LINER LTC4078 Dual input li-ion battery charger with overvoltage protection Datasheet

LTC4078/LTC4078X
Dual Input Li-Ion Battery
Charger with Overvoltage Protection
FEATURES
DESCRIPTION
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The LTC®4078/LTC4078X are standalone linear chargers
that are capable of charging a single-cell Li-Ion/Polymer
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.
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APPLICATIONS
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No external sense resistor or blocking diode is required
for charging due to the internal MOSFET architecture. The
LTC4078/LTC4078X feature a maximum 22V rating for both
wall adapter and USB inputs, although charging stops if
the selected power source exceeds the overvoltage limit.
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
LTC4078/LTC4078X terminate the charge cycle when the
charge current drops below the programmed termination
threshold after the final float voltage is reached.
Other features include battery present detection, automatic
recharge, undervoltage lockout, charge status outputs, and
“power present” status outputs to indicate the presence of
wall adapter or USB power. The device is offered in a low
profile (0.75mm) 3mm × 3mm 10-lead DFN package.
L, 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, 6700364.
Cellular Telephones
Handheld Computers
Portable MP3 Players
Digital Cameras
TYPICAL APPLICATION
Charger Current vs Supply Voltage
900
High Voltage Dual Input Battery Charger
for Li-Ion Battery Pack
USB
PORT
1μF
800mA (WALL)
500mA (USB)
LTC4078
WALL
ADAPTER
DCIN
BAT
USBIN
1μF
BATDET
3.9k
IUSB
2k
IDC
1% 1.24k
1%
ITERM
GND
+
700
RIDC = 1.24k
RIUSB = 2k
VBAT = 3.5V
VBATDET = 0V
600
CHARGE FROM DCIN
800
4.2V
Li-Ion
BATTERY
PACK
2k
1%
IBAT (mA)
n
22V Maximum Voltage for Wall Adapter and
USB Inputs
Charge 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
Overvoltage Lockout for Wall Adapter and USB Inputs
Battery Detection Input Disables Charger When No
Battery is Present
No External MOSFET, Sense Resistor or Blocking
Diode Needed
Thermal Regulation Maximizes Charge Rate Without
Risk of Overheating*
Preset Charge Voltage with ±0.6% Accuracy
Programmable Charge Current Termination
40μA USB Suspend Current in Shutdown
Charge Status Output
Automatic Recharge
Available Without Trickle Charge (LTC4078X)
Available in a Thermally Enhanced, Low Profile
(0.75mm) 10-Lead (3mm × 3mm) DFN Package
500
400
CHARGE
FROM USBIN
300
200
100
0
4078X TA01
2
3
4
5
6
7
8
SUPPLY VOLTAGE (V)
19
20
4078x TA01b
4078xfb
1
LTC4078/LTC4078X
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
Input Supply Voltage (DCIN, USBIN) ............–0.3 to 22V
ENABLE, CHRG, PWR, BATDET, BAT ...............–0.3 to 6V
IDC, IUSB, ITERM Pin Current .................................1mA
DCIN, USBIN, BAT Pin Current ....................................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 BATDET
CHRG
5
6 ENABLE
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 INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4078XEDD#PBF
LTC4078XEDD#TRPBF
LCYP
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 85°C
LTC4078EDD#PBF
