LMH0050 won't lock

Thanks.  That did the trick. I am going to use 148.5Mhz frequency, but I was just checking the basic setup and the datasheet says the clock can be between 27 to 149 Mhz.  I am using the IP and have it instantiated in my code.  I am waiting for a balun to go from 100ohm diff to 75ohm single to get it into a monitor to check if it is correct.  I'll let you know.  Thanks again.

Mike

Well, I got my balun to go from 100ohm diff to 75ohm.  I am not able to get the test pattern out, however,   I have a little box that "locks" to an hd-sdi stream, and it won't lock.  I am not sure if it is parsing a bit or simply the clock rate (docs are terrible), but I would assume if the serializer is locked, the output would be at the correct freq and the little box would lock.  Any suggestions on things to check?  I am driving a DS15BA101SD from the lmh0050. This drives 100ohm differential cable to the balun and then 75ohm coax to the little box.

Michael

If you want to drive a 75 Ohm output, it should be much easier to use the LMH0040 rather than the LMH0050 - this will provide you with a 75 Ohm output directly, and you won't need a Balun.

Is the LOCK output pin on the LMH0050 LOW? - If LOCK is low, then this would indicate that the PLL in the LMH0050 is locked, and that the output  should be toggling.

Do you have a scope or waveform monitor which will allow you to look at the serial output from the LMH0050?

What is the input to your 'little box?'  Is it an HD-SDI input?, if so, I am a bit confused about your exact configuration: LMH0050>Balun>DS15BA101>Balun>Box?  How long are the cables?

Mark

Ultimately, I need to go through a slip ring and the interface is 100 ohm, so the lmh0050 should work nicely.  Just to test  I have LMH0050->DS15BA101->100ohm tp cable->balun->75ohm cable->monitor.  Right now the cables are <6".  The LMH0050 is locked and I "see" basically the same signal on either side of the DS15BA101.  Nothing recognizes the signal as far as I can tell.   It is toggling as I can make it stop by holding either the firmware or the LMH0050 in reset.

Still struggling here.  I am using the firmware from Xilinx XAPP514 as the one that I downloaded from you guys has a lot of things I don't need.  The code is basically the same, in fact, some of the modules are exactly the same.  Any suggestions?  The LMH0050 is locked but nothing detects its output.  I can "see" a digital signal with my scope, so I know it is transmitting, but nothing detects it.  Any help would be appreciated.

Mike

Mike

I'd like to understand what you mean by 'nothing detects it'.   You are seeing a signal on an oscilloscope - are you able to verify that it is at the correct data rate for what you are expecting?

What instruments are you using to detect the signal?

A couple of things to check - the device has an option for 8b10b encoding which can be turned on either by a pin, or through registers, please make sure that it is in the correct position (for most video signals, you will want 8b10b OFF).

Is the output that you are putting into the SDI input of whatever you are using to detect the signal of the proper amplitude, impedance etc?

Mark,

I have an HD-DVI converter as well as some h,264 encoders that will detect proper video signals.  I've tested that these work correctly with known good signals.  I checked the amplitude and it matches the signal that works.  I am hunting around (at Naval Research) for a scope with enough bandwidth to make some proper quantitative measurements (eye patterns, etc.)  The signal chain is the same as that used for the "working" hdi output off my sensor.  Is the 8b10b encoder on by default?

Mike

thanks.  I 'll have to see if I can make that work on the current board.  I have the dvb_asi turned off.  frustrating.