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CD4504B: The output level is not stable when powering up

Wayne Wang20
Expert 4390 points
Part Number: CD4504B


Hi team,

My customer is using CD4504 as the level shifter to communicate between C2000 and external parts. When the system is powered up, the DSP and CD4504 are powered up at the same time. C2000 outputs a high level when it is powered up while the output of CD4504 has both low level and high level. This brings risk to the external parts while powering up. Do you have any advise on how to avoid this issue?

Best regards，

Wayne

  • 0
    TI__Mastermind 46195 points
    Hi Wayne,

    The solution would be to have them in high impedance during power up. A lot of our devices have output enable pins for this reason. Unfortunately, this device doesn't have that pin. I don't have any schematic or block diagram to look at so I'm not really sure how the device is implemented, but if the output is connected to the external parts then finding a way to put the C2000 into high impedance and adding a weak pull-down to the input side of the CD4504B could also work.