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TPS560430: TPS560430YF for 9v or 12v output from 14-15v input

Hossam Moghrabi
Intellectual 360 points
Part Number: TPS560430
Other Parts Discussed in Thread: LM317

Tool/software:

Hello

I made a design using TPS560430YF, please check the images here: https://imgur.com/a/tV1q3US

I optimized the layout as much as possible in the current board, no other space is available. input caps are not perfect but very good. 2x100nF 0402 caps are very close to Vin pin as well as other 1x10u 0805 + 2x22u 1206 caps.

the selected feedback resistors as follows:

12v
R_top = 243k
R_bot = 22k


9v
R_add = 649k -> this is switched using the switch to either be out of the circuit or in parallel with top resistor 243k to form about 176.5k top resistor for 9v.

please check the calculations as well as layout and provide your feedback

thanks for your kind support.

  • 0
    TI__Genius 9460 points

    Hi,

    Schematic and layout look okay to me. Make sure you don't toggle the switch on feedback during operation. 

    Regards,

    Rahil

  • 0 in reply to Rahil Ajani
    Intellectual 360 points

    hello

    what happened when i change it during operation? i mean, it is just a feedback resistor.

    i tried the exact same circuit using lm317 and it worked fine.

    please explain

    thanks!!

  • 0 in reply to Hossam Moghrabi
    TI__Genius 9460 points

    Hi,

    In the case of some converters, it can cause instability when changing the Vout while the buck in operation. I do not know for sure if this will be an issue with this part.

    Regards,

    Rahil

  • 0 in reply to Rahil Ajani
    Intellectual 360 points

    hello

    notice that the output current won't exceed 150-200 mA, and in some cases will be 0mA since the PSU will be installed in multiple revisions of a certain device.

    changing from 9v to 12v or the reverse is the same issue?

    please try to check for this particular device and see if it really can cause an issue.

    i will instruct the customers to never change while in operation but still it is good measure to know.

    another thing, it is rated at 600 mA but to my knowledge it does have short circuit protection. my question is at which current does it do that? is it reliable and can protect the device? i don't need it to be very precise though.

  • 0 in reply to Hossam Moghrabi
    TI__Genius 9460 points

    Hi,

    Yes, there could be a problem switching to 9V to 12V and the reverse while the buck is regulating. We recommend only switching the FB resistors while the buck is not regulating. 

    Regards,

    Rahil

  • 0 in reply to Rahil Ajani
    Intellectual 360 points

    hello

    can you tell me what could happen? like, will get it out of regulation or what exactly? and if the circuit powered down, then on again, will it recover and returns back to normal operation?

    and you didn't answer me about short circuit protection, please check above.

    thanks

  • 0 in reply to Hossam Moghrabi
    TI__Genius 9460 points

    Hi Hossam,

    Potential issues include overvoltage, under voltage, instability on fb, current spikes, stress on cout or load, trigger hiccup mode, shut down behavior, etc.

    Short circuit protection:

    You can read more about this in the datasheet.

    Regards,

    Rahil