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AMC3311-Q1: AMC33xx powering DCDC

Stas Shamanin
Intellectual 450 points
Part Number: AMC3311-Q1
Other Parts Discussed in Thread: AMC3302, AMC3311

Tool/software:

Hi!

I am designing pretty standard application - 3phase motor driver.

I have 3xAMC331 to measure voltage and 3xAMC3302 to measure current.

I guess AMC33xx have pretty the same internals with just different gain over delta-sigma.

I have pretty clean, but still buck-output 5V to power digital nets and 3v3 with low-noise/high PSRR LDO to power analog electronics (sensors, opamps, adc, dacs).

What is bothering me - high consumption on DCDC integrated in  AMC33xx.

If I power all together it requires more than 600mA for 3v3 analog in my application and I am forced to use higher noise LDO because of power

Also DCDC consumption is pulsed, that I think may create extra problems for noise in 3v3 analog.

I am thinking to power VDD with 5v0 I have, or maybe take extra LDO just for AMC33xx.

Also I see there is LDO (low side). Is delta-sigma + filters in AMC33xx powered by this ldo?

Because if it is powered by dedicated LDO I think I can apply 5v0 with more confidence that my output signal will be pretty nice.

Thanks!

Stas

  • 0
    TI__Expert 8455 points

    Hi Stas,

    Thank you for your questions. Based on what you have described so far, drawing over 600mA for this application seems high. Either 3.3V or 5V on VDD should be fine. 

    AMC3302: 

    AMC3311: 

    Note these figures are based on VDD=3.3V. 

    Would I be able to see your schematic to get a better understanding of your setup please? Then I can better advise, thank you.

    Best regards,
    Eva

  • 0 in reply to Eva Mason
    Intellectual 450 points

    Yes I have 4x both and also my analog op-amp circuits as integrating/filtering may consume 150mA.

    So 42x4 +49x4 up to 360mA.

    I also use 3xTMCS1133 - I want to compare performance to AMC.

    So current consumption breaks 500mA.

    So I think I will power AMC from regular 5V.

    Or powering them throw dedicated 3v3 ldo may improve SNR? I guess not too much.

  • 0 in reply to Stas Shamanin
    TI__Expert 8455 points

    Hi Stas,

    Are you seeing 500mA or 600mA on your setup? Does this include the 3xTMCS1133? 360mA is assuming the maximum current draw. You can try the 5V source instead and see if this reduces the power consumption. I would need to see the schematic to suggest something more specific. Thank you.

    Best regards,

    Eva