Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

[SOLVED] Increasing the maximum fan out value a cell by buffer insertion?

Status
Not open for further replies.
B

biju4u90

Full Member level 3
Joined
Dec 10, 2014
Messages
172
Helped
3
Reputation
6
Reaction score
3
Trophy points
18
Activity points
1,437
Suppose the maximum fan out of an AND gate is 4 and the output of this AND gate is connected to 4 similar AND gates. If the current coming out of the driver AND gate is i, then assuming each of the four devices get equal current, each driven AND gate gets i/4 of the current. Since the maximum fan out of the driver AND gate is 4, I cannot connect more gates to the driver since the current will be splitted again and the current in each branch will get reduced further. Suppose I insert buffers prior to the 4 driven AND gates so that the i/4 current is boosted back to i in all the four branches. Can I use this method to increase the fanout value of a cell because the current requirement in the branches get satisfied?
 

Hi,

i hope I understand your question right...

Increasing fanout, that´s why there are buffers.

Adding buffers will add some delay.


Klaus
 

biju4u90 said:
Suppose I insert buffers prior to the 4 driven AND gates so that the i/4 current is boosted back to i in all the four branches. Can I use this method to increase the fanout value of a cell because the current requirement in the branches get satisfied?
Click to expand...

Surely, but as far as I know, regardless the fanout required, the optimum gain ratio that you should consider at the transistor level is something near to 2,7n ( ~7,3 at this case ).
 

KlausST said:
Increasing fanout, that´s why there are buffers.

Klaus
Click to expand...

If fanout is a varying parameter or adjustable parameter, whats the significance of the term?? Why should we bother about fanout of a cell??
 

Hi,

as said before:
* benefit: increased fan out
* disadvantage: added delay

Klaus
 
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top