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TPS24720: SET and SENSE signal routing

William Sung36
Intellectual 395 points
Part Number: TPS24720

Hi,

I am using the TPS24720 on my design and i looked at the kelvin routing for the SET and SENSE pins on the TI eval board so that i can try to make it similar on my design. Unfortunately with the location of the sense resistor and the TPS24720, i cannot rout the SET and SENSE signal in the same way. In my layout, SET and SENSE are actually crossed. From the datasheet, it mentions that these signals should be wired side by side but there will be portions of the track that will not be like this due to the cross over. Do i just try and run these side by side for as long as possible and the break into another layer when when i need to run the SET wire to its pin?  Also, how important is it to run the VCC wire next to these wires as per the dev board?

Thanks

  • 0
    TI__Guru 57737 points
    Hi William,

    We recommend that Traces to SET and SENSE to be short and run side-by-side to maximize common-mode rejection. Use via's only if necessary.
    Make sure these traces are not close to noise sources.
    Also, use Kelvin connections at the points of contact with RSENSE. If kelvin connections are not used, the current limit accuracy reduces and Current limit can trip too soon.
  • 0 in reply to Praveen GD
    Intellectual 395 points

    Hi Praveen,

    Thanks for the reply. How about the VCC signal, does it need to run next to these lines like the dev board?

    Also, is length matching important on the SET and SENSE wires?

    Thanks

    William

  • 0 in reply to William Sung36
    TI__Guru 57737 points
    Hi William,

    The trace to the VCC pin need not be run in parallel with SET and SENSE line. Make sure that the decoupling capacitors on VCC pin have minimal trace lengths to the pin and to GND.
    Traces to SET and SENSE are recommended to run side-by-side so that any noise coupled will be same on both the lines. This common mode noise will be rejected by the internal amplifier thus minimising the effect of noise coupling on these lines.
    So, try to run these lines as long as possible. As you run these lines side by side you end up matching the lengths. As such matching the lengths is not required.