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Query based on SLAA554 – August 2012 and paper titled Start with the right op-amp when driving SAR ADCs

Nandakumar Ramaswamy
Prodigy 20 points


1. Refer Fig 1 and Fig 3 in SLAA554. Does it mean that till we give CONVST_x signal, the switch S1 is closed. The moment CONVST_x is given the switch S1 is open?

2. If answer to question 1 is 'yes', CSH will definitely be tracking CFLT as it is 20 to 60 times smaller and comes with a low series resistor

3. If answer to question 1 is 'no', I am unable to understand how CSH will get charged to CFLT voltage within the 280 ns specification as the time constant involved will be increased by CFLT.

Kindly clarify

Nandakumar

  • 0
    TI__Mastermind 46235 points

    Hi Nandakumar,

    When the CONVST signal is available,the S1 will be open and start conversion,when the conversion is finished(BUSY to low),the S1 will be closed and start the acquisition for next conversion,so yes.

    Best regards

    Dale Li