Description

What is the maximum junction temperature allowed for Xilinx CPLDs?

Solution

For the XC9500/XL/XV parts, an absolute maximum junction temperature of 150C is specified for ceramic packages. The absolute maximum junction temperature for plastic packages is 125C.

For the XPLA3 CoolRunner and CoolRunner-II devices, the absolute maximum junction temperature is 150C (as listed in the family data sheet).

The temperature ranges specified for commercial (0C to 70C) and industrial (-40C to 85C) grades refer to the ambient temperature limits. As the power consumed by the CPLDs are relatively low the upper limit for ambient temperature is also effectively the maximum operating junction temperature.

Maximum operating junction temperature is the maximum die temperature allowable such that data sheet timing values can be guaranteed.

The relationship between TJ and TA is documented in Xilinx UG112 Device Package User Guide:

http://www.xilinx.com/xlnx/xweb/xil_publications_index.jsp?category=User+Guides

ThetaJA = (TJ - TA)/PD

An example: XC2C64A-PC44 C Grade

Information taken from the Package Thermal Query:

http://www.xilinx.com/cgi-bin/thermal/thermal.pl

ThetaJA = 53.3 degC/W

Ta max = 70 degC

PD (either measured or estimated) = 10mW

ThetaJA = (TJ - TA)/PD

53.3 = (TJmax - 70)/10mW

TJmax = 70.5 degC