What is better for I²S level shifting

Heinrich Geiger

Other Parts Discussed in Thread: SRC4192, TXB0104, SN74LVC3G34, SN74LVC1G34, SN74LVC3G07

Hello TI-Team,

in my project I have to interface I²S IC and have to use a kind of level shifter.

In my case I've got just three signals, BCLK, LRCLK and DATA, the BCLK frequency is 48kHz. The cause for different directions is I²S is running in slave mode, so the target IC is clocking an SRC (SRC4192) and streams some bits from it. Target IC is OS8104 (MOST transceiver) and running with 5v.

The problem is a different directions, that means BCLK and LRCLK are going 5v --> 3.3v and DATA is going 3.3v -> 5v.

After some searching here I found two possibilities to solve this:

TXB0104, 4 bit bidirectional level shifter
SN74LVC3G34 with VCC 3.3v for BCLK and LRCLK + SN74LVC1G34 with VCC 5v for data

But, which solution is better? Price is doesn't matter.

Thanks and kind regards

Heinrich

over 8 years ago

0 Emrys Maier over 8 years ago

TI__Guru* 97046 points

The simplest solution here would be to use an open-drain buffer such as SN74LVC3G07. If you power it from 3.3V, then the outputs can be pulled up to 3.3V for the two channels that need 3.3V outputs, and pulled up to 5V for the channel that needs a 5V output.

I chose a 3.3V supply so the input thresholds are valid for the 3.3V input and the 5V input.

0 Heinrich Geiger over 8 years ago in reply to Emrys Maier

Prodigy 50 points

Hello Emrys,

thank you for the fast answer.

Do you mean like this:

SRC4192 is powered with 3.3v and OS8104 with 5v.

Thanks & kind regards

0 Emrys Maier over 8 years ago in reply to Heinrich Geiger

TI__Guru* 97046 points

Each output will need a pull-up resistor to the appropriate supply - an open-drain device cannot drive the output high by itself.

Logic

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What is better for I²S level shifting