[AVR] 74HCT541 to translate 5V logic to 3.3V logic

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sreepss

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Shall we use 74HCT541 to translate from a 5V logic to 3.3 logic? I mean from a 5V processor lines to a 3.3V display lines?

I have tried this, but a 3.3V powered HCT 541 gives wrong output (4.1 V) and disturbing the 3.3V supply rail. :roll:

here's my schematic
 

You are simulating with the 74HCT541 ( 4.5v-5.5v ), but should use the 74HC541 ( 2.0v-5.5v ) instead. Anyway, according to datasheet the maximum allowed input is VCC.
 

Hi,

What's the idea behind using a HCT device? I can't see it.

Use a AHC device, but supplied with 3.3V.
Then the output is 0V/3.3V....while the input may be higher than it's supply voltage.

Klaus
 

thanks for the replays,

Negative Negative



I have actually used HC541 not HCT. Sorry for the mistake whenever I give the input to the buffer from a 5V ATMEGA port, the output goes beyond (4.1V the HCT's VCC( 3.3V ) and the 3.3V power rail raised by 4.1V.
 
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Hi,

from a 5V ATMEGA port,
Click to expand...
May I ask why you don't use 3.3V supply for the Atmega?

Klaus
 

hi KlaussT,

I have already running design of ATMEGA with 16MHz clock. I need to run it with 8MHz for 3.3V design. currently I cannot change the design
 

Hi,

Again: use AHC, supplied with 3V3.
HC are not 5V input tolerant with 3V3 supply.

Klaus
 

Hi,

Any AHC family member has this 5V tolerant inputs.
If you need 541 functionality... then

Yes, use 74AHC541.

Klaus
 
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