LINER LTC4077EDD

LTC4077
Dual Input Standalone
Li-Ion Battery Charger
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DESCRIPTIO
FEATURES
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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/10 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
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APPLICATIO S
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Cellular Telephones
Handheld Computers
Portable MP3 Players
Digital Cameras
The LTC®4077 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 LTC4077
terminates the charge cycle when the charge current drops
below the termination threshold after the final float voltage
is reached. The LTC4077 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 adjustable mode for USB compatible applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. patents, including 6522118
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TYPICAL APPLICATIO
USB
PORT
1mF
800mA (WALL)
500mA (USB)
LTC4077
WALL
ADAPTER
BAT
DCIN
1mF
USBIN
HPWR
+
IUSB
2k
IDC
1% 1.24k
1%
4.2V
SINGLE CELL
Li-Ion BATTERY
IUSBL
GND
2k
1%
4077 TA01
BATTERY
CHARGE
VOLTAGE (V) CURRENT (mA)
Dual Input Battery Charger for Single-Cell Li-Ion
1000
800
600
400
200
0
4.2
4.0
3.8
3.6
3.4
DCIN
VOLTAGE (V)
Complete Charge Cycle (1100mAh Battery)
5.0
CONSTANT VOLTAGE
USBIN = 5V
TA = 25°C
RIDC = 1.24k
RIUSB = 2k
HPWR = 5V
2.5
0
0
0.5
1.0
2.0
1.5
TIME (HR)
2.5
3.0
"%% 6)>
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LTC4077
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Notes 1, 9)
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, IUSBL ................................. –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
IUSBL
3
PWR
4
7 HPWR
CHRG
5
6 EN
9 BAT
11
8 IDC
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
ORDER PART NUMBER
LTC4077EDD
DD PART MARKING
LBWD
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
VIUSBL
IC/IO
IDC Pin Regulated Voltage
IUSB Pin Regulated Voltage
IUSBL Pin Regulated Voltage
Charge Current Termination Threshold
CONDITIONS
MIN
TYP
MAX
UNITS
●
●
150
50
20
8
8
700
100
40
V
V
µA
µA
µA
●
●
0.95
0.95
0.18
150
50
18
10
4.2
4.2
800
476
100
50
–3
–1
±1
1
1
0.2
700
100
36
20
4.225
4.242
840
500
108
56
–6
–2
±2
1.05
1.05
0.22
µA
µA
µA
µA
V
V
mA
mA
mA
mA
µA
µA
µA
V
V
V
0.09
0.09
0.1
0.1
0.11
0.11
mA/mA
mA/mA
●
●
Charge Mode (Note 4), RIDC = 10k
Standby Mode; Charge Terminated
Shutdown Mode (EN = 5V)
Charge Mode (Note 5), RIUSB = RIUSBL = 10k,
VDCIN = 0V
Standby Mode; Charge Terminated, VDCIN = 0V
Shutdown (VDCIN = 0V, EN = 5V)
VDCIN > VUSBIN
IBAT = 1mA (Note 9)
IBAT = 1mA, 0°C < TA < 85°C, 4.3V < VCC < 8V
RIDC = 1.25k, Constant-Current Mode
RIUSB = 2.1k, Constant-Current Mode
RIDC = 10k or RIUSB = 10k
RIUSBL = 4k, HPWR = 0
Standby Mode, Charge Terminated
Shutdown Mode (Charger Disabled)
Sleep Mode (VDCIN = 0V, VUSBIN = 0V)
