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DRV425EVM: Output ringing

Jason Silver
Prodigy 75 points
Part Number: DRV425EVM
Other Parts Discussed in Thread: DRV425

We are evaluating the DRV425 fluxgate IC using the DRV425EVM evaluation module, and are seeing a substantial amount of ringing on VOUT. Please see the attached (YELLOW is Vout, Blue is Vref). The only loading is the scope probe.

It seems like there is a periodic disturbance to the diff amp at ~500kHz (the chopper clock, perhaps?), which excites ringing in the 2-3MHz range, which is in line with the diff amp bandwidth. 

I assume this behavior is not expected. Any insight here is greatly appreciated!

  • 0
    TI__Mastermind 32290 points

    Hello Jason,

    This is actually the frequency of the flux-gate excitation.  The bandwidth of the is device is below 47kHz so placing a low pass filter at the output should do the trick.  If you are measuring with respect the the reference you should also see some improvements.  Please keep in mind the noise density will be your biggest challenge if trying to measure accurate field at higher frequency. 

    If you are using the full 47KHz bandwidth you can expect about 1.5uT Peak to Peak noise.