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TPS7B7701-Q1: test the stability of Vout, both iload and Vout have fluction.

user3894159
Prodigy 210 points
Part Number: TPS7B7701-Q1

Hi：

  I use TPS7B7701 to generate 8.5V for tuner ANT power in automotive radio. pic1 is my shcematic. 

And i want to test the stability of Vout.

step1: disconnect L501;

step2: add electrical load and generate the iload(0->50mA, 100Hz/50% duty, 100mA/us);

setp3: test the stability of Vout

pic2 is the test result.

I don't know why the  current and Vout both have fluctuation? can you help to do some analysis?

I tested all the DCDC and LDO in my project, this is the only one that have problem.

and i also do the simulation in pspice, result is no problem

  • 0
    TI__Mastermind 23361 points

    Hi 

    The Pspice model is highly simplified and only the basic functions of the IC may have been modeled. The ringing looks like some load transients plus some inductive ringing that could be due to the electrical loads as the loads are also ringing. I would suggest you applying load using voltage to drive pass-FET with resistance loads. 

    I do see you have a 220uF output capacitor, which is higher than the recommended max value for the cap. As the IC has been designed and validated up to 100uF, is it possible for you to reduce the output cap? 

    Regards, 

    Jason Song