Hi all,
I'm faced with some unpredictible behaviour of the ADUM3154BRSZ-RL7 chip. I'm using this chip for the isolation between temperature measurement ADCs and MCU. SPI bus has 3 MHz SCK. Glitch on MISO line when the initial state was "low" (blue channel on the photos below) from SCK line (violet channel) latched the MISO signal to "high" on the output of ADuM IC (green channel). The same glitch for the initial state "high" changed the output state but then it is returned to "high".
https://drive.google.com/file/d/1lxLqebOQR37RPP3ROwRzIFK1sPym-6z0/view?usp=sharing
https://drive.google.com/file/d/1lxBCevz923YtjChjBkNxHPDWQ_DH3z4W/view?usp=sharing
So, as you can see, in such cases MISO signal from Thermocouple IC to ADuM and from ADuM to MCU are different. Is it correct for ADuM chip and what can I do? I know, that right now termination of SPI is not perfect, but anyway, such behaviour of ADUM chip is not as described in the datasheet.