LINER LTC4075XEDD Dual input usb/ac adapter standalone li-ion battery charger Datasheet

LTC4075/LTC4075X
Dual Input USB/AC
Adapter Standalone Li-Ion
Battery Chargers
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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
No External MOSFET, Sense Resistor or Blocking
Diode Needed
Thermal Regulation Maximizes Charging Rate
Without Risk of Overheating*
Preset Charge Voltage with ±0.6% Accuracy
Programmable Charge Current Termination
18µA USB Suspend Current in Shutdown
Independent “Power Present” Status Outputs
Charge Status Output
Automatic Recharge
Available Without Trickle Charge (LTC4075X)
Available in a Thermally Enhanced, Low Profile
(0.75mm) 10-Lead (3mm × 3mm) DFN Package
U
APPLICATIO S
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The LTC®4075/LTC4075X are standalone linear chargers
that are capable of charging a single-cell Li-Ion battery
from both wall adapter and USB inputs. The chargers 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 LTC4075
terminates the charge cycle when the charge current drops
below the programmed termination threshold after the
final float voltage is reached. With power applied to both
inputs, the LTC4075/LTC4075X 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.
Other features include automatic recharge, undervoltage
lockout, charge status outputs, and “power present”
status outputs to indicate the presence of wall adapter
or USB power.
Cellular Telephones
Handheld Computers
Portable MP3 Players
Digital Cameras
, 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, 6700364
U
Complete Charge Cycle (1100mAh Battery)
USB
PORT
1µF
800mA (WALL)
500mA (USB)
LTC4075
WALL
ADAPTER
DCIN
BAT
USBIN
1µF
+
IUSB
2k
IDC
1% 1.24k
1%
ITERM
GND
4.2V
SINGLE CELL
Li-Ion BATTERY
2k
1%
4075 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)
TYPICAL APPLICATIO
5.0
CONSTANT VOLTAGE
USBIN = 5V
TA = 25°C
RIDC = 1.25k
RIUSB = 2k
2.5
0
–2.5
0
0.5
1.0
2.0
1.5
TIME (HR)
2.5
3.0
4075 TA01b
4075Xf
1
LTC4075/LTC4075X
U
W W
W
ABSOLUTE
AXI U RATI GS
U
W
U
PACKAGE/ORDER I FOR ATIO
(Note 1)
Input Supply Voltage (DCIN, USBIN) ........... –0.3 to 10V
EN, ⎯C⎯H⎯R⎯G, ⎯P⎯W⎯R, USBPWR.......................... –0.3 to 10V
BAT, IDC, IUSB, ITERM .................................. –0.3 to 7V
DCIN Pin Current (Note 7) ..........................................1A
USBIN Pin Current (Note 7) .................................700mA
BAT Pin Current (Note 7) ............................................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
ORDER PART
NUMBER
TOP VIEW
10 DCIN
USBIN
1
IUSB
2
ITERM
3
PWR
4
7 USBPWR
CHRG
5
6 ENABLE
LTC4075EDD
LTC4075XEDD
9 BAT
11
8 IDC
DD PART
MARKING
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 40°C/W (NOTE 3)
EXPOSED PAD IS GND (PIN 11)
MUST BE SOLDERED TO PCB
LBSC
LBRK
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 unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
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
ITRIKL
Trickle Charge Current (Note 6)
VTRIKL
Trickle Charge Threshold (Note 6)
VUVDC
DCIN Undervoltage Lockout Voltage
From Low to High
Hysteresis
VUVUSB
USBIN Undervoltage Lockout Voltage
From Low to High
Hysteresis
MIN
●
●
TYP
MAX
UNITS
8
8
800
100
40
V
