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SN74LVCH16T245-EP: SN74LVCH16T245: Question about the input voltage drop of ports

Prodigy 170 points

Replies: 3

Views: 118

Part Number: SN74LVCH16T245-EP

Hi, there.

I am using SN74LVCH16T245-EP in one of my project. Here I am driving 16 IO's of SN74LVCH16T245 from B port to A port. A port is referenced to 3.3V and B port is referenced to 5V.

A and B ports of SN74LVCH16T245-EP do not have external pull-up or pull-down resistors in my system. 

(I know that external pull-up resistor is not required because  the device has a built-in bus hold function.)

Also, I applied a 5V signal to the B ports and kept the ~OE signal 'HIGH'(3.3V).

In this environment, the voltage level at B ports is 1.2V, not 5V. 

why is the 1.2V voltage measured at B Ports?

(I know that the B ports stay 'Hi-Z' when the OE signal is 'HIGH'. Also, if 5V signal is supplied to B port in 'Hi-Z' state, I think it should keep 5V.)

Please answer in my question. 

I will wait your answer. 

Thanks. 

  • When you are applying a 5 V signal to a B port pin, it should not be possible for the voltage at the pin to be anything but 5 V.

    Where does that 5 V signal come from? Can you check whether a current flows?

  • Can you provide a schematic and scope shot of your issue?  This will help make sure to understand your issue completely.

    A schematic with annotated voltages would be helpful if you do not have scope shots.

    Regards,

    Wade

  • In reply to Wade Vonbergen:

    I am going to assume that you resolved your issue.

    Please reply back with more information if the issue is not resolved.

    If your issue is resolved,  please click "This Resolved My Issue"
    Regards,
    Wade

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