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UC-08-M32 EN R1.0 Power Supply 9
3.3 Backup Power Supply
When using the hot start function of UM980, you need to provide backup power for the
module.
The input range of V_BCKP is 2.0 V to 3.6 V.
BT1
MS621T-FL11E
Figure 3-5 Backup Power Circuit
Figure 3-6 Backup Power Circuit on the Bottom of UM980eb
Notes:
When the backup battery supplies power to V_BCKP, the battery charging circuit 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 D52
shows in Figure 3-5.
According to the maximum charging current of the battery, a current-limiting resistor
should be added, as the R84 shows in Figure 3-5.
V_BCKP can also be powered through the test point TP9. Removing R85, connecting a
power supply wire at TP9 and a ground wire at TP6, you can use an external power to
supply V_BCKP. This method can be used to measure the supply voltage and current of