4mm² power management solution targets wearables

23rd March 2015

Nat Bowers

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ams has introduced an integrated power management unit with an especially small footprint for use in wearables and other space-constrained devices. The AS3701 micro-PMIC with low quiescent current implements multiple power-regulation, power-saving, battery-charging, protection and start-up functions in a WL-CSP measuring just 2x2x0.4mm.

Power system designers using the AS3701 will be able to realise space savings and provide advanced power management functionality 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 rails include two 200mA LDOs, a 500mA step-down DC/DC converter and two 40mA (maximum) programmable current sinks. The synchronous step-down (buck) converter, which switches at high frequencies up to 4MHz, only requires a small inductor and a 10µF output capacitor.

The micro-PMIC’s integrated li-ion battery charger can operate in trickle-charge, constant current and constant voltage modes and supplies a maximum charging current of 500mA. 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.

Many designs will use the AS3701's I²C interface to enable configuration by a host processor or MCU. But 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 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, simplifying the development process and consolidating inventory. Integrated battery temperature monitoring, power-on reset and over-current protection help to ensure reliable and safe operation.

Bernd Krafthoefer, Product Marketing Manager, ams, comments: "The AS3701 draws on many years of experience at ams in the design and fabrication of very small and efficient power circuits. It represents the state of the art today in power circuit miniaturisation, providing a foundation for compact wearable devices that offer long battery life."

The AS3701 micro-PMIC is available now in production volumes, priced at $0.82 each in 1,000 unit orders. An evaluation board for the AS3701 is also available.