74HC/HCT423

General description

The 74HC/HCT423 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A.

The 74HC/HCT423 are dual retriggerable monostable multivibrators with output pulse width control by two methods. The basic pulse time is programmed by selection of an external resistor (R_EXT) and capacitor (C_EXT). The external resistor and capacitor are normally connected

Once triggered, the basic output pulse width may be extended by retriggering the gated active LOW-going edge input (nA) or the active HIGH-going edge input (nB). By repeating this process, the output pulse period (nQ = HIGHnQ = LOW) can be made as long as desired. When nRD is LOW, it forces the nQ output LOW, the nQ output HIGH and also inhibits the triggering.

. The basic output pulse width is essentially determined by the values of the external timing components R_EXT and C_EXT .
For pulse widths, when C_EXT < 10 000 pF, . When C_EXT > 10 000 pFthe typical output pulse width is defined as:

t_W = 0.45 x R_EXT x C_EXT (typ.)
wheret_W = pulse width in ns;
R_EXT = external resistor in kW;
C_EXT = external capacitor in pF.

Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slower input rise and fall times.

The '423' is identical to the '123' but cannot be triggered via the reset input.

Features

• DC triggered from active HIGH or active LOW inputs
• Retriggerable for very long pulses up to 100% duty factor
• Direct reset terminates output pulse
• Schmitt-trigger action on all inputs except for the reset input
• Output capability: standard (except for nR_EXT /C_EXT )
• I_CC category: MSI

Products/packages

Pricing/ordering/availability

Technical documents

Support Documents

HCT_USER_GUIDE; HC/T User Guide (1997-11-01)

Parametrics/similar products

Similar products

74HC/HCT423 links to the similar products page containing an overview of products that are similar in function or related to the type number(s) as listed on this page. The similar products page includes products from the same catalog tree(s), relevant selection guides and products from the same functional category.

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