SN74HC191: About component characteristics of SN74HC191

yusuke otake

Prodigy 210 points

Part Number: SN74HC191

Hi, Please tell me.

When / LD pin or QC (output pin) at the time of power supply startup is logic indefinite, QC is either H or L?

When ON / OFF is repeated with a circuit like an image, QC sticks to H when turning on the power supply.

Also, if C5: 4.7 uF discharges, it will operate normally.

best regards,

otake

over 7 years ago

0 Dylan Hubbard over 7 years ago

TI__Mastermind 45115 points

Hi Otake,

The initial state of any clocked device on power up is usually unknown or undefined until a valid clock signal comes in .There are few techniques which helps in defining a state which includes using CLR and PRESET pins to define initial state regardless of clock input.

More about the initial states and solutions to it in this app report: www.ti.com/.../scha005a.pdf

0 yusuke otake over 7 years ago in reply to Dylan Hubbard

Prodigy 210 points

Thank you for your answer.

Consider referring to the file of the following URL.

Logic

Logic forum

SN74HC191: About component characteristics of SN74HC191