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TPS71933

Sansu
Prodigy 90 points

Hi,

    I have problem in using TPS71933 IC, I need 3.3V at different times for 2 different channels. My input power supply is 5V and  my controlelr needs 3.3V.  So i started using TPS71933, Intially it worked fine TPS71933 provided regulated voltage 3.3 at the output of it. Later though it produces it is consuming more power and hanging my system from working.

  Initially total system used to consume 8mA  current (every module working). Nowthat, it started consuming 15mA and no device works in the circuit. If I detach a TPS71933 IC and provide 3.3V to my circuit individually it works fine. What am I supposed to do with the TPS, I have clearly checked there in no continuity problem assaosiated with the TPS IC. Please suggest me what went wrong.

 

 

  • 0
    TI__Mastermind 36110 points

    Thank you for choosing Texas Instruments.  There are several things that could have gone wrong.  The solution will take some troubleshooting on your part.  I would start with replacing the Linear Regulator with a new one and comparing input and output voltages and currents.  Is there a difference between the two?  Measure the output voltage with an oscilloscope to ensure the output voltage is stable.  Perhaps your output capacitor does not meet the >1uF or <1ohm requirement and your design is unstable.  Don't forget to account for DC bias effects in the capacitor.  A 0805 sized capacitor may work while a 0402 may not work because the actual capacitance may be much less than rated capacitance.  In a lab environment, ESD damage is always a possibility.

    Also, it is important to include a short description of the problem or question in the forum post subject line.

  • 0 in reply to Matthew Day
    Prodigy 90 points

    I have replaced the Linear regulators 3 times, yet the response is same. There is no difference as such, I gave 5V input and got 3.3V output(seen on scope).  I am using 0603 capacitor of 22 uF. Entire circuit gets hanged after the placement of the above component. But iF i supply 3.3 V directly it runs well. 

  • 0 in reply to Sansu
    TI__Mastermind 36110 points

    Let me make sure I understand your situation correctly.  When you power on your system, it works propery.  While power is still applied, the system input current starts to rise, and at some point, the system hangs.  If you then turn the system off and restart it, does it work properly and then hang again, or is the linear regulator damaged and never works again?  What is the time between turning the system on and it hanging up?  What causes your system to hang?  Is it due to the 3.3V voltage being too low?  Does is dip out of regulation during a transient load condition in your system?  What is the voltage difference between the output of the LDO and the system load on your board?  It could be that your PWB traces are too long and cause a voltage drop.  One thing that is important for you to investigate is to find the root cause of the system hanging and to identify the LDO functionality that could cause this to happen.

    I'm curious about your project and it's application.  More details about it may help provide more clues to the root cause of the problem.