LTM2892 3-wire SPI use

Hi Jianjia,

If by 3-wire we mean not making use of the MISO channel, that is certainly possibly. Just tie the input high/low or repurpose it as another reverse channel. 

Regards,

Jason

Hi Jason

I'm sorry, the explanation was insufficient.
For example, the SPI communication of the AD9634 is SCLK, SDIO, and CSB. Can this device be used for isolated LTM2892 SPI communication?

Regards

Hi Jianjia,

Understood. Thanks for the clarification. So this is half duplex scenario where a bidirectional data channel is needed. 

The problem is we cannot simply connect an input and output from the LTM2892-S to the SDIO pin. The LTM2892 does not have any ability to recognize which direction the SDIO data is moving, so there would be contention between the isolator output and the SDIO channel when it was being driven.

I have not worked through an example like this before and I don't have an immediate eloquent solution. My first attempt would be to reduce the drive strength of the isolators output channels. The intention would be that the SPI master and slave would have the dominant drive strength when transmitting, and SDIO would go HiZ when expecting to receive data.

This would be my first attempt at inserting an isolator into the signal chain.

Regards,

Jason

It is possible just LTM2892 should be connected using 3 wire spi by SDIO pull down resistor