Part Number: LMH1297
Other Parts Discussed in Thread: LMH0397,
We use LMH0397 3G-SDI Bidirectional I/O With Integrated Reclocker and
LMH1297 12G UHD-SDI Bidirectional I/O With Integrated Reclocker
We use the devices in EQ mode by feeding an SDI video into SDI_IO through cable EQ and CDR and output via OUT0 to FPGA.
The chips are running in the power up default. From 0 to 85°C the chips are running fine.
They fail to function at -40°C for 720p60 or 1080p60 so 1.5G or 2.97G speeds, while 270Mbit do work.
Spec says –40°C to +85°C Operating Temperature Range
For debugging tests we used the "Cable EQ Bypass Override" feature
With EQ bypassed the cold issue is gone. But we did not implement these chips to disable the EQ.
CMD REG VALUE MASK //COMMENTS
RAW FF 05 07 //Select ConfigIO Register Page
RAW 27 08 08 //Enable EQ Bypass override with value in Reg 0x27[2]
RAW 27 04 04 //Bypass Adaptive Cable EQ
As alternative to enable the "–6-dB Launch Amplitude" feature also seem to fix the failing EQ.
But the launch amplitude is ~800mV where this setting is usually not required.
We see that this setting reduces the readback value of the Cable EQ Index (CEI) after adaptation.
COMMAND REGISTER VALUE MASK //COMMENTS
RAW FF 05 07 //Select ConfigIO Register Page
RAW 34 80 80 //Enable –6-dB splitter mode
At cold temperatures the read value of the Cable EQ Index (CEI) after adaptation was higher than at room temperature.
We have the feeling that higher EQ CEI or EQ gain values are in correlation with the cold error.
Is this a known issue ?
What is your advice?
Can we have manual control over the SDI_IO cable EQ settings like gain or SDI_IO CTLE etc?
Is there a newer programming guide than SNAU204C–March 2017–Revised January 2018
Many Thanks in advance
Marcello
