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DAC9881 VBIP(CODE)

itabi
Expert 1295 points
Other Parts Discussed in Thread: DAC9881

Hi!


BIPOLAR OPERATION USING THE DAC9881 (data sheet page31)


Is the calculation formula of VBIP(CODE) right?

VBIP(CODE)=[ 1+R3/R2+R3/R1 ] x [ CODE/262144 - R3/R1 ] x VREF


For example,

R1=1K
R2=2K
R3=2K
VREF=5V

CODE=0 --> VBIP=-40 ?
CODE=262143 --> VBIP=-20 ?


I think the following calculation formula is right.

VBIP(CODE)=[ (1+R3/R2+R3/R1) x CODE/262144 - R3/R1 ] x VREF


For example,

R1=1K
R2=2K
R3=2K
VREF=5V

CODE=0 --> VBIP=-10
CODE=262143 --> VBIP=+10


Best regards,
itabi

  • 0
    TI__Expert 3996 points

    Hi Itabi ,

    Great job , thanks for pointing it out

    I believe what you have derived is correct

    I will get in touch with my team to rectify the typo in the datasheet

    By superposition theorem

    Vbip (due to Vout)= 1+ (R3(R1+R2)/(R1*R2))Vout               Non inverting amplifier

                                        = (1 + R3/R2 + R3/R1)Vout

    Also

    Vout = code /262144* Vref

    Vbip (due to Vref) = - R3/R1 * Vref

    Vbip = Vbip (due to Vout) + Vbip (due to Vref)

    Vbip = [ ((1+R3/R2+R3/R1) x CODE/262144) – (R3/R1) ] x VREF

  • 0 in reply to Shreenidhi Patil
    Expert 1295 points

    Hi Shreenidhi Patil,

    Thank you for your confirmation.

    Best regards,
    itabi