LTC4078EDD#TRPBF
LDJY
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
The l 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
VDCIN
Operating Supply Voltage
l
4.3
5.5
V
VUSBIN
Operating Supply Voltage
l
4.3
5.5
V
IDCIN
DCIN Supply Current
Charge Mode (Note 4), RIDC = 10k
Standby Mode; Charge Terminated
Shutdown Mode (ENABLE = 5V)
Overvoltage Mode (VDCIN = 10V)
l
l
350
70
40
70
800
120
80
140
μA
μA
μA
μA
IUSBIN
USBIN Supply Current
Charge Mode (Note 5), RIUSB = 10k, VDCIN = 2V
Standby Mode; Charge Terminated, VDCIN = 2V
Shutdown (VDCIN = 2V, ENABLE = 0V)
Overvoltage Mode (VUSBIN = 10V)
VDCIN > VUSBIN
l
l
350
70
40
70
23
800
120
80
140
40
μA
μA
μA
μA
μA
VFLOAT
Regulated Output (Float) Voltage
IBAT = 1mA
IBAT = 1mA, 0°C < TA < 85°C
4.185
4.165
4.2
4.2
4.215
4.235
V
V
IBAT
BAT Pin Current
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)
770
455
93
800
476
100
–7.5
–7.5
–7.5
830
495
107
–12
–12
–12
l
l
l
TYP
MAX
UNITS
mA
mA
mA
μA
μA
μA
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LTC4078/LTC4078X
ELECTRICAL CHARACTERISTICS
The l 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
VIDC
IDC Pin Regulated Voltage
Constant-Current Mode
MIN
1
V
VIUSB
IUSB Pin Regulated Voltage
Constant-Current Mode
1
V
ITERMINATE
Charge Current Termination Threshold
RITERM = 1k
RITERM = 2k
RITERM = 10k
RITERM = 20k
ITRIKL
Trickle Charge Current (Note 6)
VTRIKL
l
l
l
l
TYP
MAX
UNITS
90
42
8
3.5
100
50
10
5
110
58
12
6.5
mA
mA
mA
mA
VBAT < VTRIKL; RIDC = 1.25k
VBAT < VTRIKL; RIUSB = 2.1k
60
30
80
47.5
100
65
mA
mA
Trickle Charge Threshold (Note 6)
VBAT Rising
Hysteresis
2.8
2.9
100
3
V
mV
VUVDC
DCIN Undervoltage Lockout Voltage
From Low to High
Hysteresis
4
4.15
190
4.3
V
mV
VUVUSB
USBIN Undervoltage Lockout Voltage
From Low to High
Hysteresis
3.8
3.95
170
4.1
V
mV
VOVDC
DCIN Overvoltage Lockout Voltage
From Low to High
Hysteresis
5.8
6
185
6.2
V
mV
VOVUSB
USBIN Overvoltage Lockout Voltage
From Low to High
Hysteresis
5.8
6
185
6.2
V
mV
VASD-DC
VDCIN – VBAT Lockout Threshold
VDCIN from Low to High, VBAT = 4.2V
VDCIN from High to Low, VBAT = 4.2V
70
10
120
40
170
70
mV
mV
VASD-USB
VUSBIN – VBAT Lockout Threshold
VUSBIN from Low to High
VUSBIN from High to Low
70
10
120
40
170
70
mV
mV
VENABLE
ENABLE Input Threshold Voltage
0.6
0.9
1.2
V
RENABLE
ENABLE Pulldown Resistance
MΩ
VBDET
BATDET Input Threshold Voltage
From Low to High
IBATDET
BATDET Pull-Up Current
VBATDET = 0V
VBOC
BATDET Open Circuit Voltage
VOL
Output Low Voltage
(CHRG, PWR)
ΔVRECHRG
Recharge Battery Threshold Voltage
VFLOAT – VRECHRG, 0°C < TA < 85°C
tRECHRG
Recharge Comparator Filter Time
VBAT from High to Low
tTERMINATE
Termination Comparator Filter Time
IBAT Drops Below Termination Threshold
RON-DC
Power FET “ON” Resistance
(Between DCIN and BAT)
600
mΩ
RON-USB
Power FET “ON” Resistance
(Between USBIN and BAT)
700
mΩ
TLIM
Junction Temperature in ConstantTemperature Mode
120
°C
l
1
2
3.5
1.25
1.75
2
V
2
4
6
μA
4
4.2
4.4
V
0.12
0.35
V
ISINK = 5mA
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 LTC4078/LTC4078X are 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.
90
125
160
mV
2.25
4.1
6.75
ms
1
1.6
2.4
ms
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 LTC4078X.
