UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 18017

Virtex-II Pro RocketIO - Why is the power consumption for VTRX pins zero?

Description

General Description: 

The RocketIO Users Guide specifies that the power consumption for the VTRX pins is zero when the receiver is AC coupled. Why is this?

Solution

No power is dissipated because there is no DC path to ground.  

 

The following circuit illustrates an AC coupled receiver: 

 

AC Coupled RocketIO Receiver
AC Coupled RocketIO Receiver
 

 

For power to be dissipated from the VTRX source, a path to ground would need to exist. 

 

- DC current cannot flow from VTRX back through the transmission line due to the AC coupling capacitor blocking DC current. 

 

- The only current that can flow is the leakage current through the receiver gate to ground. This is a very high impedance path, which sinks little current. 

 

- The current sourced from VTRX in an AC coupling link has been measured to be less than 50 nA (nanoamps) per transceiver during 3.125 Gbps operation on the ML321 characterization board. 

 

- Note that this number might vary depending on your transmission line, coupling capacitors, termination resistance, and VTRX voltage.

AR# 18017
Date Created 09/03/2007
Last Updated 05/16/2014
Status Archive
Type General Article