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Use of CMOS Driver for Circuit Temperature Measurement

IP.com Disclosure Number: IPCOM000120845D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Dhong, SH: AUTHOR [+4]

Abstract

In the operation of CMOS circuits at near liquid nitrogen temperature, there is a need to know the temperature of the circuit. Present techniques rely on measuring the temperature of the circuit package, cooling block, or wafer chuck. The temperature is obtained by using the forward current-voltage (I-V) relationship of an inserted diode, which has a well-known temperature dependence.

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Use of CMOS Driver for Circuit Temperature Measurement

      In the operation of CMOS circuits at near liquid nitrogen
temperature, there is a need to know the temperature of the circuit.
Present techniques rely on measuring the temperature of the circuit
package, cooling block, or wafer chuck.  The temperature is obtained
by using the forward current-voltage (I-V) relationship of an
inserted diode, which has a well-known temperature dependence.

      Disclosed is a technique for measuring the temperature on the
circuit substrate itself.  By appropriately biasing an output driver
of a CMOS circuit, the driver can be operated as a diode, making
temperature measurement possible.  The output circuit is shown in
Fig. 1. The p-type FET sits in an n-well, as shown in Fig. 2.  If
the Vdd terminal is grounded, the n-type FET is off, and the output
is thereby connected to ground through a p-n junction, i.e., a diode.
By forward biasing the output with respect to ground, a forward
biased I-V curve is obtained, the slope of which is a function of
temperature.

      An example of this behavior is shown in Fig. 3.  The Vdd
terminal is grounded, as described, and the currents measured as the
output voltage is forced.  At room temperature, a shallow slope is
observed, whereas at liquid nitrogen temperature, obtained in this
case by immersing the chip, the slope is much steeper, as expected.
Thus, the slope of such a curve can be used to measure temperature.
With suitab...