• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 63 subscribers
  • Views 835 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TPS54240: DC buck with two Split-Rail output

Xianrong Shang
Intellectual 855 points
Part Number: TPS54240
Other Parts Discussed in Thread: LM5160, LM5161, LM5017

Hello, My customer will use the TPS54240 in the +/- power supply, the parameter condition is:  9Vin, +15Vout/0.18A, -15Vout/0.18A.

Because TPS54240 is buck converter,  there's a coupled inductor on the output, Is TPS54240 Suitable for this application??  

  • 0
    TI__Expert 3840 points
    Hi Xianrong,

    For a coupled inductor/Fly-buck type of operation you need to have a Synchronous regulator. The TPS54240 is non-synchronous so it won't allow negative inductor currents, that means the regulation on the secondary winding (-15Vout) will be lost. Please use the LM5017 for such application; the LM5160 and LM5161 are also built for this but for higher load currents.

    Best Regards,
    -JP
  • 0 in reply to Juan Paulo Fung
    Intellectual 855 points
    TPS54240 is a DC BUCK, can it be used in the boost circuit ?? 9Vin, +15Vout/180mA, -15Vout/180mA, the absolute value of the output voltage is bigger than the input.
  • 0 in reply to Xianrong Shang
    TI__Genius 11085 points
    It cannot be used as a boost converter. It is a buck. The output voltage will always be lower than input. When Vin is 9V, +Vout can only be a voltage below 9V. The -Vout rail can maintain if it is generated using a inverting buck-boost design. If you want to use one buck converter to generate +Vout and -Vout with a coupled inductor, the recommendation is to pick a synchronous buck with FPWM operation mode, as JP mentioned above.

    -Yang
  • 0 in reply to YangZhang
    Intellectual 855 points
    What does the FPWM mean?

    such as： 19Vin，+12Vout/3A，-12Vout/1.5A;
    or
    19Vin， +15Vout/180mA, -15Vout/180mA.
    Both of them(output is positive and negative, the load is different or not)， I can choose the DC synchronous buck, is it?
  • 0 in reply to Xianrong Shang
    TI__Genius 11085 points
    FPWM stands for forced PWM, meaning it allows negative current to flow on the low side FET

    Yes, buck converter can be configed to supply positive output and negative output. Note that when used to supply negative output, the input voltage rating of the buck should be higher than Vin+|-Vout|. Buck rated current also need to be higher than the max load current needed by the negative rail.

    -Yang