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3
LTC4078/LTC4078X
TYPICAL PERFORMANCE CHARACTERISTICS
Regulated Output (Float) Voltage
vs Charge Current
Regulated Output (Float) Voltage
vs Temperature
4.220
VDCIN = VUSBIN = 5V
1.008
VDCIN = VUSBIN = 5V
1.006
4.22
4.210
1.004
4.205
1.002
4.20
RIDC = 1.24k
4.18
RIDC = RIUSB = 2k
VIDC (V)
4.215
4.200
0.998
4.14
4.190
0.996
4.12
4.185
0.994
4.10
100 200 300 400 500 600 700 800 900
IBAT (mA)
4.180
–10
10
30
50
TEMPERATURE (°C)
70
IUSB Pin Voltage vs Temperature
(Constant-Current Mode)
900
900
VDCIN = 5V
RIDC = 1.24k
IBAT (mA)
1.000
0.998
500
RIDC = 2k
400
0.2
0.4
0.6
0.8
VIDC (V)
1.0
1.2
0
0.2
0.4
0.6
0.8
VIUSB (V)
4078x G05
PWR Pin I-V Curve
1.0
1.2
4078x G06
CHRG Pin I-V Curve
60
VDCIN = VUSBIN = 5V
50
50
40
40
ICHRG (mA)
IPWR (mA)
RIUSB = 10k
0
0
4078x G04
60
RIUSB = 2k
100
0
90
400
200
RIDC = 10k
100
70
500
300
200
0.994
RIUSB = 1.24k
600
300
0.996
VUSBIN = 5V
700
600
1.002
90
800
700
1.004
30
50
TEMPERATURE (°C)
70
Charge Current
vs IUSB Pin Voltage
800
1.006
10
30
50
TEMPERATURE (°C)
4078x G03
Charge Current
vs IDC Pin Voltage
VUSBIN = 5V
0.992
–10
10
4078x G02
4078x G01
1.008
0.992
–10
90
IBAT (mA)
0
VDCIN = 5V
1.000
4.195
4.16
VIUSB (V)
IDC Pin Voltage vs Temperature
(Constant-Current Mode)
4.24
VFLOAT (V)
VFLOAT (V)
4.26
TA = 25°C, unless otherwise specified.
30
VDCIN = VUSBIN = 5V
30
20
20
10
10
0
0
0
1
2
3
4
5
6
VPWR (V)
4078x G07
0
1
2
3
4
VCHRG (V)
5
6
4078x G08
4078xfb
4
LTC4078/LTC4078X
TYPICAL PERFORMANCE CHARACTERISTICS
Charge Current
vs Ambient Temperature
Charge Current
vs Supply Voltage
1000
Charge Current vs Battery Voltage
1000
900
900
800
RIDC = 1.24k
800
800
700
700
RIDC = RIUSB = 2k
500
400
IBAT (mA)
600
600
IBAT (mA)
IBAT (mA)
TA = 25°C, unless otherwise specified.
500
400
600
400
300
300
200 V
DCIN = VUSBIN = 5V
100 VBAT = 4V
θJA = 30°C/W
0
70
50
–10 10
30
90
TEMPERATURE (°C)
200
0
4.0
130
110
200
RIDC = 1.24k
VBAT = 4V
θJA = 30°C/W
100
4.5
5.0
5.5 6.0 6.5
VDCIN (V)
4078x G10
7.0
7.5
VDCIN = VUSBIN = 5V
RIDC = 1.24k
θJA = 30°C/W
0
2.4
8.0
2.7
3.0
3.3 3.6
VBAT (V)
3.9
4.2
4078x G12
4078x G11
900
VBAT = 4V
IBAT = 200mA
750
850
700
800
RDS(ON) (mΩ)
RDS(ON) (mΩ)
800
USBIN Power FET On-Resistance
vs Temperature
650
700
550
650
10
30
50
TEMPERATURE (°C)
70
880
10
30
50
TEMPERATURE (°C)
70
60
55
35
25
25
0
25
50
TEMPERATURE (°C)
75
2.2
VDCIN = 5V
40
30
100
4078x G16
20
–50
90
2.3
45
30
–25
70
2.4
RENABLE (MΩ)
IDCIN (μA)
IUSBIN (μA)
VUSBIN = 4.3V
30
50
TEMPERATURE (°C)
ENABLE Pin Pulldown Resistance
vs Temperature
VENABLE = 5V
50
40
10
4078x G15
55
VUSBIN = 5V
45
20
–50
860
–10
90
DCIN Shutdown Current
vs Temperature
VENABLE = 0V
35
920
4078x G14
USBIN Shutdown Current
vs Temperature
50
940
900
4078x G13
60
VDCIN = VUSBIN = 5V
980
960
600
–10
90
1000
VBAT = 4V
IBAT = 200mA
750
600
500
–10
ENABLE Pin Threshold Voltage
(On-to-Off) vs Temperature
VENABLE (V)
DCIN Power FET On-Resistance
vs Temperature
4.5
VDCIN = 4.3V
2.1
2.0
1.9
1.8
1.7
–25
0
25
50
TEMPERATURE (°C)
75
100
4078x G17
1.6
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4078x G18
4078xfb
5
LTC4078/LTC4078X
TYPICAL PERFORMANCE CHARACTERISTICS
Undervoltage Lockout Threshold
vs Temperature
Overvoltage Lockout Threshold
vs Temperature
6.10
4.25
4.20
6.05
DCIN UVLO
4.15
6.00
VOV (V)
4.10
VUV (V)
TA = 25°C, unless otherwise specified.
