General description

The 74HC123; 74HCT123 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 74HC123; 74HCT123 are dual retriggerable monostable multivibrators with output pulse width control by three methods:

1. The basic pulse is programmed by selection of an external resistor (REXT) and

capacitor (CEXT).

2. 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.

3. An internal connection from nRD to the input gates makes it possible to trigger the

circuit by a HIGH-going signal at input nRD as shown in the function table.

Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slower

input rise and fall times.

The 74HC123; 74HCT123 are identical to the 74HC423; 74HCT423 but can be triggered

via the reset input.

Features and benefits

■ 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

■ ESD protection:

◆ HBM JESD22-A114F exceeds 2000 V

◆ MM JESD22-A115-A exceeds 200 V

■ Specified from -40°C to +85°C and from -40°C to +125°C

74HCT123屬于集成電路（IC） > 多諧振蕩器。恩智浦半導體公司制造生產(chǎn)的74HCT123多諧振蕩器多諧振蕩器是簡單的雙態(tài)器件，盡管它們的典型使用方式在很大程度上具有模擬特性，但通常被認為是數(shù)字邏輯元器件。單穩(wěn)型也稱為“單發(fā)”，具有一種穩(wěn)定狀態(tài)；但施加觸發(fā)信號可使它們離開此狀態(tài)一段時間，該時間通常由所連接電容器的值來確定。這些器件對于去彈跳開關(guān)觸頭等應(yīng)用非常有用。非穩(wěn)型沒有穩(wěn)定狀態(tài)，在兩個狀態(tài)之間按一定頻率持續(xù)轉(zhuǎn)換，該頻率通常也是由所連接電容器的值來確定。