• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 19 subscribers
  • Views 444 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.

SN74LVC8T245PWR Incorrect Output at start-up

masahiko shimizu
Guru 11235 points

Hi,

My customer is using SN74LVC8T245PWR.
They have a issue.
Issue is incorrect output at start-up.
Detail waveform and circuit of this issue is showed the attached file.


VCCA side is 5V.
VCCB side is 3.3V.
_OE is connected 5V via pullup resistor.
DIR is connected GND.

At start up sequence,
They apply 5V (VCCA) apply first, then apply 3.3V(VCCB).
The prpblem occur during this sutart up sequence.
If the 5V (VCCA) apply, at this time not apply 3.3V(VCCB), we will see a 2ms High on B side.
This issue does not occur every time.
Only cold start up.
It does not occur after first start up.
It is occur three of Dozens.


Q1: Customer uses 10k-ohm of pullup resistor at _OE.
　　Is it problem that resistor volue is 10k-ohm?

Q2: Could you advice me about the reason of this issue, please?

SN74LVC8T245PWR.pptx

Best regards,
Shimizu

  • 0
    TI__Expert 6335 points

    Shimizu,

    Please refer to the post below for possible workarounds:

    Best Regards,
    Nirav

  • 0 in reply to Nirav Patel
    Guru 11235 points
    Hi Nirav,

    Thank you for your workaround advice.

    Please give me answer for below?
    I want to get information of reason of this situation.
    The following is customer questions.
    I guess reason is _OE ramp at start up.
    About _OE ramp waveform, Please see ppt which is posted the last time.　

    Q1: Customer uses 10k-ohm of pullup resistor at _OE.
    　　Is it problem that resistor value is 10k-ohm?

    Q2: Could you advice me about the "reason" of this issue, please?

    Best regards,
    Shimizu