LTC4078X [Linear]
Dual Input Li-Ion Battery Charger with Overvoltage Protection; 双输入锂离子电池充电器,具有过压保护![LTC4078X](http://pdffile.icpdf.com/pdf1/p00136/img/icpdf/LTC40_753452_icpdf.jpg)
型号: | LTC4078X |
厂家: | ![]() |
描述: | Dual Input Li-Ion Battery Charger with Overvoltage Protection |
文件: | 总16页 (文件大小:182K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
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LTC4078X
Dual Input Li-Ion Battery
Charger with Overvoltage Protection
FEATURES
DESCRIPTION
The LTC®4078X is a standalone linear charger that is
capable of charging a single-cell Li-Ion/Polymer 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.
■
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
■
■
No external sense resistor or blocking diode is required
for charging due to the internal MOSFET architecture.
The LTC4078X features 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
currenttomaintainaconstantdietemperatureduringhigh
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 LTC4078X
terminatesthechargecyclewhenthechargecurrentdrops
below the programmed termination threshold after the
final float voltage is reached.
■
■
■
■
Thermal Regulation Maximizes Charge Rate Without
Risk of Overheating*
■
■
■
■
■
■
■
Preset Charge Voltage with 0.ꢀ6 ꢁccuracy
Programmable Charge Current Termination
40µꢁ USB Suspend Current in Shutdown
Charge Status Output
ꢁutomatic Recharge
Otherfeaturesincludebatterypresentdetection,automatic
recharge,undervoltagelockout,chargestatusoutputs,and
“powerpresent”statusoutputstoindicatethepresenceof
wall adapter or USB power. The device is offered in a low
profile (0.75mm) 3mm × 3mm 10-lead DFN package.
No Trickle Charge
ꢁvailable in a Thermally Enhanced, Low Profile
(0.75mm) 10-Lead (3mm × 3mm) DFN Package
APPLICATIONS
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All
other trademarks are the property of their respective owners.
*Protected by U.S. Patents including 6522118, 6700364.
■
Cellular Telephones
■
Handheld Computers
■
Portable MP3 Players
Digital Cameras
■
Charger Current vs Supply Voltage
TYPICAL APPLICATION
900
R
R
= 1.24k
= 2k
IDC
IUSB
High Voltage Dual Input Battery Charger
800
700
600
500
400
300
200
100
0
V
V
= 3.5V
BAT
BATDET
for Li-Ion Battery Pack
= 0V
CHARGE FROM DCIN
800mA (WALL)
500mA (USB)
LTC4078X
WALL
ADAPTER
DCIN
BAT
USB
USBIN BATDET
IUSB
4.2V
+
CHARGE
FROM USBIN
PORT
1µF
2k
3.9k
Li-Ion
BATTERY
PACK
IDC
ITERM
GND
1µF
1%
1.24k
1%
2k
1%
2
3
4
5
6
7
8
19 20
4078X TA01
SUPPLY VOLTAGE (V)
4078x TA01b
4078xf
1
LTC4078X
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
Input Supply Voltage (DCIN, USBIN) ............–0.3 to 22V
ENꢁBLE, CHRG, PWR, BꢁTDET, BꢁT...............–0.3 to ꢀV
IDC, IUSB, ITERM Pin Current .................................1mꢁ
DCIN, USBIN, BꢁT Pin Current....................................1ꢁ
BꢁT Short-Circuit Duration............................Continuous
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range (Note 2) ... –40°C to 85°C
Storage Temperature Range................... –ꢀ5°C to 125°C
TOP VIEW
USBIN
IUSB
1
2
3
4
5
10 DCIN
9
8
7
6
BAT
ITERM
PWR
11
IDC
BATDET
ENABLE
CHRG
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
T
JMꢁX
= 125°C, θ = 40°C/W (Note 3)
Jꢁ
EXPOSED PꢁD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
10-Lead (3mm × 3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
LTC4078XEDD#PBF
LTC4078XEDD#TRPBF
LCYP
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
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. V
= 5V, V
USBIN
= 5V unless otherwise noted.
