Noise in TXB0108

Basavaraj Hiremath

Other Parts Discussed in Thread: TXB0108, ADS8361

Hello,

I am using TXB0108 (from Adafruit http://www.adafruit.com/products/395) for my beagle board application. I using it between beagle board and ADC ADS8361. When the McBSP starts running, I noise of about 200mV on the ground line. This noise also affects the input signal to the ADC. The noise looks like coming from the clock.

Any solutions to filter or minimize this noise?

Thank you

over 14 years ago

0 Basavaraj Hiremath over 14 years ago

Intellectual 795 points

Here is the scope picture

0 Hattie over 14 years ago in reply to Basavaraj Hiremath

TI__Genius 9085 points

What frequency is that noise? Is it coming from your power supply?

Some of the 'wall-worts' can be very noisy. Connecting the board directly to a bench power supply may help.

0 Basavaraj Hiremath over 14 years ago in reply to Hattie

Intellectual 795 points

Thank you Hattie,

I will check on that. i think this could be part of the problem. But I see this only when the Beagle Board is hooked up and the McBSP on BB starts running. I can tap the input of ADC (pin 14 on ADS8361 EVM) and see the noise start. My output signals on the level shifters is also not clean.

Thank you

Basu

0 Basavaraj Hiremath over 13 years ago in reply to Basavaraj Hiremath

Intellectual 795 points

Here is one more picture of the noise.

The blue is the output of the level shifter which is connected to the McBSP clock on the expansion port. The other signal is the noise that we see.

is this normal behavior of the level shifters? What are the alternatives to this?

Thank you.

Best Regards,

Basu

0 Hattie over 13 years ago in reply to Basavaraj Hiremath

TI__Genius 9085 points

Hello Basu,

That noise looks different from the other noise. +-50mV switching noise can be caused by coupling on the lines, and doesn't normally cause problems in systems. Are those two signals close together on the board.

I would try to increase the bypass capacitance on all the devices.

0 Basavaraj Hiremath over 13 years ago in reply to Hattie

Intellectual 795 points

Thank you Hattie,

I think the previous noise was related to the probes I was using. That is solved with the use of better probes.

The other signal that you see is the input applied to the ADS8361 (pin 14) which is driven by the level shifter.

Thank you,

Basu

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Noise in TXB0108