UC-08-M31 EN P1.0.3 Power Supply 9
3.3 Backup Power Supply
When using the hot start function of UM982, you need to provide backup power for the
module.
The input range of V_BCKP is 2.0 V to 3.6 V.
Figure 3-5 Backup Power Circuit
Figure 3-6 Backup Power Circuit on the Bottom of UM982-EB
Note:
The power supply for V_BCKP can be provided by the backup battery. The circuit that
charges the backup battery should be designed to prevent reverse current to ensure that
the battery only supplies power to V_BCKP and the current does not flow back into the
3.3 V power domain, as the D64 shows in Figure 3-5.
According to the maximum charging current of the battery, a current-limiting resistor
should be added, as the R86 shows in Figure 3-5.
V_BCKP can also be powered through the test point TP10. Removing R86, connecting a
power supply wire at TP10 and a ground wire at TP7, you can use an external power to
supply V_BCKP. This method can be used to measure the supply voltage and current of
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