144nA buck converter for energy harvesting

February 12, 2018 // By Nick Flaherty
Ricoh Electronic Devices has launched a buck DC-DC converter with a quiescenet current of 144nA for energy harvesting devices which are able to collect and store energy obtained from sources such as solar or vibration energy.

Currents generated by energy harvesting in application such as wearables for sports and healthcare, wireless sensors and IoT devices.can be very low, so a low quiescent current is essential for DC-DC converters. 

The R1800 collects energy generated from a photovoltaic or vibration energy harvester cell and stores it in a super capacitor or rechargeable battery. The 144 nA current allows the converter to be used in a low-illumination environment and when the generated level of energy is moderate. The input voltage range is 2.0 V to 5.5 V, with an output of 2.0 V to 4.5 V ±3.0% witha 2mA putput current and 92% peak efficiency.

As soon as there is sufficient energy available on the input side, the buck converter is enabled to transfer energy from input to output. During this phase the transferred energy is stored in a super capacitor or battery on the output until the energy left on the input drops below a threshold. The converter is then disabled and the energy will be collected on the input. This process repeats and increases the energy level in the capacitor or battery until the required output voltage is reached.

A reverse current protection circuit prevents that a current flow will occur from output to input as soon the energy harvesting cell does not provide energy, the circuit is triggered when the input voltage drops below the output voltage.

The R1800 is available in a DFN(PLP)2730-12 package.