• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 33 subscribers
  • Views 1420 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DP83848IVV clock Input X1 with DC Offset & PFBIN/OUT < 1,72V

schaefer1
Prodigy 180 points
Other Parts Discussed in Thread: DP83848I

Hello,

i have a few questions to the DP83848IVV. My situation: I tried to evaluate my own board with the DP83848I(VV) and AT32UC3C164C microcontroller from Atmel (µC is sitting on a Atmel STK600 Evaluationboard).

The DP83848I is on an extern own layouted board. Supply Voltage and Ground is used from the STK600. Signalconnections from own board to STK600 are realized with some usual wires (10cm long - i know it is not ideal for xx MHZ signals). The schematic of my own board is referred to the EVK1100 & EVK1105 evaluation boards from Atmel. I read in some forum posts about the DC checkpoints and checked them out:

Pin     Description   DC Value       MY DC-VALUES (DP83848I-Board referred to the connected STK600 Ground)

15     AGND            0 Volts                       1,3mV

18     PFBIN1         1.73 to 1.8 Volts         1,725V

19     AGND            0 Volts                        1,3mV

22     AVDD33        3.3 Volts                      3,26V

23     PFBout          1.73 to 1.8 Volts         1,725V

24     RBIAS            1.19 to 1.2 Volts        1,183V

29     RESET_N     3.3 Volts                      3,26V

35     IOGND          0 Volts                         1,3mV

36     DGND           0 Volts                         1,3mV

37     PFBIN2         1.73 to 1.8 Volts          1,725V

47     IOGND          0 Volts                         1,3mV

48     IOVDD33     3.3Volts                         3,26V

The Resistor Values are okay: RBIAS=4,87k and MDIO Pullup=1,5k.
Reset Pin got also 10k Pullup.

So here are the first part of my questions:

1. Is the PFBIN1/2 / OUT voltage critically low?
2. Is the RBIAS voltage critically low?
3. Is it necessary to connect the Reset Pin to a PullUp?


I measured some additional testpoints because my focus was also on my used CMOS-OSC (frequency).
The used oscillator is connected to Pin 34 (X1). I used the 7W-50.000MBA-T CMOS-Oscillator from TXC. It is a different one than the CFPS73 (HCMOS) which is chosen by ATMEL on EVK1100/1105.

Pin     Description   DC Value      MY DC-VALUES (DP83848I-Board referred to the connected STK600 Ground)

34      X1                     ??               ~1,5/~1,6V (after removed OSC output-pin !)



On the removed output-pin of this CMOS-Oscillator there was a DC-Voltage(~1.7V) with a 50MHZ AC-signal. The low-level was ~1.2V and high-level was approx 2.2V.


Second part and very important part of my questions:

4. Is the CMOS-OSC damaged?
5. Why is there a DC-Value at PIN 34 (X1)?
6. What High/Low-level is needed to get a correct oscillation for the DP83848IVV?


In the attachement is my schematic. Reset and PWR_DOWN/INT Pin are connected through wires afterwards (because i forgot them). RESET_N Pin got a PullUp to 3,26V Supply and the PWR_DOWN/INT Pin is directly connected to my microcontroller pin.

Hint: RBIAS is 4.87k (not 4.868k which you see in schematic)



Third and last part of my questions:

6. The resulting values of my resistors on Pins TD+/TD- ; RD+/RD-  have always value ~1Ohm when i measure from RD- to TD+ or TD+ to TD- or RD+ to TD- ord RD+ to RD- because of the magnetics on the middle tap. These values are okay i think?

I hope somebody can help and support me.

Best Regards
Sebastian

  • 0
    TI__Mastermind 31600 points

    Sebastian,

    You have provided many measurement results and many observations about the state of your board(s).  I do not see a description of a specific problem however.  Are you experiencing problems with the design or are you just asking for confirmation on your measurements? 

    What have you seen in your testing that led you to make these measurements?  Can you read and write registers?  Were you able to achieve a link?  Can you pass packets? 

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 180 points

    Hello Patrick,

    okay the main problem of my DP83848I board is that i can't ping my µC from PC. I used the example software from Atmel (from Atmel Studio) and i have adjusted the example C-Files to my board. 

    DP83848I board with EthernetJack is connected to PC. Microcontroller is connected to the DP83848I board.

    The two status leds are working when ethernet cable is connected. Software is also working. But ping is not working: "Target Host is not reachable".. so i know there is a big hardware problem on my board. I measured the listed checkpoints and i also checked the oscillator.

    The main problem is that my oscillator have the behaviour which i described at my first post (50Mhz; 1.2V LOW and 2.2V High). I can't believe that this is a normal operation mode for an CMOS-oscillator, so i asked for the DC-Voltage at Pin X1. I want to understand why this oscillator type isn't working.

    So, at the one hand i am asking for a confirmation on my measurements to exclude simple errors and on the other hand i want to understand why the mounted oscillator type wasn't working.

    For the sake of completeness: I don't know whether i can read or write registers, because oscillator isn't working.

    Thank you and Best Regards,
    Sebastian