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Hall Transducer Circuit with Voltage and Current Regulation

IP.com Disclosure Number: IPCOM000083165D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Braun, RJ: AUTHOR [+2]

Abstract

Integrated Hall transducers are generally made with the Hall cell formed by part of the N-doped epilayer of a silicon chip, which has a temperature dependent resistance which changes at about 7% per 10 degrees centigrade. This means that the current through the Hall cell and with it the Hall cell sensitivity in mV/gauss will decrease at about the same rate with increasing temperature, if a constant voltage is applied.

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Hall Transducer Circuit with Voltage and Current Regulation

Integrated Hall transducers are generally made with the Hall cell formed by part of the N-doped epilayer of a silicon chip, which has a temperature dependent resistance which changes at about 7% per 10 degrees centigrade. This means that the current through the Hall cell and with it the Hall cell sensitivity in mV/gauss will decrease at about the same rate with increasing temperature, if a constant voltage is applied.

To overcome this problem, a constant-current regulator is used together with a constant-voltage regulator. This combination produces a constant current through the Hall cell over a supply voltage range of about 7.5V to 13.2V, with the help of a 6.4V Zener diode.

Below 7.5V the current would drop faster than the supply voltage and the sensitivity of 5V would be unreasonably low. However, 5V is a popular supply voltage, especially for low-cost applications where high accuracy (current regulation) is usually not critical, but where reasonable sensitivity is still essential.

In order to cover both high performance and low-performance applications which have only 5V available with the same Hall circuit (IC) chip, an automatic cutoff feature is provided for the constant-current regulator. In addition to covering both application categories, the present circuit eases a potentially serious yield problem in.that any chips that do not meet the more stringent requirements for the high-performance applications can be used for the low- performance category down to 5V.

The curren...