Translator and cmos driver

[_Mark81_]

[SOLVED]: Translator and cmos driver

Hi,
I need to translate a 3.3V clock signal to 5V in order to feed 100 cmos logic gates.
The clock frequency is very low, but I do need very sharp edges, say a rise/fall time below 50 ns.

What do you recommend?

I think any open-drain configuration is not suitable due to the pull-up resistor. I'm going to use a standard level-translator and a push-push mosfet driver.

Anyway I'm looking for a solution with very few parts.
Thanks in advance

 

[steveelliott]

Your idea is good. A typical part is called a "Low-side Mosfet driver". Most have TTL inputs so you don't need a translator.

Here's a kind of a neat part in a SOT-143 package.
https://www.digikey.com/product-detail/en/MIC4417YM4 TR/576-1188-2-ND/771657
Here's a common part in a 8-pin dip package.
https://ww1.microchip.com/downloads/en/DeviceDoc/21393D.pdf

both parts have TTL or near-TTL input voltage thresholds.

 

[_Mark81_]

Thanks for the link. I see the Vih is below 3V so I don't need a translator, indeed. Now I know exactly what I have to looking for.

 

[dick_freebird]

You might consider a simple 74HCT or 74ACT series Schmitt
trigger (e.g. 74ACT14) and a high drive octal buffer (or just
use the remaining 5 Schmitt inverters of the hex). The input
of the T (TTL compatible) input ought to be tolerant of not
being driven to rail.

 

[steveelliott]

Let's see... cost might be a little lower, but the parts count is doubled, board space is quadrupled (one 8-pin and Vcc capacitor versus one 14-pin plus one 20-pin plus 2 Vcc capacitors) and output current is halved (1+A versus 8*48mA = 0.4A).

 

[_Mark81_]

I'll give it a try with this IC:

https://www.ti.com/lit/ds/symlink/ucc27323.pdf

it costs about 1 euro for 100+ pieces, it has a huge current output (no need so much current, though) and it doesn't require any voltage translator at input. Furthermore it's a double driver - my board has 2 clock signals to handle :lol:

 

[steveelliott]

Good choice. You may actually NEED the drive current because your cmos inputs are highly capacitive and the driver chip will give you good clean transitions without clock skew.

 

[_Mark81_]

I will report back the result of the tests, if anyone is interested.

 

[_Mark81_]

It seems it does the trick. Now the duration of the edges is about 50-60 ns.