A
DCIN
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
5.5
UNITS
●
V
V
Operating Supply Voltage
Operating Supply Voltage
DCIN Supply Current
4.3
V
V
DCIN
USBIN
DCIN
●
4.3
5.5
●
●
I
Charge Mode (Note 4), R = 10k
350
70
40
70
800
120
80
µꢁ
µꢁ
µꢁ
µꢁ
IDC
Standby Mode; Charge Terminated
Shutdown Mode (ENꢁBLE = 5V)
Overvoltage Mode (V
= 10V)
140
DCIN
●
I
USBIN Supply Current
Charge Mode (Note 5), R
= 10k, V
= 0V
DCIN
= 0V
DCIN
350
70
40
70
23
800
120
80
140
40
µꢁ
µꢁ
µꢁ
µꢁ
µꢁ
USBIN
IUSB
●
Standby Mode; Charge Terminated, V
Shutdown (V
= 0V, ENꢁBLE = 0V)
DCIN
Overvoltage Mode (V
DCIN
= 10V)
USBIN
V
> V
USBIN
V
Regulated Output (Float) Voltage
BꢁT Pin Current
I
I
= 1mꢁ
4.185
4.1ꢀ5
4.2
4.2
4.215
4.235
V
V
FLOꢁT
BꢁT
BꢁT
= 1mꢁ, 0°C < T < 85°C
ꢁ
●
●
●
I
R
R
R
= 1.25k, Constant-Current Mode
770
455
93
800
47ꢀ
100
–7.5
–7.5
–7.5
830
495
107
–12
–12
–12
mꢁ
mꢁ
mꢁ
µꢁ
µꢁ
µꢁ
BꢁT
IDC
= 2.1k, Constant-Current Mode
IUSB
= 10k or R
= 10k
IDC
IUSB
Standby Mode, Charge Terminated
Shutdown Mode (Charger Disabled)
Sleep Mode (V
= 0V, V
= 0V)
DCIN
USBIN
4078xf
2
LTC4078X
ELECTRICAL CHARACTERISTICS The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. V
= 5V, V
USBIN
= 5V unless otherwise noted.
A
DCIN
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
1
MAX
UNITS
V
V
IDC Pin Regulated Voltage
IUSB Pin Regulated Voltage
Charge Current Termination Threshold
Constant-Current Mode
Constant-Current Mode
V
V
IDC
1
IUSB
●
I
R
ITERM
R
ITERM
R
ITERM
R
ITERM
= 1k
90
100
50
10
5
110
58
12
ꢀ.5
mꢁ
mꢁ
mꢁ
mꢁ
TERMINꢁTE
●
= 2k
42
●
= 10k
= 20k
8
●
3.5
V
V
V
V
DCIN Undervoltage Lockout Voltage
USBIN Undervoltage Lockout Voltage
DCIN Overvoltage Lockout Voltage
USBIN Overvoltage Lockout Voltage
From Low to High
Hysteresis
4
4.15
190
4.3
4.1
ꢀ.2
ꢀ.2
V
UVDC
mV
From Low to High
Hysteresis
3.8
5.8
5.8
3.95
170
V
mV
UVUSB
OVDC
From Low to High
Hysteresis
ꢀ
185
V
mV
From Low to High
Hysteresis
ꢀ
185
V
mV
OVUSB
V
V
V
– V Lockout Threshold
V
V
from Low to High, V = 4.2V
70
10
120
40
170
70
mV
mV
ꢁSD-DC
DCIN
BꢁT
DCIN
DCIN
BꢁT
from High to Low, V = 4.2V
BꢁT
V
– V Lockout Threshold
V
USBIN
V
USBIN
from Low to High
from High to Low
70
10
120
40
170
70
mV
mV
ꢁSD-USB
USBIN
BꢁT
V
ENꢁBLE Input Threshold Voltage
ENꢁBLE Pulldown Resistance
BꢁTDET Input Threshold Voltage
BꢁTDET Pull-Up Current
0.ꢀ
1
0.9
2
1.2
3.5
1.85
ꢀ
V
MΩ
V
ENꢁBLE
●
R
ENꢁBLE
BDET
V
From Low to High
1.ꢀ5
2
1.75
4
I
V = 0V
BꢁTDET
µꢁ
V
BꢁTDET
V
V
BꢁTDET Open Circuit Voltage
V
= 5V, V
= 5V
USBIN
4
4.2
0.12
4.4
0.35
BOC
OL
DCIN
SINK
Output Low Voltage
(CHRG, PWR)
I
= 5mꢁ
V
ΔV
Recharge Battery Threshold Voltage
Recharge Comparator Filter Time
Termination Comparator Filter Time
V
V
– V
, 0°C < T < 85°C
90
2.25
1
125
4.1
1.ꢀ
ꢀ00
1ꢀ0
ꢀ.75
2.4
mV
ms
RECHRG
FLOꢁT
RECHRG
ꢁ
t
t
from High to Low
RECHRG
TERMINꢁTE
BꢁT
BꢁT
I
Drops Below Termination Threshold
ms
R
Power FET “ON” Resistance
(Between DCIN and BꢁT)
mΩ
ON-DC
ON-USB
LIM
R
Power FET “ON” Resistance
(Between USBIN and BꢁT)
700
120
mΩ
T
Junction Temperature in Constant-
Temperature Mode
°C
Note 1: Stresses beyond those listed under ꢁbsolute Maximum Ratings
may cause permanent damage to the device. Exposure to any ꢁbsolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC4078X is guaranteed to meet the performance
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3: Failure to correctly solder the exposed backside of the package to
the PC board will result in a thermal resistance much higher than 40°C/W.
