CLR

C ext

R ext/C ext

R

B

A

Q

Q

10

SN74LV123A-Q1

SCLS467F – FEBRUARY 2003 – REVISED JUNE 2016

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8 Detailed Description

8.1 Overview

This edge-triggered multivibrator features output pulse-duration control by three methods. In the first method,

the A input is low, and the B input goes high. In the second method, the B input is high, and the A input goes

low. In the third method, the A input is low, the B input is high, and the clear (CLR) input goes high.

The output pulse duration is programmable by selecting external resistance and capacitance values. The

obtain variable pulse durations. The output pulse duration also can be reduced by taking CLR low.

Pulse triggering occurs at a particular voltage level and is not directly related to the transition time of the

input pulse. The A, B, and CLR inputs have Schmitt triggers with sufficient hysteresis to handle slow input

transition rates with jitter-free triggering at the outputs.

When triggered, the basic pulse duration can be extended by retriggering the gated low-level-active (A) or

high-level-active (B) input. Pulse duration may be reduced by taking CLR low. The input-output timing

diagram (Figure 1) shows pulse control by retriggering the inputs and early clearing.

The Q outputs are in the low state, and the Q outputs are in the high state during power up. The outputs are

glitch free, without applying a reset pulse.

outputs, which prevents damaging current backflow through the device when it is powered down.

8.2 Functional Block Diagram

Figure 10. Logic Diagram, Each Multivibrator (Positive Logic)

8.3 Feature Description

The SN74LV123A operates over a wide supply range from 2 V to 5.5 V. The propagation delay has a maximum

of 11 ns at 5-V supply. The typical output ground bounce is less than 0.8 V at 3.3-V supply and 25°C. The typical

These parts support mixed-mode voltage operation on all ports.

Schmitt-trigger circuitry on the A, B, and CLR inputs allow for slow input transition rates and noisy input signals.

This device can be configured for rising or falling edge triggering.

This device supports partial-power-down mode operation.

This device is retriggerable for very long output pulses up to 100% duty cycle.

The clear signal overrides an output pulse and terminates it early.

Glitch-free power-up reset on outputs.