4.05
4.00
DCIN OVLO
5.90
USBIN UVLO
3.95
USBIN OVLO
5.95
5.85
3.90
3.85
–10
10
30
50
TEMPERATURE (°C)
70
5.80
–10
90
10
30
50
TEMPERATURE (°C)
70
4078x G20
4078x G19
Recharge Threshold Voltage
vs Temperature
4.11
90
Battery Drain Current
vs Temperature
9.0
VDCIN = VUSBIN = 5V
VDCIN = VUSBIN = NOT CONNECTED
VBAT = 4.2V
8.5
8.0
IBAT (μA)
VRECHRG (V)
4.09
4.07
7.5
7.0
4.05
6.5
4.03
–10
10
30
50
TEMPERATURE (°C)
70
6.0
–50
90
–25
0
25
50
TEMPERATURE (°C)
75
4078x G21
4078x G22
BATDET Pin Threshold Voltage
(On-to-Off) vs Temperature
2.0
100
BATDET Voltage/Current
vs Temperature
4.4
VDCIN = VUSBIN = 5V
6.00
VDCIN = VUSBIN = 5V
1.9
VBOC
4.3
5.25
VBOC (V)
VBDET (V)
1.7
4.2
4.50
IBATDET
IBATDET (μA)
1.8
1.6
4.1
3.75
1.5
1.4
–10
10
30
50
TEMPERATURE (°C)
70
90
4078x G23
4.0
–10
3.00
10
30
50
TEMPERATURE (°C)
70
90
4078x G24
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LTC4078/LTC4078X
PIN FUNCTIONS
USBIN (Pin 1): USB Input Supply Pin. This input provides
power to the battery charger assuming a voltage greater
than VUVUSB and less than VOVUSB is present (typically
3.95V to 6V respectively). However, the DCIN input will
take priority if a voltage greater than VUVDC is present at
DCIN (typically 4.15V). The USBIN input allows charge
currents up to 850mA. 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 CHRG 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.
PWR (Pin 4): Open-Drain Power Supply Status Output.
When the DCIN or USBIN pin voltage is valid to begin charging (i.e. when the supply is greater than the undervoltage
lockout threshold, less than the overvoltage lockout threshold and at least 120mV above the battery terminal), the
PWR pin is pulled low by an internal N-channel MOSFET.
Otherwise PWR is high impedance. This output is capable
of driving an LED.
CHRG (Pin 5): Open-Drain Charge Status Output. When the
LTC4078/LTC4078X are charging, the CHRG pin is pulled
low by an internal N-channel MOSFET. When the charge
cycle is completed, CHRG becomes high impedance. This
output is capable of driving an LED.
ENABLE (Pin 6): Enable Input. When the LTC4078/LTC4078X
are charging from the DCIN source, a logic low on this
pin enables the charger. When the LTC4078/LTC4078X are
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 LTC4078/LTC4078X
to charge when a wall adapter is applied and to shut down
if only the USB source is applied.
BATDET (Pin 7): Battery Detection Input. When the voltage on this pin falls below VBDET (typically 1.75V), the
charger is on and ready for charging a battery. If this
input is left floating, an internal pull-up resistor will disable charging.
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): Battery 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. This input
provides power to the battery charger assuming a voltage
greater than VUVDC and less than VOVDC is present (typically 4.15V to 6V respectively). A valid voltage on the DCIN
input will always take priority over the USBIN input. The
DCIN input allows charge currents up to 950mA. This pin
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.
