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UCC27524: Output is 1/2 VDD. Confused Why

Part Number: UCC27524

Sometimes when using this part, I notice The signal in is 1/2 the voltage, and the output is half.

i.e. Vin = 3.3, VDD = 5. However, When using a multimeter on the chip I'll see Vin = 1.7, and the output will be 2.5V instead of 5.

Any idea what is causing this? Both EN pins are left floating.

  • Hi Nicholas,

    thanks for asking about UCC27524, sorry to hear about this confusion.

    I have seen the outputs at half the VDD voltage before but only because during start up for example in a pre-uvlo condition when the totem pole structures both fets are off, this forms a voltage divider with the Mohm off resistances of the totem pole structure. This might be what you are seeing.

    To make sure, we need to know if the driver pins are functioning correctly.
    assuming we need to focus on chA.
    Can you probe VDD, INA,ENA,OUTA (all wrt to GND on the same div scale)?

    thanks,

  • Thanks for getting back Jeff...that makes sense. I'm placing these parts on the boards manually and part of it involves desoldering and resoldering a connector. When resoldering the connector on a second board I noticed the heat from the process caused the solder on the pads of the UCC to reflow, and it fell off. I'm guessing a similar thing happened to the first board, but instead of falling off some of the pins on the chip lost contact with the pad. I went ahead and placed the component again and it worked this time around.
    Below is what I was seeing on the pins (EN left floating):
    VDD: 5 V
    INA: 1.7 V (Should have been 3.3)
    OUTA: 2.5 V

    When the connection was fixed:
    VDD: 5 V
    INA: 3.3 V
    OUTA: 5 V

  • Hi Nicholas,

    Awesome! Thanks for letting us know. If you need anything, we are standing by!