M74HC423ARM13TR View Datasheet(PDF) - STMicroelectronics

Part Name

Description

MFG CO.

M74HC423ARM13TR

DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATOR

STMicroelectronics 

TIMING CHART

M74HC423A

BLOCK DIAGRAM

1) Cx, Rx, Dx are external components.

(2) Dx is a clamping diode.

The external capacitor is charged to Vcc in the stand-by-state, i.e. no trigger. When the supply voltage is turned off Cx is di scharged mainly

trough an internal parasitic diode(see figures). If Cx is sufficiently large and Vcc decreases rapidly, there will be some possibility of damaging

the I.C. with a surge current or latch-up. If the voltage supply filter capacitor is large enough and Vcc decrease slowly, the surge current is

automatically limited and damage to the I.C. is avoided. The maximum forward current of the parasitic diode is approximately 20 mA. In cases

where Cx is large the time taken for the supply voltage to fall to 0.4 Vcc can be calculated as follows :

tf > (Vcc - 0.7) x Cx/20mA

In cases where tf is too short an external clamping diode is required to protect the I.C. from the surge current.

3/12

Share Link: