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DP83848K: Problem for TD+/TD- pin waveform

Guru 19475 points
Part Number: DP83848K
Other Parts Discussed in Thread: OPA2677

About captured TD+(16 pin) and TD-(14 pin) by differential probe, waveform ware saturated, oscillation, and not smoothed.

But competitor is smoothed on the same condition, waveform is attached.

(Power supply is clean 3.3V)

※DP83848K                                         ※Competitor

                

Please let me know about question points below;

【Customer concerned point】

・We guess that the reason is internal Filter.

 If influence internal filter, this waveform is normal or abnormal.

・If normal operation, customer will relieved for get IEEE 802.3 test data.

・Whether wrong point for external circuit or not.

【Question】

①Are these waveform normal operation?

②Is internal filter influence this waveform?

 If yes, is there way to setting internal filter?

③About external circuit,

 ・OPAMP(OPA2677) and Zener diode is connecting Between TD+/TD- to Output Transformer, is this no problem? 

 ・Termination is connecting 51Ω for TX and Rx side, is this require change? (25Ω, 100Ω, etc)

 ・Is there possibility reason for matching Transformer?

④If availability IEEE 802.3 test data, please let me know.

If need more information, please contact direct E-mail.

Best regards,

Satosh