We need help with an issue with the L9963T (SPI to isolated SPI transceiver).
Please help find the cause and solution.
PROBLEM DESCRIPTION:
- We use L9963Ts on each side of a communication link between two boards.
- Board 1 sends data to board 2, which responds with data.
- When we power up both boards at the same time, everything works.
- But when we turn on board 2 after board 1, the L9963T on board 2 does not indicate that data is being received (i.e. BNE is not set), even though we can see that board 1 is sending data. Then board 2 does not respond.
HARDWARE CONFIGURATION:
Both boards:
- Slave mode (NSLAVE tied to GND)
- 1MHz SPI clock (SPICLKFREQ tied to GND via 9.09k resistor)
- BNE/CPOL and TXEN/CPHA used as GPIOs
- Transformer-Based insulation as stated in datasheet chapter 4.1 (Application information)
Board #1:
- ISOFREQ, TXAMP tied to GND
- DIS tied to GND via 10k resistor
Board #2:
- ISOFREQ, TXAMP, DIS tied to GND via one 1k resistor
