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ADS8881: synchronisation of 10 ADS8881 for simultaneous conversion

Part Number: ADS8881
Other Parts Discussed in Thread: SN74LVC1T45


What is the recommended solution to drive 10 CONVST signals to get synchronous conversion on the 10 channels if I have 10 ADS8881?



  • Hello Yves,

    The input capacitance of the ADS8881 CONVST pin is less than 1pF.  You will likely have much more board capacitance than the ADC input pin.  The maximum frequency is 1MHz for CONVST, so it is not a very fast signal.

    Most FPGA IO pins can easily drive this level, but if you have longer board traces times 10 CONVST pins, an additional buffer may be helpful.  If each of the ADC's are located on separate daughter cards, then you may need to buffer the signal for each board.

    If the ADC's are close to each other and the processor(FPGA) IO pin, then you can probably directly connect all pins together.  If you have quite a bit of distance between ADC's, then an external buffer would be helpful.  Something like SN74LVC1T45 would be an option.  It has specifications with up to 30pF of load capacitance.