LTC4009 pdf

The LTC4009 is a constant-current/constant-voltage battery
charger controller. It uses a synchronous quasi-constant
frequency PWM control architecture that will not gener-
ate audible noise with ceramic bulk capacitors. Charge
current is set by the combination of external sense, input
and programming resistors. Current being delivered by
the charger can be monitored as a voltage across the
programming resistor.
The LTC4009 features fully adjustable output voltage. An
external resistor divider and precision internal reference
set the fi  nal output voltage at which charge current will
be reduced to zero.
The device includes AC adapter input current limiting,
which maximizes charge rate for a fi  xed input power level.
An external sense resistor programs the input current
limit, and the  ICL status pin indicates when the battery
charge current is being reduced as a result of AC adapter
current limiting.
The CHRG status pin is active during all charging modes,
including special indication when the charge current has
decreased below 10% of the programmed current.