Constant-Current Mode
Constant-Current Mode
Constant-Current Mode
VDCIN = 5V, RIDC = 1.25k (Note 7)
VUSBIN = 5V, VDCIN = 0V
●
●
●
●
●
●
4.3
4.3
4.175
4.158
760
450
92
44
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LTC4077
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 unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
IC/2
ITRIKL
Charge Current Termination Threshold
Trickle Charge Current
VTRIKL
Trickle Charge Threshold Voltage
HPWR = 0V (Note 8)
VBAT < VTRIKL; RIDC = 1.25k
VBAT < VTRIKL; RIUSB = 2.1k
VBAT < VTRIKL; RIUSBL = 4k
VBAT Rising
Hysteresis
MIN
TYP
MAX
UNITS
0.45
60
30
17
2.8
0.5
80
47.5
25
2.9
100
0.55
100
65
33
3
mA/mA
mA
mA
mA
V
mV
VUVDC
DCIN Undervoltage Lockout Voltage
From Low to High
Hysteresis
4
4.15
200
4.3
V
mV
VUVUSB
USBIN Undervoltage Lockout Voltage
From Low to High
Hysteresis
3.8
3.95
200
4.1
V
mV
VASD-DC
VDCIN – VBAT Lockout Threshold
VDCIN from Low to High, VBAT = 4.2V
VDCIN from High to Low, VBAT = 4.2V
VASD-USB
VUSBIN – VBAT Lockout Threshold
VUSBIN from Low to High
VUSBIN from High to Low
VEN
REN
VHPWR
RHPWR
V⎯C⎯H⎯R⎯G
V⎯P⎯W⎯R
ΔVRECHRG
tRECHRG
tTERMINATE
tSS
RON-DC
EN Input Threshold Voltage
EN Pulldown Resistance
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)
140
20
140
20
0.4
1
0.4
1
180
50
180
50
0.7
2
0.7
2
0.35
0.35
100
6
1.5
250
400
220
80
220
80
1
5
1
5
0.6
0.6
135
10
2.2
325
mV
mV
mV
mV
V
MΩ
V
MΩ
V
V
mV
ms
ms
µs
mΩ
RON-USB
Power FET “ON” Resistance
(Between USBIN and BAT)
550
mΩ
TLIM
Junction Temperature in
Constant-Temperature Mode
105
°C
●
●
●
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 = 0 to Full-Scale
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC4077E is guaranteed to meet the performance
specifications from 0°C to 70°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.
Note 4: Supply current includes IDC pin current (approximately 100µA)
but does not include any current delivered to the battery through the BAT
pin.
65
3
0.8
175
Note 5: Supply current includes IUSB and IUSBL pin currents
(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: IC/10 is expressed as a fraction of measured full charge current.
Note 8: IC/2 is expressed as a fraction of measured full charge current.
Note 9: VCC is greater of DCIN or USBIN
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LTC4077
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TYPICAL PERFOR A CE CHARACTERISTICS
Regulated Output (Float) Voltage
vs Temperature
Regulated Output (Float) Voltage
vs Charge Current
4.220
VDCIN = VUSBIN = 5V
1.008
VDCIN = VUSBIN = 5V
4.215
1.006
4.22
4.210
1.004
4.20
4.205
1.002
4.18
4.16
VIDC (V)
4.24
VFLOAT (V)
VFLOAT (V)
4.26
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
0
25
50
TEMPERATURE (°C)
75
4077 G01
0.208
0.206
1.004
0.204
VIUSBL (V)
1.000
VUSBIN = 4.3V
0.998
0.194
75
100
600
VUSBIN = 8V
VUSBIN = 4.3V
RIDC = 10k
100
–25
0
50
25
TEMPERATURE (°C)
