74AHC123A; 74AHCT123A

General description

The 74AHC123A; 74AHCT123A 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 74AHC123A; 74AHCT123A are dual retriggerable monostable multivibrators with output pulse width control by three 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 as shown in Figure 11.

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 = HIGH, nQ = LOW) can be made as long as desired. Alternatively an output delay can be terminated at any time by a LOW-going edge on input nRD, which also inhibits the triggering.

An internal connection from nRD to the input gate makes it possible to trigger the circuit by a positive-going signal at input nRD as shown in Table 3. Figure 8 and Figure 9 illustrate pulse control by retriggering and early reset. The basic output pulse width is essentially determined by the value of the external timing components R_EXT and C_EXT. When C_EXT ≥ 10 nF, the typical output pulse width is defined as: t_W = R_EXT x C_EXT where t_W = pulse width in ns; R_EXT = external resistor in kOhm; C_EXT = external capacitor in pF. Schmitt-trigger action at all inputs makes the circuit highly tolerant to slower input rise and fall times. The 74AHC123A; 74AHCT123A is identical to the 74AHC423; 74AHCT423 but can be triggered via the reset input.

Features

• All inputs have a Schmitt-trigger action
• Inputs accept voltages higher than V_CC
• DC triggered from active HIGH or active LOW inputs
• Retriggerable for very long pulses up to 100 pct duty factor
• Direct reset terminates output pulse
• For 74AHC123A only: operates with CMOS input levels
• For 74AHCT123A only: operates with TTL input levels
• ESD protection:
  • HBM JESD22-A114E exceeds 2000 V
  • MM JESD22-A115-A exceeds 200 V
  • CDM JESD22-C101C exceeds 1000 V
• Multiple package options
• Specified from -40 Cel to +85 Cel and from -40 Cel to +125 Cel

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Pricing/ordering/availability

Block diagrams/pinning

Parametrics/similar products

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74AHC123A; 74AHCT123A 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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Disclaimers

• General product disclaimer
• Quality and reliability disclaimer