bi-directional voltage conversion for BB's expansion pins

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1

Hi,

My expansion card needs 5V siganls for operation so I made an op-amp based voltage converter. This works fine for the output only pins I need on the expansion card. But, I can’t use it for Input operations on any pin. I do need a few input/ouput pins for my application.

Does any of you know how to create a bi-directional voltage converter that would take the 1.8v from BB and convert it to 5V at the same time if there’s a 5V on the pin it should convert to 1.8v for the OMAP chip to understand.

Thanks in advance.

–Krishna/.

2

Hi,

My expansion card needs 5V siganls for operation so I made an op-amp based voltage converter. This works fine for the output only pins I need on the expansion card. But, I can’t use it for Input operations on any pin. I do need a few input/ouput pins for my application.

Does any of you know how to create a bi-directional voltage converter that would take the 1.8v from BB and convert it to 5V at the same time if there’s a 5V on the pin it should convert to 1.8v for the OMAP chip to understand.

Opamps are too slow. Use TI TXS0108 or TXB0108 or search for TRANSLTR on Digikey.

Thanks in advance.

–Krishna/.

3

Look at the TXS10x and TXB10X series from TI. These are also used on the Beagleboard itself and you can find it listed on the schematic and the BOM. One note is that these devices may have issues driving larger capacitive loads if you need to run fast, so I suggest you read the datsheet carefuly and make sure it will work with your desgn. These come in 2, 4 and 8 port devices.

http://focus.ti.com/lit/ds/symlink/txs0102.pdf
http://focus.ti.com/lit/ds/symlink/txs0104.pdf
http://focus.ti.com/lit/ds/symlink/txs0108.pdf

http://focus.ti.com/lit/ds/symlink/txb0102.pdf
http://focus.ti.com/lit/ds/symlink/txb0104.pdf
http://focus.ti.com/lit/ds/symlink/txb0108.pdf

Gerald

4

Geral/John, Thankx! This undid my whole weekend’s work but, is a much better solution than what I got … thankx again .

–Krishna/.

5

Geral/John, Thankx! This undid my whole weekend’s work but, is a much better solution than what I got … thankx again .

BTW, if you are concerned about working with SOIC devices, you may want to get this adaptor from Digikey:

http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=438-1017-ND&x=0&y=0

–Krishna/.

Look at the TXS10x and TXB10X series from TI. These are also used on the Beagleboard itself and you can find it listed on the schematic and the BOM. One note is that these devices may have issues driving larger capacitive loads if you need to run fast, so I suggest you read the datsheet carefuly and make sure it will work with your desgn. These come in 2, 4 and 8 port devices.

http://focus.ti.com/lit/ds/symlink/txs0102.pdf

http://focus.ti.com/lit/ds/symlink/txs0104.pdf

http://focus.ti.com/lit/ds/symlink/txs0108.pdf

http://focus.ti.com/lit/ds/symlink/txb0102.pdf

http://focus.ti.com/lit/ds/symlink/txb0104.pdf

http://focus.ti.com/lit/ds/symlink/txb0108.pdf

Gerald