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REF2033: provide common mode voltage for an ADC

xyz xyz
Intellectual 1000 points
Part Number: REF2033
Other Parts Discussed in Thread: TLVH431

Hello

I have an ADC driver.  the supply is 5V and the Vcm (common mode voltage) should be 1.65V.

usually the common way to provide the Vcm is, using a voltage divider with two 1K resistors and one 100nF capacitor.

but when I connect the the divided voltage (3.3V/2), the output voltage is 1.68 due to the Vocm input circuit :)

another technique is, buffering the divided voltage using an op-amp to achieve better result like below :

3.3V--(using voltage divider+100nF)-->1.65V--->unity gain buffer----> connect to Vocm pin

I'm thinking of using REF2033 to provide 1.65V. when I simulate the circuit the result is outstanding! Even the SNR of the circuit is improved!

now I have a question! my circuit uses ultra low noise FDA and low distortion FDA and ICs and an 14Bit/65MSPS ADC.

is REF2033 a good option to provide the Common mode voltage?

Regards

  • 0
    TI__Mastermind 19370 points

    Hi xyz xyz,

    Yes! That is the purpose of the REF2033 as it will work for that intended application with its dual output capability. There is also other options such as the TLVH431 that are able to do this as a lower cost but with poorer noise performance.

    The reason you are seeing an improvement is due to the noise from voltage source that was used to supply the Vcm and the mismatch of the resistors.
    A series voltage reference, such as the REF2033, is typically used in ADCs are a VREF so their noise and temperature specifications are excellent and a huge improvement over any resistor divider.

    -MZ

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