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TPS732: TPS73250 Current Limit

Zeming Kong
Expert 3515 points
Part Number: TPS732

Hi team,

My customer is evaluating TPS73250, he noticed that fig.10 current limit vs. vout was tested with TPS73233, can we provide a similar figure for TPS73250?

Or should we consider that the same as TPS73233, -0.2V~0.5V will be the short circuit range so current limit threshold will be decreased, and in 0.5V~5.0V range it will be typ. 425mA?

Also, the current limit has a min value of 250mA. in which condition will the min value occur? The application will have about 250mA current spike, so the customer is worrying if this will hit the current limit and bring problem.

Best regards,
Zeming

  • 0
    TI__Expert 3515 points

    Additionally, how long will this LDO need to response to the current limit? For example, if a 600mA current is output, how long will TPS732 start to limit it?

    And if LDO is working in a condition over recommended current range but not hit the current limit continuously, what will happen? Assuming no overheat.

    Best,
    Zeming

  • +1 in reply to Zeming Kong
    TI__Genius 14245 points

    Hi Zeming, 

    Your assessment is correct, the 5.0V output device will have a current limit that behaves similarly to the 3.3V device and it will fold back at approximately 250mV. 

    As for the minimum current limit value listed in the EC table, many of our old datasheets used to set the minimum current limit value equal to the maximum rated current (250mA for TPS732) to let customers know that it would always be able to provide the max rated current (assuming it doesn't go into thermal shutdown). Looking at the plots it doesn't seem likely that any devices would really have a current limit of 250mA, the worst case condition is for low input voltages (<2V) but even that has a typical value of 425mA. For a 5V output device the input should be much higher and this shouldn't be a concern.  

    To answer your questions about response time, current limit circuits typically have a response time of 50us to 100us. 

    If you are above the max rated current but less than the actual current limit then technically the EC table specs no longer apply and you may see worse performance. Specifically the output voltage may be lower than the accuracy spec, also the dropout voltage will increase proportionally (dropout voltage is linear to output current) so the input voltage may need to be increased to stay out of dropout. 

  • 0 in reply to Kyle Van Renterghem
    TI__Expert 3515 points

    Thank you very much Kyle!

    That is very clear.

    Best regards,
    Zeming