CCS/LMH1297: I/O( Standard on IN+- and OUT+-

joe lindula

Part Number: LMH1297

Tool/software: Code Composer Studio

Hello, I am using the LMH1297 for an SDI Video application. I have the IN+- and OUT+- Differential pairs going to an FPGA transceiver pins. I've looked through the LMH1297 datasheet to determine is those diff pairs are CML or PECL or something else. The Xilinx Ultrascale+ FPGA supports LVDS, DIFF_HSTL and many others. I have tied the VIN pin to 2.5V.

Can anyone tell me what is the I/O Standard on the IN/OUT Diff pairs?

Thank you,

Joe

over 6 years ago

0 Nasser Mohammadi over 6 years ago

TI__Guru* 93570 points

Hi Joe,

100-ohm differential IOs are CML type IOs. Please AC couple using 4.7uF capacitors.

Regards,, Nasser

0 joe lindula over 6 years ago in reply to Nasser Mohammadi

Mastermind 6940 points

Hello, thank you for responding to my message. I'm looking on page 12 of the LMH1297 datasheet under the Driver Output box VODout0 "Output Differential Voltage at OUT+-, is the mVp-p the same as VDM (Differential Mode Voltage)?

On CML I've seen VOH to be 1.9V and VOL to be 1.1V which a swing 800mV. For the LMH1297 what would the values be for LMH1297 if you chose HOST_EQ0=L which would be 810mVp-p?

Thank you very much,

Joe

0 joe lindula over 6 years ago in reply to joe lindula

Mastermind 6940 points

I did a quick picture:

Is this the CML lines IN/OUT?

Thank you,

Joe

0 Nasser Mohammadi over 6 years ago in reply to joe lindula

TI__Guru* 93570 points

Hi Joe,

1). Yes differential voltage is (OUT+) - (OUT-). It is essentially double single ended output.

2). DC common mode voltage is about 2V. For 810mVp-p, it means single ended swing would be 410mVp-p riding on 2V. Therefor VOH would be 2+(410/2)=2.2 and VOL= 2-(410/2) = ~1.8V.

Regards,, Nasser

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CCS/LMH1297: I/O( Standard on IN+- and OUT+-