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TPS7A39: Driven by TPS65131 and the output is 0V

TI-CSC
Genius 11995 points
Part Number: TPS7A39
Other Parts Discussed in Thread: TPS65131

Tool/software:

Hello E2E Experts,

Good day.

I have used TPS65131 to generate +14V and -14V and used TPS7A39 to step down the output voltage to +12V and -12V respectively. Whenever a load is connected to TPS7A39 the output voltage drops near 0V. Could you help to resolve the issue?

We tested with an external supply as input to TPS7A39. It is able to properly power up the circuit, but when it is driven using TPS65131, output voltage drops under load conditions.
I tried by shorting  INP1, INP2 pins and OUTN1, OUTN2 pins, but there is no change in the output.
Is it possible for the TPS65131 to drive the required current for TPS7A39? How can I check?
Regards,
TICSC
  • 0
    TI__Genius 11995 points

    Hello E2E Experts,

    Good day.

    Additional information:

    I am using inductors XAL4030-472MEC instead of B82462G4472M000 due to size constraints, will this be a problem?
    And +14V is not dropping when connected to load whereas -14V is dropping to zero volts. Could you please help us to resolve this?
    Regards,
    TICSC
  • 0
    TI__Genius 9470 points

    Hi,

    Please share scopeshots of your test and please provide the details requested below:

    • Confirm the rating and type of the input and output capacitors of the LDO
    • For start-up tracking to function correctly, a minimum 4.7-nF capacitor is required. As the time constant formed by the feedback resistors and feed-forward capacitors increases, the value of the CNR/SS capacitor must also be increased for startup tracking to work correctly

    I have some more points to add here but please know that I have received the information below and I will need a week to follow up with more information

    BR

    Ishaan