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Application Note 222 Using the DS2770 as a 3-Cell NiMH Charger

INTRODUCTION
In order to achieve maximum efficiency when charging a battery, it is necessary to implement charging techniques geared specifically for a battery cell chemistry. For example, negative V or dT/dt termination criteria is used for NiMH cells, while a CC/CV or pulsed-charged technique is appropriate for rechargeable lithium cells. The DS2770 battery monitor and charge controller can be configured to charge either NiMH or Li+ cells. This application note addresses several key things to consider when using the DS2770 to charge a NiMH battery pack.

NiMH CHARGING BASICS
A NiMH cell has a nominal voltage of 1.2V. Therefore, stacking three NiMH cells together results in a battery pack with a nominal volt