STEF01 eFuse Enable/Fault function in the same pin

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josmA

Joined Jun 12, 2019
22
Hello,

I am trying to add the eFuse STEF01 IC from STMicroelectronics. I would like to use the enable/disable option to turn on and off the output to reduce consumption when I am not using the device (sensor). At the same time, I would like to use the Faul functionality to receive the alert in my microcontroller. The datasheet says "The EN/fault pin is internally pulled up to 5 V". I am confused about how I should connect this pin to the microcontroller, directly? Could this 5V damage the microcontroller (works at 3.3V)?
How do I manage the situation from the microcontroller programming perspective, as I guess the port pin needs to act as an input to receive the fault condition and as an output to disable the eFuse?

On the other hand, I would also like to use the PG (Power Good) function. Similarly, should I connect the output PG pin to the microcontroller directly? It needs a pullup resistor connected to the voltage input (20V in my case), is it safe for the microcontroller?
The datasheet says that high impedance at PG pin means the power is ok, low impedance -> not ok. what signal do I receive in the microcontroller for each case?

Sorry for too many questions. I guess this has to be pretty simple for someone used to it. Any help will be appreciated. Thanks!
 

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LowQCab

Joined Nov 6, 2012
525
The Monitoring/Shut-Down-Pin on the STEF01 doesn't care whether the
Monitoring/Shut-Down-Pin was pulled-down by
its own Internal-Circuitry, or by some sort of External-Circuitry.

If the Monitoring/Shut-Down Pin is made low ..... some-how ....... any-how ........
the Output of the STEF01 will be Shut-Down.
Micro-Controller Interface FLAT .png
 

ElectricSpidey

Joined Dec 2, 2017
1,653
If you want to connect a pin that is internally pulled to 5 volts to a micro using 3.3 v you need to know the value of the pullup so you can calculate a pulldown at the pin to derive 3.3 v and the input must be highz as to not affect the division.

If the output is push/pull then you need 2 resistors as a divider.

Check the data sheet for the micro, the input might be 5 volt tolerant.

If it is not possible to determine the pullup value and the pin is not 5 volt tolerant, then active level shifting should be used or a zener.
 
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