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TS5A22364: Noise rejection on power supply

ErwanLG marport
Prodigy 100 points
Part Number: TS5A22364


Hello,

I have a noise sensitive application and I have added TS5A22364 on our RX path. I notice that our noise level increase at certain frequency due to the noise on our power supply.

I measure signal with a noise level down to -120dBV from 10kHz to 400kHz.

I wonder if there is any existing measurement  for the noise rejection between the power supply and the output of the switch as I can't find it in the datasheet.

I will probably add a filter on its power supply but it will be better if I can know where the switch in more sensitive.

Regards,

Erwan Le Guével

  • 0
    TI__Guru 53182 points

    Hi Erwan,

    This is a specification that we don't spec in our analog multiplexer datatsheets - However setting the cutoff frequency low will have the best results in mitigating noise performance.  The noise will affect the resistance of the closed switch - very slightly and having frequencies at and above the power supply switching frequency ( if supply is SMPS) attenuated will lead to best performance. 

    However using the supply decoupling capacitor in a 2nd Order RC filter could be implemented to help reduce higher frequency noise generated from the power supply.  Typically we recommend between 100nF and 10uF on the VDD line, for this device we specify 100nF but going up to 10uF wouldn't be terrible.  A 2nd order RC Low Pass filter with R1 = R2 = 4.7K and C1= 100nF and C2 = 1uF would put a -3dB cut-off around 100Hz  and at 10KHz ~ -80dB and 400KHz  ~ < -120dB. Bumping up the Resistor to ~20K and C2 to 4.7uF will get an approximate -3dB cut-off ~11 Hz which at 10KHz ~ -120dB  and 400KHz ~ < -160dB (realistically thermal noise from passives will degrade the performance - but the noise level on the bias for the switches will be less likely to be affected by noise).

    If you have any other questions please let me know!

    Best,

    Parker Dodson