TXB0104-Q1: TXB0104-Q1 for Uart Issue

Xiaoxiang Liu

Part Number: TXB0104-Q1
Other Parts Discussed in Thread: TXS0104E-Q1, TXU0304-Q1, TXU0104-Q1, TXU0204-Q1, TXB0104, TXS0104E

Hi team,

As you can see, we have the following connection method. We used TXB0104-Q1.

There are no pull-up and pull-down resistors inside the SOC. And there are no pull-up and pull-down resistors throughout the entire sequence.

The signal is a low-rate UART signal.

Is this connection method feasible?

We found a strange phenomenon. After passing the first TXB0104-Q1, the data appeared at an intermediate level, and the UART recognized garbled characters.

But when we replaced all the TXB0104-Q1 in the middle with TXS0104E-Q1, this problem did not occur.

Can you explain this phenomenon? I think TXB0104-Q1 should be fine too. Do you have any suggestions if we are too late to replace the TXB0104-Q1?

Thanks

Xiaoxiang

over 1 year ago

Clemens Ladisch over 1 year ago

Guru 281350 points

Two TXB I/Os must no be connected to each other. The outputs on both sides of the TXB are always active, and one output is not strong enough to override the voltage of the other one.

For unidirectional signals, you should use a unidirectional translator like the TXU0104-Q1/TXU0204-Q1/TXU0304-Q1.

Xiaoxiang Liu over 1 year ago in reply to Clemens Ladisch

TI__Expert 4845 points

Hi Clemens,

If I use two TXS0104-Q1, can it be connected to each other?

Thanks

Xiaoxiang

Xiaoxiang Liu over 1 year ago in reply to Xiaoxiang Liu

TI__Expert 4845 points

Hi Clemens,

The customer needs bidirectional translator because there are other signals.

Replace the second TXB0104-Q1 with TXS0104E-Q1.

Why does this situation still exist? We can no longer communicate normally.

Then we both Replace the second TXB0104-Q1 with TXS0104E-Q1.

The problem disappears.

We are curious why it can't work with a TXB0104+TXS0104E?

Thanks

Xiaoxiang

Clemens Ladisch over 1 year ago in reply to Xiaoxiang Liu

Guru 281350 points

The TXS has integrated pull-up resistors; this does not work with the TXB.

Using multiple TXSes is possible. But the TXS is a passive switch; check that the 1.8 V device has enough drive strength to sink the current through all four pull-up resistors.

You need an auto-bidirectional translator only if individual signals are bidirectional. What are those other signals?

Xiaoxiang Liu over 1 year ago in reply to Clemens Ladisch

TI__Expert 4845 points

Hi Clemens,

There are some SPI and other signals, UART is just one of them.

Thanks

Xiaoxiang

Clemens Ladisch over 1 year ago in reply to Xiaoxiang Liu

Guru 281350 points

SPI (but not QSPI) signals are unidirectionals. (The various TXU variants have different number of channels in each direction.)

Jack Guan over 1 year ago in reply to Clemens Ladisch

TI__Mastermind 26431 points

Hey Xiaoxiang,

Clemens is correct here, the only series connection that is possible here is the TXS <-> TXS. The configurations where TXS <-> TXB and TXB <-> TXB will cause errors due to TXB's weak drivers and the contention with the TXS 10kohm pullups. Do all signals need to be level shifted to 3.3V and then to 5V? If not, can we potentially separate the auto bi-directional from the unidirectional signals?

Regards,

Jack

Logic

Logic forum

TXB0104-Q1: TXB0104-Q1 for Uart Issue