V
µA
µA
µA
4.3
4.3
Charge Mode (Note 4), RIDC = 10k
Standby Mode; Charge Terminated
Shutdown Mode (ENABLE = 5V)
●
●
250
50
20
Charge Mode (Note 5), RIUSB = 10k, VDCIN = 0V
Standby Mode; Charge Terminated, VDCIN = 0V
Shutdown (VDCIN = 0V, ENABLE = 0V)
VDCIN > VUSBIN
IBAT = 1mA
IBAT = 1mA, 0°C < TA < 85°C
RIDC = 1.25k, Constant-Current Mode
RIUSB = 2.1k, Constant-Current Mode
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
VBAT < VTRIKL; RIDC = 1.25k
VBAT < VTRIKL; RIUSB = 2.1k
VBAT Rising
Hysteresis
●
●
250
50
18
10
4.2
4.2
800
476
100
–3
–1
±1
1
1
100
50
10
5
80
47.5
2.9
100
800
100
36
20
4.225
4.242
840
500
107
–6
–2
±2
1.05
1.05
110
55
11.5
6
100
65
3
µA
µA
µA
µA
V
V
mA
mA
mA
µA
µA
µA
V
V
mA
mA
mA
mA
mA
mA
V
mV
4
4.15
200
4.3
V
mV
3.8
3.95
200
4.1
V
mV
●
●
●
●
●
●
●
4.175
4.158
760
450
93
0.95
0.95
90
45
8.5
4
60
30
2.8
4075Xf
2
LTC4075/LTC4075X
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
MIN
TYP
MAX
UNITS
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
VENABLE
RENABLE
V⎯C⎯H⎯R⎯G
V⎯P⎯W⎯R
VUSBPWR
ΔVRECHRG
tRECHRG
tTERMINATE
ENABLE Input Threshold Voltage
ENABLE Pulldown Resistance
⎯C⎯H⎯R⎯G Output Low Voltage
⎯P⎯W⎯R Output Low Voltage
USBPWR Output Low Voltage
Recharge Battery Threshold
Recharge Comparator Filter Time
140
20
140
20
0.4
1.2
180
50
180
50
0.7
2
0.35
0.35
0.35
100
6
220
80
220
80
1
5
0.6
0.6
0.6
135
9
mV
mV
mV
mV
V
MΩ
V
V
V
mV
ms
1.5
250
400
2.2
325
ms
µs
mΩ
tSS
RON-DC
Termination Comparator Filter Time
Soft-Start Time
Power FET “ON” Resistance
(Between DCIN and BAT)
●
I⎯C⎯H⎯R⎯G = 5mA
I⎯P⎯W⎯R = 5mA
IUSBPWR = 300µA
VFLOAT – VRECHRG, 0°C < TA < 85°C
VBAT from High to Low
65
3
IBAT Drops Below Termination Threshold
IBAT = 0 to Full-Scale
0.8
175
RON-USB
Power FET “ON” Resistance
(Between USBIN and BAT)
550
mΩ
TLIM
Junction Temperature in
Constant-Temperature Mode
105
°C
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC4075E/LTC4075XE are 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 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: This parameter is not applicable to the LTC4075X.
Note 7: Guaranteed by long term current density limitations.
4075Xf
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LTC4075/LTC4075X
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Regulated Output (Float) Voltage
vs Charge Current
4.220
VDCIN = VUSBIN = 5V
1.008
VDCIN = VUSBIN = 5V
1.006
4.22
4.210
1.004
4.20
4.205
1.002
4.18
VIDC (V)
4.215
4.16
4.200
0.998
4.14
4.190
0.996
4.12
4.185
0.994
RIDC = 1.25k
100 200 300 400 500 600 700 800
CHARGE CURRENT (mA)
0
4.180
–50
–25
75
0
25
50
TEMPERATURE (°C)
IUSB Pin Voltage vs Temperature
(Constant-Current Mode)
0.992
–50
1.008
900
1.006
800
1.004
700
900
VDCIN = 5V
VUSBIN = 4.3V
0.998
600
RIDC = 2k
500
400
–25
0
25
50
TEMPERATURE (°C)
75
0
0
0.4
0.2
0.6
0.8
VIDC (V)
4075X G04
1.2
1.0
0
5
TA = 25°C
IUSBPWR (mA)
ICHRG (mA)
15
TA = 90°C
20
15
10
10
5
5
0
1
2
4
3
VPWR (V)
5
6
7
4075X G07
4
TA = 90°C
3
2
1
0
0
TA = – 40°C
TA = 25°C
25
TA = 90°C
VDCIN = 5V
VUSBIN = 0V
TA = –40°C
30
TA = 25°C
20
6
VDCIN = VUSBIN = 5V
TA = –40°C
1.2
1.0
USBPWR Pin I-V Curve
35
35
25
0.6
0.8
VIUSB (V)
4075X G06
⎯C⎯H⎯R⎯G Pin I-V Curve
VDCIN = VUSBIN = 5V
0.4
0.2
4075X G05
⎯P⎯W⎯R Pin I-V Curve
30
RIUSB = 10k
100
0
100
400
200
RIDC = 10k
100
