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ADA4522-4 in a severe EMC environment

I have an EMC client using chains of ADA4522 op amps. The input sweeps from 20 KHz to 300 KHz. Sometimes the outputs become slew rate limited. I am concerned the ADA4522 is susceptible to large signal triangle waveform harmonic products causing aliasing within the signal sampling system of the op amp. The following text is on page 22 of 33 of the datasheet: The EMI filter is composed of two 200 Ω input series resistors (RS1 and RS2), two common-mode capacitors (CCM1 and CCM2), and a differential capacitor (CDM). These RC networks set the −3 dB low-pass cutoff frequencies at 50 MHz for common mode signals, and at 33 MHz for differential signals. The ADA4522 internal input and output sampling rate is at 4.8 MHz. If I’m right, at specific frequencies related to the 4.8 MHz sampling rate the distortion will reinforce until there is a loss of the input signal.  Please let me know what you think.

  • Hi Joanna,

    Yes, you're correct that there will be some distortion when your input signal becomes too close to the chopping frequency of 4.8MHz. In addition, the ADA4522 employs a ripple and offset correction loop that operates at 800KHz, so you also need to keep your input signal below this frequency to avoid any distortion on your input signal.

    Let me know if this helps!

    Thanks,

    Donnie