPWR = 5V
RIDC = 1.25k
600
VUSBIN = 8V
0.192
–50
Charge Current vs IUSB Pin
Voltage
100
700
4076 G04
900
VDCIN = 5V
800
0.198
0.196
–25
75
0
25
50
TEMPERATURE (°C)
Charge Current vs IDC Pin
Voltage
HPWR = 0V
0.200
0.996
0.992
–50
–25
4076 G03
IBAT (mA)
1.006
VIUSB (V)
VIUSB (V)
0.208
VUSBIN = 8V
0.992
–50
IUSB Pin Voltage vs Temperature
(Constant-Current Mode)
HPWR = 5V
1.000
VDCIN = 4.3V
4076 G02
IUSB Pin Voltage vs Temperature
(Constant-Current Mode)
1.008
100
IPWR (mA)
RIDC = RIUSB = 2k
VDCIN = 8V
1.000
4.195
4.10
IBAT (mA)
IDC Pin Voltage vs Temperature
(Constant-Current Mode)
4.215
VFLOAT (V)
VFLOAT (V)
Regulated Output (Float) Voltage
vs Temperature
5
0
50
150
100
VIUSBL (mV)
200
250
4076 G25
0
0
1
2
4
3
VPWR (V)
5
6
7
4076 G07
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LTC4076
TYPICAL PERFOR A CE CHARACTERISTICS
U W
Charge Current vs Ambient
Temperature
CHRG Pin I-V Curve
VDCIN = VUSBIN = 5V
TA = 90°C
20
IBAT (mA)
15
700
RIDC = RIUSB = 2k
400
600
500
200
5
0
1
2
4
3
VCHRG (V)
6
5
HPWR = 5V
VDCIN = VUSBIN = 5V
VBAT = 4V
θJA = 40°C/W
0
–50 –25
7
50
25
75
0
TEMPERATURE (°C)
400
100
4076 G09
Charge Current vs Battery Voltage
DCIN Power FET “On” Resistance
vs Temperature
550
500
RDS(ON) (mΩ)
800
600
400
200
VDCIN = VUSBIN = 5V
θJA = 40°C/W
RIDC = 1.25k
2.4
2.7
3.0
3.3 3.6
VBAT (V)
3.9
750
700
350
50
25
75
0
TEMPERATURE (°C)
100
900
800
700
650
4076 G14
100
125
45
40
35
750
600
–50
VDCIN = 8V
30
25
20
15
10
650
100
50
25
75
0
TEMPERATURE (°C)
50
700
–25
500
DCIN Shutdown Current vs
Temperature
IDCIN (µA)
800
VHPWR (mV)
850
75
550
4076 G13
VDCIN = VUSBIN = 5V
850
50
25
0
TEMPERATURE (°C)
600
350
–50 –25
125
900
VDCIN = VUSBIN = 5V
600
–50
650
HPWR Pin Threshold (Rising) vs
Temperature
750
VBAT = 4V
IBAT = 200mA
HPWR = 5V
4076 G12
4076 G11
EN Pin Threshold (Rising) vs
Temperature
8.0
400
250
–50 –25
4.5
7.5
450
300
4.2
7.0
USBIN Power FET “On” Resistance
vs Temperature
800
400
5.5 6.0 6.5
VDCIN (V)
5.0
4076 G10
VBAT = 4V
IBAT = 200mA
450
RIDC = 1.25k
VBAT = 4V
θJA = 35°C/W
300
4.0 4.5
125
4076 G08
1000
IBAT (mA)
800
600
10
VEN (mV)
ONSET OF
THERMAL REGULATION
RIDC = 1.25k
RDS(ON) (mΩ)
ICHRG (mA)
800
TA = 25°C
25
0
900
ONSET OF
THERMAL REGULATION
TA = –40°C
30
0
Charge Current vs Supply Voltage
1000
IBAT (mA)
35
VDCIN = 5V
VDCIN = 4.3V
5
–25
50
25
0
TEMPERATURE (°C)
75
100
4076 G15
0
–50
EN = 5V
–25
50
25
0
TEMPERATURE (°C)
75
100
4076 G16
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LTC4076
TYPICAL PERFOR A CE CHARACTERISTICS
U W
USBIN Shutdown Current vs
Temperature
40
IUSBIN (µA)
REN (MΩ)
VUSBIN = 8V
30
25
20
VUSBIN = 5V
15
10
2.8
2.8
2.6
2.6
2.4
2.4
RHPWR (MΩ)
45
35
HPWR Pin Pulldown Resistance
vs Temperature
EN Pin Pulldown Resistance vs
Temperature
2.2
2.0
VUSBIN = 4.3V
0
–50
EN = 5V
–25
50
25
0
TEMPERATURE (°C)
75
100
1.6
–50
–25
50
25
0
TEMPERATURE (°C)
1.6
–50
100
75
4076 G17
–25
100
4076 G19
4.16
4.25
4.14
DCIN UVLO
4.20
VRECHRG (V)
4.15
4.10
4.05
4.12
VDCIN = VUSBIN = 4.3V
4.10
VDCIN = VUSBIN = 8V