4078xfb
7
LTC4078/LTC4078X
BLOCK DIAGRAM
DCIN
BAT
USBIN
10
9
1
CC/CV
REGULATOR
CC/CV
REGULATOR
VBOC
TRICKLE
CHARGE*
2.9V
DC_ENABLE
CHARGER CONTROL
+
TRICKLE
PWR
BAT
4
4.15V
BAT
6V
ENABLE
USB_ENABLE
+
–
–
+
+
–
DCIN UVLO
USBIN UVLO
+
–
–
+
+
DCIN OVLO
USBIN OVLO
+
6
–
+
–
7 BATDET
DISABLE
–
1.75V
3.95V
BAT
6V
+
TDIE
–
120°C
2M
0.9V
CHRG
–
4.075V
+
BAT
–
THERMAL
REGULATION
RECHARGE
–
5
0.1V
IBAT/1000
TERMINATION
IBAT/1000
IBAT/1000
+
GND
11
ITERM
3
IDC
RITERM
IUSB
2
8
RIDC
4078X BD
RIUSB
*TRICKLE CHARGE DISABLED ON THE LTC4078X
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LTC4078/LTC4078X
OPERATION
The LTC4078/LTC4078X are 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 850mA of charge current
from the USB supply with a final float voltage accuracy of
±0.6%. The LTC4078/LTC4078X have two internal P-channel power MOSFETs and thermal regulation circuitry. No
blocking diodes or external sense resistors are required.
Charge current out of the BAT pin can be determined at
any time by monitoring the IDC or IUSB pin voltage and
applying the following equations:
Power Source Selection
By default, the BATDET pin is pulled high with an internal
resistor, disabling the charger. To enable the charger, the
BATDET pin must be pulled below the VBDET threshold
(typically 1.75V). An external resistor to ground less than
100k (typically 3.9k) located in the battery pack is used to
detect battery presence.
The LTC4078/LTC4078X can charge a battery from either the wall adapter input or the USB port input. The
LTC4078/LTC4078X automatically sense the presence of
voltage at each input. If both power sources are present,
the LTC4078/LTC4078X default to the wall adapter source
provided a valid voltage is present at the DCIN input. “Valid
voltage” is defined as:
• Supply voltage is greater than the UVLO threshold
and less than the OVLO threshold.
• Supply voltage is greater than the battery voltage by
40mV.
The open-drain power status output (PWR) indicates which
power source has been selected. Table 1 describes the
behavior of this status output.
Programming and Monitoring Charge Current
The charge current delivered to the battery from the wall
adapter or USB supply is programmed using a single resistor from the IDC or IUSB pin to ground. Both program
resistors and charge currents (ICHRG) are calculated using
the following equations:
RIDC =
1000V
ICHRGDC
RIUSB =
, ICHRGDC =
1000V
ICHRGUSB
1000V
RIDC
, ICHRGUSB =
1000V
RIUSB
IBAT =
VIDC
• 1000, (charging from wall adapter)
RIDC
IBAT =
VIUSB
• 1000, (charging from USBsupply)
RIUSB
Battery Detection
Programming Charge Termination
The charge cycle terminates when the charge current
falls below the programmed termination threshold level
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
The termination condition is detected using an internal
filtered comparator to monitor the ITERM pin. When the
ITERM pin voltage drops below 100mV* for longer than
tTERMINATE (typically 1.6ms), charging is terminated. The
charge current is latched off and the LTC4078/LTC4078X
enter 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
*Any external sources that hold the ITERM pin above 100mV will prevent the LTC4078X from
terminating a charge cycle.
4078xfb
9
LTC4078/LTC4078X
OPERATION
programmed termination current. The 1.6ms 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
LTC4078/LTC4078X terminate the charge cycle and stops
providing current out of the BAT pin. In this state, any load
on the BAT pin must be supplied by the battery.
battery voltage falls below 4.075V (which corresponds to
approximately 80% to 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.
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 low disables the charger and logic high enables it
(the default is the shutdown state).
Low-Battery Charge Conditioning (Trickle Charge)
This feature ensures that near-dead batteries are gradually
charged before applying full charge current. If the BAT pin
voltage is below 2.9V, the LTC4078 supply 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 DCIN input draws 40μA when the charger is in shutdown
mode. The USBIN input draws 40μA during shutdown if
no voltage is applied to DCIN, but draws only 23μA when
VDCIN provides valid voltage (see Table 1).
The LTC4078X 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 LTC4078X are useful
in applications where the trickle charge current may be
insufficient to supply a load during low-battery voltage
conditions.