See Thermal Considerations.
Note 4: Supply current includes IDC and ITERM pin current (approximately
100µꢁ each) but does not include any current delivered to the battery
through the BꢁT pin.
Note 5: Supply current includes IUSB and ITERM pin current
(approximately 100µꢁ each) but does not include any current delivered to
the battery through the BꢁT pin.
4078xf
3
LTC4078X
TYPICAL PERFORMANCE CHARACTERISTICS T = 25°C, unless otherwise specified.
A
Regulated Output (Float) Voltage
vs Charge Current
Regulated Output (Float) Voltage
vs Temperature
IDC Pin Voltage vs Temperature
(Constant-Current Mode)
4.220
4.215
4.210
4.205
4.200
4.195
4.190
4.185
4.180
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992
4.26
4.24
4.22
4.20
4.18
4.16
4.14
4.12
4.10
V
= V
= 5V
USBIN
V
= V
= 5V
USBIN
V
= 5V
DCIN
DCIN
DCIN
R
= 1.24k
IDC
R
= R
= 2k
IUSB
IDC
–10
10
30
50
70
90
0
100 200 300 400 500 600 700 800 900
(mA)
–10
10
30
50
70
90
TEMPERATURE (°C)
I
TEMPERATURE (°C)
BAT
4078x G02
4078x G01
4078x G03
IUSB Pin Voltage vs Temperature
(Constant-Current Mode)
Charge Current
Charge Current
vs IDC Pin Voltage
vs IUSB Pin Voltage
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992
900
800
700
600
500
400
300
200
100
0
900
800
700
600
500
400
300
200
100
0
V
= 5V
V
= 5V
V
= 5V
USBIN
USBIN
DCIN
R
= 1.24k
R
= 1.24k
IUSB
IDC
R
= 2k
IDC
R
= 2k
IUSB
R
= 10k
R
= 10k
IUSB
IDC
–10
10
30
50
70
90
0
0.2
0.4
0.6
(V)
0.8
1.0
1.2
0
0.2
0.4
0.6
0.8
1.0
1.2
TEMPERATURE (°C)
V
V
(V)
IUSB
IDC
4078x G04
4078x G05
4078x G06
PWR Pin I-V Curve
CHRG Pin I-V Curve
60
50
40
30
20
10
0
60
50
40
30
20
10
0
V
= V
= 5V
V
= V
= 5V
USBIN
DCIN
USBIN
DCIN
0
1
2
3
4
5
6
0
1
2
3
4
5
6
V
(V)
V
(V)
PWR
CHRG
4078x G07
4078x G08
4078xf
4
LTC4078X
TYPICAL PERFORMANCE CHARACTERISTICS T = 25°C, unless otherwise specified.
A
Charge Current
vs Ambient Temperature
Charge Current
vs Supply Voltage
Charge Current vs Battery Voltage
1000
900
800
700
600
500
400
300
200
100
0
900
800
700
600
500
400
300
200
100
0
1000
800
600
400
200
0
R
R
= 1.24k
IDC
IDC
= R
= 2k
IUSB
V
V
θ
= V
= 4V
= 30°C/W
= 5V
USBIN
R
V
JA
= 1.24k
= 4V
DCIN
BAT
JA
V
= V
= 5V
USBIN
IDC
BAT
= 30°C/W
DCIN
IDC
R
= 1.24k
θ
θ
= 30°C/W
JA
–10
30
50
70
90 110 130
10
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0
(V)
2.4 2.7 3.0 3.3 3.6 3.9 4.2 4.5
(V)
TEMPERATURE (°C)
V
4078x G10
V
BAT
DCIN
4078x G11
4078x G12
DCIN Power FET On-Resistance
vs Temperature
USBIN Power FET On-Resistance
vs Temperature
ENABLE Pin Threshold Voltage
(On-to-Off) vs Temperature
800
750
700
650
600
550
500
1000
980
960
940
920
900
880
860
900
850
800
750
700
650
600
V
I
= 4V
= 200mA
V
= V
= 5V
USBIN
V
I
= 4V
= 200mA
BAT
BAT
DCIN
BAT
BAT
–10
10
30
50
70
90
–10
10
30
50
70
90
–10
10
30
50
70
90
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4078x G13
4078x G15
4078x G14
USBIN Shutdown Current
vs Temperature
DCIN Shutdown Current
vs Temperature
ENABLE Pin Pulldown Resistance
vs Temperature
60
55
50
45
40
35
30
25
20
60
55
50
45
40
35
30
25
20
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
V
= 0V
V
= 5V
ENABLE
ENABLE
V
= 5V
USBIN
V
= 5V
DCIN
V
= 4.3V
USBIN
V
= 4.3V
DCIN
–50
–25
0
25
50
75
100
–50
–25
0
25
50
75
100
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4078x G16
4078x G17
4078x G18
4078xf
5
LTC4078X
TYPICAL PERFORMANCE CHARACTERISTICS
T = 25°C, unless otherwise specified.
