SN75DP159: SI fail

Hi,

For VSwing failed test item, you can refer to Figure 3 and section 10.3.1 of the DP159 datasheet. You can use Vsadj to tune it. When Vsadj decreases, the Vswing increases and VL decreases. When Vsadj increases, the Vswing decreases and VL increases. 

For the inter-pair skew, have they calibrated their scope probe first? Can you please share the compliance report with the inter-pair skew waveform?

Thanks

David

Hi David,

1. Adjusting the VSwing resistor from 6.49k to 4.7k ohms increased the VSwing as follows: from 309mV to 395mV (see the complete report attached as below).

This is a 1790-ohm change, but the VSwing increase doesn't match the spec's 20mV per 100 ohms. We will try further adjusting it down to 4.53k ohms.

2. The scope was calibrated before each test. The inter-pair skew failure report is attached. Additionally, we've included pass reports from other device models for your reference.

New Device1_Report_2024-12-10_05-33-36_UTC+0800_MXM A380E modify 4.7Kohm 1.pdfNew Device1_Report_2024-11-26_02-09-33_UTC+0800D0_D1 FAIL.pdfNew Device1_Report_2024-11-26_02-09-33_UTC+0800D0_D2 FAIL.pdf

Hi Jeff,

Was the setup the exact same for the other devices that passed? 

We haven't had many issue with skew in the past. Is there a common mode choke on this design?

What the skew test look like from just the source?

Hi Vishesh,

Was the setup the exact same for the other devices that passed? 

=> Yes

We haven't had many issue with skew in the past. Is there a common mode choke on this design?

=> have common mode choke design as below.

What the skew test look like from just the source?

=> Source side have no connector so can't meansure.

Jeff

For the inter-pair skew, what is the trace length from the DP159 output to the HDMI receptacle? Can you please share the layout?

Thanks

David

Hi David,

Please see below. thanks!