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STEF01 Design Assistance

mkladis
Associate

Hey everyone,

I am currently working on adding the STEF01 eFuse to my design and I have run into a roadblock. 

For starters, I can't seem to get the eval board to function. I have added the resistors to the board and I have a load on the output side but my power supply shows its still just an open circuit. 

 

As for the design, my current specifications are as follows:

Vin = 24V (+/- 1V)

Ilimit = 4A (22Ω resistor)

Auto-retry enabled

EN/Fault = sent to 3.3V pin on microcontroller (using 20k|10k voltage divider)

EN/Fault is also connected to the collector of an NPN transistor. (Base is also controlled by the microcontroller).

 

I followed the datasheet and I believe I picked out the correct resistors for the Vclamp and UVLO.
I chose 470k and 20k for both sides (around 25V and 23V respectively).

The EN/Fault pin is something I am worried about. I am using the transistor to create a short to ground but I have a voltage divider also connected to the collector side to allow the 5V coming from this pin to lower to 3.3V. 

This should be fine to use to monitor and control the eFuse, right?

Do you see any glaring issues with this design?

AndrewNeil_0-1751014047690.png

Edit: image placed in post for better visibility.

2 REPLIES 2
Rob1
Associate II

you have pin 2 connected to gnd. Leave it open.

Andrew Neil
Super User

@mkladis wrote:

I followed the datasheet 


As @mkladis said, not quite:

AndrewNeil_0-1751014256525.png

https://www.st.com/resource/en/datasheet/stef01.pdf#page=3

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.