CES: Energy harvester optimised for small solar cells

A cold start is possible from an input voltage as low as 275mV if 5µW of power is available.

There are two versions, which optimise loading of the photovoltaic source in two different ways to get the best out of different solar cells:

AEM00920 regulates the photovoltaic terminal voltage to a fixed value, permanently programmed by the PCB to one of 32 values between 250mV and 3.2V using five IC pads.

AEM10920 regulates the loaded photovoltaic terminal voltage to a fixed fraction of its open-circuit value – the latter of which is measured periodically by briefly unloading the solar cell. Eight fraction values between 35% and 90% are programmed using three IC pads, and a further two pads allow the period between open-circuit measurements to be programmed (15 or 25s*) and set the measurement’s duration (250 or 500ms*).

Both ICs have a boost converter (diagram left) that lifts the voltage at the solar cell up to a voltage suitable for a storage element – a battery or supercapacitor.

Separately, a 5V input is also available to charge the storage element.

Two configuration pins set limits on the storage element terminal voltage, with settings for a: Li-ion super-capacitor, Li-ion battery or Li-Po battery. A fourth setting is for a Li-ion battery, but with thresholds altered to increase battery life considerably.

An integrated buck converter takes stored energy and delivers it to the device’s output at 2.2, 2.5 or 2.8V at up to 135mA – ‘off’ is another setting.

Both dc-dc converters can operate above 90%.

For transport and storage, a shipping mode pad is available to shut the IC down completely.

Packaging is 4 x 4mm 24pad QFN.

The fixed input voltage AEM00920 is sampling now, while input-voltage tracking AEM10920 will come later in January 2024.

The AEM00920/10920 product page can be found here

*data sheet figures, e-peas has been asked to confirm.