How to interface 3.3v logic IDE/ATA device to 5v controller?

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kyndal

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use sn74cb3t3245

Hi. i need to interface a 3.3v (logic) IDE/ATA device to a 5v (logic) IDE/ATA controler
how is this made the easyest way?

3.3v <=> 5v

any suggestions
Special chips for this??, maxim has af few (hundreds)

or could i use simple logic chips that will do the chip when only supplyied with 3.3v?
will my ata controller work with signals of only 3.3v?
and can my 3.3 ata work with 5v (FZzzzz)

/Kyndal
 

Re: 3.3v logic to 5v logic

There is a 3V3 only ATA/IDE device?
Never heard of...maybe I'm wrong (o;

CompactFlash cards are 3V3 and 5V always...

But if you really need some 3V3<->5V converter then I would go for a cheap CPLD like EPM7 series from Altera or some XC95xx from Xilinx which are powered 3V3 and IO pins are 5V compatible...
 

Re: 3.3v logic to 5v logic

i have a 1.8" harddrive from a toshiba portege computer,
in the spec sheet it says 3.3 voltage ??
maby 5v will work just fine?

**broken link removed**

/Kyndal
 

Re: 3.3v logic to 5v logic

3.3 V TTL-Logic is Compatible to 5V TTL Logic. High (True) Value > 2.4V
In the other way, the easyest way to reduce the 5V TTL to 3.3V TTL is to use a SN74CB3T3245 (Texas Instruments).

Phytex
 

Re: 3.3v logic to 5v logic

OK Thanks
looks really good.
so if i get this right, i just "downconvert" the 5v from the controller to 3.3v
and the controller will understand the 3.3v from the disk as this is okay for high on ttl logic? (>2.4v)

/Kyndal
 

Re: 3.3v logic to 5v logic

Yes, it is right! If you have an uni-directional Signal it is better to use buffers (74LVTH244) for the reduction of the voltage or you can take buffers with direction bit like an 74LVTH16245.
But the SN74CB3T3245 is the low-cost way, but not the best!
Have a look in the datasheet of the components, they work with 3.3 V supply, but 5V on the inputs don't destroy the chip!

Phytex
 

Re: 3.3v logic to 5v logic

You can still keep your 5v micro,because 3v is more than enough for a ttl high.
 

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