0.992
–50
RIUSB = 2k
500
300
200
0.994
RIUSB = 1.25k
700
300
0.996
100
VUSBIN = 5V
800
RIDC = 1.25k
IBAT (mA)
IBAT (mA)
1.000
75
0
25
50
TEMPERATURE (°C)
Charge Current vs IUSB Pin
Voltage
600
VUSBIN = 8V
–25
4075X G03
Charge Current vs IDC Pin
Voltage
1.002
VDCIN = 4.3V
4075X G02
4075X G01
VIUSB (V)
100
VDCIN = 8V
1.000
4.195
RIDC = RIUSB = 2k
4.10
IPWR (mA)
IDC Pin Voltage vs Temperature
(Constant-Current Mode)
4.24
VFLOAT (V)
VFLOAT (V)
4.26
Regulated Output (Float) Voltage
vs Temperature
0
1
2
4
3
VCHRG (V)
5
6
7
4075X G08
0
0
1
2
4
3
5
VUSBPWR (V)
6
7
4075X G09
4075Xf
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LTC4075/LTC4075X
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Charge Current vs Ambient
Temperature
Charge Current vs
Supply Voltage
1000
900
ONSET OF
THERMAL REGULATION
Charge Current vs Battery Voltage
1000
ONSET OF
THERMAL REGULATION
LTC4075X
800
800
800
RIDC = 1.25k
RIDC = RIUSB = 2k
400
IBAT (mA)
IBAT (mA)
IBAT (mA)
700
600
600
600
400
500
200
VDCIN = VUSBIN = 5V
VBAT = 4V
θJA = 40°C/W
0
–50 –25
400
50
25
75
0
TEMPERATURE (°C)
100
300
4.0 4.5
125
200
RIDC = 1.25k
VBAT = 4V
θJA = 35°C/W
0
7.5
7.0
5.5 6.0 6.5
VDCIN (V)
5.0
2.4
8.0
2.7
3.0
3.3 3.6
VBAT (V)
3.9
4.2
DCIN Power FET “On” Resistance
vs Temperature
USBIN Power “On” Resistance
vs Temperature
800
VBAT = 4V
IBAT = 200mA
750
4.5
4075X G12
4075X G11
4075X G10
550
VDCIN = VUSBIN = 5V
θJA = 40°C/W
RIDC = 1.25k
LTC4075
ENABLE Pin Threshold (On-to-Off)
vs Temperature
900
VBAT = 4V
IBAT = 200mA
VDCIN = VUSBIN = 5V
500
850
400
350
650
VENABLE (mV)
450
RDS(ON) (mΩ)
RDS(ON) (mΩ)
700
600
550
500
800
750
700
450
300
650
400
250
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
350
–50 –25
125
50
25
75
0
TEMPERATURE (°C)
100
4075X G13
45
45
40
15
10
0
–50
ENABLE Pin Pulldown Resistance
vs Temperature
2.6
VUSBIN = 8V
RENABLE (MΩ)
VDCIN = 5V
25
20
VUSBIN = 5V
15
VDCIN = 4.3V
5
10
ENABLE = 5V
–25
100
2.8
30
IUSBIN (µA)
IDCIN (µA)
20
75
35
VDCIN = 8V
30
25
50
25
0
TEMPERATURE (°C)
4075X G15
USBIN Shutdown Current vs
Temperature
50
35
–25
4075X G14
DCIN Shutdown Current vs
Temperature
40
600
–50
125
50
25
0
TEMPERATURE (°C)
75
100
4075X G16
VUSBIN = 4.3V
5
0
–50
2.4
2.2
2.0
1.8
ENABLE = 0V
–25
50
25
0
TEMPERATURE (°C)
75
100
4075X G17
1.6
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
4075X G18
4075Xf
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LTC4075/LTC4075X
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Undervoltage Lockout Threshold
vs Temperature
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)
100
4075X G20
4075X G19
Battery Drain Current
vs Temperature
5
75
Charge Current During Turn-On
and Turn-Off
VBAT = 4.2V
VDCIN, VUSBIN (NOT CONNECTED)
4
IBAT
500mA/DIV
IBAT (µA)
3
2
ENABLE
5V/DIV
1
0
–1
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4075X G21
VDCIN = 5V
RIDC = 1.25k
100µs/DIV
4075X G22
4075Xf
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LTC4075/LTC4075X
U
U
U
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 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
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 can draw
large currents and 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 LTC4075 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.
