UT986eb User Manual
UC-08-M37 EN R1.0
Power Supply
9
3.3
Backup Power Supply
When using the hot start function of the module UT986, you need to provide backup power
for the module.
The input range of V_BCKP is 2.0 V to 3.6 V.
V_BCKP
BT1
MS621T-FL11E
MS621T-FL11E
Nominal Voltage:3V
Nominal Capacity:3.0mAh
Figure 3-5 Backup Power Circuit
Figure 3-6 Backup Power Circuit on the Bottom of EB
Note
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 D29 shows in Figure 3-5.
According to the maximum charging current of the battery, a current-limiting
resistor should be added, as the R41 shows in Figure 3-5.
V_BCKP can also be powered through the test point TP7. Removing R42,
connecting a power supply wire at TP7 and a ground wire at TP4, you can use an
external power to supply V_BCKP. This method can be used to measure the supply