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need a bidirectional level shifter

craig239955_st
Associate II

‎2007-05-04 08:09 PM

Posted on May 05, 2007 at 05:09

need a bidirectional level shifter

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12 REPLIES 12
craig239955_st
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

Hi,

I want to use a STR912 in combination with TTL IC's. I need a bidirectional level shifter (3.3V <-> 5V) for my GPIO's.

Any idea where I can find such a device.

Luc Vercruysse

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roger_lynx
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

....I need a bidirectional level shifter (3.3V <-> 5V) for my GPIO's.

 

Any idea where I can find such a device...

Why?

STR91x's I/O is 5V tolerant (5.5V max), from datasheet first page:

5 V tolerant, 16 have high sink current (8 mA)

and section:

6.4 DC electrical characteristics.

In case I am missing something, check:

ti.com

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craig239955_st
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

I agree, but I need a voltage shifter from 3.3V => 5V to drive my CMOS inputs...

Luc

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roger_lynx
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

I want to use a STR912 in combination with TTL IC's....

 

I need a voltage shifter from 3.3V => 5V to drive my CMOS inputs

...and now I am confused like a baby in a topless bar!

:o

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craig239955_st
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

OK TTL is not correct.(English is not my native...)

I mean that I want to use the STR912 to access 5V devices (all technologies, 74LS, 74HCT, CMOS ...)

I think CMOS is the worst case concerning input levels (input voltage seen as ''high'' is above 3.3V). For that reason I need voltage shift.

Luc

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richardmauruschat9
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

look at 74LVC4245 :)

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k_arthur
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

maybe 74LCX244 will help you

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akaiser9
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

Unless the system is battery powered, pullup resistors should do the job as well.

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roger_lynx
Associate II

‎2011-05-17 12:42 AM

Posted on May 17, 2011 at 09:42

...worst case concerning input levels (input voltage seen as ''high'' is above 3.3V)

True. You may want to look at this:

http://focus.ti.com/lit/an/scea021a/scea021a.pdf

http://focus.ti.com/lit/an/scea021a/scea021a.pdf

>

but, it looks like you got some hints what to use already....

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