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IC with Li-Ion battery charger suits portable devices

Linear Technology Corp. announces the LTC4155, a high power, high efficiency PowerPath manager, ideal diode controller, and lithium-ion battery charger for single-cell portable devices. Examples of such devices include tablet PCs, ultra-mobile PCs (UMPCs), personal video players, smart phones, digital cameras, PDAs, portable medical devices, portable industrial devices, and personal navigation devices.

The IC is designed to transfer up to 15 W from a wide range of sources while minimizing power dissipation and easing thermal budgeting limits. The new IC's switching PowerPath topology manages power distribution from two input sources (such as a wall adapter and USB port) to the device’s rechargeable lithium-ion battery while also providing power to the system load when input power is limited.

Because it is designed to conserve power, the LTC4155 allows the output load current to exceed the current drawn by the input supply, which maximizes use of available power for battery charging without exceeding the input supply power delivery specifications. As an example, when powered from a 5V/2A wall adapter, the IC’s switching regulator transfers more than 90% of the available 10 W, thereby enabling up to 2.4 A charge current and leading to faster charge times. Unlike traditional switching battery chargers, the LTC4155 features instant-on operation to ensure that system power is available at plug-in even with a deeply discharged battery.

A basic 2-wire I2C port offers adjustability for many of the system control parameters including charge current, input current, and float voltage. In addition, the communications bus allows the LTC4155 to provide status information such as battery temperature, input supply status, charger status, and fault status.

The IC's autonomous single-cell Li-Ion/Polymer battery charger handles up to 3.5 A charge current and features four float voltage settings and 15 charge current settings. For an improved safety margin, an optional integrated over-temperature battery conditioning circuit can reduce battery voltage in case both high battery temperature and high battery voltage occur at the same time. What's more, the charger includes automatic recharge, bad cell detection, trickle charge, programmable safety timer, thermistor temperature qualified charging, programmable end-of-charge indication/termination, and programmable interrupt generation.

The LTC4155’s dual input, priority multiplexing overvoltage protection (OVP) circuit prevents damage from accidental application of high voltage. And, the ideal diode controller guarantees that plenty of power is always available to VOUT even if input power is insufficient or absent. To minimize battery drain when a device is connected to a suspended USB port, an LDO from VBUS to VOUT provides the allowable USB to suspend current to the application. To eliminate battery drain between manufacture and sale, a ship-and-store feature reduces the already low battery standby current to nearly zero.

The LTC4155 is housed in a low profile (0.75 mm) 28-pin 4 x 5 mm QFN package and is guaranteed for operation from -40° to 85° C.

For more information, contact Linear Technology Corp., 1630 McCarthy Blvd., Milpitas, CA 95035. Phone: (408) 432-1900.

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