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ADP2442 shutdown output after some seconds


We are evaluating the ADP2442 ic. Our prototype is a basic dc dc converter, from 24V to 5V

This is the schematic (basically a copy&paste of the reference design):

If we connect the pin 6 (SYNC/MODE) to gnd (pulse skip mode), the circuit seems to work. We have 5V and we can supply current for a test load.

But if we use the fixed mode (pin 6 to vcc), the circuit works for a couple of seconds, and then, it shutdowns. We were looking for something strange, but at first, we dont see anything.

any idea or suggestion?

Thank you very much!!!

  • Hi!

    We didnt find anything yet  

    Maybe the gerber file can help?

    This is the top side

    And the back side

    do you see anything strange? it is a test board, so, we can see how this chip will work

    Thank you very much

  • Hi,

    The schematic looks fine. For the layout, it seems that the AGND and PGND planes are not connected together on the PCB?

    When doing PCB layout, it is fine the separate AGND and PGND. But usually, we will connect these two ground planes on the PCB board.

    Another thing is, when setting to FPWM mode, how many load did you draw from Vout or even under no load condition, the ADP2442 will shut down after a while?


  • Thank you for your reply!!

    AGND and PNGD are connected under the ic. You can see it on the schematics, on the pin 13. I followed the layout guidelines for this. Do you see anything strange here then?

    We damaged the chip doing tests (short playing with the multimeter pin) and we are waiting for a new one. I will post more infor about this. But I remember using a led to drive some current, with the same result.

    For sure, with no load, the ADP2442  shutdown after 3 or 4 seconds in fixed mode.

    Also, in skip mode and fixed mode, the LED on the PGOOD pin does not turn on :/ that is the most disturbing issue here.

  • I noticed that the AGND and PGND are connected together through pin13, that should be fine. Then the layout has no strange things.

    Did you encounter this "shut down" issue on every unit, or just this particular one?

    For the skip mode, have you tried to draw some load current to see if the ADP2442 can enter into FPWM mode smoothly?

    For the external LED, since the PGOOD is open-drain and when output is ready, it becomes high-Z. According to the schematic, the LED connection is not correct. Whatever the PGOOD is pulled low or released (high-Z), the LED will not be ON.

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