TC74HC123AP/AF/AFN

2007-10-01

3

Block Diagram (Note 1)(Note 2)

Note 1: Cx, Rx, Dx are external

capacitor, resistor, and diode, respectively.

Note 2: External clamping diode, Dx;

If the supply voltage is turned off, Cx is discharges mainly through the internal (parasitic) diode. If Cx is

in rush current is automatically limited and damage to the IC is avoided.

The maximum value of forward current through the parasitic diode is

±20 mA.

In the case of a large Cx, the limit of fall time of the supply voltage is determined as follows:

In the event a system does not satisfy the above condition, an external clamping diode (Dx) is needed to

protect the IC from in rush current.

Truth Table

Inputs

Outputs

A

B

CLR

Q

Q

Function

H

H

Output Enable

X

L

H

L

H

Inhibit

H

X

H

L

H

Inhibit

L

H

Output Enable

L

H

Output Enable

X

X

L

L

H

Inhibit

X: Don’t care