I see that ADI's AD7656YSTZ converter is functional and pin compatible to TI's ADS8556IPM.
I already have a design based on ADS8556. Are there any specific precautions to take in order to replace the TI part with AD7656?
When designing the AD7656 please follow the decoupling requirements as outlined in the datasheet. We also have the AD7656-1 which is pin compatible to the AD7656 but has a reduced decoupling requirement compared to the AD7656. Please check figure 28 on page 22 of the AD7656-1 datasheet for the typical connection diagram. Here are other considerations in operating the part:
1. In all modes, the parts should receive a RESET pulse after power-up.
2. If the CONVST pin is held low during the RESET pulse, then after the RESET pulse, the AD7656-1 needs to receive a complete CONVST pulse to initiate the first conversion.