LTC4052-4.2
Lithium-Ion Battery
Pulse Charger with
Overcurrent Protection
FEATURES
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DESCRIPTIO
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Very Low Power Dissipation: 350mW at 1A
Complete Standalone Pulse Charger for 1-Cell
Lithium-Ion Batteries
Requires No Microcontroller, MOSFET or
Blocking Diode
Sense Resistor Limits Maximum Current for Safety
Programmable Charge Termination Timer for
Maximum Capacity Charging
±1%
Float Voltage Accuracy
Near End-of-Charge (C/10) Detection Output
AC Wall Adapter Present Output
Low Battery Drain when Input Supply Is Removed
Automatic Trickle Charge for Low Battery
Automatic Battery Refresh
Thermal Shutdown Protection
Tiny Thermally Enhanced MSOP Package
The LTC
®
4052 is a complete standalone pulse charger
with integrated MOSFET for 1-cell lithium-ion batteries.
An external sense resistor provides overcurrent limiting as
a safety precaution against a user connecting a wall
adapter with the incorrect or no current limit. The internal
MOSFET prevents reverse battery current from flowing if
the input voltage is shorted to ground, eliminating the
need for a blocking diode.
As the battery accepts charge and approaches the
programmed float voltage, the internal MOSFET begins
switching off and on with the duty cycle gradually decreas-
ing as the battery approaches a fully charged condition.
A programmable timer terminates the charge cycle. The
near end-of-charge C/10 condition is indicated at the
CHRG pin when the average charge current falls to one-
tenth of the wall adapter current. Removing the input
voltage puts the LTC4052 into a sleep mode, dropping the
battery current drain to less than 1µA.
The LTC4052 is available in a tiny 8-pin thermally
enhanced MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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Handheld Computers
Cellular Telephones
Cradle Chargers
TYPICAL APPLICATIO
V
IN
= 4.5V TO 10V
WITH 1A
CURRENT LIMIT
Single Cell 4.2V, 1A, Standalone Li-Ion Battery Charger
4.5
4.7Ω
1k
1µF
1k
V
IN
LTC4052
GATE
6
CHRG
ACPR
SENSE
BAT
TIMER
5
GND
4
1
8
7
10k
0.047µF
R
SENSE
0.05Ω
BATTERY
VOLTAGE (V)
3
4.0
3.5
3.0
1.0
0.5
0
5
0
0
0.5
1.0
1.5
2.0
TIME (HOURS)
2.5
3.0
C/10
CONSTANT
CURRENT
PULSING
CURRENT
CHARGE
CYCLE
ENDS
AC PRESENT
2
0.022µF
1-CELL 4.2V
Li-Ion
BATTERY
C
TIMER
0.1µF
4052 TA01
CHRG (V)
CHARGE
CURRENT (A)
CHARGE STATUS
U
LTC4052 Charge Profile
4052 • TA01b
U
U
405242f
1
LTC4052-4.2
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SENSE 1
ACPR 2
V
IN
3
GND 4
8 BAT
7 GATE
6 CHRG
5 TIMER
Input Supply Voltage (V
IN
)....................................... 12V
BAT Voltage ...............................................– 0.3V to 12V
GATE (Note 2) .............................................– 0.3V to 8V
SENSE, TIMER .................................. – 0.3V to V
IN
+0.3V
CHRG, ACPR .............................................– 0.3V to 12V
SENSE, BAT Peak Current ...................................... 1.5A
Operating Temperature Range (Note 3) .. – 40°C to 85°C
Junction Temperature (Note 4) ............................. 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC4052EMS8E-4.2
MS8 PART MARKING
LTYY
MSE EXPOSED PAD PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 35°C/W
EXPOSED PAD IS GROUND.
(MUST BE SOLDERED TO PCB).
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
I
IN
V
BAT
V
RECHRG
V
MARGIN
V
IMAX
I
TRICKLE
V
TRICKLE
R
DS(ON)
V
GATE
T
TIMER
I
LEAK
V
SLEEP
V
ACPR
I
LEAKACPR
V
CHRG
I
LEAKCHRG
I
CHRG
PARAMETER
Input Supply Voltage
Input Quiescent Supply Current
Battery Float Voltage
Recharge Battery Voltage Threshold
V
BAT
– V
RECHRG
Margin
Overcurrent Trip Sense Voltage
Trickle Charge Current
Trickle Charge Threshold Voltage
Internal Switch On-Resistance
GATE Pin Voltage
TIMER Period Accuracy
V
BAT
= 2V
V
BAT
Rising
V
BAT
= 2.6V
V
BAT
= 4V
V
BAT
= 2.6V
V
BAT
= 4V
CONDITIONS
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 6V unless otherwise noted.
