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[LDC1101] RP_SET (0x01) RPMAX_DIS field

Minkyun Noh
Prodigy 170 points
Other Parts Discussed in Thread: LDC1101

Hello,

I am trying to configure LDC1101 for LHR measurement. 

In the datasheet (SNOSD01C –MAY 2015–REVISED FEBRUARY 2016) p.42, Table 41, it instructs to set RPMAX_DIS = b0, meaning "Programmed RP_MAX is driven". Shouldn't it be the other way around: RPMAX_DIS = b1, meaning "RP_MAX current is ignored; current drive is off"?

Otherwise, the Rp_max = b111 (Table 41) takes lower value than Rp_min = b101 (Table 41), which violates the setting rule in p.15: The programmed Rp_min setting must not exceed the programmed Rp_max setting.

Please let me know if I misunderstand it.

Best regards,

Minkyun

  • 0
    Prodigy 170 points
    By the way, I observed that in LDC1101 evm gui, if I try to set RP_SET = 0x75 (RPMAX_DIS = 0, RP_MAX = b111, RP_MIN = b101) it automatically changes as RP_SET = 0xF5 ((RPMAX_DIS = 1, RP_MAX = b111, RP_MIN = b101).
  • 0 in reply to Minkyun Noh
    TI__Genius 13650 points
    Hi Minkyun,
    I will look into this issue and get back to you tomorrow.
  • 0 in reply to Ben Kasemsadeh
    TI__Genius 14270 points

    Hello Minkyun-san,

    I can see why the datasheet is confusing at that point. First, the RP_MAX_DIS should be disabled (set to 0). It is better to think of RPMAX_DIS as a "High Q Sensor" setting. Step 3 of section 9.2.2.1 addresses this point. 

    However, the datasheet is unclear about the RP_MAX setting to b111. If LDC1101 is in L-only mode, the LDC1101 would be fine. But the text doesn't say the LDC1101 is in that mode, and doesn't state what the settings are. This functionality is discussed in section 9.1.10. 

    My apologies for the confusion on this. Thank you for bringing this to our attention. We will have an update to the datasheet which clarifies this.

    So, in summary:

    1) RPMAX_DIS should be set to 0.

    2) The field value of b111 for RPMAX could indeed be invalid if the Rp measurements are not disabled as detailed in section 9.1.10.

    Regards,

    ChrisO