Digital I/O

Showing results for 
Search instead for 
Did you mean: 

Howto drive a differential ECL receiver with a PXI-6552

I want to drive an ON Semiconductor MC100ELT23 with a PXI-6552. Do I need to provide termination resistor/resistors for this application? The only reference I could find to this application only includes a block diagram for the connection. The need for a termination resistor is not discussed.
0 Kudos
Message 1 of 3
Hi bsexton,

The Digital Waveform Generator/Analyzer Help file describes the source impedance of the 6552 [1]. Using the information there and the data sheet for your On Semi IC will allow you to find the appropriate termination resistor value.

[1] 655x Source Impedance
NI Digital Waveform Generator/Analyzer Help » Devices » NI 655x » Hardware Architecture » Channel Electronics
Joe Friedchicken
NI Configuration Based Software
Get with your fellow OS users
[ Linux ] [ macOS ]
Principal Software Engineer :: Configuration Based Software
Senior Software Engineer :: Multifunction Instruments Applications Group (until May 2018)
Software Engineer :: Measurements RLP Group (until Mar 2014)
Applications Engineer :: High Speed Product Group (until Sep 2008)
0 Kudos
Message 2 of 3

The 6552 is source series terminated so you do not require any additional termination.  You may, however, place additional differential parallel termination at your MC100ELT23 receiver of 100ohms and drive two channels of the 6552 with complementary data.  Keep in mind, though, that this will result in a voltage divider. 

If you are powering the
MC100ELT23 with a 5V supply (Table 4 specs of the data sheet at then the 6552 will need to provide a VHIGH of > 3.84 and a VLOW < 3.52 at the pins of the receiver.  If you don't add additional termination then you can achieve this by setting VOH > 3.84 and VOL to < 3.52 with the recommendation of keeping the common mode (VOH + VOL / 2) between 2.2V and 5V.  With the additional termination, your swing will be cut in half so in order to have the same 3.52 to 3.84 swing, your VOH would need to be 4V and VOL would need to be 3.36V.

Hope that helps.
0 Kudos
Message 3 of 3