New micro PMIC targets Li-Ion battery based mobile applications

May 09, 2011 // By Paul Buckley
austriamicrosystems has introduced a highly integrated power management integrated circuit (PMIC) designed specifically for portable devices powered by a single-cell Li-Ion battery. The AS3605 integrates seven low dropout regulators (LDOs), a DC/DC converter, a complete battery charger, LED backlight driver and an audio power amplifier on one die.

The features and performance of the cost-efficient AS3605 Micro PMIC allow it to be used in many portable devices powered by one Li-Ion battery such as high-end blood glucose meters, high-end remote controls, GPS equipment, mobile meters, e-dictionaries and entry level mobile phones. It can be used for any entry level mobile phone handset standard, including CDMA, WCDMA, GSM, GPRS, EDGE, UTMS and other American and Japanese standards.

The seven high-performance programmable LDOs feature low noise – typically 30 μV RMS from 100 Hz to 100 kHz -- as well as line/load regulation < 1 mV static, < 10 mV transient, and power supply rejection less than 70 dB @ 1 kHz. The integrated step-down DC/DC converter requires no external Schottky diode yet provides very high efficiency (up to 95%) throughout the whole operating range.

The DC/DC converter’s 2.2 MHz switching frequency saves PCB space by enabling the use of a tiny, low-profile inductor. In addition, a 60 mA 5 V charge pump together with five programmable current sinks is included to supply LEDs for backlighting the display. The on-chip low-distortion audio power amplifier provides 1 W at 8Ω for speaker-phone operation, Hi-Fi ringtones or other audio uses. The AS3605 Micro PMIC also features a battery charger for Li-Ion batteries, including the charging algorithms for automatic trickle charging, programmable constant voltage and constant current charging.

Processor and memory power supplies must follow precise start-up sequences to prevent serious damage. Therefore it is critical that the voltages are switched on and off in the correct order. Compared to a discrete solution consisting of a collection of standalone DC/DC converters, LDOs and chargers, the task is greatly simplified with the AS3605. With its software-programmable start-up sequences, the AS3605 brings new flexibility to the market for Micro PMICs. Other competitors offer PMICs with fixed start-up sequences that must be selected with external resistors.

The AS3605’s output voltage and the timing of all regulators