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PRECHARGE CIRCUIT FOR ONE-SHOT

IP.com Disclosure Number: IPCOM000005511D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2001-Oct-10
Document File: 1 page(s) / 45K

Publishing Venue

Motorola

Related People

Chuck Barker: AUTHOR

Abstract

The circuit shown in the figure has been used successfully to minimize the time required before ap- plication of a re-trigger pulse to a CMOS one-shot design.

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Volume 3 March 1983

PRECHARGE CIRCUIT FOR ONE.SHOT

By Chuck Barker

The circuit shown in the figure has been used successfully to minimize the time required before ap- plication of a re-trigger pulse to a CMOS one-shot design.

   Because of the low gain of inverter M2-M3, its output node is slow in responding to a change in in- put voltage. For large values of RxCx, this can be particularly pronounced since a long time constant will exist. Upon an input trigger pulse occuring, Ml will rapidly discharge Cx. Because of the slow response of M2-M3 when its switchpoint is reached, avery wide reset pulse will occur thus preventing any re-triggering during this time.

   This problem can be minimized by using the circuit composed of M4 and Tl as shown in the figure. Once the switchpoint of M2-M3 has been reached, Ml will be turned "OFF" allowing RxCx node to charge toward VDD. At this time, Tl will also be turned "OFF" and M4 turned "ON" rapidly charging the input node of inverter M2-M3 and quickly removing the reset signal from the input trigger flip-flop thus allowing acceptance of any re-trigger pulses. Of course when Ml is"ON", M4 will be"OFF" and Tl will be turned "ON" for normal trigger operation.

-- PRECHARCE CIRCUITFOR ONE-SHOT --

('4538 h '528)

f RX

INPUT

0 Motorola. Inc. 1983 73

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