75
0
100
0
0.4
0.2
0.6
0.8
VIDC (V)
4077 G05
Charge Current vs IUSBL Pin
Voltage
RIUSB = 1.25k
⎯P⎯W⎯R Pin I-V Curve
35
VDCIN = VUSBIN = 5V
VUSBIN = 5V
HPWR = 0V
200
TA = – 40°C
30
RIUSBL = 1k9
TA = 25°C
25
400
150
RIUSBL = 2k9
100
300
200
0
0
0
0.2
0.4
0.6
0.8
VIUSB (V)
1.0
1.2
4077 G06
TA = 90°C
20
15
10
RIUSBL = 4k9
50
RIUSB = 10k
100
IPWR (mA)
RIUSB = 2k
IBAT (mA)
IBAT (mA)
600
500
1.2
1.0
4077 G24
VUSBIN = 5V
HPWR = 5V
700
400
200
250
800
RIDC = 2k
500
300
4077 G04
900
RIDC = 1.25k
VDCIN = 5V
700
0.192
–50
Charge Current vs IUSB Pin
Voltage
100
800
0.198
0.994
0
25
50
TEMPERATURE (°C)
900
0.200
0.196
–25
75
0
25
50
TEMPERATURE (°C)
Charge Current vs IDC Pin
Voltage
HPWR = 0V
0.202
0.996
0.992
–50
–25
4077 G03
IBAT (mA)
1.006
VUSBIN = 8V
0.992
–50
IUSBL Pin Voltage vs Temperature
(Constant-Current Mode)
HPWR = 5V
1.002
VDCIN = 4.3V
4077 G02
IUSB Pin Voltage vs Temperature
(Constant-Current Mode)
1.008
100
VDCIN = 8V
1.000
4.195
RIDC = RIUSB = 2k
4.10
VIUSB (V)
IDC Pin Voltage vs Temperature
(Constant-Current Mode)
5
0
0
50
150
100
VIUSBL (mV)
200
250
4077 G25
0
1
2
4
3
VPWR (V)
5
6
7
4077 G07
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LTC4077
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TYPICAL PERFOR A CE CHARACTERISTICS
Charge Current vs Ambient
Temperature
⎯C⎯H⎯R⎯G Pin I-V Curve
Charge Current vs Supply Voltage
1000
35
VDCIN = VUSBIN = 5V
900
ONSET OF
THERMAL REGULATION
TA = –40°C
30
800
800
TA = 25°C
RIDC = 1.25k
700
15
600
RIDC = RIUSB = 2k
400
200
5
0
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
4077 G09
Charge Current vs Battery Voltage
DCIN Power FET “On” Resistance
vs Temperature
550
5.5 6.0 6.5
VDCIN (V)
5.0
7.0
7.5
8.0
4077 G10
USBIN Power FET “On” Resistance
vs Temperature
800
VBAT = 4V
IBAT = 200mA
750
500
800
RIDC = 1.25k
VBAT = 4V
θJA = 35°C/W
300
4.0 4.5
125
4077 G08
1000
VBAT = 4V
IBAT = 200mA
HPWR = 5V
600
400
3.0
3.3 3.6
VBAT (V)
3.9
350
300
0
2.7
400
650
600
550
500
450
VDCIN = VUSBIN = 5V
θJA = 40°C/W
RIDC = 1.25k
2.4
450
RDS(ON) (mΩ)
RDS(ON) (mΩ)
700
200
4.2
400
250
–50 –25
4.5
50
25
75
0
TEMPERATURE (°C)
100
4077 G11
350
–50 –25
125
900
50
VDCIN = VUSBIN = 5V
800
800
45
40
35
IDCIN (µA)
850
VHPWR (mV)
850
750
700
650
30
25
20
15
10
650
VDCIN = 8V
VDCIN = 5V
VDCIN = 4.3V
5
600
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
4077 G14
125
DCIN Shutdown Current vs
Temperature
900
VDCIN = VUSBIN = 5V
700
100
4077 G13
HPWR Pin Threshold (Rising) vs
Temperature
750
50
25
75
0
TEMPERATURE (°C)
4077 G12
EN Pin Threshold (Rising) vs
Temperature
VEN (mV)
600
500
10
IBAT (mA)
IBAT (mA)
TA = 90°C
20
IBAT (mA)
ICHRG (mA)
25
ONSET OF
THERMAL REGULATION
600
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
0
–50
EN = 5V
–25
50
25
0
TEMPERATURE (°C)
75
100
4077 G16
4077 G15
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LTC4077
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TYPICAL PERFOR A CE CHARACTERISTICS