4.08
USBIN UVLO
4.00
4.06
3.95
3.90
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4.04
–50
–25
0
25
50
TEMPERATURE (°C)
4076 G20
75
100
4076 G21
Battery Drain Current
vs Temperature
4
75
Recharge Threshold Voltage
vs Temperature
4.30
5
50
25
0
TEMPERATURE (°C)
4076 G18
Undervoltage Lockout Threshold
vs Temperature
VUV (V)
2.0
1.8
1.8
5
2.2
Charge Current at Turn-On and
Turn-Off
VBAT = 4.2V
VDCIN, VUSBIN (OPEN)
IBAT
500mA/DIV
IBAT (µA)
3
2
EN
5V/DIV
1
0
–1
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4076 G22
VDCIN = 5V
RIDC = 1.25k
100 s/DIV
4076 G23
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LTC4076
PI FU CTIO S
U
U
U
USBIN (Pin 1): USB Input Supply Pin. Provides power to
the battery charger. The maximum supply current is 650mA.
This pin should be bypassed with a 1µF capacitor.
IUSB (Pin 2): Charge Current Program for USB Power.
The charge current is set by connecting a resistor, RIUSB,
to ground. When charging in constant-current mode, this
pin servos to 1V. The voltage on this pin can be used to
measure the battery current delivered from the USB input
using the following formula:
VIUSB
• 1000 (HPWR = HIGH)
RIUSB
V
= IUSB • 200 (HPWR = LOW)
RIUSB
IBAT =
IBAT
ITERM (Pin 3): Termination Current Threshold Program.
The termination current threshold, ITERMINATE, is set by
connecting a resistor, RITERM, to ground. ITERMINATE is set
by the following formula:
ITERMINATE =
100V
RITERM
When the battery current, IBAT, falls below the termination
threshold, charging stops and the CHRG output becomes
high impedance.
This pin is internally clamped to approximately 1.5V. Driving this pin to voltages beyond the clamp voltage should
be avoided.
PWR (Pin 4): Open-Drain Power Supply Status Output.
When the DCIN or USBIN pin voltage is sufficient to begin
charging (i.e. when the supply is greater than the undervoltage lockout threshold and at least 180mV above the
battery terminal), the PWR pin is pulled low by an internal
N-channel MOSFET. Otherwise PWR is high impedance.
This output is capable of sinking up to 10mA, making it
suitable for driving an LED.
CHRG (Pin 5): Open-Drain Charge Status Output. When
the LTC4076 is charging, the CHRG pin is pulled low by
an internal N-channel MOSFET. When the charge cycle is
completed, CHRG becomes high impedance. This output
is capable of sinking up to 10mA, making it suitable for
driving an LED.
EN (Pin 6): Charge Enable Input. A logic low on this pin
enables the charger. If left floating, an internal 2MΩ pulldown resistor defaults the LTC4076 to charge mode . Pull
this pin high for shutdown.
HPWR (Pin 7): HPWR Enable Input. Used to control the
amount of current drawn from the USB port. A logic high
on the HPWR pin sets the charge current to 100% of the
current programmed by the IUSB pin. A logic low on the
HPWR pin sets the charge current to 20% of the current
programmed by the IUSB pin. An internal 2MΩ pull-down
resistor defaults the HPWR pin to its low current state.
