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The Table 12. of DAC Input Override of LMP92066's datasheet does not work definitely.

K.N
Expert 4445 points
Other Parts Discussed in Thread: LMP92066

Hello team

From a customer who used LMP92066, the following questions came to Japan PIC.


The following URL is the datasheet of LMP92066.
www.tij.co.jp/.../getliterature.tsp

Table 12.（I2C Bus Transfer Sequence:Externally Supplied Data Sourcing Input to DACs）
is listed in page 31 of the data sheet.

Sequence_A:(Table 12.)
(1)I write the "password" in ACC_CNTL.
(2)I read the access level L2 in ACC_CNTL.
(3)I write Ox800 in DAC0*_OVRD.
(4)I write Ox400 in DAC1*_OVRD.

(5):I write 0X02 in OVRD_CTL.

The outputs are listed in the Table 12. with VDAC0=2.5V, VDAC1=1.25V.

However, really, The output are VDAC0=0V, VDAC1=0V.
Why the Sequence_A(:Table 12.) does not work definitely.


The customer confirmed the following.
Sequence_B:
(1)I write the "password" in ACC_CNTL.
(2)I read the access level L2 in ACC_CNTL.

(3):I write 0X02 in OVRD_CTL.

(4)I write Ox800 in DAC0*_OVRD.
   The output is VDAC0=2.5V.
(5)I write Ox400 in DAC1*_OVRD.
   The output is VDAC1=1.25V.

Please tell me the reason why Sequence_A(:Table 12.)
does not work definitely.

When the information is not enough, please contact me.


Best regards,
Keishi,Nishijima
Japan PIC

  • 0
    TI__Genius 16890 points
    Hello,

    I tried this on the eval board and they are correct. You have to write the OVRD_CTL register first and then the DACxy_OVRD registers. The output updates when you write to the lower byte, so write the DACxM_OVRD register first and then the DACxL_OVRD register.

    Mike
  • 0 in reply to Michael Stout
    TI__Expert 4445 points

    Hello Mike san

    Like following Sequence, I would like the correction
    of the Table 12. of LMP92066's datasheet.

    Sequence:
     (1)Write the "password" in ACC_CNTL.
     (2)Read the access level L2 in ACC_CNTL.(Option)
     (3)Write 0X02 in OVRD_CTL.
     (4)Write Ox08 in DAC0M_OVRD.
        Write Ox00 in DAC0L_OVRD.
        The output is VDAC0=2.5V.
     (5)Write Ox04 in DAC1M_OVRD.
    　  Write Ox00 in DAC1L_OVRD.
        The output is VDAC1=1.25V.

    Best regards,
    Keishi,Nishijima
    Japan PIC

  • 0 in reply to K.N
    TI__Genius 16890 points

    Hello,


    Yes, that is the correct sequence for writing the registers. 

    I will begin the process of updating the datasheet.  It will take some time though.

    Thanks for letting us know,

    Mike

  • 0 in reply to Michael Stout
    TI__Expert 4445 points

    Hello Mike san

    I am sorry that the reply is late.
    There is no reply from the customer afterwards.

    I think that the customer understood your answer.


    Best regards,
    Keishi,Nishijima
    Japan PIC