TPS7A02: Reverse current protection of LDO and Battery

Wuup

Part Number: TPS7A02

Tool/software:

I have a circuit that is battery powered (3.6V lithium), uses an LDO(TPS7A0230PDQNR) to get a stable voltage and then a nrf52840, where we use the NFC peripheral. In the MCU spec there is the following note:

nRF52840 Product Spec v1.11 [p. 416]
6.14.11 Battery protection
If the antenna is exposed to a strong NFC field, current may flow in the opposite direction on the supply due to parasitic diodes and ESD structures. If the battery used does not tolerate return current, a series diode must be placed between the battery and the device in order to protect the battery.

In Ti Tech Article SSZT658, I want to use protection method shown in figure 4. (Reverse Current Prevention Using a Diode before the LDO) but I have trouble understanding how it will protect the LDO against backward current?

6 months ago

+1 Vahnroy Hosear 6 months ago

TI__Expert 4891 points

Hey

I understand the confusion. The key part of the LDO we need to protect from reverse current is its internal transistor. When a reverse current-condition occurs, having the diode in front of the input ensure it becomes reverse-biased and stops current from flowing back into the supply. If the diode were placed on the output side instead, the internal transistor would still have a direct path to the supply, leaving it exposed to reverse current.