IDC (Pin 8): Charge Current Program for Wall Adapter
Power. The charge current is set by connecting a resistor, RIDC, to ground. When charging in constant-current
mode, this pin servos to 1V. The voltage on this pin can
be used to measure the battery current delivered from the
DC input using the following formula:
IBAT =
VIDC
•1000
RIDC
BAT (Pin 9): Charger Output. This pin provides charge
current to the battery and regulates the final float voltage
to 4.2V.
DCIN (Pin 10): Wall Adapter Input Supply Pin. Provides
power to the battery charger. The maximum supply
current is 950mA. This should be bypassed with a 1μF
capacitor.
Exposed Pad (Pin 11): GND. The exposed backside of the
package is ground and must be soldered to PC board ground
for electrical connection and maximum heat transfer.
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LTC4076
BLOCK DIAGRA
W
DCIN
BAT
USBIN
10
9
1
CC/CV
REGULATOR
HPWR
+
7
RHPWR
PWR
CHRG
4
5
+
DC
SOFT-START
–
4.15V
USB
SOFT-START
DCIN UVLO
10mA MAX
BAT
10mA MAX
+
–
3.95V
USBIN UVLO
+
+
–
–
BAT
4.1V
RECHARGE
–
RECHRG
BAT
TRICKLE
DC_ENABLE
–
TERM
TRICKLE
CHARGE
6
USB_ENABLE
2.9V
+
100mV
THERMAL
REGULATION
REN
TERMINATION
+
TDIE
–
105°C
CHARGER CONTROL
+
LOGIC
EN
CC/CV
REGULATOR
IBAT/1000
IBAT/1000
IBAT/1000
–
ITERM GND
3
11
RITERM
IDC
8
IUSB
2
RIDC
4076 BD
RIUSB
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LTC4076
U
OPERATIO
The LTC4076 is designed to efficiently manage charging of
a single-cell lithium-ion battery from two separate power
sources: a wall adapter and USB power bus. Using the
constant-current/constant-voltage algorithm, the charger
can deliver up to 950mA of charge current from the wall
adapter supply or up to 650mA of charge current from the
USB supply with a final float voltage accuracy of ±0.6%.
The LTC4076 has two internal P-channel power MOSFETs
and thermal regulation circuitry. No blocking diodes or
external sense resistors are required.
Power Source Selection
The LTC4076 can charge a battery from either the wall
adapter input or the USB port input. The LTC4076 automatically senses the presence of voltage at each input. If both
power sources are present, the LTC4076 defaults to the
wall adapter source provided sufficient power is present
at the DCIN input. “Sufficient power” is defined as:
• Supply voltage is greater than the UVLO threshold.
• Supply voltage is greater than the battery voltage by
50mV (180mV rising, 50mV falling).
The open drain power status output (PWR) indicates that
sufficient power is available. Table 1 describes the behavior
of this status output.
Table 1. Power Source Selection
VDCIN > 4.15V and
VDCIN > BAT + 50mV
VDCIN < 4.15V or
VDCIN < BAT + 50mV
VUSBIN > 3.95V and
VUSBIN > BAT + 50mV
Device powered from
wall adapter source;
USBIN current < 25µA
PWR: LOW
Device powered from
USB source;
PWR: LOW
VUSBIN < 3.95V or
VUSBIN < BAT + 50mV
Device powered from
wall adapter source
PWR: LOW
No charging
PWR: Hi-Z
Programming and Monitoring Charge Current
The charge current delivered to the battery from the wall
adapter supply is programmed using a single resistor from
the IDC pin to ground.
RIDC =
1000 V
ICHRG(DC)
, ICHRG(DC) =
Similarly, the charge current from the USB supply is
programmed using a single resistor from the IUSB pin
to ground. Setting HPWR pin to its high state will select
100% of the programmed charge current, while setting
HPWR to its low state will select 20% of the programmed
charge current.
