TXB0304: unexpected behavior

Noriyuki Takahashi

Genius 11360 points

Part Number: TXB0304
Other Parts Discussed in Thread: TXU0304, SN74AXC4T774

Hi team

Customer observes the unexpected behavior of TXBN0304RUTR. Please see the attached for the detail.

TXBN0304.pptx

As you can see P.3 silde, TXBN0304RUTR can't send the signal. Are there any possible causes?

They can't measure the waveform of VCCB = 1.8V due to the lack of # of oscilloscope channels, although I am asking to measure it at same timing with VCCA.

Regards,

Noriyuki Takahashi

over 3 years ago

0 Dylan Hubbard over 3 years ago

TI__Mastermind 46555 points

Hi Takahashi-san,

If the device is left enabled like it is, the I/O can power up in any state so I don't see any real abnormal behavior.

0 Noriyuki Takahashi over 3 years ago in reply to Dylan Hubbard

TI__Genius 11360 points

Hi Dylan,

I found that the 47kOhm pull-up resisters are placed in Bx-pins. Please see the attached for all schematic.

TXBN0304_1.pptx

They use TXBN0304RUTR for SPI communication. Do you think the pull-up resisters are suitable for their use-case?

Are there any other good devices for this? or Is it good ideas to make the OE-pin High during the power up?

Any advice will be helpful.

Regards,

Noriyuki Takahashi

0 Clemens Ladisch over 3 years ago in reply to Noriyuki Takahashi

Guru 318760 points

The TXB should not be used with pull-up/-down resistors. (This is because it is designed for bidirectional signals.)

SPI signals are unidirectional; a better solution would be a buffered translator like the TXU0304 or SN74AXC4T774.

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TXB0304: unexpected behavior