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.

Flip flop delay for measuring nanosecond events

Status
Not open for further replies.

aloishis89

Junior Member level 2
Joined
Jan 8, 2012
Messages
21
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,447
I'd like to measure propagation delay through a chip. This is often on the order of 5-7 ns, and I'd like to be able to sense down to a nanosecond or less so I can get good accuracy. Here's the approach I'm thinking: https://i.imgur.com/Tnksf.png
I'm interested in measuring delay through a logic chip (this whole project is for a demonstration) so in the schematic there, I would send a pulse to one input of the AND gate, and the output goes through a bunch of flip flops, where each stage slows down the pulse by half. Then by the time it gets to the end, the pulse is slow enough to read in a microcontroller. The problem is, this requires knowing the propagation delay of the flip flops really accurately. I know that some PICs have a feature that let you measure really fast events, and the other method I know of involves charging a capacitor and reading how much it's charged to see how long the pulse was. I'm not sure how accurate the capacitor method is, and I'd like to use the flip flop version over the PIC version for demonstration purposes if possible. What's the best approach for this?
 

Maybe your method can work but you can use a 30-cm long coaxial line to get one ns delay. If your coaxial line is filled with a dielectric like in cables, the "shortening" coefficient should be applied. You will need less than 30 cm (usually 0.65...0.85) of a coaxial cable for it. You can cascade several such cable sections to get taps in a line, 1, 2, 3... 5 ns etc.
 

Having lengths of cables to delay the signal seems a little impractical, especially because I'm trying to slow the signal down so much.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top