User manual

LPC4357 Developer’s Kit - User’s Guide

Page 21

4.9 SP6: VBAT/ALARM Handling

The board can power the VBAT input supply (to the OEM board) from two different sources:

 The +3.3V power supply, via D1 (when board is normally powered).

 A 3V Lithium CR1025 size coin battery, via D2. Note that battery is not included.

See the LPC4357 datasheet for details about VBAT voltage range.

The ALARM signal control LED21. Note that LED21 will consume a lot of current from the battery

and/or super-capacitor. Restrict on/high time to preserve energy.

Figure 10 – VBAT and ALARM circuit

ALARM-LED

LED21

Battery Holder

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