5V on 3V3 Altera CPLD I/O

[pyroesp]

So I have this idea where I have to use a CPLD to do some logic on a 5V board, but the CPLD (EPM240T100) is 3V3 only.
I can't just change the 5V board into 3V3.

So my question is: Can I connect 5V on a 3V3 I/O, without a level shifter ?
My thought on this is you can, but I'll have to limit the current and power dissipated on those pins, right ?

[RoadRunner]

i guess this may be helpful

http://ww1.microchip.com/downloads/en/DeviceDoc/chapter%208.pdf

[mikeselectricstuff]

Series resistor and clamp diode. According to the datasheet, some MAX II devices have internal clamp diodes

[pyroesp]

Oups, EPM240 is altera... not Lattice . Changed the title.
Thanks for the pdf Gaurav and thanks for the help Mike.
I have to find out if the EPM240 has clamping diodes.

Cheers,
pyroesp

EDIT:
Doesn't seem like it has clamp diodes.

The I/O clamp diode is only supported in the EPM1270 and EPM2210 devices’ I/O
Bank 3. An external protection diode is needed for other I/O banks in EPM1270 and
EPM2210 devices and all I/O pins in EPM240 and EPM570 devices.

Which is strange because if you look at the image below, I can't see any clamp diodes, just a couple of 100 ohm resistors to limit the current.

[marshallh]

He's cheating on that pcb... not surprising.

Buy a few proper octal level converters, problem solved.

[pyroesp]

Goddamn lead free components...
I've looked a bit on digikey and found the SN74LVCC3245ADWR (1.26$) and EPM240T100C5N (6$).

Hopefully, soldering with non lead free solder won't do anything bad.

[hlavac]

If what this plugs into is using 5V TTL logic you may get away with using 3,3V CMOS with series resistors on the inputs.

ESD protection diodes will clamp the TTL inputs which are weak TTL pullups and together with the series resistors the current from logic high into the protection diode will be limited.

For outputs, TTL logic threshold for high is only 2V so you are fine with 3,3V high from CMOS.

Only problem will be that the 3,3V rail will have current dumped into it from 5V through all these pullups to 5V, you need a regulator that can survive this and not allow the 3,3V to go higher than 3,3V.

[c4757p]

Goddamn lead free components...
Hopefully, soldering with non lead free solder won't do anything bad.

Huh?

[pyroesp]

@hlavac: I think I'm going to use the level shifters, just to be sure.

@c4757p: Sorry, I must have phrased that incorrectly.
What I'm trying to say is that I don't have any lead free solder and I am hoping that I can use tin-lead solder.
Though it will be a while before I have a board to solder components on so I might buy some lead free solder in the meantime.

[FrankBuss]

Goddamn lead free components...
I've looked a bit on digikey and found the SN74LVCC3245ADWR (1.26$) and EPM240T100C5N (6$).

I've used the SN74LVC8T245 in one of my last projects, works fine. Same price, but compared to the SN74LVCC3245, it doesn't matter on which port is the 3.3V level and it works down to 1.65V instead of 2.3V (but not important for 3.3V/5V level translation).

If you need more than 8, take a look at the 16 bit (dual 8 bit) level converter SN74ALVC164245. Cheaper than two 8 bit chips and needs less board space.

Hopefully, soldering with non lead free solder won't do anything bad.

Works fine, I solder with leaded solder all the time for my hobby projects (unfortunately can't do this for customer projects). The usual copper wire is just copper, too, and you can solder it just fine

[pyroesp]

If you need more than 8, take a look at the 16 bit (dual 8 bit) level converter SN74ALVC164245. Cheaper than two 8 bit chips and needs less board space.

I'm going to check that one. I've never done SMD soldering at home, so I hope it's not too small ^^.

Works fine, I solder with leaded solder all the time for my hobby projects (unfortunately can't do this for customer projects). The usual copper wire is just copper, too, and you can solder it just fine

Awesome!

[alm]

Goddamn lead free components...

Where have you been buying non-lead-free parts the last ~6 years? Almost all components have been lead free for years.

[pyroesp]

Like you said, almost all... 
I haven't bought/built anything special in a while and If I do, I can find some/most of the components at home.

The university was going to throw away like 4 boxes of resistors/inductors and 40XX/74XX ICs.
And I get free microcontrollers from microchip every once in a while.

The last thing I built was a ball-in-a-maze puzzle with accelerometer and GLCD for a universyti project. The only thing I bought was the PCB and the accelerometer. Everything else got recycled from other electronic devices.