AN2818

Example of USB NiMH charger implementation using the STEVAL-ISB003V1

11/24

3.2.1

Negative temperature coefficient (NTC) resistor selection

Unlike Li-Ion batteries which have an in-built NTC, there is no such internal NTC in NiMH

batteries. Therefore, an external NTC (+/- 5% accuracy) is used in close proximity to the

battery.

3.2.2

Man-machine interface

The charger (ST7FLIT15BY0) periodically checks for the presence of a battery, therefore no

buttons are needed to start or stop charging. The demonstration board has two LEDs that

show the charging status, as mentioned in Section 4.3. A reset button is also included on

the demonstration board to manually reset the application if necessary.