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TPS92520-Q1: TPS92520 LED Open circuit detection

zhang lin
Prodigy 80 points
Part Number: TPS92520-Q1

Hello, we encountered some problems when using tps92520.

We detected the LED open circuit according to the 3 conditions mentioned in the manual. During the actual test, it is found that the values of each STATUS1 and STATUS2 register are randomly changing.

There are 7 cases listed above. For example, if the 6th case above occurs, we cannot judge whether the circuit is open.

Q1: please help us provide an algorithm or idea for detecting LED, thanks；

Q2: Is it okay if we only test the content of the CHxCOMPOV as a judgment condition?

Q3: if we only test the VCSNx ADC data to judge the LED open condition, can we?

  • 0
    TI__Mastermind 18445 points

    Hello Zhang,

    It isn't uncommon to be switching between Open Circuit Cases as outlined in the datasheet.

    Q1. Here is an example algorithm that you can use but please make sure it works for you test conditions.  You need make sure that you record your STATUS register information because they are read clear registers.  Case 3 has changes in status registers that might change as your polling so you might have to concatenate those bits.   

    Q2.  COMPOV is only good for Open Circuit Case 1, you won't see it triggered on Case 2 or 3.  You need to look at all Open Circuit Cases to make sure you are in an open.

    Q3.  In Case 3, the output can stair step down to ~ 0V , so it depends on when you sample the output, it might be close to Vin, half way to Vin, or almost 0V, depending on where you poll/read status registers.

  • +1 in reply to fhoude
    Prodigy 80 points

    Thank you very much for your answer.

    We have actually tested the algorithm you provided and can use it.

    I have another question for help, that is, can the output channel of the 92520 be short-circuited to ground.

    Now there is such a scenario: If I use TPS92662A, if a string of LEDs in 92662A are all turned off, it means that the output of the 92520 is directly grounded through the DS of the MOS inside 92662A;

    what is the operation of the 92520 in this case and will the current output be normal?

    If this situation continues, 92520 there be any problems? Do you need to close the 92520.

  • +1 in reply to zhang lin
    TI__Mastermind 18445 points

    Hello Zhang,

    The is a constant current buck driver which means it regulates current, even into a short.  The TPS92520 was designed to work with 66x LED Matrix Managers and is ideally suited for this application.  

    -fhoude