Hi If you are getting 11 V p-p, I'd bet you don't have the 10 MHz output terminated in 50 ohms.
Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of beale Sent: Monday, December 12, 2011 1:29 PM To: [email protected] Subject: [time-nuts] FE-5680A internal signal waveforms (60, 30, 10 MHz) I have two of the FE-5680A (FEI P/N 217400-30352-1) Rb references, and I'm looking at the signals on digital side of the PCB inside, in particular the Xilinx CPLD, that is the XC9572XL in a 64-pin package. Here is a photo with the signals marked: https://picasaweb.google.com/109928236040342205185/FE5680A#56853041347181331 38 pin 64 has a nice looking 60.00 MHz sine wave, I gather this is the input signal to the CPLD. pin 22 has a 30 MHz square wave, although it has some ripples (see scope trace in same Picasa album) pin 49 has a 10 MHz "square" wave but with a very odd shape. Pin 49 is the signal which is LC filtered (?) to become the 10 MHz sine wave out on the internal J8 mini-connector, and the external DB9. The signal is about 3.3 Vpp, but becomes an 11 Vpp sine wave at the far side of a blue part (inductor?) marked 2R2J. The 10 MHz sine out on my unit has some noticeable amplitude noise, at least a few %. Since I'm only using the signal as a digital clock, I prefer a square wave, assuming the fast edge will give me lower jitter. A 200 MHz Rigol scope reads a risetime of 2 ns on CPLD pin 49, but the waveform looks so noisy and odd (see below), maybe I would be better off just squaring up the output sine. ...maybe if pin 49 was disconnected from the sine output filter, it would be more square (?) https://picasaweb.google.com/109928236040342205185/FE5680A#56853041438595262 58 -John Beale _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
