SN74AVC4T245: SPI data error from 1.25V to 3.3V

Part Number: SN74AVC4T245

Hi team,

My customer translate 1.25V to 3.3V from 1B1 to 1A1. 7 units shows data error on 1A1. We measured the impedance of 1A1 is lower than other units, then took these 7 units to failure analysis, all units passed assemble and test qualification. Therefore, we go back to check the application. 

We input , 1 1 1 1 1 1 1 1:1 1 1 0 1 1 1 1: 0 1 0 0 0 0 0 0: 0 0 0 1 0 1 1 1 ,  as below shows (CH2, blue). But some '1' bits in output is captured as '0'. In the screenshot as below, we found some '1' bits timing is not at the rising edge of clock, which is captured as '0'. The clock(CH1, yellow) level shift is on another SN74AVC4T245 unit. We don't pass the clock signal in the same SN74AVC4T245 unit.

I would like to know what is the possible cause for this issue. And, anyway to solve the data output timing issue?

Thanks

  • Hi,
    Our voltage translation expert will get back to you on this when we return to the office tomorrow morning. 
    Thanks!
    Chad Crosby

  • Hi,

    Below is the summary of input and output bits. You could see the error always happens at 0 transmit to 1 of input. In the screenshot, you could see the set up time of the output, 1A1, is reduced a lot. We measured the units with this issue only have 600kohm impedance on 1B1 pin. Other units are 3Mohm.  Even these units passed CT, our failure analysis team is doing the bench test.  

    I would like to know the possible cause for this issue.

    Thanks.

  • Hey Jerry,

    Can I get a scope shot that shows the waveform of the problem bit? It would be helpful to see both the input and output waveform (not overlapped).