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UCC39002: UCC39002 R_ADJ calculation

Alex Yeh
Expert 5435 points
Part Number: UCC39002

Hi team,

Would you please help to explain the detail how to derive the equation 6 and 7 in datasheet page 16 and 17? 

Since R_ADJ = ∆VADJ(max)/I_ADJ

For the numerator of equation 6, why it uses ∆VADJ(max) instead of Vsense(the voltage on Rsense)? 

For the the denominator of equation 7, why it is I_ADJ(max) - ∆VADJ(max)/Rsense instead of I_ADJ(max) - Vsense/Rsense?

Rds,

Alex

  • 0
    TI__Mastermind 34465 points
    Hello Alex,
    There are two conditions required to be satisfied for the calculation of R_ADJ.
    One is equation 6 and the other is equation 7
    Equation 6 sets a max value based on the required adjust range and the saturated output value of the adjust amplifier.
    Equation 7 ensures that the max sink current will not exceed its rated 6mA max.
    So all you have to do is choose a value based on these equations.
    If R_ADJ is too big (based on 6) then you will not reach the full adjusting range
    and if R_ADJ is too small (based on 7 )you will exceed the current rating for the adjust amplifier.
    You will need to choose a value between these too limits.

    Regards
    John