October 26, 2023 Subject: Identification and Schematic Retrieval for Component/Module LAC781P
The schematic top shows no internal reverse polarity protection. If you connect input voltage backwards, the parasitic body diode of the pass transistor will conduct, destroying the regulator. Always add a series protection diode on the input. lac781p schematic top
Confirm 3.3V is present at the RTC battery connector. If missing, the 3V/5V regulator IC ( RT8243 ) may be damaged. lac781p schematic top