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TPSM265R1: Generating non-standard voltage with 3.3 V version of this part

Part Number: TPSM265R1

Hi,

For some reasons (e.g I want to order only one part when I need 3.3 V and some other non-standard voltages on my board), I would like to generate some non-standard voltages with 3.3V output version of this device (TPSM265R1V3SILR). I plan to do so by connecting a resistor (Rx) between VOUT and SENSE+/FB pin to form a voltage divider with internal R1 and R2, as shown in the attached schematic. To do this I need to know the resistance of R1 and R2 to calculate the Rx that will result in my desired output voltage. Can the resistance of R1 and R2 be shared?

Thank you

  • Hello

    The typical values for the 3.3Vout version are R1=540k and R2=309k.

    Unfortunately, although the ratio of these resistors is accurate and stable, the absolute values

    can vary as much as +/- 20%.  Also, these resistors have a rather high temperature coefficient.

    Therefore, they will not match nor track with your single external resistor.  The result will be a very

    inaccurate output voltage.

    The best solution would be to use the adjustable device and use an external resistor divider.

    Another solution is to use an external resistor divider that is much smaller than the internal divider of the 3.3Vout device.

    Selecting resistors that draw between 10x and 100x the current in the internal divider will help to 

    reduce the error.

    Thanks