• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 21 subscribers
  • Views 491 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TXB0108: txb0108

Gilad Friefeld
Intellectual 330 points
Part Number: TXB0108
Other Parts Discussed in Thread: TXS0108E, SN74LVC244A

Hello.

i'm using the TXB0108 to translate discrete signals from 5V (Port B) to 1.8V (Port A).

On the Driver side there is 5V via 100KOhm pull up ('1') or GND ('0') - push button triggered. 

On the receiving side there is a FPGA input (no internal pull up). 

On steady state there is 5V (via 100K pull up) on the driving side and once i push the button, there is GND on the driving side. this is the logic design. 

'1' = button is open and '0' = button is close.

When i'm pushing the button, the output is latched to '0' and the input is latched to 200mV. this situation can't be changed until the next power up. translation doesn't work at all. 

Please advise,

Gilad. 

  • 0
    Guru 317750 points

    Section 8.3.2 of the datasheet says:

    For proper operation, the device driving the data I/Os of the TXB0108 must have drive strength of at least ±2 mA.

    The 100 kΩ pull-up results in a drive strength of 50 µA. Use 2.2 kΩ or less.

    In this application, you could use the TXS0108E, which has integrated pull-up resistors, but for unidirectional downtranslation, a buffer with overvoltage-tolerant inputs (e.g., SN74LVC244A) would be enough.