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ADS7945EVM-PDK: Dual-Channel Sampling

Part Number: ADS7945EVM-PDK
Other Parts Discussed in Thread: ADCPRO, ADS7945


    I am currently working with the ADS7945EVM-PDK trying to measure two signals on the two differential channels of the ADS7945EVM.  I am looking to calculate a phase shift between the two signals.   Is there a way to log data from both channels 'simultaneously' (like alternating samples from the two channels) using the included ADCPro software and corresponding plugin for the ADS794xEVM-PDK.  If not, is there another plugin for the ADCPro software that can?  Thank you in advance.  I am open to any suggestions or alternate ways of gathering phase shift data.

Thanks again, 


  • Hi Russell,

    The ADCPro plug In for the ADS7945EVM only works with one channel at a time.  Unfortunately there is no way to do what you want to do through the evaluation software.  That being said, trying to measure the phase difference between two signals with the ADS7945 may be a little difficult due to the muxed input and single sample/hold circuit.  If the phase difference between your input is always exactly the same, you could potentially back calculate the phase difference taking into account the sample and hold time of the ADC, the mux settling time, etc.  It would be a lot easier to do with a simultaneously sampled multi-channel ADC though.

  • Hey Tom, 

        Thanks for the reply.  I see why the ADC software does not support Dual-Channel sampling now.  Thanks for your advise and help.  I am not using very high-frequencies for the analog inputs (only up to 5KHz), so I will most likely end up coding an external FPGA or MCU to perform SPI communication with the ADS7945EVM without the supplied MMB0 and ADCPro software.  Since my analog inputs have lower frequencies, the latency from the muxed input and single sample hold circuit, should still allow me to sample from both channels at a high enough frequency to avoid aliasing and get a decent signal resolution right? Based on the ADS7945 Datasheet (Fig 77) it looks like I could just toggle the channel select pin every sample, meaning each channel's sampling frequency is half of what it would normally be if I were sampling from the same channel repeatedly.  Is this true?  Could I potentially sample from each channel at around 1MSPS, alternating the channel I am sampling from after each sample, or would the aforementioned latency slow this down even further?  I anticipate only needing a sampling frequency of 50KHz at each channel, where anything faster would be welcomed but not needed.  Is this possible? It seems it is based on what I have read in the datasheets. 

    Thank you in advance,  


  • Hi Russell,

    Yes, you could ping-pong between the channels which would give you (max) 1MSPS/CH. You would need to be sure your inputs are fully settled within the tACQ time shown in Figure 77. You could also sample at a slower rate (50K for example) giving more time for data acquisition (more tACQ time), which could simplify your ADC input a bit as well. Take a look at this link:

    The SAR ADC Input Driver Design video might be of interest to you.