Battery chip powers USB devices

Device combines an autonomous high-efficiency power manager, ideal diode controller and battery charger for portable USB devices.

The LTC4088 from Linear Technology combines an autonomous high-efficiency power manager, ideal diode controller and battery charger for portable USB devices.

The LTC4088's switching front-end topology features PowerPath control that optimises the power available from the USB port to charge the battery and power the application device with minimum power dissipation.

This feature eases thermal management issues in space-constrained media players, digital cameras, PDAs, GPS units and smart phones.

The IC also allows the load current to exceed the current drawn from the USB port while conforming to USB load specifications.

Featuring an input voltage range of 4.25 to 5.5V, the LTC4088 automatically limits its input current to a maximum of 1x (for USB 100mA), 5x (for USB 500mA) or 10x for wall-adapter powered applications (1A).

If the power source is removed, the IC ensures that system power is available from the battery to the application's load via current flow through an internal low loss 200mohm ideal diode, minimizing voltage drop and power dissipation.

An optional external ideal diode controller is provided for driving a PFET to reduce the overall ideal diode impedance below 40mohm.

The LTC4088's full-featured single-cell Li-ion/polymer battery charger has a constant-voltage, constant-current topology and allows for up to 1.2A charge current capability.

Its Bat-Track operation keeps power dissipation low in the battery charger for optimum charge time and less heat.

"Instant-on" operation allows the portable product to run immediately when power is applied without waiting for a discharged battery to charge.

Furthermore, the charger includes thermal limiting, automatic recharge, standalone operation with automatic charge termination and fixed duration safety timer, low voltage trickle charging, bad battery cell detection and a thermistor input for temperature-qualified charging.

Additional features of the IC are an "always-on" 3.V, 25mA LDO for system microprocessor rails, and a suspend LDO that prevents battery drain when a device is connected to a suspended USB port.

The LTC4088 is housed in a low-profile (0.75mm) 14-pin 3 x 4mm DFN package and is guaranteed for operation from -40 to +85C.

1000-piece pricing starts at US $2.20 each.

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