TXS0104E: TXS0104ERGYR

Nishanth Muthusamy

Part Number: TXS0104E
Other Parts Discussed in Thread: SN74AHC4066, SN74AXC4T774, TXB0104, TXB0304

Hi,

We are using the Texas part: TXS0104ERGYR for one of our applications. But it is not used for Level translation. We are using it as a buffer. 3.3V is fed to Both the voltages Vcca and Vccb. We are using enable signal to control the data flow. Default the enable is pulled low with a 10k resistor and the controller makes it high whenever necessary. The 4 channels are used for SPI lines Chip select, Clock, MOSI and MISO. We are using this part as a bridge between WiFi chip SPI lines and Flash Memory SPI lines using Enable as control. 'A' channel is given to Flash side and 'B' channel is given to WiFi chip side. Also the SPI lines from 'A' channel output is being shared to controller and FPGA. The SPI lines is not working when we mount the translator part on board. When the part is removed it is working fine. Not sure where am I missing.

Thank You.

over 7 years ago

0 Clemens Ladisch over 7 years ago

Guru 325520 points

The TXS makes compromises on speed and allowed load capacitance in order to allow automatic direction sensing.

If you just want to disconnect the signals, better use an analog switch with the desired bandwidth.

0 Nishanth Muthusamy over 7 years ago in reply to Clemens Ladisch

Prodigy 100 points

Hi Clemens Ladisch,

Thank you for the reply.

When we tie OE Pin low(via 10k pull down), the outputs are placed in High-Impedance state as per the datasheet. This High-Impedance has any impact on SPI bus lines on other side connections? Since SPI bus is being used by other device on the board which is not working. We are using at a speed of 4MHz.

0 Clemens Ladisch over 7 years ago in reply to Nishanth Muthusamy

Guru 325520 points

In theory, pulling OE low should disable everything. Please show the schematic.

(And it still would be a better idea to use an analog switch like the SN74AHC4066.)

0 Nishanth Muthusamy over 7 years ago in reply to Clemens Ladisch

Prodigy 100 points

Hi Clemens Ladisch ,

Thank You for reply and Part Suggestion .

Please Find attached image.

0 Clemens Ladisch over 7 years ago in reply to Nishanth Muthusamy

Guru 325520 points

This is not a complete schematic. Are there any pull-up/-down resistors?

Does the problem occur when OE is low, or high, or in both states?

0 Nishanth Muthusamy over 7 years ago in reply to Clemens Ladisch

Prodigy 100 points

Hi Clemens Ladisch,

Thanks Again! Please find below schematic image. The problem is occurring in both OE pin low and high states. Let me know if you need any other part of schematics or information.

0 ShreyasRao over 7 years ago in reply to Nishanth Muthusamy

TI__Guru 64010 points

Nishanth,

With OE low, the A/B ports are disconnected from each other. There is no translation being done here with both sides at 3.3V.

Is it the complete schematics? Are there no external pullup or pulldown resistors anywhere else?

I would either suggest going with a buffered translator like the SN74AXC4T774 or the TXB0104(or TXB0304).

0 Nishanth Muthusamy over 7 years ago in reply to ShreyasRao

Prodigy 100 points

Hi Shreyas,

Thank You for the reply. Sorry for not sharing the complete schematic. I have captured all the SPI lines going to different sections. Please find the below image. At first we used TXB0104RGYR and then replaced with TXS0104ERGYR. Same behavior in both the cases. If no one is accessing the flash, if the lines are pulled up in software will it be a problem? If OE is pulled low and all outputs will be in High-Impedance state, so this High-Impedance will affect capacitive loading on SPI lines.

0 Nishanth Muthusamy over 7 years ago in reply to Nishanth Muthusamy

Prodigy 100 points

Hi All,

For better understanding I am posting the issue with a block diagram of how are we using it. Please find image and let me know your thoughts or suggestions?

0 ShreyasRao over 7 years ago in reply to Nishanth Muthusamy

TI__Guru 64010 points

TXS or the TXB devices are weak autobidirectional devices without enough drive strength( 20uA max per channel) in them to act as a fanout device or buffer.

This is due to the internal series 4K limiting resistors which restricts the drive current.

For active buffering and fanout, I would recommend going with the SN74AXC4T774 device. This device has 12ma drive strength per channel enough to fan-out the 3 master/slave devices.

Please let me know.

Logic

Logic forum

TXS0104E: TXS0104ERGYR