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TPS758A01 is not working

Hari5670
Prodigy 50 points
Other Parts Discussed in Thread: UCC383, TPS758

Hello All,

I'm facing an issue in getting TPS758A01LDO regulator to work, which i have implemented as per the below circuit from data sheet.

R1 = 39K, R2=27K. Co = 100uF (electrolytic). Vi = 5V.  Expected Vout = 1.25 (1 + (39/27)) = 3V. (approx).

The thermal pad id connected the GND.

When the circuit is connected, the output voltage is 1.2V, and FB pin voltage is also 1.2V.  

I have tried using different resistor values for R1 and R2, but still no change in the voltages.

Also the voltages are the same with load (100 ohm between Vout and GND) and without load.

Has anyone faced a similar issue. please help.

Regards

Hari

 

  • 0
    TI__Expert 5640 points

    It sounds like it is regulating to 1.2V even with a load.  This can occur if the FB pin is shorted to OUT.  check for solder blobs or incorrect board routing.  This can also occur if the connection on either side of R2 is broken due to a broken trace, bad solder connection, or broken terminal on the resistor.  Use an ohm meter from the pin of the IC to the pin of R2 to verify connection.  Also use an ohm meter from the pin of the IC to the board ground to verify connection. Also check the values of R1 and R2 to make sure they are correct.

  • 0 in reply to Scot Lester
    Prodigy 30 points

    Hi, I need to know if TPS758A01 and TPS798xx-Q1 can regulate load less than 1mA.

  • 0 in reply to Scot Lester
    Prodigy 50 points

    Looks to be a mistake on my part. 

    I have swapped the connections of FB pin (pin number 5) and VOUT pin (pin number 4).

    I was working with UCC383 voltage regulator parallelly which has FB pin (pin number 4) and VOUT pin (pin number 5).

    I'll rewire TPS758 circuitry in a day and update you.

    Thanks for the help.

  • 0 in reply to Hari5670
    Prodigy 50 points

    After fixing the connections the voltage regulator is working both with and without load.

    Sorry for disturbing and thanks for the help.