MIN
q
q
q
TYP
0.7
MAX
10
1.4
4.242
4.242
4.110
4.110
225
120
34
2.55
0.7
0.5
UNITS
V
mA
V
V
V
V
mV
mV
mA
V
Ω
Ω
V
V
Wall Adapter Open Circuit Voltage
Full Charge Mode
0°C
≤
T
A
≤
85°C
Battery Voltage Falling 0°C
≤
T
A
≤
85°C
4.5
4.158
4.137
3.990
3.969
75
90
14
2.35
4.200
4.200
4.050
4.050
150
105
24
2.45
0.45
0.35
6.5
10.5
q
q
q
q
q
C
TIMER
= 0.1µF, Full Charge Mode
q
±10
1
20
0
q
q
q
q
Battery Leakage Current Through Charger V
BAT
= 4V, V
IN
= 0V
Sleep Threshold Voltage
(V
IN
– V
BAT
) Low to High
(V
IN
– V
BAT
) High to Low
ACPR Pin Output Low Voltage
ACPR Pin Leakage Current
CHRG Pin Output Low Voltage
CHRG Pin Leakage Current
CHRG Pin Weak Pull-Down Current
I
ACPR
= 3mA
V
IN
= 0, V
ACPR
= 6V
I
CHRG
= 3mA, Charging, C/10 Not Reached
V
IN
= 0, V
CHRG
= 6V
V
CHRG
= 1V, Charging, C/10 Reached
45
15
0.5
0.5
70
0.8
1
0.8
1
70
20
40
405242f
2
U
%
µA
mV
mV
V
µA
V
µA
µA
W
U
U
W W
W
LTC4052-4.2
ELECTRICAL CHARACTERISTICS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Absolute Maximum Rating for GATE pin applies only to externally
applied voltage. During normal operation the LTC4052-4.2’s internal
charge pump can generate GATE pin voltage exceeding absolute
maximum but it is internally current limited.
Note 3:
The LTC4052EMS8E-4.2 is guaranteed to meet 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 4:
Junction temperature T
J
is calculated from the ambient
temperature T
A
and power dissipation P
D
according to the following
formula: T
J
= T
A
+ (P
D
•
θ
JA
°C/W)
Note 5.
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
TYPICAL PERFOR A CE CHARACTERISTICS
Trickle Charge Threshold Voltage
vs Temperature
2.47
24.2
24.0
2.46
23.8
30
I
TRICKLE
(mA)
V
TRICKLE
(V)
2.45
23.6
23.4
23.2
23.0
22.8
I
TRICKLE
(mA)
2.44
2.43
2.42
–50 –25
50
25
75
0
TEMPERATURE (°C)
Normalized Timer Duration
vs Temperature
103
C
TIMER
= 0.1µF
4.200
102
4.195
4.205
T
TIMER
(%)
V
BAT
(V)
4.190
4.185
4.180
I
CHRG
(µA)
101
100
99
4.175
98
–50 –25
4.170
–50 –25
50
25
75
0
TEMPERATURE (°C)
U W
100
125
4052 G01
Trickle Charge Current
vs Temperature
35
Trickle Charge Current vs Input
Supply Voltage
V
BAT
= 2V
T
A
= 25°C
25
20
22.6
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
15
5
6
7
V
IN
(V)
8
9
10
4052 G03
4052 G02
Battery Float Voltage
vs Temperature
55
50
45
40
35
30
CHRG Pin C/10 Pulldown Current
vs Temperature
100
125
50
25
75
0
TEMPERATURE (°C)
100
125
25
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
4052 G04
4052 G05
4052 G06
405242f
3
LTC4052-4.2
TYPICAL PERFOR A CE CHARACTERISTICS
Overcurrent Sense Voltage
105.8
105.6
105.4
650
600
550
R
DS(ON)
(mΩ)
V
IMAX
(mV)
105.2
105.0
104.8
104.6
–50 –25
PI FU CTIO S
SENSE (Pin 1):
Overcurrent Sense Input. A sense resistor
(R
SENSE
) should be connected from V
IN
to the SENSE pin
to program the current limit level. When overcurrent limit
is tripped, the pass transistor immediately turns off and
turns back on after a 640ms time-out period (C
TIMER
=
0.1µF). The on-off cycle will continue as long as the
overcurrent condition persists or until the timer runs out.
