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DP83630 Bias Resistor

Vladimir Naumenkov
Expert 2970 points
Other Parts Discussed in Thread: DP83630

Dear Patrick

Please, answer

We found out, that there is no any voltage at  the  pin20 (VREF), which is connected to a resistor 4.87k, and the other end of this resistor connected to GND . At the same time, we looked this voltage at  the same resistor (R50) at the Ethernet Starter Kit board (which has DP83848 controller and PIC32 microcontroller) and this voltage at the pin RBIAS is 1.18 V.  It seems, that we all still have to change the DP83630?

http://ww1.microchip.com/downloads/en/DeviceDoc/61159B.pdf

TIA

Sincerely yours,

Vladimir Naumenkov.

www.agat.by

  • 0
    TI__Mastermind 31600 points

    Vladimir,

    The VREF resistor for the DP83630 and the RBIAS resistor for the DP83848 perform the same function.  They set the internal reference bias for the device.  If there is no voltage on this pin, the device will not operate correctly.

    The question here is why there is no voltage on the pin.  The two most likely causes that I can think of are:

    1. Connectivity issue for the resistor or the pin due to a solder problem or a bad trace connection to the pin or to ground.
    2. Supply issue for the 3.3V supplies.  Without the 3.3V supply, the circuitry connected to the VREF pin inside the chip will not operate.

    How many parts / boards have shown this behavior?  Has this been discovered during early prototyping of the the design?

    Patrick

  • 0 in reply to Patrick OFarrell
    Expert 2970 points

    Dear Patrick

    Thank you

    We still have only one board - it is a prototype. 

     Sincerely yours 

    Vladimir Naumenkov

    www.agat.by