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TMCS1133: Reference design of TMCS1133 for differential ADC sampling

Mingjin Hu
Prodigy 20 points
Part Number: TMCS1133
Other Parts Discussed in Thread: TMCS1123

Tool/software:

I intend to utilize TMCS1133 with a differential ADC to enhance the SNR. However, I have observed that TMCS1133 lacks a common point for pseudo-differential routing. Consequently, I am seeking assistance in devising the circuit design. Moreover, the TMCS1133 will be incorporated in a current sampling board, while the C2000 with a differential ADC will be situated on a separate board.

  • 0
    TI__Expert 8115 points

    Hello,

    I would recommend just using a sense line from the GND pin of the TMCS1133 and using differential routing from the TMCS1133 to the C2000. This will allow you to have all the benefits of using differential routing, so in terms of signal integrity it will act as though the TMCS1133 had a "common point". The signal read by the ADC will still have a DC offset, this can be subtracted out of the measured voltage in software.

    Let me know if you have any more questions,

    Levi DeVries

  • 0 in reply to Levi DV
    Prodigy 20 points

    Dear Levi,

    Thank you for your suggestion. While it could be effective, I aim to maximize the differential ADC's full range. Furthermore, considering that the common mode voltage supplied to the C2000's differential ADC should be approximately 1.5V and the highest allowable input voltage is 3V, the proposed setup might further limit the measurement range.

    Best regards,
    Mingjin

  • 0 in reply to Mingjin Hu
    TI__Expert 8115 points

    Hello Mingjin,

    I am assuming you mean 1.65V, as we don't sell a variant of the TMCS1133 with a zero-current voltage output of 1.5V.

    You could use a 1.65V reference voltage generator to provide the pseudo-differential reference voltage. Layout the device close to the TMCS1133 and use the same GND as the TMCS1133.

    In terms of SNR you might also just be experiencing low SNR due to the inherent noise of the device - the TMCS1133's high bandwidth means the output will be noisy. The noise density of the device is 170 μA/√Hz. If you don't need the higher bandwidth, you could switch to a lower bandwidth part like the TMCS1123, which also has an output for the voltage output you could use.

    Let me know if you have any more questions about this,

    Levi DeVries