AM2431: What is the status of "The input buffer is disabled.

Hello futoshi kawarazaki,

Sorry for the delayed response as I was on sick leave.

I am routing your query to Hw experts to comment on your issue.

Regards,

S.Anil.

Hello futoshi kawarazaki,

futoshi kawarazaki said:

Is there any problem if the pin is HIZ when "The input buffer is disabled.

Can you please help me understand if the traces are connected to these IOs or these are unconnected.

Regards,

Sreenivasa

Hello Sreenivasa

The traces are connected to these IOs.

Note that the CMOS input in question is the internal CMOS input of the AM2431.

Hello futoshi kawarazaki,

Thank you.

futoshi kawarazaki said:

Note that the CMOS input in question is the internal CMOS input of the AM2431.

Noted.

It is not a good design practice to leave unterminated signal traces connected to the SOC pins.  Without any termination, these signal are very high impedance.  This makes it easy for noise to couple energy on these floating signal trace and develop a potential that could exceed our recommended operating conditions, which would create an Electrical Over-Stress (EOS) on the IOs.

Regards,

Sreenivasa

Hello Sreenivasa

I control the LEDs with GPIO pins.
The GPIO pins are connected as follows

”IO pin to resistor to LED to 3.3V”

My question in this case is.

After reset, the pin is HIZ until the GPIO_DIR** register is set to output.
At this time, I am concerned about through-current flow to the CMOS input stage.

When "The input buffer is disabled." is it safe to assume that the pin is in a state where measures have been taken to prevent through-current flow?

Thank you.

Hello futoshi kawarazaki,

Thank you.

futoshi kawarazaki said:

When "The input buffer is disabled." is it safe to assume that the pin is in a state where measures have been taken to prevent through-current flow?

I assume the reset and after reset state.

If an LED and a current limit resistor has been connected to the SoC pin, this should not be a concern since the TX and RX buffers are off during reset and after reset until the software configures the required functionality.  

Regards,

Sreenivasa

Hello Sreenivasa,

So here's my question.
Does "the RX buffers are off" mean that measures have been taken to prevent feed-through current on the CMOS input?

Best regards,

Hello futoshi kawarazaki,

Thank you.

futoshi kawarazaki said:

Does "the RX buffers are off" mean that measures have been taken to prevent feed-through current on the CMOS input?

When the LVCMOS inputs is not used and the pin does not have a trace connected, the required measures have been taken.

When a trace is connected, and the signal is not being actively driven - in case there is a noise pick up externally that exceeds the input range, it is recommended to add an external pull.

Regards,

Sreenivasa