A
Undervoltage Lockout Threshold
vs Temperature
Overvoltage Lockout Threshold
vs Temperature
4.25
4.20
4.15
4.10
4.05
4.00
3.95
3.90
3.85
6.10
6.05
6.00
5.95
5.90
5.85
5.80
DCIN UVLO
USBIN OVLO
DCIN OVLO
USBIN UVLO
–10
10
30
50
70
90
–10
10
30
50
70
90
TEMPERATURE (°C)
TEMPERATURE (°C)
4078x G19
4078x G20
Recharge Threshold Voltage
vs Temperature
Battery Drain Current
vs Temperature
4.11
4.09
4.07
4.05
4.03
9.0
8.5
8.0
7.5
7.0
6.5
6.0
V
= V
= 5V
USBIN
V
V
= V
= NOT CONNECTED
USBIN
DCIN
DCIN
BAT
= 4.2V
–10
10
30
50
70
90
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
4078x G21
4078x G22
BATDET Pin Threshold Voltage
(On-to-Off) vs Temperature
BATDET Voltage/Current
vs Temperature
2.0
1.9
1.8
1.7
1.6
1.5
1.4
4.4
4.3
4.2
4.1
4.0
6.00
V
= V
= 5V
USBIN
V
= V
= 5V
USBIN
DCIN
DCIN
V
BOC
5.25
4.50
3.75
3.00
I
BATDET
–10
10
30
50
70
90
–10
10
30
50
70
90
TEMPERATURE (°C)
TEMPERATURE (°C)
4078x G23
4078x G24
4078xf
6
LTC4078X
PIN FUNCTIONS
USBIN (Pin 1): USB Input Supply Pin. This input provides
an internal N-channel MOSFET. When the charge cycle is
completed, CHRG becomes high impedance. This output
is capable of driving an LED.
power to the battery charger assuming a voltage greater
than V
and less than V
is present (typically
UVUSB
OVUSB
3.95V to ꢀV respectively). However, the DCIN input will
take priority if a voltage greater than V is present at
DCIN (typically 4.15V). The USBIN input allows charge
currents up to 850mꢁ. This pin should be bypassed with
a 1µF capacitor.
ENABLE (Pin 6): Enable Input. When the LTC4078X is
charging from the DCIN source, a logic low on this pin
enables the charger. When the LTC4078X 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 LTC4078X to charge when
a wall adapter is applied and to shut down if only the USB
source is applied.
UVDC
IUSB (Pin 2): Charge Current Program for USB Power.
The charge current is set by connecting a resistor, R
,
IUSB
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:
BATDET (Pin 7): Battery Detection Input. When the volt-
age on this pin falls below V
(typically 1.75V), the
BDET
charger is on and ready for charging a battery. If this
input is left floating, an internal pull-up resistor will dis-
able charging.
V
RIUSB
IUSB
IBAT
=
•1000
IDC (Pin 8): Charge Current Program for Wall ꢁdapter
ITERM (Pin 3): Termination Current Threshold Program.
Power. The charge current is set by connecting a resis-
The termination current threshold, I
, is set by
is set
tor, R , to ground. When charging in constant-current
TERMINꢁTE
IDC
connecting a resistor, R
, to ground. I
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:
ITERM
TERMINꢁTE
by the following formula:
100V
RITERM
ITERMINATE
=
V
RIDC
IDC
IBAT
=
•1000
When the battery current, I , falls below the termination
BꢁT
threshold, charging stops and the CHRG output becomes
high impedance. This pin is internally clamped to approxi-
mately 1.5V. Driving this pin to voltages beyond the clamp
voltage should be avoided.
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 ꢁdapter Input Supply Pin. This input
PWR (Pin 4): Open-Drain Power Supply Status Output.
