Backplane logic and 3v3

Hi all,

We are redesigning some 3U/6U Cards inserted in a chassis where 
backplane is specified to be driven by ABT logic (74ABT245/244), the 
problem we are facing is that the FPGA on some cards has 3v3 only IO's 
tolerant.

Anyone here has got an elegant solution for interfacing +5V backplane 
(TTL ABT) to 3v3 device such as uP or FPGA's ? We have been looking for 
transceivers like 74LVC3245 but after carefully reading the datasheet it 
may not fit the ABT technology especially for driving backplane bus line 
and capacitive loads...

Thanks in advance for any advice.

Habib

On 4/13/2011 9:19 AM, Habib Bouaziz-Viallet wrote:
> Hi all,
>
> We are redesigning some 3U/6U Cards inserted in a chassis where
> backplane is specified to be driven by ABT logic (74ABT245/244), the
> problem we are facing is that the FPGA on some cards has 3v3 only IO's
> tolerant.
>
> Anyone here has got an elegant solution for interfacing +5V backplane
> (TTL ABT) to 3v3 device such as uP or FPGA's ? We have been looking for
> transceivers like 74LVC3245 but after carefully reading the datasheet it
> may not fit the ABT technology especially for driving backplane bus line
> and capacitive loads...
>
> Thanks in advance for any advice.
>
> Habib

TI makes (and several second source) some good 16-bit byte-wide 
transceivers that'll do it.  If you need to actually drive 5V onto the 
backplane, look at the SN74ALVC164245, which can do about +/- 24mA onto 
the backplane side.  If you need more current than that but the 
backplane is TTL compatible (i.e. 2.4V is a logic high), then an 
SN74LVT162245A running from 3.3V has 5V tolerant inputs and will drive 
+64/-128 mA.  They make vicious VME transceivers.

-- 
Rob Gaddi, Highland Technology
Email address is currently out of order

Le 13/04/2011 18:34, Rob Gaddi a �crit :
> then an SN74LVT162245A running from 3.3V has 5V tolerant inputs and will
> drive +64/-128 mA.  They make vicious VME transceivers
  houuuuu ! rrright !! thank you so much for the topic i'll see deeper 
those parts tomorrow.

Habib.