• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

74HC series Fanout into AT28C256

Status
Not open for further replies.

PAUL BAAS

New Member
Hi friends,

I need to feed a signal from one 74HC273 flip flop into 15 of the eeproms part number AT28C256.

I need to know if it;s fine for me to directly feed the signals into 15 AT28C256 at once ?

Or should I divide the signals into 2 parts and feed each into a 244, and then from the 244 into 7 and 8 of the AT28C256 each ?

In other words, can the 273 cope with feeding 15 AT28C256 ?

From what I know 74HC has virtually infinite fanout into CMOS, and the AT28C256 are CMOS.

Thanks!
 

gophert

Well-Known Member
Most Helpful Member
Hi friends,

I need to feed a signal from one 74HC273 flip flop into 15 of the eeproms part number AT28C256.

I need to know if it;s fine for me to directly feed the signals into 15 AT28C256 at once ?

Or should I divide the signals into 2 parts and feed each into a 244, and then from the 244 into 7 and 8 of the AT28C256 each ?

In other words, can the 273 cope with feeding 15 AT28C256 ?

From what I know 74HC has virtually infinite fanout into CMOS, and the AT28C256 are CMOS.

Thanks!
The cmos inputs are not drawing any current from the 74HC chip on a continuous basis but there is come capacitance on the cmos so it take a few nanoseconds to charge. Now, multiply the few nanoseconds into 244x more capacitance and you'll see that you run into switching speed issues. A high may not have enough time to go high in one clock cycle (depending on frequency).

Good luck.
 

gophert

Well-Known Member
Most Helpful Member
Status
Not open for further replies.

EE World Online Articles

Loading
Top