Browse Prior Art Database

ACTIVE CLAMP CIRCUIT

IP.com Disclosure Number: IPCOM000007853D
Original Publication Date: 2002-Apr-29
Included in the Prior Art Database: 2002-Apr-29
Document File: 2 page(s) / 97K

Publishing Venue

Motorola

Related People

MICHAEL BATTY: AUTHOR [+2]

Abstract

This method provides an accurate method of maintaining the voltage differential condition imposed on a power system. It requires no external circuitry and takes up less space than known methods.

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ACTIVE CLAMP CIRCUIT

 MICHAEL BATTY, JASON JACKSON

Abstract

This method provides an accurate method of maintaining the voltage differential condition imposed on a power system. It requires no external circuitry and takes up less space than known methods.   

Introduction

This paper describes improvements in the field of power rail sequencing using MOSFET technology that requires no external voltage source.

Problem(s) To Be Solved

In multi rail on board Power Systems there is a requirement not to exceed a maximum voltage differential between two of the voltage rails. This is a common requirement for DSP’s and Microprocessors          with different core and I/O voltages.

For example, a typical device on a board could have a core and I/O section that have voltages of 1v8 and 3v3 respectively. Due to the internal architecture of the device the I/O voltage cannot exceed the core by more than 2v without damaging the silicon of the device. This condition must be maintained under all conditions including start up, normal operation, power down and fault conditions.

Known methods have used combinations of diodes in series strapped between the two rails, or active FET solutions that require an external power source.

Proposed Solution to the Problem(s)

This proposal uses an MOSFET and voltage reference to achieve a more accurate method of preventing the voltage differential from been exceeded and does not require an external power source.

The known diode method works on the basis that if all the diodes become forward biased the rails will clamp together. The limitations are that the precision is determine...