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# Noise Immune on Chip Temperature Sensing

IP.com Disclosure Number: IPCOM000107337D
Original Publication Date: 1992-Feb-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 83K

IBM

Fahr, GJ: AUTHOR

## Abstract

Disclosed is a technique for taking fast, two-point, resistance-independent, and relatively noise-insensitive measurements of chip junction temperatures by passing multiple currents through, and reading multiple voltages across, a diode-type sensor.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Noise Immune on Chip Temperature Sensing

Disclosed is a technique for taking fast, two-point,
resistance-independent, and relatively noise-insensitive measurements
of chip junction temperatures by passing multiple currents through,
and reading multiple voltages across, a diode-type sensor.

Two-point, chip junction temperature measurements are made on a
diode-type sensor, for a given technology, by passing multiple
currents through the diode and remotely reading the corresponding
voltages across the sensor.  The measured voltages, along with a
diode forward voltage reference value and temperature reference
value, are used in an algorithm to calculate the junction temperature
of the sensor located on a chip.  The algorithm uses the diode
current versus voltage logarithmic relationship, and the diode
voltage versus temperature relationship (approximately polynomial
over a reasonable, but limited, temperature range) for a specific
sensor technology.

By passing two different currents through the sensor (I2 and
I3), in a ratio to two  (i.e., I2=2xI2=4xI1), the diode forward
voltage (VF) can be calculated using the corresponding two voltage
values measure across the sensor (V2 and V3), as shown in Eq. 1. The
calculated voltage value (VF) is actually the diode's forward voltage
at a current level half of that of I2 (i.e., I1) plus any voltage
offsets (VOFF), buy is independent of any voltage drops due to loop
resistance.  The diode forward voltage and temperature reference
values (VF1 and T1, respectively) are the nominal forward voltage (at
I1), at a chosen temperature (T1), for specific sensor technology.
The difference voltage (VF12), calculated in Eq. 4A, between the
reference forward voltage value (VF1) and the present calculated
forward voltage value (VF2) plus offsets (VOFF), is used in an Nth
order polynomial equation to determine a temperature difference value
(T12).  The coefficients, used in Eq. 5, are predetermined and
characterize the nominal voltage versus temperature relationship for
the sensor technology being measured.  The calculated...