Linear Charger. AF4057 Datasheet
1.1A Lithium Ion Battery Linear Charger
AF4057 is a complete CC/CV linear charger for single cell lithium-ion batteries. It is specifically designed
to work within USB power Specifications.
No external sense resistor is needed and no blocking diode is required due to the internal P-MOSFET
architecture. Thermal feedback regulates the charge current to limit the die temperature during high power
operation or high ambient temperature .The charge voltage is fixed at 4.35V, and the charge current can be
programmed externally with a single resistor. The AF4057 automatically terminates the charge cycle
when the charge current drops to 1/10th the programmed value after the final float voltage is reached.
When the input supply (wall adapter or USB supply) is removed the AF4057 automatically enters a
low current state dropping the battery drain current to less than
2μA.The AF4057 can be put into shutdown mode reducing the supply current to 55μA.
Other features include Battery temperature monitor, under-voltage lockout, automatic recharge and
two status pins to indicate charge and charge termination.
Protection of battery cell reverse connection
Programmable charge current up to 1.1A
No MOSFET sense resistor or blocking diode required
Complete linear Charger for single Cell Lithium-Ion Batteries
CC and CV operation with thermal regulation to maximize Rate without risk of overheating
Preset 4.35V charge voltage with ±1% accuracy
Two Status Indication for Charge status, no battery and battery failure indicators
C/10 charge termination
55μA supply current in shutdown
2.9V trickle current charge threshold
Soft-Start limits inrush current
Battery Temperature Sensing
Available in ESOP-8 package
Mobile Power Supply
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USB Bus-Powered Chargers
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3 GND STDBY
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Temperature sense input
Connecting TEMP pin to NTC thermistor’s output in Lithium ion
battery pack. If TEMP pin’s voltage is below 45% or above 80%
of supply voltage VCC, this means that battery’ s temperature is
too low or too high, charging is suspended. The temperature
sense function can be disabled by grounding the TEMP pin.
Constant Charge Current Setting and Charge Current
The charge current is programmed by connecting a resistor
RPROG from this pin to GND. When in precharge mode, the
PROG pin ’ s voltage is regulated to 0.1V. When charging in
constant-current mode this pin’s voltage is regulated to 1V. In all
modes during charging, the voltage on this pin can be used to
measure the charge current using the following formula:
I = VPROG ×1200
Positive input supply voltage
Provides power to the internal circuit. When VCC drops to within
80mV of the BAT pin voltage, the AF4057 enters low power sleep
mode, dropping IBAT to less than 2μA.
Battery connection Pin
Connect the positive terminal of the battery to this pin. Dropping
BAT pin’s current to less than 2μA when IC in disable mode or in
sleep mode. BAT pin provides charge current to the battery and
provides regulation voltage of 4.35V.
Charge terminated status output
STDBY is pulled low by an internal switch to indicate a battery
charge terminated; this means Charge termination. Otherwise
pin is in high impedance state.
Open-Drain charge status output
When the battery is being charged, the CHRG pin is pulled low
by an internal switch,otherwise, CHRG pin is in high impedance
Chip enable input
A high input will put the device in the normal operating mode.
Pulling the CE pin to low level will put the AF 4057 into disable
mode. The CE pin can be driven by TTL or CMOS logiclevel.
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