TXB0108: How to detect the direction

K.Hamamoto

Guru 12155 points

Part Number: TXB0108

I read the following document. However I do not understand how does this device detect the directions.

http://www.tij.co.jp/jp/lit/an/scea043/scea043.pdf

(2 Auto-Direction Sensing Voltage Translator Architecture)

Could you give any detail about how this device the direction?

Regards,

Koji Hamamoto

over 8 years ago

0 aozer over 8 years ago

TI__Mastermind 30165 points

Hello Koji,

In short, the device does not detect the direction. It has a weak 4k buffer driving the output so any direction changes on the line are initiated by over-driving the output buffer.

For example, imagine that A1 is the input and B1 is the output. If B1 is driving a logic high at the output and the device on the B port decides that it wants to drive the line low it will have to sink all of the current provided by that 4k buffer. Once the device on B port sinks the current and pulls the line low, A1 will output a logic low. Now A1 is the output and B1 is the input.

Logic

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TXB0108: How to detect the direction