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Battery charger charges from wall adapter, USB power sources

Posted: 08 Sep 2005 ?? ?Print Version ?Bookmark and Share

Keywords:linear technology? linear battery charger? ltc4076? ltc4077?

Linear Technology Corp. rolled out standalone dual-input linear battery chargers that charge single-cell Li-ion batteries from a wall adapter or a USB power source. The new LTC4076 and LTC4077 use a constant-current/constant-voltage algorithm for charging, with charge current programmable up to 950mA from a wall adapter supply, or programmable up to 650mA from a USB supply while automatically sensing the presence of voltage at each input.

The LTC4076 features programmable C/x charge current termination, while the LTC4077 offers fixed C/10 termination. The LTC4076 features a choice of fixed C or C/5 USB charge current for low-power USB operation (via the HPWR pin), and the LTC4077 offers programmable C or C/x low-power USB charge current (via the HPWR pin). Target applications include PDAs, MP3 players, digital cameras, lightweight portable medical and test equipment, and large color screen cellphones.

Both the LTC4076 and LTC4077 devices feature final float voltage accuracy of 0.6 percent and are equipped with a patented thermal regulation scheme that maximizes the charging rate without the risk of overheating. These new products are said to be extremely flexible with the following features programmable via a single resistor: wall adapter supply charge current, USB supply charge current and charge termination currents. As standalone chargers, they also feature trickle charge for battery pre-conditioning, undervoltage lockout, automatic recharge, a charge status indicator and "power present" status outputs to indicate the presence of wall adapter or USB power.

The new linear battery chargers are offered in a low profile (0.75mm) 10-lead 3-by-3mm DFN package. The total solution footprint is less than 25mm? since no external MOSFET, sense resistors or blocking diodes are required. To preserve battery energy, these two new products draw <6?A from the battery terminal in standby and <2?A in shutdown mode.

The LTC4076 and LTC4077 are rated for operation from -40C to 85C. In 1,000-piece orders, pricing begins at $1.88 each.

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