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RTOS/TPS7A8300: I am using TPS7A8300 for generating 5v 3.3V and 1.8v,but there are some problem in my design

user4598708
Prodigy 20 points
Part Number: TPS7A8300

Tool/software: TI-RTOS

I am using TPS7A8300 for generating 5v 3.3V and 1.8v, I designed the circuit according to the chip datasheet. However,after power on the output pin does not have voltage output.

The 3.3V 1.8V circuit when power up, make the chip TPS7A8300 IN pin and NR/SS connection short time the output pin will output 3.3V and 1.8v successfull, but 5v still not output.

Here is my circuit design.I don't know how why,please help me to find out the problem

hi,

  • 0
    TI__Guru 55940 points
    In order to help debug, please provide scope shots of Vin, Vbias (if you have one), Vout, and Iout (if possible).

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 20 points
    Thanks for your reply,
    For generating 5V:
    Vin=5.3V OUT=-0.17V NR/SS=0V Vbias=0V PG=0V FB=0V
    For generating 3.3V:
    Vin=5.3V OUT=0V NR/SS=0V Vbias=0V PG=0V FB=0V
    For generating 1.8V:
    Vin=3.3V OUT=0V NR/SS=0V Vbias=0V PG=0V FB=0V

    If connect the VIN to NR/SS short time these value will change
    Vin=5.3V OUT=0V NR/SS=0.78V Vbias=0V PG=0V FB=0V
    For generating 3.3V:
    Vin=5.3V OUT=3.3V NR/SS=0.7842V Vbias=0V PG=3.3V FB=0.8V
    For generating 1.8V:
    Vin=3.3V OUT=1.8V NR/SS=0.7844V Vbias=0V PG=1.79V FB=0.8V

    All my boards used four chips of TPS7A8300 to generate 5V, but there are only one chip's output voltage is correct.
  • 0 in reply to user4598708
    TI__Guru 55940 points

    A couple of comments, the Absolute Maximum Rating for NR/SS is 3.6V.  Exceeding the Absolute Maximum Rating may cause permanent damage to the LDO.

    Additionally I see that you state that your output voltage is negative before you startup the 5V rail.  TPS7A8300 is not able to startup with a negative biased output due to the foldback current limit.

    Scope shots will be useful in helping to debug your application.

    Very Respectfully,

    Ryan