Status Indicators
Automatic Recharge
The charge status open-drain output (CHRG) has two states:
pulldown and high impedance. The pulldown state indicates
that the LTC4078/LTC4078X are in a charge cycle. Once the
charge cycle has terminated or the LTC4078/LTC4078X are
disabled, the pin state becomes high impedance.
In standby mode, the charger sits idle and monitors the
battery voltage using a comparator with a 4.1ms filter time
(tRECHRG). A charge cycle automatically restarts when the
The power supply status open-drain output (PWR) has two
states: pulldown and high impedance. The pulldown state
indicates that power is present at either DCIN or USBIN.
Table 1. Power Source Selection (VBATDET < 1.75V)
VUSBIN < 3.95V or
VUSBIN < BAT + 50mV
ENABLE
HIGH
LOW or No Connect
6V > VUSBIN > 3.95V and
VUSBIN > BAT + 50mV
HIGH
LOW or No Connect
22V > VUSBIN > 6V
HIGH
LOW or No Connect
No Charging.
VDCIN < 4.15V or
VDCIN < BAT + 50mV PWR: Hi-Z
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
6V > VDCIN > 4.15V
and VDCIN > BAT +
50mV
No Charging.
PWR: LOW
CHRG: Hi-Z
Charging from DCIN No Charging.
source.
PWR: LOW
PWR: LOW
CHRG: Hi-Z
CHRG: LOW
Charging from DCIN No Charging.
source.
PWR: LOW
PWR: LOW
CHRG: Hi-Z
CHRG: LOW
Charging from DCIN
source.
PWR: LOW
CHRG: LOW
22V > VDCIN > 6V
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
No Charging.
PWR: LOW
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
Charging from
USBIN source.
PWR: LOW
CHRG: LOW
No Charging.
PWR: LOW
CHRG: Hi-Z
No Charging.
PWR: LOW
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
4078xfb
10
LTC4078/LTC4078X
OPERATION
This output is strong enough to drive an LED. If no valid
voltage is applied at either pin, the PWR pin is high impedance, indicating that the LTC4078/LTC4078X lack valid
input voltage (see Table 1) to charge the battery.
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 120°C. This feature protects
DCIN POWER REMOVED
the LTC4078/LTC4078X 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 worst case conditions. DFN package power
considerations are discussed further in the Applications
Information section.
NO POWER
USB POWER REMOVED
POWER APPLIED
ENABLE = LOW
ENABLE = HIGH
YES
DCIN > 4.15V
AND DCIN > BAT
NO
6V > DCIN > 4.15V
AND DCIN > BAT
NO
NO
YES
YES
NO
BATDET < 1.75V
YES
6V > USBIN > 3.95V
AND USBIN > BAT
NO
BATDET < 1.75V
YES
FULL CURRENT (BAT > 2.9V)
FULL CURRENT (BAT > 2.9V)
1/10TH FULL CURRENT
(BAT < 2.9V)*
1/10TH FULL CURRENT
(BAT < 2.9V)*
CHRG STATE: PULLDOWN
CHRG STATE: PULLDOWN
IBAT < ITERMINATE
IN VOLTAGE MODE
IBAT < ITERMINATE
IN VOLTAGE MODE
STANDBY MODE
(DCIN)
STANDBY MODE
(USBIN)
NO CHARGE CURRENT
NO CHARGE CURRENT
CHRG STATE: Hi-Z
CHRG STATE: Hi-Z
SHUTDOWN MODE
(DCIN)
SHUTDOWN MODE
(USBIN)
CHRG STATE: Hi-Z
CHRG STATE: Hi-Z
BAT < 4.075V
BAT < 4.075V
4078X F01
*LTC4078 ONLY
Figure 1. LTC4078 State Diagram of a Charge Cycle
4078xfb
11
LTC4078/LTC4078X
APPLICATIONS INFORMATION
Using a Single Charge Current Program Resistor
Stability Considerations
The LTC4078/LTC4078X 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.
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.
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.
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.
