1 Reply Latest reply on Dec 9, 2018 7:52 AM by sujoybha_3178756

    PSOC5, Delta Signa ADC with Analog Mux - Adjacent channel leakage.

    sujoybha_3178756

      I am trying to multiplex 8 differential channels into a Delta sigma ADC (17 bit) in a PSOC-5 059 kit. The ADC is in Multi-Sample Turbo mode at a clock freq of 3 MHz and 6300 samples per second. The input to the ADC is through an Analog Mux.

       

      Presently only Channel 2 has voltage (3.2V) but the issue is that Channel 3 also reads about 2.5V while the lead is connected to ground with the ADC buffer bypassed.

       

      With buffer active, all 8 channels read voltages, some more than 3.2 V.

       

      I have tried Analog Mux, Analog Sequencer Mux and Analog Hardware mux but I have seen no improvement in the results. Only way to improve results seems to be to add a delay between ADC_StopConvert() and ADC_StartConvert() but while the ADC finishes conversion in less than 160us while the channels seem to be isolated only with a delay of more than 1ms between conversions. This seems to defeat the entire point of the system.

       

      Analog mux was used in maximum isolation mode.

       

      All the analog inputs are tied to ground via a 4.7k resistor and a 100nF cap in parallel.

       

      Is there anyway that I can ensure faster switching of the signals or is there any standard delay involved for the Mux?