DP83822I: HX1198FNL Pulse Transformer drawing more current

Hi Mani,

Under what condition does this current draw happen? Link down, link up, link up + data transfer?

Thank you,

Nikhil

Hi Nikhil, 

Just board assembled and powered up.

Regards

Mani

Hi Nikhil,

I removed HX1198FNL pulse transformer and checked current was normal. So i have a doubt that voltage

applied at pin-2 and 7 for HX1198FNL transformer should be pulse voltage or DC voltage? If it is pulse voltage what frequency voltage need to be applied.

Regards

Mani

Hi Mani,

Pins 2 and 7 of the transformer should be connected to the AVD supply as specified by Section 9.2.1 in the datasheet.

If you have register access, can you provide a register read of the following registers:

• 0x0
• 0x1
• 0x9
• 0x10
• 0x11

Thank you,

Nikhil

Hi Nikhil,

Thank you very much for your information.

We applied 3.3VDC derived from LDO at pin 2 & 7 of transformer. What will be other reason to draw more current.

Regards

Mani

Hi Mani,

We are looking into this issue and will provide feedback by Friday this week latest.

Thank you,

Nikhil

Hi Mani,

Some follow up questions:

• How often is this issue seen? If you have multiple boards is this issue seen across all boards or is it only this one?
• Is the PHY still functional even with this current draw (is register access available, is there link to link partner)?
• If replaced with a different PHY is current draw still seen?
• You mention current draw is ok when Transformer is removed. Is this issue seen across different transformers of the same model?

Thank you,

Nikhil

Hi Nikhil,

• How often is this issue seen? If you have multiple boards is this issue seen across all boards or is it only this one?
  • We built 3 boards and seen same issue on all boards
• Is the PHY still functional even with this current draw (is register access available, is there link to link partner)?
  • We removed the transformer and seen current was normal... we tried by connecting 10ohm resistor between 3.3V DC and pin 2, similarly we connected 10 ohm resistor between 3.3V DC and Pin7 and observed both resistors getting heat and drawn more then 300mA. Actually we powered with Agilent U8001A power supply by keeping current limit as 0.8A... further we increased to1A the current limit and observed current drawing more and voltage dipping. So we can't able to check PHY functionality.
  • Let me know how to access registers in PHY IC?

• If replaced with a different PHY is current draw still seen?
  • We seen in all three boards. PHY IC was soldered in outside vendor due to pins under IC.
• You mention current draw is ok when Transformer is removed. Is this issue seen across different transformers of the same model?
  • We seen same issue by changing 3 transformer in each board. We also ordered HX1188FNLT transformer to replace and check. 

Regards

Mani