RIUSB =
1000 V
ICHRG(USB)
ICHRG(USB) =
ICHRG(USB) =
(HPWR = HIGH)
1000 V
(HPWR = HIGH)
RIUSB
200 V
(HPWR = LOW)
RIUSB
Charge current out of the BAT pin can be determined at
any time by monitoring the IDC or IUSB pin voltage and
using the following equations:
IBAT =
VIDC
• 1000, (ch arg ing from wall adapter )
RIDC
IBAT =
VIUSB
• 1000, (ch arg ing from USB sup ply,
RIUSB
HPWR = HIGH)
IBAT =
VIUSB
• 200, (ch arg ing from USB sup ply,
RIUSB
HPWR = LOW)
Programming Charge Termination
The charge cycle terminates when the charge current falls
below the programmed termination threshold during constant-voltage mode. This threshold is set by connecting an
external resistor, RITERM, from the ITERM pin to ground.
The charge termination current threshold (ITERMINATE) is
set by the following equation:
RITERM =
100V
ITERMINATE
, ITERMINATE =
100V
RITERM
1000 V
RIDC
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LTC4076
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OPERATIO
The termination condition is detected by using an internal
filtered comparator to monitor the ITERM pin. When the
ITERM pin voltage drops below 100mV* for longer than
tTERMINATE (typically 1.5ms), the charge cycle terminates,
charge current latches off and the LTC4076 enters standby
mode.
When charging, transient loads on the BAT pin can cause
the ITERM pin to fall below 100mV for short periods of
time before the DC charge current has dropped below the
programmed termination current. The 1.5ms filter time
(tTERMINATE) on the termination comparator ensures that
transient loads of this nature do not result in premature
charge cycle termination. Once the average charge current
drops below the programmed termination threshold, the
LTC4076 terminates the charge cycle and ceases to provide
any current out of the BAT pin. In this state, any load on
the BAT pin must be supplied by the battery.
If the battery is removed from the charger, a sawtooth
waveform of approximately 100mV appears at the battery
output. This is caused by the repeated cycling between
termination and recharge events. This cycling results in
pulsing at the CHRG output; an LED connected to this pin
will exhibit a blinking pattern, indicating to the user that
a battery is not present. The frequency of the sawtooth is
dependent on the amount of output capacitance.
Manual Shutdown
The EN pin has a 2MΩ pulldown resistor to GND. A logic
low enables the charger and logic high disables it (the
pulldown defaults the charger to the charging state).
The DCIN input draws 20µA when the charger is in shutdown. The USBIN input draws 18µA during shutdown if
no power is applied to DCIN, but draws only 10µA when
VDCIN > VUSBIN.
Low-Battery Charge Conditioning (Trickle Charge)
Charge Current Soft-Start and Soft-Stop
This feature ensures that deeply discharged batteries are
gradually charged before applying full charge current . If
the BAT pin voltage is below 2.9V, the LTC4076 supplies
1/10th of the full charge current to the battery until the
BAT pin rises above 2.9V. For example, if the charger is
programmed to charge at 800mA from the wall adapter
input and 500mA from the USB input, the charge current
during trickle charge mode would be 80mA and 50mA,
respectively.
The LTC4076 includes a soft-start circuit to minimize
the inrush current at the start of a charge cycle. When a
charge cycle is initiated, the charge current ramps from
zero to full-scale current over a period of 250µs. Likewise,
internal circuitry slowly ramps the charge current from
full-scale to zero in a period of approximately 30µs when
the charger shuts down or self terminates. This minimizes
the transient current load on the power supply during
start-up and shut-off.
Automatic Recharge
In standby mode, the charger sits idle and monitors the
battery voltage using a comparator with a 6ms filter time
(tRECHRG). A charge cycle automatically restarts when the
battery voltage falls below 4.1V (which corresponds to
approximately 80%-90% battery capacity). This ensures
that the battery is kept at, or near, a fully charged condition and eliminates the need for periodic charge cycle
initiations.
Status Indicators
 H
 R
 G
 ) has two states: pull-down
The charge status output (C
and high impedance. The pull-down state indicates that
the LTC4076 is in a charge cycle. Once the charge cycle
has terminated or the LTC4076 is disabled, the pin state
becomes high impedance. The pull-down state is capable
of sinking up to 10mA.
*Any external sources that hold the ITERM pin above 100mV will prevent the LTC4076 from
terminating a charge cycle.
