Linear Tech Adds USB Power Manager & Li-Ion Battery Charger
Linear Technology Corp. introduced the LTC4098, an autonomous high efficiency power manager, ideal diode controller and battery charger for portable USB powered devices such as media players, digital cameras, PDAs, personal navigators and smart phones.
The LTC4098’s switching topology features PowerPath™ control which manages power flow between a wall adapter or USB port and the device’s Li-Ion/Polymer battery while preferentially providing power to the system load. For automotive, Firewire, or other high-voltage applications, the LTC4098 provides Bat-Track™ control of a Linear Tech companion switching regulator up to 38V operating input (60V transient), which the company says maximizes battery charger efficiency, minimizes heat dissipation, and provides for a seamless transition between USB and higher voltage power sources.
The LTC4098 provides an over-voltage protection (OVP) circuit up to 66V on the USB input – requiring only an external NFET/resistor combination – preventing damage caused by accidental application of high voltage. 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 power is always available to VOUT 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 30mΩ or less.
The LTC4098’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 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 housed in an ultra-thin (0.55mm) 20-pin 3 x 4mm QFN package and is guaranteed for operation from -40 to 85°C. 1,000-piece pricing starts at $2.50 each.
