I have one ad7768-4 evm and trying to disable the precharge buffer. I have two differential input right now and I cannot turn off all of the precharge buffer. May I know how I can make the setup?
The PreQ buffers operate slightly differently in that the writes to these two registers are inverted. So for example if Ch0 and Ch1 PreQ buffers are all on, to turn Ch0 off I must write 0x03 to the Precharge Buffer 1 register.
If Ch0 and Ch1 PreQ buffers are all off, to turn Ch0 on I must write 0x0C to the Precharge Buffer 1 register. The register will read back as normal.
(Changing individual bits won't work in the program due to the fact the SPI write must be 8 bits long)
This is detailed in the evaluation board user guide. See figure 22.
Hopefully this helps.