ENABLE (Pin 6): Enable Input. When the LTC4075 is
charging from the DCIN source, a logic low on this pin
enables the charger. When the LTC4075 is charging from
the USBIN source, a logic high on this pin enables the
charger. If this input is left floating, an internal 2MΩ
pulldown resistor defaults the LTC4075 to charge when
a wall adapter is applied and to shut down if only the USB
source is applied.
USBPWR (Pin 7): Open-Drain USB Power Status Output.
When the voltage on the USBIN pin is sufficient to begin
charging and there is insufficient power at DCIN, the USBPWR pin is high impedance. In all other cases, this pin is
pulled low by an internal N-channel MOSFET, provided that
there is power present at the DCIN, USBIN, or BAT inputs.
This output is capable of sinking up to 1mA, making it
suitable for driving high impedance logic inputs.
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 and Regulator Input. 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.
4075Xf
7
LTC4075/LTC4075X
W
BLOCK DIAGRA
DCIN
BAT
USBIN
10
9
1
CC/CV
REGULATOR
USBPWR
7
+
1mA MAX
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
–
ENABLE
*TRICKLE
CHARGE
USB_ENABLE
+
TDIE
–
105°C
CHARGER CONTROL
+
TERM
2.9V
+
100mV
THERMAL
REGULATION
6
RENABLE
IBAT/1000
TERMINATION
IBAT/1000
IBAT/1000
–
ITERM GND
3
11
IDC
8
IUSB
2
4075 BD
*TRICKLE CHARGE DISABLED ON THE LTC4075X
RITERM
RIDC
RIUSB
4075Xf
8
LTC4075/LTC4075X
U
OPERATIO
The LTC4075 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 LTC4075 has two internal P-channel power MOSFETs
and thermal regulation circuitry. No blocking diodes or
external sense resistors are required.
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. The program resistor
and the charge current (ICHRG) are calculated using the
following equations:
Power Source Selection
The LTC4075 can charge a battery from either the wall
adapter input or the USB port input. The LTC4075 automatically senses the presence of voltage at each input. If both
power sources are present, the LTC4075 defaults to the
wall adapter source provided sufficient power is present
at the DCIN input. “Sufficient power” is defined as:
RIUSB
• Supply voltage is greater than the battery voltage by
50mV (180mV rising, 50mV falling).
IBAT
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
USBPWR: LOW
Device powered from
USB source;
⎯P⎯W⎯R: LOW
USBPWR: Hi-Z
VUSBIN < 3.95V or
VUSBIN < BAT + 50mV
Device powered from
wall adapter source
⎯P⎯W⎯R: LOW
USBPWR: LOW
No charging
, ICHRG−DC =
VIDC
• 1000, (ch arg ing fromwall adapter)
RIDC
V
= IUSB • 1000, (ch arg ing fromUSB sup ply)
RIUSB
IBAT =
Table 1. Power Source Selection
1000V
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:
• Supply voltage is greater than the UVLO threshold.
The open drain power status outputs (⎯P⎯W⎯R and USBPWR)
indicate which power source has been selected. Table 1
describes the behavior of these status outputs.
1000V
ICHRG−DC
RIDC
1000V
1000V
=
, ICHRG−USB =
ICHRG−USB
RIUSB
RIDC =
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
⎯P⎯W⎯R: Hi-Z
USBPWR: LOW
4075Xf
9
LTC4075/LTC4075X
U
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), charging is terminated. The
charge current is latched off and the LTC4075 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
LTC4075 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 near-dead batteries are gradually
charged before reapplying full charge current . If the BAT
pin voltage is below 2.9V, the LTC4075 supplies 1/10th
of the full charge current to the battery until the BAT pin
rises back 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 LTC4075X does not include the trickle charge feature;
it outputs full charge current to the battery when the
BAT pin voltage is below 2.9V. The LTC4075X is useful
in applications where the trickle charge current may be
insufficient to supply the load during low battery voltage
conditions.
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 condi*Any external sources that hold the ITERM pin above 100mV will prevent the LTC4075 from
terminating a charge cycle.
tion and eliminates the need for periodic charge cycle
initiations.
