Forums

interface between 3.3v and 5v

Started by Unknown October 14, 2005
hi....

i'm designing a circuit including 5v and 3.3v for the
first time and need support to interact them with each
other.

except dsp all circuit elements feeds from 5v.

i'll drive a 2x16 lcd ..
i'll read from 4 ADC input
and i'll use 4 PWM signal...

which buffers (easy to find) should i use?

bye...

isa gok

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Hi Isa,
if you use HCT ICs (e.g. 74HCT541) you can power it with 5V and drive it
with an input signal range 0-3.3V(they have a 2V of treshold high level
input voltage). If the DSP is not 5V tolerant, you must interface with VHC
ICs that is it.

Bye
Marco isa "g"
<olemp_isa@yahoo.
com> Per
Inviato da: motoroladsp@moto...
motoroladsp@yahoo CC
groups.com
Oggetto
[motoroladsp] interface between 3.3
14/10/2005 14.57 v and 5v

hi....

i'm designing a circuit including 5v and 3.3v for the
first time and need support to interact them with each
other.

except dsp all circuit elements feeds from 5v.

i'll drive a 2x16 lcd ..
i'll read from 4 ADC input
and i'll use 4 PWM signal...

which buffers (easy to find) should i use?

bye...

isa gok

__________________________________
Yahoo! Music Unlimited
Access over 1 million songs. Try it free.
http://music.yahoo.com/unlimited/


Maybe you could try the LVT or LVX or other families. Just look at
http://www.fairchildsemi.com/parametric/select.jsp, under the LOGIC
section.

Bye.
Roberto

-----Messaggio originale-----
Da: motoroladsp@moto... [mailto:motoroladsp@moto...] Per
conto di isa g
Inviato: venerd14 ottobre 2005 14.58
A: motoroladsp@moto...
Oggetto: [motoroladsp] interface between 3.3v and 5v hi....

i'm designing a circuit including 5v and 3.3v for the
first time and need support to interact them with each
other.

except dsp all circuit elements feeds from 5v.

i'll drive a 2x16 lcd ..
i'll read from 4 ADC input
and i'll use 4 PWM signal...

which buffers (easy to find) should i use?

bye...

isa gok

__________________________________
Yahoo! Music Unlimited
Access over 1 million songs. Try it free.
http://music.yahoo.com/unlimited/



marco and Roberto thank you ...
74HCT541 looks ok. for 3.3v to 5v...

what about to 5v to 3.3v.... is a basic resistive
divider enough for that???

or : i am using 56f8323.....so can i connect the its
logic input pin to the 5v (for example read pin of the
lcd).........

isa...

--- marco.pe@marc... wrote:

>
>
> Hi Isa,
> if you use HCT ICs (e.g. 74HCT541) you can power it
> with 5V and drive it
> with an input signal range 0-3.3V(they have a 2V of
> treshold high level
> input voltage). If the DSP is not 5V tolerant, you
> must interface with VHC
> ICs that is it.
>
> Bye
> Marco >
> isa "g"
>
> <olemp_isa@yahoo.
>
> com>
> Per
> Inviato da:
> motoroladsp@moto...
> motoroladsp@yahoo
> CC
> groups.com > Oggetto
> [motoroladsp]
> interface between 3.3
> 14/10/2005 14.57 v and 5v > hi....
>
> i'm designing a circuit including 5v and 3.3v for
> the
> first time and need support to interact them with
> each
> other.
>
> except dsp all circuit elements feeds from 5v.
>
> i'll drive a 2x16 lcd ..
> i'll read from 4 ADC input
> and i'll use 4 PWM signal...
>
> which buffers (easy to find) should i use?
>
> bye...
>
> isa gok >
>
> __________________________________
> Yahoo! Music Unlimited
> Access over 1 million songs. Try it free.
> http://music.yahoo.com/unlimited/

__________________________________
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Hi Isa,

For your digital output, you can use a HCT buffer. For your analog and
digital input, you can use a simple resistive voltage divider (like 10k/20k
or 1k/2k).

For your LCD, do you need bidirectional IO? If yes, you can build a simple
shift level circuit using a small signal N channel MOSFET (like the 2N7002).

For each signal:
Connect your 3.3v signal to the source of the MOSFET.
Connect your 5v signal to the drain of the MOSFET.
Connect the gate directly on the 3.3v supply.
Put a pull-up to the 3.3v on the source.
Put a pull-up to the 5v on the drain.

The value of the pull-up depends mostly on rise time you need. I usually
take around 5k.

Personally, I like this circuit because it scalable for not too fast small
data bus, it don't use a lot of board space and it don't cost a lot. Bruno Tremblay

-----Message d'origine-----
De: motoroladsp@moto... [mailto:motoroladsp@moto...] De la
part de isa g
Envoy 14 octobre 2005 08:58
: motoroladsp@moto...
Objet: [motoroladsp] interface between 3.3v and 5v

hi....

i'm designing a circuit including 5v and 3.3v for the
first time and need support to interact them with each
other.

except dsp all circuit elements feeds from 5v.

i'll drive a 2x16 lcd ..
i'll read from 4 ADC input
and i'll use 4 PWM signal...

which buffers (easy to find) should i use?

bye...

isa gok

__________________________________
Yahoo! Music Unlimited
Access over 1 million songs. Try it free.
http://music.yahoo.com/unlimited/