74HCT4538DB 查看數據表（PDF） - Philips Electronics

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74HCT4538DB

Dual retriggerable precision monostable multivibrator

Philips Electronics 

Philips Semiconductors

Dual retriggerable precision monostable

multivibrator

Product specification

74HC/HCT4538

Fig.4 Functional diagram.

FUNCTION TABLE

INPUTS

nA0

nA1

nRD

↓

L

H

OUTPUTS

nQ

nQ

H

↑

H

X

X

L

L

H

Notes

1. H = HIGH voltage level

L = LOW voltage level

X = don’t care

↑ = LOW-to-HIGH transition

↓ = HIGH-to-LOW transition

= one HIGH level output pulse

= one LOW level output pulse

(1) Connect CTC (pins 1 and 15) to GND (pin 8).

Fig.5 Connection of the external timing

components Rt and Ct.

(1) Positive edge triggering.

(2) Positive edge retriggering (pulse

lengthening).

(3) Negative edge triggering.

(4) Reset (pulse shortening).

(5) Vref1 and Vref2 are internal reference voltages.

(6) T = 0.7 × Rt × Ct (see also Fig.5).

Fig.6 Timing diagram.

September 1993

4

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