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TPS732: TPS732 and TPS736 datasheet waveform questions

Randy Wang
Intellectual 1705 points
Part Number: TPS732
Other Parts Discussed in Thread: TPS736,

Hi Team

  My customer Zhuzhou had some questions about TPS732 and TPS736 datasheet:

  SBVS037P-“TPS732xx Capacitor-Free, NMOS, 250-mA Low-Dropout Regulator With Reverse Current Protection”

  SBVS038U-“TPS736xx Cap-Free, NMOS, 400-mA Low-Dropout Regulator with Reverse Current Protection”

  1. In SBVS037P and SBVS038U, Figure 20 and 28 is exactly the same, although these two devices are the same family, but the Iout is different, so the waveform should be slightly different;
  2. In SBVS037P and SBVS038U, figure 28  has a curve for Cout=10uF, and in figure 20 has a curve for Cout=100uF, actually the whole datasheet don’t have much data for Cout=100uF, should this curve is also Cout=10uF?

Thanks. 

  • 0
    TI__Guru 55940 points
    Hi Randy,

    1. Both of these figures are line transient curves. As long as the load is constant and the load does not force the LDO into dropout, the load will not be a noticeable effect on the line transient.

    2. The curve is labeled correctly at 100uF.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Intellectual 1705 points

    Hi Ryan

      I'm wondering could we support Iout=160mA, Cout=10uF line transient curve? thanks. 

    Best Regards,

    Randy Wang

  • 0 in reply to Randy Wang
    TI__Guru 55940 points
    Hi Randy,

    Figure 28 of both datasheets show a line transient with an output capacitor of 10uF. While this curve was not taken at 160mA, load has a negligible effect on a line transient. Please refer to the 10uF curve of Figure 28.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Intellectual 1705 points

    Hi Ryan

      Figure 28 actually confused me a little, it seems Cout=100uF overshoot is bigger than Cout=10uF. My customer is using fixed output version, so I don't know how to compare this.  

  • 0 in reply to Randy Wang
    TI__Guru 55940 points
    Hi Randy,

    The scope shots were taken with a different time scale and voltage scale as well as a different slew rate for the line transient. The addition of Cfb for Figure 28 does improve the transient response for an adjustable device; however, the provided curves are still able to provide you a reference for transient performance of these LDOs.

    In order to determine if the transient performance satisfies your specific application, we recommend that you prototype your application. For your convenience TPS73201DRBEVM-518 Evaluation Module can be used. Without a Cfb the adjustable version will have the same transient performance as a fixed version. We recommend that you configure the EVM as close to your intended application with input and output capacitors and then perform your worst case transients.

    Very Respectfully,
    Ryan