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TPS7A57: Noise Injection

Harrison Le
Prodigy 20 points
Part Number: TPS7A57

Tool/software:

Hi - I've got an odd question.
I am currently attempting to characterize our IC and trying to push it to failure.
We currently have it powered by the TPS7A57 - I would like to somehow create noise on the output (which goes to the input of the IC) in order to stress it.
My idea is as follows - 
- have a noise source of some sort, probably a function generator and some sort of transformer to step up voltage, and pass that through a capacitor to the input of the LDO (adding noise to what the LDO sees) or to the output of the LDO (adding noise to what the IC sees - which is preferable)
Analog design is not my forte - so I would like to ask for some help in modifying the existing TPS7A57 circuitry to see what I can do.
I assume that noise injection on the output is preferable, as to not possibly have the LDO filter anything.
Is there a preferred or proven method that TI has used - either on the input or the output?
Thank you for your time!
  • 0
    TI__Prodigy 40 points

    Hi Harrison,

    We do not have a standardized method of injecting noise to a system as that is dependent on the application needs.

    For this case, it is dependent on the frequency of noise that you would like to inject. For low frequency noise (roughly less than 1MHz) I would inject the noise from your function generator into the NR/SS pin directly as this connects to the positive input of the error amplifier inside the 7A57, directly adjusting the reference voltage that the LDO is trying to regulate to. However, for higher frequency noise, the error amplifier does not have the bandwidth to handle it and it would therefore be better to inject the noise at the output of the LDO. I would not inject the noise into the input of the LDO as the PSRR will strongly attenuate it (varies by frequency but roughly 40-80dB attenuation).

    As far as noise generation I think just the function generator capacitively coupled into the NR/SS pin should be good enough for noise generation. I am not entirely sure why the step up transformer is needed as stepping up past ~6.5V will cross the absolute maximum ratings of the LDO and likely damage the part.

    Best Regards,

    Aden Taylor