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 ENABLE pin has a 2MΩ pulldown resistor to GND. The
definition of this pin depends on which source is supplying
power. When the wall adapter input is supplying power,
logic low enables the charger and logic high disables it (the
pulldown defaults the charger to the charging state). The
opposite is true when the USB input is supplying power;
logic high disables the charger and logic high enables it
(the default is the shutdown 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 LTC4075 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.
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 LTC4075 is in a charge cycle. Once the charge cycle
has terminated or the LTC4075 is disabled, the pin state
becomes high impedance. The pull-down state is capable
of sinking up to 10mA.
4075Xf
10
LTC4075/LTC4075X
U
OPERATIO
⎯ W
⎯ R
⎯ ) has two states: pullThe power supply status output (P
down and high impedance. The pull-down state indicates
that power is present at either DCIN or USBIN. This output
is strong enough to drive an LED. If no power is applied at
either pin, the ⎯P⎯W⎯R pin is high impedance, indicating that
the LTC4075 lacks sufficient power to charge the battery.
The pull-down state is capable of sinking up to 10mA.
The USB power status output (USBPWR) has two states:
pull-down and high impedance. The high impedance
state indicates that the LTC4075 is being powered from
the USBIN input. The pull-down state indicates that the
charger is either powered from DCIN or is in a UVLO
condition (see Table 1). The pull-down state is capable of
sinking up to 1mA.
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 LTC4075 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.
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*
1/10th 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
ENABLE
DRIVEN LOW
STANDBY
MODE
STANDBY
MODE
NO CHARGE CURRENT
NO CHARGE CURRENT
CHRG STATE: Hi-Z
CHRG STATE: Hi-Z
ENABLE
DRIVEN HIGH
SHUTDOWN
MODE
ENABLE
DRIVEN LOW
IDCIN DROPS TO 20µA
CHRG STATE: Hi-Z
*LTC4075 ONLY
2.9V < BAT
IBAT < ITERMINATE
IN VOLTAGE MODE
IBAT < ITERMINATE
IN VOLTAGE MODE
BAT < 4.1V
BAT < 2.9V
1/10th FULL CURRENT
SHUTDOWN
MODE
BAT < 4.1V
ENABLE
DRIVEN HIGH
IUSBIN DROPS TO 18µA
DCIN POWER
REMOVED
USBIN POWER
REMOVED OR
DCIN POWER
APPLIED
CHRG STATE: Hi-Z
4075 F01
Figure 1. LTC4075 State Diagram of a Charge Cycle
4075Xf
11
LTC4075/LTC4075X
U
U
W
U
APPLICATIO S I FOR ATIO
Using a Single Charge Current Program Resistor
The LTC4075 can program the wall adapter charge current
and USB charge current independently using two program
resistors, RIDC and RIUSB. Figure 2 shows a charger circuit
that sets the wall adapter charge current to 800mA and
the USB charge current to 500mA.
800mA (WALL)
500mA (USB)
LTC4075
WALL
ADAPTER
DCIN
USB
PORT
BAT
USBIN
1µF
1µF
RIUSB
2k
1%
+
IUSB
RIDC
1.24k
1%
IDC
ITERM
GND
RITERM
1k
1%
4075 F02
Figure 2. Full Featured Dual Input Charger Circuit
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 3 shows a charger circuit that uses one
charge current program resistor.
LTC4075
WALL
ADAPTER
USB
PORT
DCIN
500mA
BAT
USBIN
1µF
1µF
+
IUSB
RISET
2k
1%
IDC
ITERM
GND
RITERM
1k
1%
4075 F03
Figure 3. Dual Input Charger Circuit. The Wall
Adapter Charge Current and USB Charge Current
are Both Programmed to be 500mA
In this circuit, the programmed charge current from both the
wall adapter supply is the same value as the programmed
charge current from the USB supply:
ICHRG−DC = ICHRG−USB =
1000V
RISET
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 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.
Power Dissipation
When designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios
because the LTC4075 automatically reduces the charge
current during high power conditions. The conditions
that cause the LTC4075 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 charger MOSFET. Thus, the
power dissipation is calculated to be:
PD = (VIN – VBAT) • IBAT
4075Xf
12
LTC4075/LTC4075X
U
W
U
U
APPLICATIO S I FOR ATIO
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:
It is important to remember that LTC4075 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
Thermal Considerations
TA = 105°C – (VIN – VBAT) • IBAT • θJA
In order to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4075 package is properly soldered
to the PC board ground. When correctly soldered to a
2500mm2 double sided 1oz copper board, the LTC4075
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 LTC4075 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.
