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REF102: The DC level of 10V has a little oscilation or ripple of f=0.16 Hz

Pablo Sulecio
Intellectual 290 points
Part Number: REF102

Hi Experts,

I am seeing through an osciloscope a ripple on the DC level in the Vout pin of my REF102 device and this is affecting my circuit performance, the Vpp of the ripple is around 15uV over the 10V DC signal, and it has a frequency of 0.16 Hz... Please refer to the circuit attached, I removed C8 and C9 and instale a 0 ohm resistor on R3 to see if capacitance load was affecting but still seeing that ripple... Could anyone help figure out the rootcase of that ripple? Thanks!!

 

  • 0
    TI__Genius 10951 points

    HI Pablo 

    15uV at 0.16 Hz is out of spec for flicker noise of REF102. I believe it is comming from the setup. Please shield all your connections to make sure it is not picking up noise from other sources. Can you please provide more information about the setup so that I can figure out if there is something? 

    Regards

    Trailokya

  • 0 in reply to Trailokya Rai
    Intellectual 290 points

    Hi Trailokya,

    Please at the end find attached the layout for the schematic. As you can see it is already on a PCB, so I am not sure if we can still shield the connections. I am placing the osciloscope probe on pin U10.6 and also on pin U11.3... I am using a 1X probe and placing it just like the picture below... I also noticed that the same noise is present when I measure the ground of the system so I think it is not due to device REF102...

    In the second picture you will see the waveform when I measure ground system... Although this is not REF102 relate still it will be good if you could suggest how to eliminate this noise or a least meation possible causes for this noise 

  • 0 in reply to Pablo Sulecio
    TI__Genius 10951 points

    Hi Pablo 

    Unfortunately I am not able to see your layout., so can't comment on noise source.

    Please use load cap (C8 in 1st diagram ) of 1000pF as mentioned in the data sheet of REF102. 

    I can suggest you few improvements for measurement - 

    * Use 10X probe. It will increase SNR. 

    * Decrease the bandwidth of scope to minimum when you are trying to see low frequency noise. I can see lot of high frequency noise in the scope shot. It will go down once you reduce the bandwidth of the scope. 

    * Try shielding your measurement setup with metal box (Faraday cage ) and ground metal cage to avoid any EMI interference.

    This should improve your noise results/

    Regards

    Trailokya