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USB battery charger withstands up to 60V input

Posted: 13 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:USB? ideal diode controller? PowerPath manager?

Linear Technology Corp. introduces the LTC4090, an autonomous linear PowerPath manager, ideal-diode controller and stand-alone high-input-voltage battery charger for portable USB devices.

For high-efficiency charging, the switching front-end topology accommodates various inputs, including high-voltage power sources up to 38V (60V max withstand capability) such as 12V regulated/unregulated AC/DC wall adapters, FireWire ports or automotive power. The IC also accepts low-voltage power sources including 5V wall adapters, USB ports and single-cell Li-ion/polymer batteries.

LTC4090 features linear PowerPath control, which provides power to the device while charging its single-cell lithium battery from the USB bus or a wall-adapter power supply. To comply with USB current-limit specifications, LTC4090 automatically reduces battery charge current as the system load current increases.

To ensure that a fully charged battery remains topped off when the bus is connected, the IC directs power to the load through the USB bus rather than extracting power from the battery. Once all power sources are removed, current flows from the battery to the load through an internal 200m low-loss ideal diode, minimizing voltage drop and power dissipation. Onboard control circuitry is provided to drive an optional external PFET to reduce the overall ideal diode impedance below 50m if required by the application, providing even higher efficiency operation.

LTC4090's front-end switching regulator also features Bat-Track adaptive output control, improving the efficiency of its 1.5A-capable battery charger, as the internal switching regulator's output-voltage automatically tracks the battery voltage by 300mV. Instant-on operation ensures system power is available as soon as the input supply is available, even with a dead or missing battery.

In addition, the battery charger's float voltage is preset at 4.2V with 1 percent accuracy from -40C to 85C. For battery pre-conditioning and qualification, fully discharged cells are automatically trickle-charged at 10 percent of the programmed current until the cell voltage exceeds 2.9V. Total charge time for charge termination is programmed by an external capacitor, and a C/10 charge-current detection output is provided.

Other functions include 5x/1x USB current limiting, thermal regulation, NTC thermistor input for temperature-qualified charging, automatic recharging of the battery, reverse current-blocking and undervoltage lockout.

The devices are available now. Pricing begins at $3.25 each in 1,000-piece quantities.

- Emily Gleason

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