Power management IC targets wearables

March 23, 2015 // By Graham Prophet
The company ams employs a 4 mm² package for an integrated power management solution aimed at wearable devices; the AS3701 micro-PMIC includes battery charger circuit, multiple power rails, protection features and I²C interface

With an especially small footprint for use in wearables and other space-constrained devices, AS3701 is a micro-PMIC (power management IC) with a low quiescent current, that implements multiple power-regulation, power-saving, battery-charging, protection and start-up functions in a chip-scale package (WL-CSP) measuring 2 x 2 x 0.4 mm. Power system designers using the AS3701 will be able to realise space savings and provide advanced power management functions in products supplied by a single lithium-ion cell, such as smart watches, sport bands, wearable medical devices, handheld GPS units and mobile phones.

The AS3701’s multiple power rail sources include two 200 mA LDOs, a 500 mA step-down DC-DC converter and two 40 mA (maximum) programmable current sinks. The synchronous step-down (buck) converter, which switches at high frequencies up to 4 MHz, only requires a small inductor and a 10 µF output capacitor. The micro-PMIC’s integrated li-ion battery charger can operate in trickle-charge, constant current or constant voltage modes and supplies a maximum charging current of 500 mA. Its power path management allows a device to start up with a dead battery, and optimises power distribution between the battery charging circuit and the system power supply when plugged in to the mains.

Designs can use the AS3701’s I²C interface to enable configuration by a host processor or microcontroller. The device also includes multi-purpose I/Os for wake-up/power-down inputs, PWM inputs and outputs, interrupts and control tasks when operating in stand-alone mode.

A one-time programmable (OTP) boot sequence gives designers the flexibility to adapt the micro-PMIC’s start-up operation for different applications and processors. This allows OEMs to use the same power solution in multiple end-product designs. Integrated battery temperature monitoring, power-on reset and over-current protection help to ensure reliable and safe operation.

AS3701 micro-PMIC is priced at $0.82 (1,000). An evaluation board for the AS3701 is available online from ams.

ams; www.ams.com/PMIC/AS3701