TXB0106: TXB0106 output waveform noise

Arumugam Palaniyandi

Part Number: TXB0106

Hi,

In our design we have used TXB0106 for SPI communication for 2 Chanel DAC from TI. When probed SCLK signal before and after voltage level translator found that the waveform is not level shifted to 5V also the waveform is very noise. We also isolated Removed R197 and checked the waveform there is no improvement. But DAC functionality wise works well.

could you please help below points to understand better

1. Why the SCLK output level not shifting to 5V logic

2. Why the waveform is noise ?

CH1 - Level Translator Output and CH2 - Level Translator Input

over 6 years ago

0 Clemens Ladisch over 6 years ago

Guru 316660 points

You must not use pull-up or pull-down resistors, and the traces must be short enough so that the entire capcitance is less than 70 pF. (See section 8.3.6 of the datasheet.)

0 Arumugam Palaniyandi over 6 years ago in reply to Clemens Ladisch

Expert 1040 points

Hi,

If you see the schematics we haven't used any pull-up or Capacities Load , We just connected DAC 7562 only. The Trace is very small. Refer below snapshot.ry less. Please find

0 ShreyasRao over 6 years ago in reply to Arumugam Palaniyandi

TI__Guru 61970 points

Please show the input of the SCLK into the TXB0106.

what is the datarate? Would also like to confirm the probe setting for measurement, is it 1Mohm / x10 probes and not 50ohm setting?

0 Arumugam Palaniyandi over 6 years ago in reply to ShreyasRao

Expert 1040 points

Hi,

Find attached input snap for Input. As i said i have isolated SCLK output pin and ensuring there is NO load connected output of the TXB0106 but still the waveform is not clear.

Yes used 1Mohm / x10 probes with 1x settings. Ensured 50 ohm settings not enabled.

0 Clemens Ladisch over 6 years ago in reply to Arumugam Palaniyandi

Guru 316660 points

Tpyically, probes in x1 mode have 100 pF or more. In general, you should always use x10 mode.

0 Arumugam Palaniyandi over 6 years ago in reply to Clemens Ladisch

Expert 1040 points

Thanks works fine ...

0 ShreyasRao over 6 years ago in reply to Arumugam Palaniyandi

TI__Guru 61970 points

Arumugam,

That is good to know.

Thank you, Clemens for all your posts!

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TXB0106: TXB0106 output waveform noise