LTC4052-4.2_15 Datasheet, PDF (4/12 Pages) Linear Technology – Lithium-Ion Battery Pulse Charger with Overcurrent Protection

LTC4052-4.2
TYPICAL PERFOR A CE CHARACTERISTICS
Overcurrent Sense Voltage
105.8
105.6
105.4
105.2
105.0
104.8
104.6
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4053 G07
Switch On-Resistance vs
Temperature
650
600
550
500
V_BAT = 2.6V
450
V_BAT = 4V
400
350
300
250
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4053 G08
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
4
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.
405242f