USBIN Shutdown Current vs
Temperature
EN Pin Pulldown Resistance vs
Temperature
45
HPWR Pin Pulldown Resistance
vs Temperature
2.8
2.8
2.6
2.6
2.4
2.4
40
35
25
20
VUSBIN = 5V
15
10
RHPWR (MΩ)
IUSBIN (µA)
REN (MΩ)
VUSBIN = 8V
30
2.2
2.2
2.0
2.0
1.8
1.8
VUSBIN = 4.3V
5
0
–50
EN = 5V
–25
50
25
0
TEMPERATURE (°C)
100
75
1.6
–50
–25
50
25
0
TEMPERATURE (°C)
75
4077 G17
1.6
–50
100
–25
50
25
0
TEMPERATURE (°C)
100
4077 G19
4077 G18
Undervoltage Lockout Threshold
vs Temperature
75
Recharge Threshold
vs Temperature
4.16
4.30
4.25
4.14
DCIN UVLO
4.20
4.12
VRECHRG (V)
VUV (V)
4.15
4.10
4.05
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)
4077 G20
100
4077 G21
Charge Current at Turn-On and
Turn-Off
Battery Drain Current
vs Temperature
5
75
VBAT = 4.2V
VDCIN, VUSBIN (OPEN)
4
IBAT
500mA/DIV
IBAT (µA)
3
2
EN
5V/DIV
1
0
–1
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4077 G22
VDCIN = 5V
RIDC = 1.25k
100ms/DIV
4077 G23
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LTC4077
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PI FU CTIO S
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 High 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:
IBAT =
VIUSB
• 1000
RIUSB
IUSBL (Pin 3): Charge Current Program for Low USB Power.
The charge current is set by connecting a resistor, RIUSBL,
to ground. When charging in constant current mode, this
pin servos to 0.2V. The voltage on this pin can be used to
measure the battery current delivered from the USB input
using the following formula:
IBAT =
VIUSBL
• 200
RIUSBL
⎯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 LTC4077 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 LTC4077 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 current limit at the current
programmed by the IUSB pin. A logic low on the HPWR
pin sets the current limit at the current programmed by the
IUSBL 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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LTC4077
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BLOCK DIAGRA
DCIN
BAT
USBIN
10
9
1
CC/CV
REGULATOR
HPWR
7
+
RHPWR
4
5
DC
SOFT-START
USB
SOFT-START
DCIN UVLO
10mA MAX
BAT
CHRG
+
–
4.15V
PWR
CC/CV
REGULATOR
10mA MAX
+
–
3.95V
USBIN UVLO
+
+
–
–
BAT
4.1V
RECHARGE
LOGIC
–
RECHRG
BAT
TRICKLE
DC_ENABLE
–
TERM
+
TDIE
–
105°C
CHARGER CONTROL
+
EN
TRICKLE
CHARGE
USB_ENABLE
2.9V
+
100mV
–
IDC
IUSB
IUSBL
THERMAL
REGULATION
6
REN
IBAT/1000
TERMINATION
GND
11
IBAT/1000
IDC
8
IUSB
2
RIDC
IBAT/200
IUSBL
3
RIUSB
4077 BD
RIUSBL
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LTC4077
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OPERATIO
The LTC4077 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 LTC4077 has two internal P-channel power MOSFETs
and thermal regulation circuitry. No blocking diodes or
external sense resistors are required.
