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Design for +/-15V supply using TPS65131

Other Parts Discussed in Thread: TPS65131

I am setting to work a digital interface board that has some legacy analogue circuitry requiring +/-15v, 200mA supply. The board is powered by +5V. Using a TPS65131, which gives -15V with no problem, however the +15V is at 4.7V and there is no switching output. The resistor divider for the positive side is 1.8M and 158K and the enable line is at 5V. Any ideas on why it is not working. I do not use the BSW output to switch off the +5V supply.

  • Hello Dave,

    Could you please check the output voltage during startup with an oscilloscope? I wonder if you can observe an overshoot. This would shut down the output immediately to make sure that nothing is damaged.

    Normally such an overshoot can just happen if something is wrong in the system.

    This part is somewhat sensitive to layout. Please make sure to stick as close as possible to the EVM layout.

    Best regards,
    Brigitte

  • Hi Brigitte

    Thanks very much for that. While checking my layout against the EVM, I realised that I had a 4.7uF capacitor on the wrong side of the inductor (effectively from INP to ground). I moved the cap and the circuit now works.

    Dave 

  • Hello Dave,

    Very good. Many thanks for the update.

    Best regards,
    Brigitte