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Power/Alternative Energy  

Stand-alone battery charger uses constant-current/constant-voltage algorithm

Posted: 26 Mar 2007     Print Version  Bookmark and Share

Keywords:battery charger  wall adapter  USB  Linear Tech  linear battery charger 

Linear Technology Corp. has introduced the LTC4097 stand-alone dual-input linear battery charger. This device charges single-cell Li-ion/polymer batteries from wall adapter or USB power sources. It uses a constant-current/constant-voltage algorithm for charging, with programmable charge current up to 0.2A 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 cell phones.

The LTC4097 features a final float voltage accuracy of ±0.6 per cent and is equipped with a patented thermal regulation scheme that maximises the charging rate without the risk of overheating. The device is 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 MCU 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 per cent or 100 per cent 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-by-3mm DFN package. The total solution footprint is compact since no external MOSFET, sense resistor or blocking diode is required. To extend battery run time, the LTC4097 draws <50µA in standby and < 20µA in shutdown mode.

The LTC4097 is rated for operation from -40°C to 85°C. Pricing for 1,000 pieces begins at Rs.68.83 ($1.56 each).




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