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10
LTC4076
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OPERATIO
 W
 R
 ) has two states:
The power supply status output (P
pull-down and high impedance. The pull-down state
indicates that power is present at either DCIN or USBIN.
If no power is applied at either pin, the PWR pin is high
impedance, indicating that the LTC4076 lacks sufficient
power to charge the battery. The pull-down state is capable
of sinking up to 10mA.
Thermal Limiting
a preset value of approximately 105°C. This feature protects
the LTC4076 from excessive temperature and allows the
user to push the limits of the power handling capability of
a given circuit board without risk of damaging the device.
The charge current can be set according to typical (not
worst-case) ambient temperature with the assurance that
the charger will automatically reduce the current in worstcase conditions. DFN power considerations are discussed
further in the Applications Information section.
An internal thermal feedback loop reduces the programmed
charge current if the die temperature attempts to rise above
STARTUP
DCIN POWER APPLIED
DCIN POWER
REMOVED
BAT < 2.9V
TRICKLE CHARGE
MODE
POWER SELECTION
ONLY USB POWER APPLIED
USBIN POWER
REMOVED OR
DCIN POWER
APPLIED
TRICKLE CHARGE
MODE
1/10th FULL CURRENT
CHRG STATE: PULLDOWN
CHRG STATE: PULLDOWN
BAT > 2.9V
2.9V < BAT
BAT > 2.9V
CHARGE
MODE
CHARGE
MODE
FULL CURRENT
FULL CURRENT⇒HPWR = HIGH
1/5 FULL CURRENT⇒HPWR = LOW
CHRG STATE: PULLDOWN
CHRG STATE: PULLDOWN
IBAT < ITERMINATE
IN VOLTAGE MODE
BAT < 4.1V
EN
DRIVEN LOW
BAT < 2.9V
1/10th FULL CURRENT
2.9V < BAT
IBAT < ITERMINATE
IN VOLTAGE MODE
STANDBY
MODE
STANDBY
MODE
NO CHARGE CURRENT
NO CHARGE CURRENT
CHRG STATE: Hi-Z
CHRG STATE: Hi-Z
EN
DRIVEN HIGH
SHUTDOWN
MODE
EN
DRIVEN HIGH
IDCIN DROPS TO 20µA
CHRG STATE: Hi-Z
SHUTDOWN
MODE
BAT < 4.1V
EN
DRIVEN LOW
IUSBIN DROPS TO 18µA
DCIN POWER
REMOVED
USBIN POWER
REMOVED OR
DCIN POWER
APPLIED
CHRG STATE: Hi-Z
4076 F01
Figure 1. LTC4076 State Diagram of a Charge Cycle
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LTC4076
APPLICATIO S I FOR ATIO
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Using a Single Charge Current Program Resistor
The LTC4076 can also program the wall adapter charge
current and USB charge current independently using two
program resistors, RIDC and RIUSB. Figure 3 shows a
charger circuit that sets the wall adapter charge current
to 800mA and the USB charge current to 500mA.
In applications where the programmed wall adapter charge
current and USB charge current are the same, a single
program resistor can be used to set both charge currents.
Figure 2 shows a charger circuit that uses one charge current program resistor. In this circuit, one resistor programs
the same charge current for each input supply.
Stability Considerations
The constant-voltage mode feedback loop is stable without
any compensation provided a battery is connected to the
charger output. However, a 1µF capacitor with a 1Ω series
resistor is recommended at the BAT pin to keep the ripple
voltage low when the battery is disconnected.
1000 V
ICHRG(DC) = ICHRG(USB) =
RISET
WALL
ADAPTER
USB
PORT
100mA
(USB, HPWR = LOW)
500mA
LTC4076
DCIN
1 F
USBIN
1 F
When the charger is in constant-current mode, the charge
current program pin (IDC or IUSB) is in the feedback loop,
not the battery. The constant-current mode stability is
affected by the impedance at the charge current program
pin. With no additional capacitance on this pin, the charger is stable with program resistor values as high as 20k
(ICHRG = 50mA); however, additional capacitance on these
nodes reduces the maximum allowed program resistor.