Example: An LTC4075 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 LTC4075 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 LTC4075 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
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 pin ratings and damage the
LTC4075. Refer to Linear Technology Application Note 88,
entitled “Ceramic Input Capacitors Can Cause Overvoltage
Transients” for a detailed discussion of this problem. The
long cable lengths of most wall adapters and USB cables
4075Xf
13
LTC4075/LTC4075X
U
W
U
U
APPLICATIO S I FOR ATIO
makes them especially susceptible to this problem. To
bypass the USB pin and the wall adapter input, add a 1Ω
resistor in series with a ceramic capacitor to lower the
effective Q of the network and greatly reduce the ringing.
A tantalum, OS-CON, or electrolytic capacitor can be used
in place of the ceramic and resistor, as their higher ESR
reduces the Q, thus reducing the voltage ringing.
The oscilloscope photograph in Figure 4 shows how
serious the overvoltage transient can be for the USB
and wall adapter inputs. For both traces, a 5V supply is
hot-plugged using a three foot long cable. For the top
trace, only a 4.7µF capacitor (without the recommended
1Ω series resistor) is used to locally bypass the input.
This trace shows excessive ringing when the 5V cable
is inserted, with the overvoltage spike reaching 10V. For
the bottom trace, a 1Ω resistor is added in series with the
4.7µF capacitor to locally bypass the 5V input. This trace
shows the clean response resulting from the addition of
the 1Ω resistor.
Even with the additional 1Ω resistor, bad design techniques
and poor board layout can often make the overvoltage
problem even worse. System designers often add extra
inductance in series with input lines in an attempt to minimize the noise fed back to those inputs by the application.
In reality, adding these extra inductances only makes the
overvoltage transients worse. Since cable inductance is
one of the fundamental causes of the excessive ringing,
adding a series ferrite bead or inductor increases the effective cable inductance, making the problem even worse.
For this reason, do not add additional inductance (ferrite
beads or inductors) in series with the USB or wall adapter
inputs. For the most robust solution, 6V transorbs or zener
diodes may also be added to further protect the USB and
wall adapter inputs. Two possible protection devices are
the SM2T from STMicroelectronics and the EDZ series
devices from ROHM.
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 5).
4.7µF ONLY
2V/DIV
DRAIN-BULK
DIODE OF FET
4.7µF + 1Ω
2V/DIV
WALL
ADAPTER
LTC4075
DCIN
4075 F05
20µs/DIV
3455 F04
Figure 4. Waveforms Resulting from Hot-Plugging a
5V Input Supply
Figure 5. Low Loss Input Reverse Polarity Protection
4075Xf
14
LTC4075/LTC4075X
U
PACKAGE DESCRIPTIO
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115
TYP
0.38 ± 0.10
6
10
5
1
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
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65 ± 0.10
(2 SIDES)
(DD10) DFN 1103
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
4075Xf
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
LTC4075/LTC4075X
U
TYPICAL APPLICATIO
Full Featured Li-Ion Charger
800mA (WALL)
475mA (USB)
LTC4075
WALL
ADAPTER
USB
POWER
DCIN
BAT
USBIN
1µF
1k
PWR
IUSB
IDC
2.1k
1%
1k
1µF
1.24k
1%
+
CHRG
ITERM
GND
1-CELL
Li-Ion
BATTERY
1k
1%
4075 TA03
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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Automatic Switching Between DC Sources, Load Sharing,
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LTC4053
LTC4054/LTC4054X
LTC4055
LTC4058/LTC4058X
LTC4061
LTC4066
LTC4410
Standalone 950mA Lithium-Ion Charger in DFN
Standalone Li-Ion Charger with Thermistor Interface
USB Power Controller and Li-Ion Linear Battery
Charger with Low-Loss Ideal Diode
Standalone Linear Li-Ion Battery Charger with
Programmable Termination
USB Power Manager and Battery Charger
LTC4411/LTC4412
Low Loss PowerPathTM Controller in ThinSOT
LTC4068/LTC4068X
ThinSOT and PowerPath are trademarks of Linear Technology Corporation
4075Xf
16 Linear Technology Corporation
LT/TP 0405 500 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
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