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TPSM8A29: Start and stop Voltage

Karthik Shenoy
Prodigy 160 points
Part Number: TPSM8A29

Given an input and Output voltage, what should be the Enable top resistor value (Rent)? Which value has to be kept fixed and on what parameters it will depend ? Venh and Venl also needs to be calculated. 

Kindly refer Eqn 22 - 24 for further insights.

  • 0
    TI__Mastermind 18605 points

    The developer determines the Vstart voltage, use the 10kohm for the Renb.   The Venh and Venl are 1.22V and 1.02V as shown in the equations and in the electrical characteristics table on page 6 of datasheet.    Typically,   the Vstart is 10% to 20% lower than the nominal input voltage. 

  • 0 in reply to David_Daniels
    Prodigy 160 points

    Hi David, irrespective of my output voltage I believe Enable top and bottom resistors will be same provided the input voltage is same in all cases

  • 0 in reply to Karthik Shenoy
    TI__Mastermind 18605 points

    If your start voltage is the same the resistors will be the same. 

    Since the device operates down to 2.7V, many developers choose to have a start voltage greater than their output voltage to prevent operating in dropout or choose to have a start close to the nominal input voltage. 

    If you are having a difficult time selecting the enable resistors,   using webench power designer link   is a good resource.

    in left panel change the enable voltage from 4V to your preferred and click redesign to get the updated resistor values.