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LDC0851: Coil sensor is more than 2 cm away from the LDC0851 chip

Part Number: LDC0851

The user guide says that if the cable connection between the sensor and the LDC0851 chip is longer than 2cm, one must use twisted pair. My question is, does it mean that 3 cables for LREF, LSENSE, and LCOM must be twisted? The term twisted pair is somehow deceiving since it should go in "pair" not 3.

  • Hello,
    Ideally there would be two twisted pair used. The first for LSENSE and LCOM and the second for LREF and LCOM. Since LCOM is the return path for both inputs, the main purpose of the twisting is to mitigate parasitic inductance loops which would change the matching between the channels or pick up unintended metal movements. Additionally, keeping the length shorter will also help mitigate the mismatch.
    Regards,
    Luke
  • Hey, thanks for giving me clarity on this. In that case, can I use rj45 or rj11 cable?
  • Hello,
    That construction should work. However, the distance between the sensor and the LDC0851 should be kept short for stable operation. With long sensor distances phase shifts can occur which prevent the LDC0851 from properly driving the LC tank at resonance. Using slower sensor frequencies can help mitigate this, but it is always recommended to use short routing whenever possible.
    -Luke