3.3v <> 5v interfacing @ 15Mhz

Bare copper on fr4. You can usually get scraps from any pcb house for free. Only one side needs copper. You can cut it with a knife, hacksaw or tin snips to the required size.

There are many ways of mounting the components. I use plain hot glue most of the time, but also screw components such as heatsinks to the board if needed. You can cut the plane to isolate components if needed.

See Terry Ritter's page for an example of Manhattan style:

Since the copper is not cut or etched, it makes a much better ground plane than a pcb, and you can get excellent analog and digital performance up to about 1GHz. However, fast risetimes do not do well with copper wire interconnections. For example, the Motorola EclInPs with 160ps risetime is a problem. You really need stripline or microstrip to handle these signals.

A big advantage is you can easily move parts around if needed to add new circuitry. But complex circuits with a wide data buss would be difficult to wire.

After a few days, you will see your fingerprints etched into the surface. The copper may eventually darken due to corrosion. Brasso may clean the oxides off, but I'd rinse the board carefully to remove any trace of acids.

The technique is ideal for testing new components or circuit concepts. People have made entire high-performance radio receivers using this method. Each circuit sits in its own shielded box for good isolation. When you want to try a different mixer or amplifier, it's easy to pop a new board in and test it under actual conditions.

Regards,

Mike Monett

Antiviral, Antibacterial Silver Solution:

Three things:

a) Vih is typically 0.7*VCC (that'd be 3.5V). Minor difference, but see..

b) A 3.3V 5V circuit contains two power supplies, each with its own tolerance. If 5V goes +5% (5.25V) and 3.3V goes -5% (3.135V) at the same time, the situation gets worse. Vih is now 0.7*5.25V = 3.675V, while the 3.3V sender can generate 3.135V max.

c) You're missing that a 1 generated by a 3.3V device is not 3.3V. It's Voh. Typically CMOS outputs tend to climb up to almost VCC, but not all do. And certainly some devices trade lower Voh for a faster timing spec (ie faster device without silicon change).

A fool who thinks that this might be related to the timing problems of the GP... ?!

Regards, Marc

I understand what you are saying, but your first few posts were not at all clear and only appeared to be attacks on others. I am not trying to place any blame for this flame war, as there is plenty of blame to go around. I would suggest that you might consider how your posts appear to a third party reading this. Take it from someone who knows, this is not the best way to promote yourself.

BTW, sort of like in the movie Chinatown, "Let it go Jack, it's just the Internet!"

Ok, this is not addressing my question. I know what copperclad is. I don't understand how you are using it.

Are you saying that you are just using the board as a mechanical mount and not to make connections? How do you make connections with point to point wires?

Ok, I guess this is a bit more clear.

This seems very difficult to me, but I do digital much more than analog and the number of connections with multi-pin packages is much higher.

One of my favorite movies... in my DVD collection ;-)

You're right, I should ignore the flack.

...Jim Thompson

I have to admit that I didn't expect the cross conduction to be that high in the HCT at 3.3V input levels. Actually it made me rethink my position. The HCTs can be used as 3.3V -> 5V level translators, however the user must be aware of the power consumption.

BTW, the maximum of cross conduction appears to be at 0.9V input (5Vdd), and it is about 4mA.

VLV

Theoretically it should be maximum at the design center of the TTL threshold, ~1.4V.

Maybe the 0.9V you measure is just process skew?

...Jim Thompson

It's generally quite poorly documented, and varies across vendors, and Logic families. The Schmitt devices tend to have lower peaks than non schmitt devices. Seems to be an after-thought to most digital designers....

-jg