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Setup to measure transient response

S.Satoshi
Guru 21685 points

Hi Team,

I'd like to know the example of test setup to measure the transient response. Specifically, I'd like to know part number of equipment, probing point and consideration to care about and so on. Please let me know if you have some technical document that include such information.

 

Best Regards,

Sonoki / Japan Disty 

  • 0
    TI__Mastermind 35165 points

    Hi Sonoki,

    The tool I use in the lab is one from Venable Instruments but I think there are some other alternatives out there.

    Following is a link to the website. I think they also have some articles you may be interested in.

    http://venable.biz/

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    TI__Mastermind 35165 points

    Sorry, I may have misread the question. The tool I posted is used to measure the loop response by getting a bode plot.

    Are you looking for a way to put a dynamic load on the output to measure the output voltage overshoot and overshoot?

  • 0
    TI__Guru**** 150650 points

    If you have larger current load steps, then an electronic load may be all you can use to create a decent load step.

    For faster edge rate steps, we typically use the load step circuit shown on this EVM: http://www.ti.com/lit/ug/slvu425a/slvu425a.pdf

  • 0 in reply to Chris Glaser
    Guru 21685 points

    Hi Fagnani-san, Chris-san,

    Thank you for your comment. I'd like to know the concrete equipment like electronic load, power supply or oscilloscope which are used when the waveform of transient response in the datasheet was measured.

    And also please give your advice to measure it correctly, for example, probing across nearest ceramic capacitor to device...

     

    Best Regards,

    Sonoki

  • 0 in reply to S.Satoshi
    TI__Guru**** 150650 points

    There is no 'correct' equipment to use.  And each device's D/S is not necessarily measured with the same equipment.

    The type of equipment to use depends on the load transient that you want to achieve.  The most difficult thing to set is the slew rate of the load current.

    Typically, the input supply is buffered with a large capacitance to keep it steady during the load step. This allows testing of the transient response and not line response, etc.

    This app note describes the correct technique to measure the ripple: http://www.ti.com/lit/an/slva494a/slva494a.pdf

    It should be measured right across the output cap nearest the device in order to evaluate the performance of the device.  Usually, we use 20 MHz BW limit on the scope as simply the PCB trace inductance and downstream bus capacitance might filter out signals above that range.  As well, there is usually lots of switching noise that might be picked up as the ripple probe is usually near the inductor.