If overcurrent protection is not needed, short SENSE to
V
IN
.
ACPR (Pin 2):
AC Wall Adapter Present Open-Drain Out-
put. When the input voltage (wall adapter) is applied to the
LTC4052, this pin is pulled to ground by an internal
N-channel MOSFET capable of driving an LED.
V
IN
(Pin 3):
Positive Input Supply Voltage (4.5V
≤
V
IN
≤
10V). Bypass this pin with a 1µF capacitor in series with a
4.7Ω resistor.
GND (Pin 4):
Electrical Ground Connection and provides
a thermal path from the IC to the PC board copper. The
exposed backside of the package is also ground and must
be soldered to the PC board for maximum power dissipa-
tion.
TIMER (Pin 5):
Timer Set Pin. The timer period is pro-
grammed by a capacitor (C
TIMER
) to ground. The timer
period is: t
TIMER
= (C
TIMER
• 3Hr)/(0.1µF). The minimum
ON time, minimum OFF time and the overcurrent time-out
period all scale with t
TIMER
.
CHRG (Pin 6):
Charge Status Open-Drain Output. When a
depleted battery is being charged, the CHRG pin is pulled
to ground by an internal N-channel MOSFET capable of
driving an LED. Once the duty cycle at the GATE pin drops
below 10%, the N-MOSFET turns off and a weak 40µA
current source to ground turns on to indicate a near end-
of-charge C/10 condition. When a time-out occurs or the
input supply is removed, the CHRG pin becomes high
impedance.
GATE (Pin 7):
Gate Drive Output Pin for Internal and
External Pass Transistors. An external N-MOSFET transis-
tor can be connected in parallel with the internal transistor
to reduce the on-resistance for higher charge current. In
this case, an external blocking diode on V
IN
is required to
prevent damage to the battery if V
IN
is shorted to ground.
A 10µA current source pulls this pin up to the charge pump
voltage when turned on and a 40µA current source pulls it
down to ground to turn it off. If an overcurrent condition
is detected, the GATE pin is immediately pulled to ground.
The voltage at this pin is internally clamped to 12V above
the GND pin.
4
U W
Switch On-Resistance vs
Temperature
500
V
BAT
= 2.6V
450
400
350
300
V
BAT
= 4V
50
25
75
0
TEMPERATURE (°C)
100
125
250
–50 –25
0
25
50
75
100
125
TEMPERATURE (°C)
4053 G07
4053 G08
U
U
U
405242f
LTC4052-4.2
PI FU CTIO S
A series RC network from the GATE to the V
IN
pin is
required to control the slew rate at the V
IN
pin when the
switch is turned on or off. The slew rate control prevents
excessive current from the capacitor usually located in the
wall adapter from flowing into the battery when the pass
transistor turns on.
BAT (Pin 8):
Battery Sense Input Pin. An internal resistor
divider presets the final float voltage to 4.2V. If the BAT pin
drops below 4.05V after the charge cycle has ended, the
timer resets and a new charge cycle begins. This pin is
clamped to 4.7V if the battery is disconnected while
charging.
BLOCK DIAGRA
+ –
45mV
V
IN
3
+
100ms
FILTER
BAT
–
GND
4
TIMER
5
OSCILLATOR
CHRG
6
40µA
THERMAL
SHUTDOWN
REFERENCE
W
U
U
U
ACPR
2
105mV
SLEEP
I
MAX
+
–
– +
V
IN
10mΩ
1
SENSE
24mA
7
CHARGE
PUMP
TRIPLER
8
BAT
GATE
TRICKLE
CLK
FAST
V
MIN
+
–
STOP
V
RECHRG
LOGIC
+
TIMERS
+
–
C/10
V
FLOAT
+
–
TEMP
V
MAX
+
–
1.23V
1.23V
4052 BD
405242f
5
Analog electronics
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