Continue to Site

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.

  • 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.

Sharing a clock between ICs

Status
Not open for further replies.

2camjohn

Member
I want to share a clock between a couple of ICs.

Lots of places talk about sharing clocks but I cant find any schematics which actually show the implementation.

My friend Mr google isnt helping much.

I guess its one of these things thats assumed to be so simple nobody goes into details about it.


Anyway, hopefully the MS Paint schematic I have attached is not too offensive.

My questions are:
Will the way I suggested work?
Is there a better way?
Any other tips?

Links to websites resources where they cover sharing clocks between devices would be immensely helpful.
 

Attachments

  • shareclock.jpg
    shareclock.jpg
    17.6 KB · Views: 149
is this what you mean by shared clock circuit?

basic method depending on IC's.
 

Attachments

  • clock circuit.PNG
    clock circuit.PNG
    17.9 KB · Views: 158
The website you need to check is the website for the chips you are hooking up. MrDEB has given you the solution to problems 1, 2, and 3 below.

1) Most chips do not like to have a load on their OSCOUT pin, while others may tolerate this.

2) Most OSCIN pins are not sensitive enough to take the OSCOUT signal from just any other chip.

3) Although some chips will function as a buffer from OSCIN to OSCOUT, this is an extremely uncommon hookup for reasons 1 and 2.
 
following the 1 and 2 rules, it is also possible to share oscillator. feed the osc output to other osc input with transistors or not gates. I mean the oscout can feed transistors biased as notgates. in that case, the output of the osc will not be affected by load.
 
following the 1 and 2 rules, it is also possible to share oscillator. feed the osc output to other osc input with transistors or not gates. I mean the oscout can feed transistors biased as notgates. in that case, the output of the osc will not be affected by load.
The transistor NOT gate cannot have zero load; you just hope it's not enough to disturb the oscillator.

The OSCOUT signal isn't usually a valid logic level, as this consumes a lot of power that's not necessary. The data sheets won't tell you what the levels are.

By the time you have converted the unknown OSCOUT signal to a stable logic level, you have used a lot of parts. IMO you're better off reading the data sheet and following MrDEB's advice. You should only use the OSCOUT signal if the data sheet says you can.

Of course you're always free to ignore the spec, if you don't expect any support. It's easy design something that usually works.
 
Just to add a few more tidbits. Clock distribution is usually done as shown in attached image. I like to use source and shunt terminations to clean up signal quality. Trace length is also important. Clock lines are critical signals and most care should be given to these lines. Daisy chain, do not use star configuration. See my image.
 

Attachments

  • clock distribution.gif
    clock distribution.gif
    4.8 KB · Views: 161
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top