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TPSM82822: Do you have any way to output 1.9V by fixed output voltage version?

Part Number: TPSM82822

Hello Experts,

I have same question as follows, instead output voltage is 1.9V. Do you have any way to output 1.9V by fixed output voltage version?
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Our customer need the adjustable TPSM82822SILR but it is not available anywhere. To solve his problem for a 1.1V (which is not available as a fixed output type) output he needs some confirmation.

Can any of the TPSM82822xSILR fixed output devices be adjusted to another output voltage? His assumption is that these devices use a fixed  internal resistor divider. If the resistor divider is accessible to the pins normally used by the adjustable version, then it may be possible to adjust the output voltage even though this is a fixed output type. Is his assumptions correct?
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Best Regards,
Fujiwara

  • Hi Fujiwara,

    Typically the method of adding an external resistor to the FB pin of a fixed VOUT version is possible when the fixed VOUT is smaller than the required VOUT. In this case the smallest fixed VOUT is 1.2V and the required VOUT is 1.1V. Adding an external resistor will make the VOUT > 1.2V. Also for this device a feedforward capacitor is required by the loop. Converting a fixed VOUT to an adjustable can lead to worse transient performance.

    Is it possible for the customer to change the 1.1V rail to a 1.2V rail and use the fixed VOUT version?

    Best regards,

    Varun

  • Hi Varun,

    Customer need VOUT=1.9V, not VOUT=1.1V. Based on your explanation as above, it will achieve VOUT=1.9V if customer uses VOUT=1.8V fixed version with external resistor, correct? If so, would you please tell how to design the value of external resistor?

    Customer would like to need a 1.9V rail and he would like to use Adj version, but it is not available anywhere...

    Best Regards,
    Fujiwara

  • Hi Fujiwara,

    I'll check the values of the internal resistors used and also double check if there is any issues with the control loop doing this. Shall come back to you by Wednesday/Thursday this week.

    Best regards,

    Varun

  • Hi Fujiwara,

    The fixed version (1.8V) has a typical internal resistance of 7.5 MOhm on the FB pin. So to get a VOUT of 1.9V, you need to add an external resistor of 417KOhm between FB and VOUT. For good transient performance you will still have to add a feedforward cap of 120pF in parallel with the 417KOhm.

    Please have the customer validate if the performance of this workaround meets his needs.

    Best regards,

    Varun