Hi Team,
Good day! Could you please help to check our customer's concern below.
Here it is:
We use ETH PHY DP83822i for 100base-TX communication module. We have measured physical layer test and the result is quite close to the limit. (Tested by Tektronix MSO 5104 – TDSET3 option, diff. active probe TDP1000, test fixture Tektronix TF-GBE-BTP)
I would like to clarify few points ….
- Ethernet magnetics
Datasheet contains transformer electrical specification, but I didn’t find any information about transformer inductance. Is there any requirement?
(Magnetics have usually inductance 150 – 350 uH)
- Low Output amplitude
We have measured approximately 960 mV, which is quite close to the limit. Generally, all our PCBs with DP83822i have lower output amplitude.
We are looking for the root cause of low voltage. I think, that transformer will be main cause. We will try several transformers to see the impact on output voltage.
We could also increase the output level by “0x0403 Line Driver Control Register (LDCTRL)”.
Do you have any other idea how to increase the output voltage?
- Rise/fall time
We would like to also improve Rise/fall time. Unfortunately, layout of the board couldn’t be change …..
I’ve found some option on Texas Instrument technical forum “DP83822I: Help to pass compliance test (rise and fall time)”
There is small manual how to decrease rise/fall by changing 0404 register. (See below)
You may try following programming options for rise/fall time decrease to tackle possible extra load on customer board :
a.x0404 = 0120
b.x0404 = 00A0
c.x0404>= 0024
I didn’t find any detailed description of the register 0404 “(0x0404 Line Driver Class Selection (LDCSEL)”. Would it be possible to provide me detailed description of register 0404. We would like to avoid side affect of the change.
Do you have any other idea how to decrease rise/fall by changing registers?
Material part numbers:DP83822i
Thank you very much for your help.
Best regards,
Jonathan