WhentheDCINorUSBINpinvoltageisvalidtobegincharg-
ing (i.e. when the supply is greater than the undervoltage
lockoutthreshold,lessthantheovervoltagelockoutthresh-
old 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.
provides power to the battery charger assuming a voltage
greater than V
and less than V
is present (typi-
UVDC
OVDC
cally4.15VtoꢀVrespectively). ꢁvalidvoltageontheDCIN
input will always take priority over the USBIN input. The
DCIN input allows charge currents up to 950mꢁ. This pin
should be bypassed with a 1µF capacitor.
Exposed Pad (Pin 11): GND. The exposed backside of the
packageisgroundandmustbesolderedtoPCboardground
for electrical connection and maximum heat transfer.
CHRG (Pin 5): Open-Drain Charge Status Output. When
the LTC4078X is charging, the CHRG pin is pulled low by
4078xf
7
LTC4078X
BLOCK DIAGRAM
DCIN
10
BAT
9
USBIN
1
CC/CV
REGULATOR
CC/CV
REGULATOR
V
BOC
DC_ENABLE
CHARGER CONTROL
DISABLE
USB_ENABLE
7
+
–
BATDET
1.75V
4
PWR
+
–
+
–
3.95V
BAT
6V
4.15V
BAT
6V
DCIN UVLO
DCIN OVLO
RECHARGE
USBIN UVLO
+
–
+
–
+
–
+
–
USBIN OVLO
T
6
ENABLE
+
–
+
–
DIE
2M
120°C
0.9V
THERMAL
REGULATION
4.075V
BAT
+
–
0.1V
CHRG
5
–
+
I
/1000
I
/1000
I
/1000
BAT
BAT
BAT
TERMINATION
GND
11
ITERM
IDC
IUSB
3
8
2
4078X BD
R
ITERM
R
R
IUSB
IDC
4078xf
8
LTC4078X
OPERATION
Charge current out of the BꢁT pin can be determined at
any time by monitoring the IDC or IUSB pin voltage and
applying the following equations:
The LTC4078X is designed to efficiently manage charg-
ing of a single-cell lithium-ion battery from two separate
power sources: a wall adapter and USB power bus. Us-
ing the constant-current/constant-voltage algorithm, the
charger can deliver up to 950mꢁ of charge current from
the wall adapter supply or up to 850mꢁ of charge current
from the USB supply with a final float voltage accuracy of
0.ꢀ6. The LTC4078X has two internal P-channel power
MOSFETs and thermal regulation circuitry. No blocking
diodes or external sense resistors are required.
V
RIDC
IDC
IBAT
IBAT
=
=
•1000,(charging from wall adapter)
V
IUSB
•1000,(charging from USBsupply)
RIUSB
Battery Detection
Power Source Selection
By default, the BꢁTDET pin is pulled high with an internal
resistor, disabling the charger. To enable the charger, the
The LTC4078X can charge a battery from either the wall
adapter input or the USB port input. The LTC4078X auto-
matically senses the presence of voltage at each input. If
both power sources are present, the LTC4078X defaults to
the wall adapter source provided a valid voltage is present
at the DCIN input. “Valid voltage” is defined as:
BꢁTDET pin must be pulled below the V
threshold
BDET
(typically 1.75V). ꢁn external resistor to ground less than
100k (typically 3.9k) located in the battery pack is used to
detect battery presence.
Programming Charge Termination
• Supply voltage is greater than the UVLO threshold
and less than the OVLO threshold.
The charge cycle terminates when the charge current
falls below the programmed termination threshold level
during constant-voltage mode. This threshold is set by
• Supply voltage is greater than the battery voltage by
40mV.
connecting an external resistor, R , from the ITERM
ITERM
pin to ground. The charge termination current threshold
(I ) is set by the following equation:
The open-drain power status output (PWR) indicates
which power source has been selected. Table 1 describes
the behavior of this status output.
TERMINꢁTE
100V
100V
RITERM
=
,ITERMINATE =
ITERMINATE
RITERM
Programming and Monitoring Charge Current
The charge current delivered to the battery from the wall
adapter or USB supply is programmed using a single re-
sistor from the IDC or IUSB pin to ground. Both program
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
resistors and charge currents (I
the following equations:
) are calculated using
t
(typically 1.ꢀms), charging is terminated. The
CHRG
TERMINꢁTE
charge current is latched off and the LTC4078X enters
standby mode.
1000V
ICHRG−DC
1000V
1000V
RIDC
RIDC
=
,ICHRG−DC =
When charging, transient loads on the BꢁT pin can cause
the ITERM pin to fall below 100mV for short periods of
time before the DC charge current has dropped below the
1000V
RIUSB
RIUSB
=
, ICHRG−USB =
ICHRG−USB
*ꢁny external sources that hold the ITERM pin above 100mV will prevent the LTC4078X from
terminating a charge cycle.