Power Source Selection
The LTC4077 can charge a battery from either the wall
adapter input or the USB port input. The LTC4077 automatically senses the presence of voltage at each input. If both
power sources are present, the LTC4077 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
VUSBIN > 3.95V and
VUSBIN > BAT + 50mV
VDCIN > 4.15V and
VDCIN > BAT + 50mV
VDCIN < 4.15V or
VDCIN < 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
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. Likewise, the charge current from
the USB supply is programmed using a single resistor
from the IUSB pin to ground if HPWR is set on its high
logic state or from the IUSBL pin to ground if HPWR is
set on its low logic state or it is left floating. The program
resistor and the charge current (ICHRG) are calculated
using the following equations:
RIDC =
1000 V
ICHRG(DC)
RIUSB =
, ICHRG(DC) =
1000 V
ICHRG(USB)
RIUSBL =
1000 V
RIDC
, ICHRG(USB) =
200 V
ICHRG(USB)
1000 V
RIUSB
, ICHRG(USB) =
200 V
RIUSBL
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:
V
IBAT = IDC • 1000, (ch arging from wall adapter)
RIDC
V
IBAT = IUSB • 1000, (charging from USB supplly,
RIUSB
HPWR = high)
V
IBAT = IUSBL • 200, (charging from USB supply,
RIUSBL
HPWR = low)
⎯P⎯W⎯R: Hi-Z
4077f
9
LTC4077
U
OPERATIO
Programming Charge Termination
Automatic Recharge
The charge cycle terminates when the voltage at the IUSB,
IUSBL and IDC pins falls below 100mV. For wall adapter
or high power USB use the charge termination is set to
1/10th of the programmed charge current. For low power
USB use (HPWR = 0V) the charge termination is set to
1/2 of the programmed charge current.
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.
The termination condition is detected by using an internal
filtered comparator to monitor the IDC, IUSB and IUSBL
pin voltages. When one of these voltages drops below
100mV* for longer than tTERMINATE (typically 1.5ms), the
charge cycle terminates, charge current latches off and
the LTC4077 enters standby mode.
When charging, transient loads on the BAT pin can cause
the active charge current program pin to fall below 100mV
for short periods of time before the steady-state 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 termination
threshold, the LTC4077 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.
Low-Battery Charge Conditioning (Trickle Charge)
This feature ensures that deeply discharged batteries
are gradually charged before reapplying full charge current. If the BAT pin voltage is below 2.9V, the LTC4077
supplies 1/10th of the full charge current to the battery,
when HPWR = high or 1/2 of the full charge current
(programmed by RIUSBL) to the battery when HPWR =
low, 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 when
HPWR is high or 50mA if HPWR is low, the charge current
during trickle charge mode would be 80mA, 50mA and
25mA respectively.
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.
Charge Current Soft-Start and Soft-Stop
The LTC4077 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.
*Any external sources that hold the pin above 100mV will prevent the LTC4077 from terminating
a charge cycle.
4077f
10
LTC4077
U
OPERATIO
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 LTC4077 is in a charge cycle. Once the charge cycle
has terminated or the LTC4077 is disabled, the pin state
becomes high impedance. The pull-down state is capable
of sinking up to 10mA.
⎯ 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 LTC4077 lacks sufficient
power to charge the battery. The pull-down state is capable
of sinking up to 10mA.
STARTUP
DCIN POWER APPLIED
ONLY USB POWER APPLIED
POWER SELECTION
DCIN POWER
REMOVED
BAT < 2.9V
TRICKLE CHARGE
MODE
USBIN POWER
REMOVED OR
DCIN POWER
APPLIED
TRICKLE CHARGE
MODE
1/2 OR 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
CHRG STATE: PULLDOWN
CHRG STATE: PULLDOWN
EN
DRIVEN LOW
2.9V < BAT
IBAT < ITERMINATE
IN VOLTAGE MODE
IBAT < ITERMINATE
IN VOLTAGE MODE
BAT < 4.1V
BAT < 2.9V
1/10th FULL CURRENT
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 20mA
CHRG STATE: Hi-Z
SHUTDOWN
MODE
BAT < 4.1V
EN
DRIVEN LOW
IUSBIN DROPS TO 18mA
DCIN POWER
REMOVED
USBIN POWER
REMOVED OR
DCIN POWER
APPLIED
CHRG STATE: Hi-Z
4075 F01
Figure 1. LTC4077 State Diagram of a Charge Cycle
4077f
11
LTC4077
U
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W
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APPLICATIO S I FOR ATIO
Thermal Limiting
An internal thermal feedback loop reduces the programmed
charge current if the die temperature attempts to rise above
a preset value of approximately 105°C. This feature protects
the LTC4077 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.
