Linear - High-efficiency I2C USB power manager and Li-ion charger

An autonomous I2C controlled, high-EFFICIENCY POWER manager, ideal diode controller and Li-Ion/Polymer battery charger has been unveiled by Linear Technology - for portable USB powered devices such as media players, digital cameras, PDAs, PNDs and smart phones.

Parameters including input current limit, charge current, termination current, and float voltage can be programmed via I2C. The I2C port also allows the user to read back system status information. The LTC4099’s switching PowerPath topology seamlessly manages power flow between a wall adapter or USB port and the device’s battery while preferentially providing power to the system load.

For automotive, Firewire, or other high-voltage applications, the device 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 38V (60V transients), the LTC4099 provides a seamless transition between USB and higher voltage power sources.

The LTC4099 prevents damage caused by accidental application of high voltage on the USB input with an overvoltage protection (OVP) circuit – protection up to 68V requires only an external NFET/RESISTOR combination. The LTC4099’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 VOUT even if there is insufficient power at the LTC4099’s two input pins. The device’s ideal diode controller can be used to drive the gate of an optional PFET, reducing the impedance between the load and the battery to 30mOhm or less.

The LTC4099’s full-featured 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 current, enabling up to 600mA charge current or 700mA system load current from a 500mA limited USB port.

There is also 1.5A charge current available when wall powered. For improved safety margin, an integrated over-temperature battery conditioning circuit can optionally reduce the battery voltage in case both high battery temperature and high battery voltage occur simultaneously. 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 LTC4099 is a suspend LDO that prevents battery drain when a device is connected to a suspended USB port.The LTC4099 is housed in an ultra-thin (0.55mm) 20-pin 3mm x 4mm QFN package and is 'guaranteed' for operation from -40C to 85C, says the company.