74LV123_15 Datasheet, PDF (1/24 Pages) NXP Semiconductors – 74LV123_15

74LV123
Dual retriggerable monostable multivibrator with reset
Rev. 7 — 12 December 2011
Product data sheet
1. General description
The 74LV123 is a low-voltage Si-gate CMOS device and is pin and function compatible
with the 74HC123; 74HCT123. It is a dual retriggerable monostable multivibrator which
uses three methods to control the output pulse width:
1. The basic pulse time is programmed by the selection of an external resistor (R_EXT)
and capacitor (C_EXT). These are normally connected as shown in Figure 9.
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 (see Figure 12).
3. Alternatively, an output delay can be terminated at any time by a LOW-going edge on
input nRD, which also inhibits the triggering (see Figure 13).
Schmitt-trigger action in the nA and nB inputs makes the circuit highly tolerant of slower
input rise and fall times.
2. Features and benefits
 Optimized for low-voltage applications: 1.0 V to 5.5 V
 Accepts TTL input levels between V_CC = 2.7 V and V_CC = 3.6 V
 Typical output ground bounce: < 0.8 V at V_CC = 3.3 V and T_amb = 25 C
 Typical HIGH-level output voltage (V_OH) undershoot: > 2 V at V_CC = 3.3 V and
T_amb = 25 C
 DC triggered from active HIGH or active LOW inputs
 Retriggerable for very long pulses up to 100 % duty factor
 Direct reset terminates output pulses
 Schmitt-trigger action on all inputs except for the reset input