LMH0397: Troubleshooting Video Flickering with LMH0397 in Equalizer Mode

Rich Brindha

Part Number: LMH0397

Dear Team,

We are currently utilizing the LMH0397 3G-SDI Equalizer/Cable Driver IC in our hardware design and are encountering a video flickering issue under specific operating conditions. We would appreciate your technical guidance in resolving this problem.

Observed Behavior & Test Results:

Equalizer Mode (Issue): When the IC is configured in Equalizer mode, we experience persistent video flickering and signal instability when connected to external 3G-SDI sources. This behavior is consistent across multiple sources, including a Blackmagic Design bidirectional HDMI-to-3G-SDI converter and a standard 3G-SDI camera.
Loopback Mode (Control): To isolate the signal path, we performed a loopback test using one channel as a cable driver and another as an equalizer, connected externally via a Belden 1694A cable. In this configuration, the output functions correctly without any flickering.

Given that the internal loopback test passes successfully, could you help us eliminate this flickering issue?

10 days ago

0 David (ASIC) Liu 10 days ago

TI__Guru**** 192851 points

Hi,

Can you please share a block diagram of the Equalizer Mode and Loopback Mode? When you are encountering the issue under specific operating conditions, what is the condition, are you using pathological test patterns?

Thanks

David

0 Rich Brindha 7 days ago in reply to David (ASIC) Liu

Prodigy 45 points

3G SDI video flickering issue is observed under normal working conditions.
We tried optimizing the VOD, Pre-emphasis, De-emphasis and Reclocker settings but the issue is not solving.
The CDR lock rate is set to 2.97Gbps data rate.

0 David (ASIC) Liu 6 days ago in reply to Rich Brindha

TI__Guru**** 192851 points

Hi,

Have you checked the CDR lock status by reading reg 0x02[5:3] in CDR page? Is the CDR locked to the right data rate?

If you use the LMH0397's eye monitor feature, are you seeing an EOM difference between the two cases on the bottom LMH0397?

Thanks

David

0 Rich Brindha 6 days ago in reply to David (ASIC) Liu

Prodigy 45 points

Hi,

1) The CDR lock status is locking to wrong data rate reading as 0x02[5:3] = 011’b 1.485 Gbps.

What could be the issue?

2) No, we didn't use EOM features.

Regards,

Rich Brindha

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LMH0397: Troubleshooting Video Flickering with LMH0397 in Equalizer Mode

Observed Behavior & Test Results: