DS125DF1610EVM: No signal was detect and and CDR remained unlocked

Hi,

Can you share a block diagram of your test setup?

Thanks,

Drew

Hi Che-Jung,

What is your input signal to the retimer?

Thanks,

Drew

Is there any internal signal can use? or It must need output signal to connect the EVM board input signal?

Which pin/port we need to connect? like RX SMA port?

Hi Che-Jung,

Yes, this is correct.  What is your application for this device?

Thanks,

Drew

Hi Drew,

The application includes:
• Data Rate (Tx): 3 Gbps
• Rise/Fall Time: 30 ps (min), 42 ps (max)
• Peak-to-Peak Swing: 0.2 – 0.45 V
• PRBS Generator: PRBS7

The plan is to first use SigCon Architect to generate and analyze the eye diagram before moving on to full ATE validation.

Hi Drew,

I provided a 1.5 GHz external clock input to the RX4A.

The eye diagram detection in the GUI program still appears as shown in the attached image.

Thanks for your reply.

I provided a 1.5 GHz external clock input to the RX4A.

My EVM settings are as shown in the attachment. Regardless of whether I enable the PRBS generator or not, the waveform I observe on the TX4A using the oscilloscope remains the same.

TX4A:

EVM Setting:

Config:

config_register_20250826_LockCDR_7.2.cfg

Hi Che-Jung,

On the CDR page, can you please select a REFCLK frequency that matches the frequency you are using on the EVM?  Depending on jumper configuration, you can select 156.25 MHz or 312.5 MHz

Thanks,

Drew

Hi Drew,

I’m now referencing your configuration settings. However, the CDR does not lock, whether or not I provide a 1.5 GHz clock to the RX4A port. Just to confirm—should the CDR be locked before the signal detector turns green, or should it lock after the signal is applied?

config_register_20250829_TI.cfg

Hi Drew,

My CDR can lock now when I provide a 1.5 GHz clock to the RX4A port. However, the eye diagram detection and PRBS generator results are still not as expected.

Result:

TX4A_P:

Setting:

config_register_20250829_TI_3.cfg

Hi Che-Jung,

I will review your settings and get back to you this week.

Thanks,

Drew

Hi Drew, 

Thanks a lot.

I have two configuration files with different behaviors:

1. First configuration:

   • The eye monitor does not function.
   • TX has output when we soured the signal to RX.
   • CDR locks before we source signal to the RX.
   • config_register_20250826_LockCDR_PRBS.cfg

2. Second configuration:

   • The eye monitor functions properly when we soured the signal to RX.
   • But there is no TX output.
   • config_register_20250829_EYE.cfg

I would like to understand the relationship between the following parameters in this context:

• PRBS generator output data rate (e.g., 3 Gbps)
• RX input frequency (e.g., 1.5 GHz)
• Reference clock (e.g., 25 MHz)
• CDR settings
• VCO frequency

Could you help clarify how these elements interact, and what might be causing the differences in behavior between the two configurations?

Now I have both TX output and eye monitor working in the following configuration. It seems that when I source a 1.5 GHz signal, the TX output is also 1.5 GHz. Similarly, when I source a 3 GHz signal, the TX output becomes 3 GHz.config_register_20250829_LockCDR_EYE_PRBS_4A.cfg

The rise/fall time is currently around 100 ps, but our target is 35–40 ps. We tried modifying the edge rate select setting, but it didn’t make any difference.