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AMC1350-Q1: AMC1350 output RC filter and stability

frederic_c
Prodigy 210 points
Part Number: AMC1350-Q1
Other Parts Discussed in Thread: AMC1350, , TINA-TI

Hello,

I am planning to connect a RC filter on the output of AMC1350.

The spec says that if R=0 the max. "OUTP to OUTN" cap is 250pF.

How can I determined the maximum capacitor with higher resistors (e.g. R = 100 or 1k) ?

Thanks

  • 0
    TI__Guru**** 169105 points

    Hi Frederic,

    I'm not seeing what you are referring to where the 'spec says that if R=0 the max. "OUTP to OUTN" cap is 250pF'.  We do have a max capacitive load of 250pF between OUTp and OUTn shown in section 6.3 (page 4, AMC1350-Q1 datasheet).  This is just a limitation of the device's ability to drive a capacitive load.  Once there are series resistors in place, your 100 ohm for example, you should be able to have capacitor values well into the 100s of nano farad range.  The limitations would fall on the rest of the signal chain after the isolation amplifier more so than the AMC1350 itself.  What are you driving downstream from the AMC1350?

  • 0 in reply to Tom Hendrick
    Prodigy 210 points

    Hello Tom,

    About" Once there are series resistors in place, your 100 ohm for example, you should be able to have capacitor values well into the 100s of nano farad range."

    How can I be sure that for example R=100ohm + C=100nF will not be an issue (stability) for AMC1350?

    Thanks,

    Frederic

  • +1 in reply to frederic_c
    TI__Guru**** 169105 points

    Hi Frederic,

    We have PSpice for TI and TINA-TI models that you can use to simulate the output of the AMC1350 with those values of RC components.  The models are located here: https://www.ti.com/product/AMC1350#design-tools-simulation

  • 0 in reply to Tom Hendrick
    Prodigy 210 points

    Hello Tom,

    Thanks. I wasn't sure the spice model was good enough to check the stability with a capacitive load.

    I will simulate this using pspice.

    Most amplifiers have a chart for "capacitive load stability" that provides R vs C limits. It would be nice to include this in spec in the future.

    Thanks,

    Frederic

  • 0 in reply to frederic_c
    TI__Guru**** 169105 points

    Thank you for the comment, we'll consider adding a similar table.