4078xf
9
LTC4078X
OPERATION
programmed termination current. The 1.ꢀms filter time
logiclowenablesthechargerandlogichighdisablesit(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).
(t ) on the termination comparator ensures that
TERMINꢁTE
transient loads of this nature do not result in premature
chargecycletermination.Oncetheaveragechargecurrent
drops below the programmed termination threshold, the
LTC4078Xterminatesthechargecycleandstopsproviding
current out of the BꢁT pin. In this state, any load on the
BꢁT pin must be supplied by the battery.
The DCIN input draws 40µꢁ when the charger is in shut-
downmode.TheUSBINinputdraws40µꢁduringshutdown
if no voltage is applied to DCIN, but draws only 23µꢁ when
V
provides valid voltage (see Table 1).
DCIN
Automatic Recharge
Status Indicators
In standby mode, the charger sits idle and monitors the
batteryvoltageusingacomparatorwitha4.1msfiltertime
The charge status open-drain output (CHRG) has two
states: pulldown and high impedance. The pulldown state
indicates that the LTC4078X is in a charge cycle. Once the
charge cycle has terminated or the LTC4078X is disabled,
the pin state becomes high impedance.
(t
). ꢁ charge cycle automatically restarts when the
RECHRG
battery voltage falls below 4.075V (which corresponds to
approximately806to906batterycapacity).Thisensures
that the battery is kept at, or near, a fully charged condi-
tion and eliminates the need for periodic charge cycle
initiations.
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. 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 LTC4078X lacks valid
input voltage (see Table 1) to charge the battery.
Manual Shutdown
TheENꢁBLEpinhasa2MΩpulldownresistortoGND. The
definitionofthispindependsonwhichsourceissupplying
power. When the wall adapter input is supplying power,
Table 1. Power Source Selection (V
< 1.75V)
BATDET
V
USBIN
< 3.95V or
6V > V
> 3.95V and
22V > V
> 6V
USBIN
USBIN
USBIN
V
< BAT + 50mV
V
> BAT + 50mV
USBIN
ENABLE
HIGH
LOW or No Connect
HIGH
LOW or No Connect
HIGH
LOW or No Connect
V
V
< 4.15V or
No Charging.
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
Charging from
USBIN source.
PWR: LOW
No Charging.
PWR: LOW
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
DCIN
DCIN
< BꢁT + 50mV PWR: Hi-Z
CHRG: Hi-Z
CHRG: LOW
ꢀV > V
> 4.15V
No Charging.
PWR: LOW
CHRG: Hi-Z
Charging from DCIN No Charging.
Charging from DCIN No Charging.
Charging from DCIN
source.
DCIN
and V
> BꢁT +
source.
PWR: LOW
CHRG: Hi-Z
source.
PWR: LOW
CHRG: Hi-Z
DCIN
50mV
PWR: LOW
CHRG: LOW
PWR: LOW
CHRG: LOW
PWR: LOW
CHRG: LOW
22V > V
> ꢀV
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: LOW
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
No Charging.
PWR: Hi-Z
CHRG: Hi-Z
DCIN
4078xf
10
LTC4078X
OPERATION
Thermal Limiting
ing 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 ꢁpplications
Information section.
ꢁninternalthermalfeedbackloopreducestheprogrammed
charge current if the die temperature attempts to rise
above a preset value of approximately 120°C. This feature
protects the 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 damag-
DCIN POWER REMOVED
ENABLE = LOW
USB POWER REMOVED
NO POWER
POWER APPLIED
ENABLE = HIGH
YES
NO
DCIN > 4.15V
AND DCIN > BAT
NO
NO
NO
6V > DCIN > 4.15V
AND DCIN > BAT
6V > USBIN > 3.95V
AND USBIN > BAT
YES
BATDET < 1.75V
YES
YES
BATDET < 1.75V
YES
NO
CHARGE MODE
(DCIN)
CHARGE MODE
(USBIN)
FULL CURRENT
FULL CURRENT
CHRG STATE: PULLDOWN
CHRG STATE: PULLDOWN
I
< I
I
< I
BAT TERMINATE
BAT TERMINATE
IN VOLTAGE MODE
IN VOLTAGE MODE
STANDBY MODE
STANDBY MODE
(DCIN)
(USBIN)
BAT < 4.075V
BAT < 4.075V
NO CHARGE CURRENT
CHRG STATE: Hi-Z
NO CHARGE CURRENT
CHRG STATE: Hi-Z
SHUTDOWN MODE
(DCIN)
SHUTDOWN MODE
(USBIN)
CHRG STATE: Hi-Z
CHRG STATE: Hi-Z
4078X F01
Figure 1. LTC4078X State Diagram of a Charge Cycle
4078xf
11
LTC4078X
APPLICATIONS INFORMATION
Using a Single Charge Current Program Resistor
Stability Considerations
TheLTC4078Xcanprogramthewalladapterchargecurrent
andUSBchargecurrentindependentlyusingtwoprogram
Theconstant-voltagemodefeedbackloopisstablewithout
any compensation provided a battery is connected to the
charger output. However, a 1µF capacitor with a 1Ω series
resistor is recommended at the BꢁT pin to keep the ripple
voltage low when the battery is disconnected.
