74922 - keypad driver IC

[anasimtiaz]

74922

i was studying my microcontroller book in which i found out the keypad interfacing, later i found ther is an IC 74922 which does everything almost with no trouble of programming! im sure its well known here...the question is: are the pull up resistors internally present in the IC, or do we need to add resistors to the keypad...since im making my own keypad, im not sure of the former part.

regards

 

[antedeluvian]

74922 datasheet

Check the data sheet here:
https://www.fairchildsemi.com/pf/MM/MM74C922.html

 

[budhy]

74922 ic

Yes, 74922 has internal resistor for keypad matrix

 

[IanP]

ic 74922

Take a look at the attached picture ..

Regards,
IanP

 

[anasimtiaz]

datasheet 74922

ok thanks all! and what value of capacitors to be used for C and 10C??

 

[Kripton2035]

n1650 keypad ic problem

did you buy already the 74922 chip ??
because you will see that it's quite an expensive chip
and you'd better code it in a small microcontroler ...

 

[anasimtiaz]

keypad driver ic

i got it pretty easily, i can program it in the MC....but the IC is a great invention! so plz let me knw abt the capacitor values

 

[IanP]

keypad driver chip

As C try 100nF and as 10C try 1µF ..

Regards,
IanP

 

[budhy]

ic 74922 datasheet

Use this graphic to define C value

Use this graphic to define 10C value