USB
PORT
C1
1μF
800mA (WALL)
500mA (USB)
LTC4078
WALL
ADAPTER
DCIN
BAT
USBIN BATDET
C2, 1μF
R1
2k
1%
+
R4
3.9k
IUSB
IDC
ITERM
GND
R2
1.24k
1%
R3
2k
1%
4.2V
Li-Ion
BATTERY
PACK
4078X F02
Figure 2. Dual Input Charger with Independent Charge Currents
LTC4078
WALL
ADAPTER
USB
PORT
C1
1μF
DCIN
500mA
BAT
USBIN BATDET
C2, 1μF
+
R4
3.9k
IUSB
IDC
R1
2k
1%
ITERM
GND
R3
2k
1%
4.2V
Li-Ion
BATTERY
PACK
4078X 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:
ICHRGDC = ICHRGUSB =
1000V
RISET
Power Dissipation
When designing the battery charger circuit, it is not
necessary to design for worst-case power dissipation
scenarios because the LTC4078/LTC4078X automatically
reduce the charge current during high power conditions.
The conditions that cause the LTC4078/LTC4078X 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
PD is the dissipated power, 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 = 120°C – PD • θJA
TA = 120°C – (VIN – VBAT) • IBAT • θJA
Example: An LTC4078/LTC4078X 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.
4078xfb
12
LTC4078/LTC4078X
APPLICATIONS INFORMATION
Assuming θJA is 40°C/W (see Thermal Considerations), the
ambient temperature at which the LTC4078/LTC4078X will
begin to reduce the charge current is approximately:
TA = 120°C – (5V – 3.3V) • (800mA) • 40°C/W
LTC4078/LTC4078X 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.
TA = 120°C – 1.36W • 40°C/W = 120°C – 54.4°C
Input Capacitor Selection
TA = 65.6°C
When an input supply is connected to a portable product,
the inductance of the cable and the high-Q ceramic input
capacitor form an L-C resonant circuit. While the LTC4078/
LTC4078X are capable of withstanding input voltages as
high as 22V, if the input cable does not have adequate
mutual coupling or if there is not much impedance in
the cable, it is possible for the voltage at the input of the
product to reach as high as 2x the input voltage before it
settles out. To prevent excessive voltage from damaging
the LTC4078/LTC4078X during a hot insertion, it is best to
have a low voltage coefficient capacitor at the input pins
to the LTC4078/LTC4078X. This is achievable by selecting an X5R or X7R ceramic capacitor that has a higher
voltage rating than that required for the application. For
example, if the maximum expected input voltage is 15V,
a 25V X5R 1μF capacitor would be a better choice than
the smaller 16V X5R capacitor. Note that no charging will
occur with 15V in.
The LTC4078/LTC4078X can be used above 70.6°C ambient, but the charge current will be reduced from 800mA.
The approximate current at a given ambient temperature
can be approximated by:
IBAT =
120°C – TA
(VIN – VBAT) • JA
Using the previous example with an ambient temperature
of 75°C, the charge current will be reduced to approximately:
120°C – 75°C
45°C
=
(5V – 3.3V) • 40°C / W 68°C / A
IBAT = 662mA
IBAT =
It is important to remember that LTC4078/LTC4078X
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 120°C.
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 LTC4078/LTC4078X DFN package is
properly soldered to the PC board ground. When correctly soldered to a 2500mm2 double sided 1oz copper
board, the LTC4078/LTC4078X 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
Using a tantalum capacitor or an aluminum electrolytic
capacitor for input bypassing, or paralleling with a ceramic
capacitor will also reduce voltage overshoot during a hot
insertion. Ceramic capacitors with Y5V or Z5U dielectrics
are not recommeded.
Alternatively, the following soft connect circuit can be
employed (as shown in Figure 4).
DCIN/USBIN
R1
40k
+15V
INPUT INPUT CABLE
C2
100nF
C1
1μF
LTC4078
MN1
GND
4078X F04
Figure 4. Input Soft Connect Circuit
4078xfb
13
LTC4078/LTC4078X
APPLICATIONS INFORMATION
In this circuit, capacitor C2 holds MN1 off when the cable
is first connected. Eventually C2 begins to charge up to the
USB input voltage applying increasing gate drive to MN1.
The long time constant of R1 and C1 prevent the current
from rapidly building up in the cable, thus dampening out
any resonant overshoot.
Reverse Polarity Input Voltage Protection
In some applications, protection from reverse polarity
voltage on the input supply pins is desired. With sufficient
supply voltage, 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).
