SN74LS122 SN74LS123

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3

LS122 FUNCTIONAL TABLE

INPUTS

OUTPUTS

CLEAR

A1

A2

B1

B2

Q

Q

L

X

X

X

X

L

H

X

H

HX

X

L

H

X

X

XL

X

L

H

X

X

XX

L

L

H

H

L

X

↑

H

H

L

XH

↑

H

X

L

↑

H

H

X

LH

↑

H

H

↓

HH

H

↓

↓

HH

H

↓

HH

H

↑

L

XH

H

↑

X

L

H

H

LS123 FUNCTIONAL TABLE

INPUTS

OUTPUTS

CLEAR

A

B

Q

Q

L

X

X

L

H

X

H

XL

H

X

X

LL

H

H

L

↑

H

↓

H

↑

L

H

TYPICAL APPLICATION DATA

connection to ground, however for the best system

monostable as possible with a minimum amount of

pin. Good groundplane and adequate bypassing should be

designed into the system for optimum performance to ensure

that no false triggering occurs.

to ground on the LS122 and LS123, but not on the LS221.

substitution of a LS221 onto a LS123 socket will cause the

LS221 to become non-functional.

The switching diode is not needed for electrolytic

capacitance application and should not be used on the LS122

and LS123.

change, as can the temperature of the LS123, LS122.

Figures 5 and 6 show the behavior of the circuit shown in

included in the graph.

to determine the output pulse width. Figure 9 shows how K

nanoseconds is approximated by

In order to trim the output pulse width, it is necessary to

kept as close to the monostable as possible.

Retriggering of the part, as shown in Figure 3, must not

For the smallest possible deviation in output pulse widths

≥ 1000 pF.