The LTC4099 from Linear Technology juggles a number of tasks, as this high-efficiency power manager also can serve as an ideal diode controller and lithium-ion (Li-ion) battery charger for portable USB-powered devices like media players, digital cameras, PDAs, personal navigation devices, and smart phones. Input current limit, charge current, termination current, float voltage, and other parameters can be programmed via I²C. Also, the I²C port lets users read back system status information.

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The device’s switching PowerPath topology seamlessly manages the power flow between a wall adapter or USB port and the battery while preferentially providing power to the system load. For automotive, FireWire, or other high-voltage applications, the LTC4099 provides Bat-Track control of a Linear Technology companion switching regulator, maximizing battery charger efficiency and minimizing power dissipation. With companion-chip input voltages ranging up to 38 V (60-V transients), the LTC4099 provides seamless transition between USB and higher-voltage power sources.

The LTC4099 prevents damage caused by the accidental application of high-voltage on the USB input with an overvoltage protection circuit. In fact, protection up to 68 V requires only an external NFET/resistor combination. The device’s instant-on operation ensures system load power at plug-in even with a dead battery. Its onboard ideal diode guarantees that ample power is always available to V_OUT even if there is insufficient power at the LTC4099’s two input pins. The ideal controller can be used to drive the gate of an optional PFET, reducing the impedance between the load and the battery to 30 mΩ or less.

With the full-featured single-cell Li-ion/polymer battery charger, the load current can 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 2.5 W available from the USB port to current, enabling up to 600-mA charge current or 700-mA system load current from a 500-mA limited USB port. A 1.5-A charge current is available with wall power as well.

An integrated overtemperature battery conditioning circuit can optionally reduce the battery voltage when high battery temperature and high battery voltage occur simultaneously. The charger also 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. A suspend low-dropout regulator (LDO) prevents battery drain during connection to a suspended USB port.

The LTC4099 comes in a 20-pin, 3- by 4- by 0.55-mm quad flat no-lead (QFN) package that’s guaranteed for operation from –40°C to 85°C. Pricing starts at $2.80 each in 1000-piece pricing.

• Linear Technology Corp.

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