SPI Bus Isolation using 2 TXB0104 chips

vineetrvce

Other Parts Discussed in Thread: TXB0104

Hi,

I have a requirement in which I want to convert the SPI bus from 3.3V to 1.8V or 3.3V to 5V. I am planning to use 2 TXB0104 chips to achieve this. Please refer to my diagram below:

I have provided both the image and attached the pdf file.

SPIBuses.pdf

Now my concern is when I am operating on Bus 1 and Bus 2 (refer file attached), I want to totally disconnect or isolate Bus 3 and Bus 4 and vice-versa. In order to achieve this, I want to use the /OE line. To disable Bus 3 and Bus 4, will it completely isolate the SPI signals when /OE = GND for bottom chip and keep Bus 1 and Bus 2 active with /OE = VCCA for top chip and vice versa?

Regards,

Vineet.

over 9 years ago

0 Jennifer Joseph over 9 years ago

TI__Intellectual 2530 points

Hi Vineet

In order to get all the requirements :

1) please advice on the frequency of the SPI interface.
2) SPI_MOSI signal is unidirectional in SPI standard interface. Is this the case in your application too?
Thanks

0 vineetrvce over 9 years ago in reply to Jennifer Joseph

Intellectual 565 points

Hi,

SPI frequency is 6Mhz max. Yes MOSI is one way.

Regards,

Vineet.

0 Jennifer Joseph over 9 years ago in reply to vineetrvce

TI__Intellectual 2530 points

Thanks. TXB0104 is a good solution for your application.

Pulling OE low will place the outputs of the respective chips in high impedance mode.

Thanks

Jennifer

0 vineetrvce over 9 years ago in reply to Jennifer Joseph

Intellectual 565 points

Hi Jennifer,

When you refer to "outputs" are you referring to both A and B side of the chip?

Regards,

Vineet.

0 Jennifer Joseph over 9 years ago in reply to vineetrvce

TI__Intellectual 2530 points

Hi

When the output enable (OE) is low, the translator buffer will be disabled and the outputs are put into a high impedance state. The OE input circuit is referenced to the VCCA power-supply and when the device is disabled, the 4-kΩ buffer and the one-shot for both the A-port and B-Port are also disabled.

Thanks

Logic

Logic forum

SPI Bus Isolation using 2 TXB0104 chips