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TPS65185 and kick-back VCOM voltage measurement

Dmitry Zakharov
Prodigy 10 points

We're trying to implement kick-back voltage measurement procedure for our e-reader device. Could you please clarify some questions:

1) documentation says that we should use null waveform for this procedure. We didn't found any information about null waveform. Is this just an empty frame sequence, or something else?

2) how long time should we apply waveform to get accurate result?

3) should we start measurement while waveform is active, or some time after waveform is complete?

Thank you!

  • 0
    TI__Prodigy 730 points

    Hello,

    1) The null waveform can be obtained from the e-paper company. It is a blank waveform that they use for testing and calibration. 

    2) Depending on the capacitance that is at the VCOM node it can be as high as 60 seconds until the VCOM node stabilizes enough for accurate measurement. The leakage current of the panel is low enough that it takes a significant amount of time to charge the bulk capacitors in a system. Without added capacitors the time is a few seconds for reliable results. 

    3) Usually you would apply the waveform for a specified amount of time (enough time for the voltage to stablize) and then make a measurement.