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TMS320F280049: external R & C for fast ADC sampling

kim hui too
Prodigy 10 points

Part Number: TMS320F280049
Other Parts Discussed in Thread: THS4031

Currently the SW setting of ACQPS is 14 and system clock is 10ns. Hence the acquisition time (S+H) is 150ns.

Could you advise the external R and C value to achieve good ADC accuracy?

Thanks!

  • 0
    TI__Guru 60865 points

    Hi Kim,

    If you have a blank slate a good starting point would be THS4031 in a voltage-follower configuration, Cs = 270pF, Rs = 33ohm.  This gives a settling time of:

    Tau = (33 + 500)*12.5p + 33*(270p + 13.7p) = 16ns

    k = 6.6

    Settling time = k*Tau = 16ns * 6.6 = 106ns. 

    So set ACQPS = 10 = 110ns S+H

    This should give close to the best possible performance.