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Dual Voltage Sensing Automatic Power on Reset

IP.com Disclosure Number: IPCOM000080924D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Spencer, JW: AUTHOR

Abstract

The present circuit prevents the destruction of other circuitry if the positive and negative voltage supplies fail. The circuit senses the presence or absence of voltages V1 and V2 and applies the proper reset signal to the logic circuitry. It also allows the user to reset the system at will.

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Dual Voltage Sensing Automatic Power on Reset

The present circuit prevents the destruction of other circuitry if the positive and negative voltage supplies fail. The circuit senses the presence or absence of voltages V1 and V2 and applies the proper reset signal to the logic circuitry. It also allows the user to reset the system at will.

For example, assume that V2 is a negative voltage derived from voltage V1. Therefore, when V1 comes up, the positive side of the differential amplifier DA is at a higher potential than the negative side. The differential amplifier is at an up level and base current is provided to transistor T1, turning it on. Therefore, the negative POR (power on reset) is at a down level or reset condition. Transistor T1 being on turns transistor T2 off, and the positive POR sets at an up level or reset condition. The USER INPUT is an open-collector device that is returned to ground and is normally off.

As voltage V2 comes up, it will pull the positive side of the differential amplifier DA below the negative side causing the amplifier to switch to a down level, turning transistor T1 off and transistor T2 on and releasing the resets. The user may now reset the system by turning the device on to pull the negative POR line down. The negative POR line is used to reset field-effect transistor (FET) logic. Voltages V1 and V2 are the V(DD) and substrate bias voltages, respectively. If either is missing, both the negative and positive POR go into a rese...