Translation from 5V to 3V
Translation from 5V to 3V
(OP)
This is just going out for opinions. The cheap and dirty way is the simple 2/3 voltage divider, and it works...sorta. For slow rise time signals, I don't see much of a problem but for faster signals, I'm see the results of the capacitance on the cable, etc that gives me the slow fall and rise times so my nice square wave now looks like...crap.
So, I've played some with resistor values but I haven't seen anything that I'm really happy with.
This is a bi-directional bus..driving an LCD module at 3V, so there are some reads going on.
Suggestions on what might be the better way...ie...what translation chips have others used to interface to 3V logic.
So, I've played some with resistor values but I haven't seen anything that I'm really happy with.
This is a bi-directional bus..driving an LCD module at 3V, so there are some reads going on.
Suggestions on what might be the better way...ie...what translation chips have others used to interface to 3V logic.





RE: Translation from 5V to 3V
Glenn
RE: Translation from 5V to 3V
Glenn
RE: Translation from 5V to 3V
Keith Cress
kcress - http://www.flaminsystems.com
RE: Translation from 5V to 3V
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Translation from 5V to 3V
Again, thanks for the suggestions.
RE: Translation from 5V to 3V
Typically the reads are just checking to see if the last command has finished executing in the LCD.
What values are you using for your dividers? What processor are you using?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Translation from 5V to 3V
These devices convert 8 signals at a time. If you are interested in just one signal, there are devices such as the SN74LVC1G14 or similar ( that one is an inverter too) that will do the trick.
If you are really cheap, you could use a simple transistor, such as a logic N-Chan mosfet. Use the gate to pick up the 3V signal and switch 5V with the source-drain.
RE: Translation from 5V to 3V
RE: Translation from 5V to 3V
I just finished a little FPGA driving a Noritake vacuum display. I ordered an analog part lpc 32 pin package?, quite small and hard to work with utlizing a soldering iron. I was looking around in my supply as found a TI74ach273 and worked great. Put a quick design on eagle produced some gcode and sent it to the shop bench pcb printer, taig cnc. a couple hours and shazam an FPGA voltage translator for a noritake vacuum display. a couple of TI74ACH273 (16 I/Os) and that TAIG CNC sure is a delight.
Regards,
Cy
RE: Translation from 5V to 3V
Keith Cress
kcress - http://www.flaminsystems.com
RE: Translation from 5V to 3V
Depending on the application, this may or may not be feasible. In the last application where I planned one of these displays, the machines usually sat in a basement and got ignored except for when they reported trouble or were getting their monthly test. During the periods of inactivity, we reduced the display brightness to about 25% and bounced a "press any key" message around the screen, greatly reducing the drain on the phosphor elements.
RE: Translation from 5V to 3V
Your handle almost sounds like the right logic choice, but have a look at this logic and part: SN74LVC4245A. My project went the other way cmos to ttl this one should go from ttl to cmos 5 to 3. There is so much logic on TI, but if this does not work look on TI site it has what you need.
regards,
Cy