resistors, R and R
. Figure 2 shows a charger circuit
IDC
IUSB
that sets the wall adapter charge current to 800mꢁ and
the USB charge current to 500mꢁ.
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 af-
fectedbytheimpedanceatthechargecurrentprogrampin.
With no additional capacitance on this pin, the charger is
stable with program resistor values as high as 20k (I
CHRG
800mA (WALL)
LTC4078X
= 50mꢁ); however, additional capacitance on these nodes
reduces the maximum allowed program resistor.
500mA (USB)
WALL
ADAPTER
DCIN
BAT
USB
USBIN BATDET
IUSB
4.2V
+
3.9k
R4
PORT
C2, 1µF
Li-Ion
Power Dissipation
BATTERY
PACK
R1
2k
1%
IDC
ITERM
GND
C1
1µF
R3
2k
1%
Whendesigningthebatterychargercircuit, itisnotneces-
sary to design for worst-case power dissipation scenarios
because the LTC4078X automatically reduces the charge
current during high power conditions. The conditions that
cause the 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:
R2
1.24k
1%
4078X F02
Figure 2. Dual Input Charger with Independent Charge Currents
LTC4078X
WALL
500mA
ADAPTER
DCIN
BAT
USB
USBIN BATDET
IUSB
4.2V
+
R4
3.9k
PORT
C2, 1µF
Li-Ion
BATTERY
PACK
P = (V – V ) • I
BꢁT
D
IN
BꢁT
C1
1µF
IDC
ITERM
GND
R3
2k
1%
R1
2k
1%
P is the dissipated power, V is the input supply volt-
D
IN
BꢁT
age (either DCIN or USBIN), V
is the battery voltage
and I is the charge current. The approximate ambient
BꢁT
4078X F03
temperature at which the thermal feedback begins to
Figure 3. Dual Input Charger Circuit. The Wall Adapter
Charge Current and USB Charge Current Are Both
Programmed to Be 500mA
protect the IC is:
T = 120°C – P • θ
Jꢁ
ꢁ
D
Inthiscircuit,theprogrammedchargecurrentfromboththe
wall adapter supply is the same value as the programmed
charge current from the USB supply:
T = 120°C – (V – V ) • I • θ
Jꢁ
ꢁ
IN
BꢁT
BꢁT
Example: ꢁn LTC4078X operating from a 5V wall adapter
(on the DCIN input) is programmed to supply 800mꢁ
full-scale current to a discharged Li-Ion battery with a
voltage of 3.3V.
1000V
ICHRG−DC = ICHRG−USB
=
RISET
4078xf
12
LTC4078X
APPLICATIONS INFORMATION
ꢁssuming θ is 40°C/W (see Thermal Considerations),
800mꢁtoabatteryfroma5Vsupplyatroomtemperature.
Withoutagoodbacksidethermalconnection, thisnumber
would drop to much less than 500mꢁ.
Jꢁ
theambienttemperatureatwhichtheLTC4078Xwillbegin
to reduce the charge current is approximately:
T = 120°C – (5V – 3.3V) • (800mꢁ) • 40°C/W
ꢁ
Input Capacitor Selection
T = 120°C – 1.3ꢀW • 40°C/W = 120°C – 54.4°C
When an input supply is connected to a portable product,
the inductance of the cable and the high-Q ceramic input
capacitorformanL-Cresonantcircuit.WhiletheLTC4078X
is 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 pos-
sible 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 LTC4078X
during a hot insertion, it is best to have a low voltage coef-
ficient capacitor at the input pins to the 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 1ꢀV X5R capacitor. Note that no
charging will occur with 15V in.
