SN74AVC4T245: Okay to tie 2A1 to OEZ?

Paul Goedeke

Part Number: SN74AVC4T245
Other Parts Discussed in Thread: SN74AVC8T245

Hello,

I'm using the SN74AVC4T245 in a SPI circuit on my board and I am seeing an issue where the input voltage at 2A1 is 0V and the output voltage at 2B1 is 0.8V. From the datasheet, it appears that V_OL is around 0.8V at 25mA of current.

Aside from possible board issues of a short or bad solder joint, I was wondering if having the same line (SPI chip select) tied to both OEZ and to one of the input data pins could cause a problem. The below picture shows the schematic. The signal that I'm asking about is labeled SPICSZ0_DLPC.

I hope that my question is clear. Thank you for any assistance!

-Paul

over 8 years ago

0 aozer over 8 years ago

TI__Mastermind 30625 points

Hello Paul,

I do not think this setup should be an issue. I will try to get a test setup in the lab and see if I have the same results.

0 Paul Goedeke over 8 years ago in reply to aozer

TI__Mastermind 30600 points

Thanks, I appreciate it!

0 Paul Goedeke over 8 years ago in reply to Paul Goedeke

TI__Mastermind 30600 points

Any progress on this issue?

Thanks!
-Paul

0 aozer over 8 years ago in reply to Paul Goedeke

TI__Mastermind 30625 points

Hello Paul,

Sorry for the late reply. One of my colleagues was going to do this while I was out last week but I don't think he ever got around to it.

I went to the lab and tried it out myself with an SN74AVC8T245 (we didn't have any 4 bit versions available at the moment) and was seeing 0.01mV at B1 with A1 at 0V (at 0.8 mV to be exact). Current consumption at B1 pin was around 10uA.

Based on these values I would say that there should be no problems with connecting the device as you have.

0 Paul Goedeke over 8 years ago in reply to aozer

TI__Mastermind 30600 points

Okay, thank you very much. My problem must be due to a short or something else on the board.

-Paul

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SN74AVC4T245: Okay to tie 2A1 to OEZ?