Rev.2.00, Feb.18.2005, page 1 of 7

HD74LS122

Retriggerable Monostable Multivibrator (with Clear)

REJ03D0428–0200

Rev.2.00

Feb.18.2005

This d-c triggered multivibrator features output pulse width control by three method. The basic pulse time is

programmed by selection of external resistance and capacitance values. The HD74LS122 has internal timing resistor

that allows the circuit to be used with only an external capacitor, if so desired. Once triggered, the basic pulse width

may be extended by retriggering the gated low-level -active (A) or high-level active (B) inputs or be reduced by use of

the overriding clear. Figure 1 illustrates pulse control by retriggering and early clear. This device is provided enough

Schmitt hysteresis to ensure jitter-free triggering from the B input with transition rates as slow as 0.1 mV/ns.

A = "L"

A = "L"

Clear = "H"

B

Retrigger Pulse

Output without

retrigger

Output without

clear

"L"

"H"

"H"

"L"

"L"

"L"

"H"

"H"

"H"

"L"

Q

B

Clear

Q

Figure 1

Typical Input / Output Pulse