Answers Database
3000, 4000E/X, 5200, 9500/X: Measuring die temperature
Record #4560
Product Family: Hardware
Product Line: 4000E
Product Part: 4000E
Problem Title:
3000, 4000E/X, 5200, 9500/X: Measuring die temperature
Problem Description:
Urgency: Standard
Problem Description:
Sometimes it is useful to get an estimate of the die
temperature of a particular device. There are two procedures
that may be used.
Solution 1:
The forward voltage drop of any silicon diode changes about
-2.2 mV per degree C. So, forward-bias the input protection
diode on an unused I/O with a constant current, a half milliamp
in this case. With the device not operating (perhaps not even
configured), read the pin-to-ground voltage (about 650 mV) at
room temperature. Then read it again at operating conditions.
Watch out for noise on the ground plane. It may make sense to
stop the clock right before the measurement. Subtract the two
millivolt numbers, divide by 2.2, and you should get the
temperature rise above room temperature.
Solution 2:
There is also a different method:
Implement ring oscillators on the chip and measure the
frequency ratio between cold and operating.
End of Record #4560 - Last Modified: 09/10/98 12:20 |
