EM Microelectronic claims lowest power solar harvester chip

EM Microelectronic is promoting its EM8500 energy harvester chip, claimed to be the lowest power photovoltaic harvester.

EM8500 low-power solar harvester chip

The Swiss chip company, which has its own fab, is owned by Swatch and has a background in ultra-low power electronics.

Designed to work with small solar cells, the new chip can start up on 300mV (3µW) and operate on 100mV (1µW).

The power figures, it claims, are the lowest in the industry for those voltages, meaning it will work off smaller solar cells than chips from competitors.

However, it will not start-up on, for example, 20mV, which is what Linear Tech’s LTC3107 can do. This would give Linear Tech the edge when working from small thermoelectric generators (TEGs).

That said, EM8500 can work form TEGs as well as photovoltaic cells, and on-chips are two peak power tracking algorithms – one for solar cells and one for TEGs.

These two modes, like other modes in the chip, can be set by programming the built-in eeprom. There are also two control bus options: SPI or I2C.

EM8500 gets its low-power edge from low quiescent current – Jean-Noel Divoux, the firm’s sales manager, was not allowed to tell Electronics Weekly whether the chip uses EM’s famed sub-threshold technology or not.

EM8500 harvesterQuiescent current is 15nA in the lowest power mode, and 125nA with the dc-dc converter running.

One of novel feaure is having two capacitive storage elements – a large one and a small one.

So that operating voltage is reached quickly, input power is initially sent to the small capacitor, and only when that one is charged to the larger one – which can also be a supercap or rechargeable battery.

EM8500 was exhibited at the Wearable Technology Show in London.

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