This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS560430: Can't get the 3.3V version of the Simple Switcher to work

Part Number: TPS560430

Just as in these queries, I can't get TPS560430X3F, the fixed 3.3V version of the Simple Switcher, to work.

https://e2e.ti.com/support/power-management/f/196/t/715590

https://e2e.ti.com/support/power-management/f/196/t/770186?TPS560430-Is-it-O-K-to-leave-FB-pin-open-when-3-3V-fix-output-version-TPS560430X3F-

I have tried all these with the FB pin:

 - leaving it open

- connecting it to SW

- connecting it after the inductor

- connecting it to a resistor divider after the inductor with values chosen from WEBBENCH designer for 3.3V

None of these work, and they all fail in different ways. 

What is the right way to the fixed 3.3V version of the part to work?

  • Hi Leonard,

    What's top marking of IC package?

    Can you upload the PCB layout for checking?

    B R

    Andy

  • Andy,

    Thank you for the response. It looks like I fixed the problem; apparently my experiments with different connections for FB must have damaged the IC. I unsoldered it and put in a new part with FB connected after the inductor (to Vout), and it works.

    I also discovered that adding a 0.1 ufd input capacitor close to the device is important for reliable startup. It's not shown in Figure 18 on page 15 of the spec sheet, although it is shown when you run WEBENCH to create a custom design. 

    Sorry for the false alarm. In addition to adding a note to the spec sheet about what to do with FB for the fixed 3.3V version, you might want to show a 0.1 ufd input capacitor in parallel to the larger one.

    Len