IoT power eval board stands-by for years

Called REFLVBMS001-EVK-001, it measures 56 x 32 x 1.6mm and the components, including the battery, stand a maximum of 1mm above the PCB.

It can accept power at 4.5 to 5.5V, and outputs up to 500mA at one of nine regulated voltages between 1.2 and 3.3V.

The store is one of NGK’s novel lithium-ion ‘EnerCera’ cells (see table below), the 0.45mm thick 27mAh EC382704P-C, which has a nominal 3.8V terminal voltage.

As the total stand-by current of the circuit is 450nA, said Rohm, it predicts the circuit could sit for 2,500 days before the battery was flat – nearly seven years.

The ICs are all from Rohm: BD71631QWZ linear charger, BD70522GUL step-down dc-dc converter and BD5230NVX reset chip – the latter used to prevent over-discharge of the cell.

Restricted by the included cell, it can be charged at ambients from 0 to +45°C and discharged across -20 to +45°C.

The charge chip does have an input for connecting an thermistor to qualify charge and discharge with the cell temperature, but this is not implemented on the board.

To change energy store attributes, three other rechargeable cells can be used (see table below) – including one that will charge and discharge over -40 to +70°C, but this has a 2.7V nominal voltage and would need other circuit changes.

*installed

The eval kit is featured on the dc-dc converter product page (scroll down), and there is an informative video