Power management IC for portable products saves PCB space

The device features a digital thermal control loop in the battery charger that automatically reduces charge current when the demand on the power system exceeds its thermal limits.

One of the challenges of squeezing three relatively high powered blocks into a single small package is that if all three operate concurrently, they can generate more heat than the single package can handle. By integrating AnalogicTech’s digital thermal control loop into the battery charger, the AAT2550 senses when the IC is self-heating and automatically throttles back the battery charge current to decrease the power being dissipated without impacting the buck converters and thus preventing a processor interrupt or system shut-down. Moreover, by determining the highest level of charge current the system can maintain, this feature plays a major role in minimising charge time.

For systems that require charging from either AC or USB sources, AnalogicTech is also introducing the AAT2551 SystemPower IC. Similar to the AAT2550, this device features a 1A charger and two 600mA buck converters. However, the charger in the AAT2551 offers dual-path AC adapter and USB charging. The USB path offers two user-programmable charge currents to support USB low and high charge levels.

The charger in the AAT2551 also adds AnalogicTech’s innovative charge reduction function that automatically reduces charge current only to the extent necessary to preserve the integrity of the USB host voltage. By allowing users to charge the battery with the maximum available current from the USB port while keeping the port voltage regulated, this feature ensures that the battery charger will not overload the USB port even when other system applications share power with the port supply, and that the battery charge time is minimised. The AAT2551 will be available in Q1 2007.

Both the AAT2550 and AAT2551 feature a constant current/constant voltage battery charger with the charge current programmable, via an external resistor, from 100mA to 1A. The charger offers an integrated pass device, reverse blocking protection, high accuracy, digital thermal regulation, charge status and charge termination. It also adds over-voltage, over-current and thermal protection.
To help reduce the size of external components, the two 600mA step-down converters in the AAT2550/51 operate at a 1.4 MHz switching frequency. Both devices operate off a 2.7 to 5.5V input and feature independent input, enable and feedback pins. Each converter consumes just 27µA of no-load quiescent current.

Both the AAT2550 and the AAT2251 are specified over the -40 to +85 degrees C temperature range. The AAT2550 is available in a Pb-free, thermally-enhanced QFN44-24 package, whilst the AAT2551 comes in a Pb-free, thermally-enhanced TQFN44-28 package.