Using a Single Charge Current Program Resistor
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
LTC4077
WALL
ADAPTER
USB
PORT
1mF
USBIN
1mF
HPWR
ICHRG(DC) = ICHRG(USB) =
1000 V
RISET
The programmed charge current for USB supply with
HPWR in its low state is:
ICHRG(USBL) =
200 V
RISET
The LTC4077 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 (HPWR
= high) or 50mA (HPWR = low).
800mA (WALL)
500mA (USB,
HPWR = HIGH)
50mA (USB,
HPWR = LOW)
100mA
(USB, HPWR = LOW)
500mA
BAT
DCIN
charge current program resistor. In this circuit, one registor
programs the same charge current for each input supply
(with HPWR = HIGH).
WALL
ADAPTER
USB
POWER
+
IUSB
LTC4077
DCIN
BAT
USBIN
1mF
1k
1k
1mF
IUSBL
RISET
2k
1%
IDC
GND
4077 F02
Figure 2. Dual Input Charger Circuit. The Wall Adapter
Charge Current and USB Charge Currents (HPWR = High)
are Both Programmed to be 500mA. If USBIN is the Supply
and HPWR = Low, the Charge Current is 100mA
RIUSBL
4.02k
1%
RIUSB
2k
1%
HPWR
PWR
IUSBL
CHRG
IUSB
IDC
GND
+
4.2V
1-CELL
Li-Ion
BATTERY
RIDC
1.24k
1%
4077 F03
Figure 3. Full Featured Dual Input Charger Circuit
4077f
12
LTC4077
U
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APPLICATIO S I FOR ATIO
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.
When the charger is in constant-current mode, the charge
current program pin (IDC, IUSB or IUSBL) 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; however, additional capacitance on these nodes
reduces the maximum allowed program resistor.
Power Dissipation
When designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios
because the LTC4077 automatically reduces the charge
current during high power conditions. The conditions
that cause the LTC4077 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:
Example: An LTC4077 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 LTC4077 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
The LTC4077 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:
IBAT =
105°C ± TA
( VIN ± VBAT ) • qJA
Using the previous example with an ambient temperature of 60°C, the charge current will be reduced to
approximately:
IBAT =
105°C ± 60°C
45°C
=
(5 V ± 3.3 V ) • 40°C / W 68°C /A
IBAT = 662mA
It is important to remember that LTC4077 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.
TA = 105°C – PD • θJA
TA = 105°C – (VIN – VBAT) • IBAT • θJA
4077f
13
LTC4077
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APPLICATIO S I FOR ATIO
Thermal Considerations
In order to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4077 package is properly soldered
to the PC board ground. When correctly soldered to a
2500mm2 double sided 1oz copper board, the LTC4077
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 LTC4077 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.
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
LTC4077. 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
LTC4077
DCIN
4077 F04
Figure 4. Low Loss Input Reverse Polarity Protection
4077f
14
LTC4077
U
PACKAGE DESCRIPTIO
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
0.675 ±0.05
3.50 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
TYP
6
3.00 ±0.10
(4 SIDES)
0.38 ± 0.10
10
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
(DD10) DFN 1103
5
0.200 REF
1
0.75 ±0.05
0.00 – 0.05
0.25 ± 0.05
0.50 BSC
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
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
4077f
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
LTC4077
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
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
LTC4076
Dual Input Standalone Li-Ion Battery Charger
LTC4410
USB Power Manager and Battery Charger
LTC4411/LTC4412
Low Loss PowerPathTM Controller in ThinSOT
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
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/X 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
LTC4053
LTC4054/LTC4054X
LTC4065/LTC4065A
LTC4066
LTC4068/LTC4068X
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
4077f
16 Linear Technology Corporation
LT/LWI/TP 0705 500 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
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