TXB0108: SPI Repeater

sonali zodage

Part Number: TXB0108
Other Parts Discussed in Thread: TXU0304, , TXU0104

Tool/software:

Hello TI Team,

We have application using SPI communication with approx. 90cm long distance form CPU to other devices, need add SPI repeater to guarantee the normal communication, can TXB0108PWR used in this application? Also, we are translating voltage level from 1.8V to 3.3V.

Thanks,

Sonali

9 days ago

0 Clemens Ladisch 9 days ago

Guru 295240 points

The TXB is not a buffer or repeater.

For SPI, use the TXU0304.

0 Jack Guan 9 days ago

TI__Mastermind 30616 points

Hi Sonali,

I agree with Clemens' recommendation here. Please see additional FAQ pertaining to this question:

https://e2e.ti.com/support/logic-group/logic/f/logic-forum/763609/faq-what-happens-when-i-connect-a-logic-device-s-output-to-a-50-ohm-transmission-line

Regards,

Jack

0 sonali zodage 7 days ago in reply to Clemens Ladisch

Intellectual 310 points

Hello Clemens,

Thank you for your quick response.

We replaced the translator TXB0108 with TXU0304PWR as you suggested. Can you please review the schematic for TXU0304 and let us know your feedback on the same.

Also, can you please confirm the pull-up values?

Following are the I2C requirement:

Approx. length of SPI Interface

Total length on port A side: PCB Track: 110mm, Cable: 160mm

Total length on port B side: PCB Track: 100mm

Actually, we have application using SPI communication with approx. total 50cm long distance form CPU to other devices, with voltage translation.

Let us know if you need more information

Thanks,

Sonali

0 Clemens Ladisch 7 days ago in reply to sonali zodage

Guru 295240 points

R277 is not needed because the A4Y output is always active.

The absence of the MOSI signal is strange, but I guess you have a reason.

Otherwise, looks OK.

0 Jack Guan 7 days ago in reply to sonali zodage

TI__Mastermind 30616 points

Hi Sonali,

Unused I/Os can be left floating here as the device has internal pulldowns on all inputs. If default state is desired to be high, please use external weak pullup for default high state on unused pins.

Please keep us updated on any new findings. I would expect the TXU0104 to handle the fixed direction SPI signals much better then the TXB0108 for this specific use case.

Regards,

Jack

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TXB0108: SPI Repeater