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LDC1101: LDC1101 / LHR RPMIN Setting

S.Satoshi
Guru 21685 points
Part Number: LDC1101

Hi,

Please let me ask about LHR RPMIN setting. There is RPMIN SETTING value in Table 36, but I'm not sure how to calculate this value. For example, how can I calculate 0.75kohm? I tried to use 0.6V that is nominal sensor amplitude of 1.2Vpp but the result is 0.785kohm, not 0.75kohm.

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Genius 13335 points
    Hello Satoshi-san,
    This table is assuming that the LOPTIMAL bit has been set to 1. This will disable the amplitude modulation and keep the current drive at a fixed value. Therefore if you sensor amplitude is 1.2Vpp that is the value you use for Vamp. However, the amplitude is determined by the RP value of the sensor (measured/estimated) and the IDRIVE value you select (from the table). Note that you can use RP+L mode to measure the actual sensor RP value and select the appropriate sensor drive current to achieve 1.2Vpp. For example, if you measure an RP of 10kΩ from RP+L mode and you want approximately 1.2Vpp you calculate from equation 15 that 94µA is required. The closest value that is less than 94µA is RPMIN = b100 which has an IDRIVE of 75µA. Using this value with an RP of 10kΩ should give approximately 950mVpp for the sensor amplitude.
    Hopefully this example clarifies things!
    Cheers,
    Luke