Charger chip is flexible about its inputs

Dual-input linear battery charger has all the circuitry required to charge single-cell Li-ion/polymer batteries from wall adapter or USB power sources.

The LTC4097 from Linear Technology is a stand-alone dual-input linear battery charger that charges single-cell Li-ion/polymer batteries from wall adapter or USB power sources.

The LTC4097 uses a constant-current/constant-voltage algorithm for charging, with programmable charge current up to 1.2A from a wall adapter supply, or up to 1A from a USB supply while automatically detecting the presence of voltage at each input.

USB current limiting is also provided.

Applications include PDAs, MP3 players, digital cameras, lightweight portable medical and test equipment and large colour display cellphones.

The LTC4097 features a final float voltage accuracy of +/-0.6% and is equipped with a patented thermal regulation scheme that maximises the charging rate without the risk of overheating.

The device is extremely flexible with the following features programmable via a single resistor: wall adapter supply charge current, USB supply charge current and charge termination current.

As a stand-alone charger, it does not require an external microcontroller to terminate charge, simplifying design.

Key features include automatic input source selection, a combined input power present output and NTC bias (VNTC) pin with 120mA drive capability, an NTC thermistor input (NTC) pin for temperature-qualified charging, and a USB charge current level select (HPWR) pin for obtaining 20 or 100% of the current programmed via the IUSB pin.

Other features include trickle charge for battery pre-conditioning, undervoltage lockout, automatic recharge, and charge status indication.

The LTC4097 is offered in a low profile (0.75mm) 12-lead 2 x 3mm DFN package.

The total solution footprint is very compact since no external MOSFET, sense resistor or blocking diode is required.

To extend battery run time, the LTC4097 draws less than 50uA in standby and less than 20uA in shutdown mode.

The LTC4097 is rated for operation from -40 to +85C.

1000-piece pricing begins at US $1.56 each.

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