Hi everyone, I am trying to use AD7173-8 in an application where 3 channels are to be used and I am a little confused about that.
What I want to do is to have a consistent way of reading all enabled channels of the ADC. The datasheet says about the DOUT/~RDY pin that goes low to indicate that a conversion has been completed. Up to now, when hooking a 'scope to check logic levels on the SPI lines, I cannot see DOUT/~RDY going low right after an SPI transaction; it remains high and then it goes Hi-Z (green trace is ~CS, yellow trace is DOUT/~RDY):
Has anyone a suggestion to move forward? What exactly should I have to do to switch channels fast enough without losing data?
When multiple channels are enabled, a complete settling time is required for every channel switch. This is to allow the digital filters and modulator to settle when switching channels. Thus, the rate at which data is available (DOUT/RDY pulls low) for multiple channels would be dependent on the corresponding settling time for the output data rate(ODR) set. Please see table 19-21 on the AD7173-8 datasheet for the complete list of settling time. The user must then read the conversion result while the ADC converts the next enabled channel; otherwise, the new conversion result is lost. So, it is really recommended to monitor the DOUT/RDY pin to check if valid conversion is available. Can you stop reading back the conversions and just monitor the DOUT/RDY pin to determine if it is pulsing at the corresponding settling time?