AN2390 datasheet(14/42 Pages) STMICROELECTRONICS

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Evaluation board implementation

AN2390

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Figure 8.

NTC resistance value indication for Li-ion

Note:

Here Rheat corresponds to 45°C as the temperature limit for Heat Condition and Rcold

corresponds to 0°C as the temperature limit for Cold condition for safe charging for both Li-

ion and NiMH batteries.

2RDET is a dummy condition to detect when no battery is in the slot. This threshold is used to

detect the battery presence for Li-ion battery only. For NiMH we use a different battery

recognition scheme as explained in the following section.

2.2.5

Battery recognition mechanism

In this demo, different techniques are used for Li-ion and NiMH batteries to recognize

whether a battery is present in the evaluation board or not.

Li-ion battery recognition scheme

As explained in the previous section, for Li-Ion batteries, the in-built NTC thermistor is used

to detect battery presence as shown in Figure 8

NiMH battery recognition scheme

In this case, there is no inbuilt NTC in the NiMH as there is in a Li-ion battery. Hence we can

not use the same technique for recognizing a NiMH battery. The NiMH battery recognition

circuit is shown in Figure 9.

Rdet

Rcold

Rheat

No battery present

Cold condition

Battery under normal temperature conditions

Heat condition

AN2390 Datasheet(PDF) 14 Page - STMicroelectronics