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Original question:

INA1650-Q1: INA1650 implemented as balanced line driver, from single ended input. Single power supply (plus INA1651 implemented...

INA1650-Q1: XLR receiver with single supply - PSRR and noise

Matteo Bonino
Prodigy 90 points
Part Number: INA1650-Q1
Other Parts Discussed in Thread: INA1651, TPS709

Tool/software:

Dears, good morning, I had previously asked a question about the INA1650-Q1, thank you again.

You'll remember this INA1651 will be deployed in single supply mode.

Hence, I've a couple of other questions, as I'm in the process to design the relevant power supply stage:

- Will the PSRR capabilities of the INA1651 be worse / same / better, due to single supply mode (against dual supply) ? 

- Reason of this question is: the only LDO regulator I've found for this application (fairly high voltage, low current) has an output voltage noise of 100uV, and a PSRR which gets worse for higher frequencies of the audio spectrum. I realize difficult question, but i'd like to estimate if this level of noise will somewhat affect the otherwise great INA performances.

Thank you very much in advance

Cheers

Matteo

  • 0
    TI__Genius 14165 points

    Hi Matteo,

    Regarding dual vs. single supply, there are sometimes differences in amplifier's PSRR for the positive supply vs. negative supply.  This can be a tricky question depending on the correlation of the noise on the supplies; but, in general, two separate supplies introduce two different uncorrelated noise sources, which will result in slightly more noise.  However, if you do use LDO's, then  I think it is unlikely the LDO noise would ever be audible for either case.

    The way I would look at this is to focus more on the noise spectral density of the LDO.  Say for example we use the TPS709:

    https://www.ti.com/lit/ds/symlink/tps709.pdf

    This is a low-power LDO and therefore not optimized for noise, total noise is 190 uV.  But it has noise spectral density of 4 uV at 1 kHz:

    This noise would be introduced as noise into the signal chain, but would be divided down by the PSRR of the INA165X to become input-referred noise.  If the PSRR at 1 kHz is 70 dB, then that is a factor of 0.3 * 10^-3, so the 4 uV becomes reduced to 1.2 nV/rtHz when referred to the input of the INA165X amplifier.  This is effectively a negligible noise value compared to the resistors and amplifier noise spectral density, so, I don't think the LDO noise will be a problem.

    Let me know if there's anything I can clarify here or other questions about this.

    Regards,
    Mike

  • 0 in reply to Michael Hartshorne
    Prodigy 90 points

    Thank you veryt much Michael ! This really helps. A good day