Hi,
I'm using LTC2862 in an RS485 interface with a Ti-MSPM0G3507 MCU.
The connections are as follows:
| DI | MCU - PA0 |
| RO | MCU - PA1 |
| RE/DE | MCU GPIO |
Issue:
MCU pin PA0 becomes non-functional after repeated power cycles, it does not toggle even when configured as GPIO. This has occurred twice in two different boards. Other MCU pins continue to function normally. Electrical continuity between PA0 and the LTC2862 DI pin is there. The MCU and LTC2862 share the same power-up sequence, with all rails coming up simultaneously.
Some more information that might help,
According to the MSPM0G3507 datasheet, PA0 and PA1 are 5-V tolerant, open-drain capable GPIOs with wake-up capability from SHUTDOWN. The same firmware operates correctly on another board where UART functionality is mapped to PA25&PA26, with no pin failures observed. In the current design, there are no external pull-up or pull-down resistors and no series resistors on the LTC2862 DI pin
Question:
Are there any known pwr up, sequencing, or input protection considerations for the LTC2862 DI pin when it is connected directly to MCU GPIOs, particularly wakeup capable pins? Additionally, are there any recommended series resistors or protection components for DI in such use cases?
Thank you.