BAT
HPWR
+
IUSB
RISET
2k
1%
IDC
ITERM
GND
RITERM
1k
1%
4076 F02
Figure 2. Dual Input Charger Circuit. The Wall
Adapter Charge Current and USB Charge Current
are Both Programmed to be 500mA
800mA (WALL)
100mA/500mA (USB)
LTC4076
WALL
ADAPTER
USB
PORT
DCIN
BAT
USBIN
1 F
HPWR
IUSB
RIUSB
2k
1%
RIDC
1.24k
1%
1k
1k
1 F
IDC
+
PWR
CHRG
ITERM
GND
4.2V
1-CELL
Li-Ion
BATTERY
RITERM
1k
1%
4076 F03
Figure 3. Full Featured Dual Input Charger Circuit
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12
LTC4076
APPLICATIO S I FOR ATIO
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Power Dissipation
When designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios
because the LTC4076 automatically reduces the charge
current during high power conditions. The conditions
that cause the LTC4076 to reduce charge current through
thermal feedback can be approximated by considering the
power dissipated in the IC. Most of the power dissipation
is generated from the internal MOSFET pass device. Thus,
the power dissipation is calculated to be:
PD = (VIN – VBAT) • IBAT
PD is the power dissipated, VIN is the input supply voltage (either DCIN or USBIN), VBAT is the battery voltage
and IBAT is the charge current. The approximate ambient
temperature at which the thermal feedback begins to
protect the IC is:
TA = 105°C – PD • θJA
TA = 105°C – (VIN – VBAT) • IBAT • θJA
The LTC4076 can be used above 50.6°C ambient, but
the charge current will be reduced from 800mA. The approximate current at a given ambient temperature can be
approximated by:
105°C – TA
IBAT =
(VIN – VBAT ) • θ JA
Using the previous example with an ambient temperature
of 60°C, the charge current will be reduced to approximately:
105°C – 60°C
45°C
=
(5V – 3.3V)• 40°C / W 68°C / A
= 662mA
IBAT =
IBAT
It is important to remember that LTC4076 applications do
not need to be designed for worst-case thermal conditions,
since the IC will automatically reduce power dissipation
when the junction temperature reaches approximately
105°C.
Thermal Considerations
Example: An LTC4076 operating from a 5V wall adapter (on
the DCIN input) is programmed to supply 800mA full-scale
current to a discharged Li-Ion battery with a voltage of 3.3V.
Assuming θJA is 40°C/W (see Thermal Considerations),
the ambient temperature at which the LTC4076 will begin
to reduce the charge current is approximately:
TA = 105°C – (5V – 3.3V) • (800mA) • 40°C/W
TA = 105°C – 1.36W • 40°C/W = 105°C – 54.4°C
TA = 50.6°C
In order to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4076 package is properly soldered
to the PC board ground. When correctly soldered to a
2500mm2 double sided 1oz copper board, the LTC4076
has a thermal resistance of approximately 40°C/W. Failure
to make thermal contact between the exposed pad on the
backside of the package and the copper board will result in
thermal resistances far greater than 40°C/W. As an example,
a correctly soldered LTC4076 can deliver over 800mA to
a battery from a 5V supply at room temperature. Without
a good backside thermal connection, this number would
drop to much less than 500mA.
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LTC4076
APPLICATIO S I FOR ATIO
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Protecting the USB Pin and Wall Adapter Input from
Overvoltage Transients
Caution must be exercised when using ceramic capacitors
to bypass the USBIN pin or the wall adapter inputs. High
voltage transients can be generated when the USB or wall
adapter is hot plugged. When power is supplied via the
USB bus or wall adapter, the cable inductance along with
the self resonant and high Q characteristics of ceramic
capacitors can cause substantial ringing which could
exceed the maximum voltage ratings and damage the
LTC4076. Refer to Linear Technology Application Note 88,
entitled “Ceramic Input Capacitors Can Cause Overvoltage
Transients” for a detailed discussion of this problem.
Always use an oscilloscope to check the voltage waveforms at the USBIN and DCIN pins during USB and wall
adapter hot-plug events to ensure that overvoltage
transients have been adequately removed.
Reverse Polarity Input Voltage Protection
In some applications, protection from reverse polarity
voltage on the input supply pins is desired. If the supply voltage is high enough, a series blocking diode can
be used. In other cases where the voltage drop must be
kept low, a P-channel MOSFET can be used (as shown in
Figure 4).
