IC manages portable USB power

Power management device combines an autonomous high efficiency power manager, ideal diode controller and battery charger in an ultrathin QFN package.

New from Linear Technology, the LTC4098 is multifunction power management device for portable USB powered devices such as media players, digital cameras, PDAs, personal navigators and smart phones.

The device combines an autonomous high efficiency power manager, ideal diode controller and battery charger in an ultrathin (0.55mm) 20-pin 3 x 4mm QFN package.

The LTC4098 uses proprietary PowerPath control to manage power flow between a wall adapter or USB port and the device's Li-ion/polymer battery while simultaneously preferentially providing power to the system load.

For automotive, FireWire or other high-voltage applications, the LTC4098 provides Bat-Track control of a Linear Technology companion switching regulator up to 38V operating input (60V transient), maximising battery charger efficiency, minimising heat dissipation, and providing for a seamless transition between USB and higher voltage power sources.

The LTC4098 includes overvoltage protection up to 66V on the USB input - with only an external NFET/resistor combination - preventing damage caused by accidental application of high voltages to the bus.

The LTC4098's "instant-on" operation ensures system load power at plug-in even with a dead battery.

Its onboard ideal diode guarantees that ample output power is always available, even if there is insufficient power at the LTC4098's two input pins.

The IC's ideal diode controller can be used to drive the gate of an optional PFET, reducing the impedance to the battery to 30mohm or less.

The single-cell Li-ion/polymer battery charger allows the load current to exceed the current drawn from the USB port while conforming to USB load specifications.

For fast charging, the IC's switching input stage converts nearly all of the 2.5W available from the USB port to system current, enabling up to 700mA from a 500mA limited USB port.

There is also 1.5A charge current available when wall powered.

Further, the charger includes thermal limiting, automatic recharge, stand-alone 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.

An additional feature of the IC is a suspend LDO that prevents battery drain when a device is connected to a suspended USB port.

The LTC4098 is guaranteed for operation from -40 to +85C, and 1000-piece pricing starts at US $2.50 each.

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