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TPS544B20: TPS544B20 STEP_VREF_MARGIN_X

Eric Shen42
Expert 2750 points
Part Number: TPS544B20

Dear TI team:
    I don't understand the setting of TPS544B20 STEP_VREF_MARGIN_X:

    1, There are STEP_VREF_MARGIN_HIGH(D5h) and STEP_VREF_MARGIN_LOW(D6h)，If my goal is to set the margin high, how to configure D6h? Otherwise, it is set to margin low, how to configure D5h?

     2, The high byte of D5h default value is all 0, and the low byte is 00011110, which is the decimal 30. The specification means that this represents margin high is 10%, and it means that 00000000 to 00011110 is 30 steps, each step is 2mV? The percentage was 0.333% each step？

     3, The high byte of D6h default value is all 1, and the low byte is 11100010,  this represents the decimal  -30.  I don't understand how this binary value is converted to decimal -30? Margin low from -30% to 0 %, how does it match binary?

      Thanks!

Regards!

Eric 

  • 0
    TI__Mastermind 23965 points

    Section 8.6.32 and 8.6.31 of  TPS544B20 datasheet cover how to used the STEP_VREF_MARGIN_HIGH and STEP_VREF_MARGIN_LOW commands. 

    The format of the numbers is 2's complement. 

    A positive number written in two's-complement notation is the same as the number written in unsigned notation.

    A negative number can be written in two's complement notation by inverting all of the bits of its absolute value, then adding one to the result

    To convert decimal -30,  convert  decimal 30 to binary  0001 1110     invert the bit and add 1    to equal 11100010. 

    David 

  • 0 in reply to David_Daniels
    Expert 2750 points

    Hi David:
        Thanks!