DRAIN-BULK
DIODE OF FET
WALL
ADAPTER
LTC4076
DCIN
4076 F04
Figure 4. Low Loss Input Reverse Polarity Protection
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14
LTC4076
PACKAGE DESCRIPTIO
U
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115
TYP
6
0.38 ± 0.10
10
0.675 ±0.05
3.50 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
3.00 ±0.10
(4 SIDES)
PACKAGE
OUTLINE
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.75 ±0.05
0.00 – 0.05
5
1
(DD) DFN 1103
0.25 ± 0.05
0.50 BSC
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
4076fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC4076
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC3455
LTC4055
Dual DC/DC Converter with USB Power
Management and Li-Ion Battery Charger
USB Compatible Monolithic Li-Ion Battery Charger
Standalone Linear Li-Ion Battery Charger
with Integrated Pass Transistor in ThinSOT
USB Power Controller and Battery Charger
LTC4058/LTC4058X
LTC4061
Standalone 950mA Lithium-Ion Charger in DFN
Standalone Li-Ion Charger with Thermistor Interface
LTC4061-4.4
Standalone Li-Ion Charger with Thermistor Interface
Efficiency >96%, Accurate USB Current Limiting (500mA/100mA),
4mm × 4mm QFN-24 Package
Standalone Charger with Programmable Timer, Up to 1.25A Charge Current
Thermal Regulation Prevents Overheating, C/10 Termination,
C/10 Indicator, Up to 800mA Charge Current
Charges Single-Cell Li-Ion Batteries Directly from USB Port,
Thermal Regulation, 4mm × 4mm QFN-16 Package
C/10 Charge Termination, Battery Kelvin Sensing, ±7% Charge Accuracy
4.2V, ±0.35% Float Voltage, Up to 1A Charge Current, 3mm × 3mm DFN-10
Package
4.4V, ±0.4% Float Voltage, Up to 1A Charge Current, 3mm × 3mm DFN-10
Package
LTC4062
LTC4075
Standalone Li-Ion Charger with Micropower
Comparator
Standalone 750mA Li-Ion Charger
in 2mm × 2mm DFN
USB Power Controller and Li-Ion Linear Battery
Charger with Low-Loss Ideal Diode
Standalone Linear Li-Ion Battery Charger with
Programmable Termination
Dual Input Standalone Li-Ion Battery Charger
LTC4077
Dual Input Standalone Li-Ion Battery Charger
LTC4410
USB Power Manager and Battery Charger
LTC4411/LTC4412
Low Loss PowerPathTM Controller in ThinSOT
LTC4053
LTC4054/LTC4054X
LTC4065/LTC4065A
LTC4066
LTC4068/LTC4068X
4.2V, ±0.35% Float Voltage, Up to 1A Charge Current, 3mm × 3mm DFN-10
Package
4.2V, ±0.6% Float Voltage, Up to 750mA Charge Current, 2mm × 2mm
DFN-6 Package
Seamless Transition Between Input Power Sources: Li-Ion Battery, USB and
Wall Adapter, Low-Loss (50Ω) Ideal Diode, 4mm × 4mm QFN-24 Package
Charge Current up to 950mA, Thermal Regulation,
3mm × 3mm DFN-8 Package
Charges Single-Cell Li-Ion Batteries from Wall Adapter and USB Inputs with
Automatic Input Power Detection and Selection, 950mA Charger Current,
Thermal Regulation, C/X Charge Termination, 3mm × 3mm DFN Package
Charges Single-Cell Li-Ion Batteries from Wall Adapter and USB Inputs with
Automatic Input Power Detection and Selection, 950mA Charger Current,
Thermal Regulation, C/10 Charge Termination, 3mm × 3mm DFN Package
Manages Total Power Between a USB Peripheral and Battery Charger,
Ultralow Battery Drain: 1µA, ThinSOTTM Package
Automatic Switching Between DC Sources, Load Sharing,
Replaces ORing Diodes
ThinSOT and PowerPath are trademarks of Linear Technology Corporation
4076fa
16 Linear Technology Corporation
LT 04/06 REV A PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
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 LINEAR TECHNOLOGY CORPORATION 2005