AD5123 ±6 dB Increment and Decrement Instructions

Dear All:

I am very confused AD5123 datasheet Ver.A page 22 "±6 dB Increment and Decrement Instructions" have "± 6 dB" and the actual resistance value conversion formula provide to me? For example:I select AD5123BCPZ10-RL7 (10 kΩ resistance) then 128 Position. So 1LSB=78.125Ω another add ±8% resistor tolerance: calculated total resistor range is 71.875Ω ~ 84.375Ω "Coupled with "±6 dB Increment and Decrement Instructions" At this point the resistance value would it be?

 

Best Regards,
Jacky


  • 0
    •  Analog Employees 
    on Jan 29, 2014 5:24 PM

    Hi Jacky,

    As you've mentioned +1LSB ideally adds/subtracts 78.125Ω

    When using the 6dB Increment and decrement feature, it doubles the contents of the RDAC register to form a logarithmic curve.

    So if we take an 'ideal' situation, where the wiper is at zero scale and using the 6dB increment:

    0LSB --> 0Ω

    1LSB --> 78.125Ω

    2LSB -->156.25Ω

    4LSB --> 312.5Ω

    At 128, the digiPOT is at full-scale and is the same as writing "1111 1111" to the part.

    The 8% tolerance is measured at full-scale, just to note at lower codes the switch resistance can become a factor.

    Please let me know if you have any further questions.

    Kind Regards,

    David

  • 0
    •  Analog Employees 
    on Aug 2, 2018 2:33 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin