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Using ADA4528 as current monitor circuit

Seleron
on Aug 17, 2020

Hi.

Can I use ADA4528 as current monitor circuit or is there a better choice?

Here's a deal.

I wanted to use the ADA4522 (Figure 84 in datasheet), but it has a minimum power supply threshold of 4.5 V. My ADC can handle a maximum of 3 volts.

So I find quite similar OpAmp with 2.5-5.5V power supply voltage - ADA4528.

Сan 4528 be used in the same scheme as 4522?

(Parameters: Rs=10 mOhm, max load less than 5 Amps, R1,R3=1k, R2,R4=50k, so Gain is 50, up to 2.5V to ADC)

  • +1
    •  Analog Employees 
    on Aug 18, 2020 8:21 AM 3 months ago

    Hi Seleron,

    The ADA4528 would be a better choice for this application, since it has a much lower offset voltage and noise voltage density to allow higher precision.

    You have to keep in mind that the ADA4528 has a lower chopping frequency of 200KHz vs the 800KHz chopping frequency of the ADA4522. You've mentioned that you're targeting a gain of 50, now by using the ADA4528 (GBW = 3MHz) your bandwidth of operation would be around 60KHz. Although a 60KHz bandwidth is modest enough to remove the switching artifact from the 200KHz chopping frequency, it would still be a good idea to design your amplifier with a gain such that your bandwidth of operation is under 1 decade of the chopping frequency. So for a 200KHz chopping frequency, a 20KHz bandwith would be a better choice.

    Lastly, if your designed isn't constrained on supply current, I suggest you lower your input resistors (R1 and R3) to a value below 1K. This is to preserved the low noise characteristic of the chip.

    Thanks,

    Donnie