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LDC1614-Q1: CHx_IDRIVE selection : Rp measurement using Network Analyzer

Shinji Tsuji
Genius 13449 points
Part Number: LDC1614-Q1

Hi team,

I measured Rp using Network analyzer according to the guideline in the apps note snoa936.pdf,

to find the right CHx_IDRIVE value in LDC1614-Q1 register.

1) I removed Cpar and no target metal close to the sensor and measured the Rs and XL.

I measured the Rs and XL at the frequency which match the target resonant frequency, since the Rs and XL changes according to it.

Is this the correct measurement? (no need to use Cpar nor target metal for Rp measurement for this purpose(CHx_IDRIVE selection?)

2) CHx_IDRIVE setting

CHx_IDRIVE should be set according to the resonant frequency?

CHx_IDRIVE should be set at the closest value and lower than measured Rp value?

For example, if measured Rp=1.09kohm, then select b11110(=1.0kohm).

regards,

  • 0
    TI__Genius 17440 points

    Hello Tsuji-san,

    1) You are correct that you do not need the parallel capacitor for these measurements. However, we do recommend measuring the Rp value both with and without the metal target. When measuring with the metal target, it's important to measure at a higher frequency than the resonant frequency without the target present. This is because the presence of the target will increase the resonant frequency compared to the nominal resonant frequency. You can use the Spiral Inductor Designer in the LDC Tools excel calculator to estimate this increased frequency with the target present.

    2) Select the Idrive value that works for both measured Rp values.

    Best Regards,