ꢁ
T = ꢀ5.ꢀ°C
ꢁ
The LTC4078X can be used above ꢀ5.ꢀ°C ambient, but
the charge current will be reduced from 800mꢁ. The ap-
proximate current at a given ambient temperature can be
approximated by:
120°C – TA
IBAT
=
(V – VBAT) • θJA
IN
Using the previous example with an ambient temperature
of 75°C, the charge current will be reduced to approxi-
mately:
120°C – 75°C
(5V – 3.3V) • 40°C / W 68°C / A
45°C
IBAT
=
=
Using a tantalum capacitor or an aluminum electrolytic
capacitorforinputbypassing,orparallelingwithaceramic
capacitor will also reduce voltage overshoot during a hot
insertion. Ceramic capacitors with Y5V or Z5U dielectrics
are not recommeded.
IBAT = 662mA
ItisimportanttorememberthatLTC4078Xapplicationsdo
notneedtobedesignedforworst-casethermalconditions,
since the IC will automatically reduce power dissipation
when the junction temperature reaches approximately
120°C.
ꢁlternatively, the following soft connect circuit can be
employed (as shown in Figure 4).
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 LTC4078X DFN package is properly sol-
dered to the PC board ground. When correctly soldered to
DCIN/USBIN
R1
+15V
INPUT
40k
C1
1µF
INPUT CABLE
LTC4078X
C2
100nF
MN1
2
a2500mm doublesided1ozcopperboard,theLTC4078X
GND
4078X F04
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. ꢁs an
example, a correctly soldered LTC4078X can deliver over
Figure 4. Input Soft Connect Circuit
4078xf
13
LTC4078X
APPLICATIONS INFORMATION
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).
In this circuit, capacitor C2 holds MN1 off when the cable
isfirstconnected. EventuallyC2beginstochargeuptothe
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.
DRAIN-BULK
DIODE OF FET
LTC4078X
WALL
ADAPTER
DCIN
Reverse Polarity Input Voltage Protection
4078X F05
In some applications, protection from reverse polarity
voltage on the input supply pins is desired. With sufficient
Figure 5. Low Loss Reverse Polarity Protection
4078xf
14
LTC4078X
PACKAGE DESCRIPTION
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1ꢀ99)
R = 0.115
0.38 0.10
TYP
6
10
0.675 0.05
3.50 0.05
2.15 0.05 (2 SIDES)
1.65 0.05
3.00 0.10
(4 SIDES)
1.65 0.10
(2 SIDES)
PIN 1
PACKAGE
OUTLINE
TOP MARK
(SEE NOTE 6)
(DD10) DFN 1103
5
1
0.25 0.05
0.50 BSC
0.75 0.05
0.200 REF
0.25 0.05
0.50
BSC
2.38 0.10
(2 SIDES)
2.38 0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
4078xf
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC4078X
TYPICAL APPLICATION
Full Featured Li-Ion Charger
800mA (WALL)
475mA (USB)
LTC4078X
WALL
ADAPTER
BAT
DCIN
USB
POWER
1k
1k
USBIN
1µF
1µF
PWR
CHRG
BATDET
4.2V Li-Ion
BATTERY
PACK
IUSB
IDC
+
3.9k
ITERM
GND
2.1k
1%
1.24k
1%
1k
1%
4078X TA02
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ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
4078xf
LT 0907 • PRINTED IN USA
LinearTechnology Corporation
1ꢀ30 McCarthy Blvd., Milpitas, Cꢁ 95035-7417
16
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FꢁX: (408) 434-0507 www.linear.com
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LTC4079 - 60V, 250mA Linear Charger with Low Quiescent Current; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C
Linear
![](http://pdffile.icpdf.com/pdf2/p00262/img/page/LTC4079EDD-P_1581822_files/LTC4079EDD-P_1581822_1.jpg)
![](http://pdffile.icpdf.com/pdf2/p00262/img/page/LTC4079EDD-P_1581822_files/LTC4079EDD-P_1581822_2.jpg)
LTC4079IDD#PBF
LTC4079 - 60V, 250mA Linear Charger with Low Quiescent Current; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C
Linear
![](http://pdffile.icpdf.com/pdf2/p00295/img/page/LTC4080EDD-T_1784738_files/LTC4080EDD-T_1784738_1.jpg)
![](http://pdffile.icpdf.com/pdf2/p00295/img/page/LTC4080EDD-T_1784738_files/LTC4080EDD-T_1784738_2.jpg)
LTC4080EDD#PBF
LTC4080 - 500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C
Linear
![](http://pdffile.icpdf.com/pdf2/p00295/img/page/LTC4080EDD-T_1784738_files/LTC4080EDD-T_1784738_1.jpg)
![](http://pdffile.icpdf.com/pdf2/p00295/img/page/LTC4080EDD-T_1784738_files/LTC4080EDD-T_1784738_2.jpg)
LTC4080EDD#TRPBF
LTC4080 - 500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C
Linear
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