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Integrated Feedback Controlled Thermally Stable Voltage Reference

IP.com Disclosure Number: IPCOM000081451D
Original Publication Date: 1974-Jun-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Blose, WL: AUTHOR [+2]

Abstract

The circuit configuration is shown in Fig. 1 and operates as follows: The reference voltage is continuously monitored by the sensor and adjusted by the thermal controller to provide a constant-output voltage reference.

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Integrated Feedback Controlled Thermally Stable Voltage Reference

The circuit configuration is shown in Fig. 1 and operates as follows: The reference voltage is continuously monitored by the sensor and adjusted by the thermal controller to provide a constant-output voltage reference.

A representative circuit implementation for the reference, sensor, and thermal controller is shown in Fig. 2. Here the branch of R1, Z1, D1, and D2 form the basic voltage reference where R1 is a resistor providing divider action for V(IN), and Z1 is a Zener or breakdown diode having a positive temperature coefficient of voltage, while D1 and D2 are base-emitter diodes having negative temperature coefficients of base-emitter voltage. The net effect at point A is to provide a small delta V/delta T due to the compensation of Z1 in series with D1, D2. This assumes that the ratio delta V/delta T is kept constant by controlling delta V as a result of T varying.

Extending this concept, this circuit provides an improved resolution of reference voltage by essentially controlling and adjusting both delta V and delta
T. This is accomplished by the sensor and thermal controller consisting of R2, R3, R4, R5, Q1, Q2, Q3, and RC, where RC is a resistance comprised of the bulk silicon chip material. Its resistance depends largely on the resistivity of the silicon, which exhibits a positive temperature coefficient and increases by approximately 0.7% per 1 degrees C rise above 25 degrees C.

As the resistance of RC increases, corresponding to a rise in T, the current, IC, decreases. This reduces power dissipation in RC which tends to lower chip temperature. Conversely, if T decreases, IC tends to increase leading to more power dissipation and a tendency to increase chip temperature. This relationship can be shown to be;

(Image Omitted)

Thus, thermal variations are inversely proportional to IC such that controlling IC will permit adjustments of chip temperature which, in turn, will control variations of reference voltage.

Feedback control of VREF is accomplished in Fig. 2 by monitoring...