DRAIN-BULK
DIODE OF FET
LTC4078
WALL
ADAPTER
DCIN
4078X F05
Figure 5. Low Loss Reverse Polarity Protection
4078xfb
14
LTC4078/LTC4078X
PACKAGE DESCRIPTION
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
3.00 ±0.10
(4 SIDES)
0.38 ± 0.10
6
10
5
1
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
(DD) DFN 1103
0.200 REF
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
4078xfb
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
LTC4078/LTC4078X
TYPICAL APPLICATION
Full Featured Li-Ion Charger
800mA (WALL)
475mA (USB)
LTC4078
WALL
ADAPTER
USB
POWER
DCIN
BAT
1k
USBIN
IUSB
IDC
2.1k
1%
1k
1μF
1μF
1.24k
1%
PWR
CHRG
BATDET
ITERM
GND
3.9k
1k
1%
+
4.2V Li-Ion
BATTERY
PACK
4078X TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC3455
Dual DC/DC Converter with USB Power
Management and Li-Ion Battery Charger
Efficiency >96%, Accurate USB Current Limiting (500mA/100mA), 4mm × 4mm
QFN-24 Package
LTC4053
USB Compatible Monolithic Li-Ion Battery
Charger
Standalone Charger with Programmable Timer, Up to 1.25A Charge Current
LTC4054/LTC4054X Standalone Linear Li-Ion Battery Charger with
Integrated Pass Transistor in ThinSOT™
Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator,
Up to 800mA Charge Current
LTC4055
Charges Single-Cell Li-Ion Batteries Directly from USB Port, Thermal Regulation,
4mm × 4mm QFN-16 Package
USB Power Controller and Battery Charger
LTC4058/LTC4058X Standalone 950mA Lithium-Ion Charger in DFN
C/10 Charge Termination, Battery Kelvin Sensing, ±7% Charge Accuracy
LTC4061
Standalone Li-Ion Charger with Thermistor
Interface
4.2V, ±0.35% Float Voltage, Up to 1A Charge Current
LTC4066
USB Power Controller and Li-Ion Linear Battery
Charger with Low-Loss Ideal Diode
Seamless Transition Between Input Power Sources: Li-Ion Battery, USB and Wall
Adapter, Low Loss (50mΩ) Ideal Diode, 4mm × 4mm QFN-24 Package
LTC4068/LTC4068X Standalone Linear Li-Ion Battery Charger with
Programmable Termination
Charge Current Up to 950mA, Thermal Regulation, 3mm × 3mm DFN-8 Package
LTC4075/
LTC4075HVX
Dual Input Standalone Li-Ion Battery Charger
950mA Charger Current, Thermal Regulation, C/X Charge Termination, USB
Charge Current Set Via Resistor, 3mm × 3mm DFN Package; LTC4075HVX Has
22V Input Protection.
LTC4076
Dual Input Standalone Li-Ion Battery Charger
950mA Charger Current, Thermal Regulation, C/X Charge Termination,
Fixed C or C/5 USB Charge Current for Low Power USB Operation, 3mm × 3mm
DFN Package
LTC4077
Dual Input Standalone Li-Ion Battery Charger
950mA Charger Current, Thermal Regulation, C/X Charge Termination,
Programmable C or C/x USB Charge Current for Low Power USB Operation,
Fixed C/10 Wall Adapter and C/10 or C/2 Charge Current Termination,
3mm × 3mm DFN Package
LTC4085
USB Power Manager with Ideal Diode Controller
and Li-Ion Charger
Charges Single-Cell Li-Ion Batteries Directly from USB Port, Thermal Regulation,
200mΩ Ideal Diode with <50mΩ Option, 4mm × 3mm DFN-14 Package
LTC4089/
LTC4089-5
USB Power Manager with Ideal Diode Controller
and High Efficiency Li-Ion Battery Charger
High Efficiency 1.2A Charger from 6V to 36V (40V Max) Input Charges Single-Cell
Li-Ion Batteries Directly from USB Port, Thermal Regulation, 200mΩ Ideal Diode
with <50mΩ Option, Bat-Track Adaptive Output Control (LTC4089), Fixed 5V
Output (LTC4089-5), 4mm × 3mm DFN-14 Package
LTC4411/LTC4412
Low Loss PowerPath™ Controller in ThinSOT
Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
4078xfb
16 Linear Technology Corporation
LT 0308 REV B • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2007