LTC4057 Datasheet, PDF (5/12 Pages) Linear Technology – Linear Li-Ion Battery Charger with Thermal Regulation in ThinSOT

LTC4057- 4.2
PI FU CTIO S
BLOCK DIAGRA
SHDN (Pin 1): Shutdown Input. Pulling this pin low puts
the LTC4057 in shutdown mode, thus stopping the charge
current. In shutdown mode, the input supply current
drops to 25µA and the battery drain current drops to less
than 2µA. This pin has an internal 1MΩ resistor to GND.
GND (Pin 2): Ground.
BAT (Pin 3): Charge Current Output. Provides charge
current to the battery and regulates the final float voltage
to 4.2V. An internal precision resistor divider from this pin
sets the float voltage and is disconnected in shutdown
mode.
V_CC (Pin 4): Positive Input Supply Voltage. Provides
power to the charger. V_CC can range from 4.25V to 6.5V
and should be bypassed with at least a 1µF capacitor.
When V_CC drops to within 30mV of the BAT pin voltage, the
LTC4057 enters shutdown mode, dropping I_BAT to less
than 2µA.
PROG (Pin 5): Charge Current Program and Charge Cur-
rent Monitor Pin. The charge current is programmed by
connecting a 1% resistor, R_PROG, to ground. When charg-
ing in constant-current mode, this pin servos to 1V. In all
modes, the voltage on this pin can be used to measure the
charge current using the following formula:
I_BAT = (V_PROG/R_PROG) • 1000
This pin is clamped to approximately 2.4V. Driving this pin
to voltages beyond the clamp voltage will draw currents as
high as 1.5mA.
120°C
T_DIE
SHDN 1
1MΩ
V_CC
4
T_A
1×
1000×
–+
MA
3 BAT
5µA
R1
CA
+1
C1
VA
R2
REF
1.21V
R3
1V
R4
0.1V
R5
2.9V TO BAT
5
PROG
R_PROG
2
GND
4-57 BD
4057f
5