Browse Prior Art Database

TEMPERATURE COMPENSATED CURRENT SENSE WITH DIODE OFFSET

IP.com Disclosure Number: IPCOM000005569D
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2001-Oct-16
Document File: 1 page(s) / 39K

Publishing Venue

Motorola

Related People

Jeffrey J. Braun: AUTHOR

Abstract

When a current source is needed to drive a load it is often desired to have some form of current limit or current fold back. The following description details a current fold back approach.

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MOTOROLA Technical Developments Volume 5 October 1985

TEMPERATURE COMPENSATED CURRENT SENSE WITH DIODE OFFSET by Jeffrey J. Braun

When a current source is needed to drive a load it is often desired to have some form of current limit or current fold back. The following description details a current fold back approach.

   The basis for operation of this circuit is the difference in forward drops of a standard PN diode (Dl) and a Schottky diode (DZ) (.65 volts and .2 volts, respectively). Dl and D2 are placed in identical resistive voltage dividers (R2, R3, R4 and R5). These two similar dividers are placed on either side of a current sense resistor Rl. When I0 is low and the drop across Rl is negligible and V, and V, differ only by a fraction of the voltage difference be- tween Dl and D2. As I0 increases, V, drops until it becomes less than V,. This in turn trips the comparator which could set a flip flop that controls drive to 01.

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P

.30 Rl

+ + Dl JE .6V D2Jc .2V

D5R - - SCHOllKY

TO

FUP FLOP WHICH CONTROLS

0 "B

ICl IB

0 Motorola, Inc. 1985 30

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