Output stages

Thread Starter

xkris

Joined Mar 13, 2011
4
Hi all,

I have a question concerning these two buffer ICs.

SN74LVC07A and SN74LV244A

My guess is for the first chip I have to provide external pull up resistors while for the second one external pull ups are not required. I suppose the output stages on the SN74LV244A are CMOS although the datasheet doesn't explicitly say so
Can anyone help please?
 

kingdano

Joined Apr 14, 2010
377
you are correct

you can use the open-drain IC to interface between a 3.3V block of logic and a 5V block of logic quite nicely.
 

Thread Starter

xkris

Joined Mar 13, 2011
4
Both devices are CMOS technology throughout.
By CMOS I actually meant a complementary transistor pair.


you can use the open-drain IC to interface between a 3.3V block of logic and a 5V block of logic quite nicely
That's what I intend to use them for (is this correct english... :confused:)

The second one (SN74LV244A) does the same job, only faster and without the need for additional resistors.
 

kingdano

Joined Apr 14, 2010
377
well depending on the particular logic family you are interfacing to a 3.3V signal may not have the correct noise margins for reliable interfacing tp a 5V system. the device without the open drain will swing all signals to within its Vcc rail and ground.

the use of the open drain is to "pull-up" the signals on the "secondary" side of the buffers to the higher (+5V) voltage level so that you get full 0V to 5V swings from your 0V to 3.3V swings on the "primary" side of the buffer. this can work the other way as well, where you pull up the "secondary" signals to +3.3V and have the inputs driven by 5V logic.

i hope that better explains the use.

-Dan
 
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