STUSB4761 FB pin

[JPZ]

If I have only 5V input. what to do with the FB pin?

[EThom.3]

The way I read the datasheet, this device is designed to regulate the VBUS voltage through an optical connection to a circuitry sitting on the primary side of a transformer:

This means that the STUSB4761 acts as part of an adjustable voltage regulator. The resistor and capacitor connected to FB act as the compensation network for this regulation. It does this not matter which voltage it needs to output, so the compensation network will be needed regardless of the VBUS voltage.

If you only need to generate 5 V, then this device may be overly complex.

[JPZ]

Hi,
thank You very much.
If I only have 5V and I need 5A. Can I leave this pin open?

[EThom.3]

If you use this device, I don't think that you can leave this pin open. But I am not sure, as I haven't seen your circuit.

What do you mean by having only 5 V? Do you have a 5 V power supply that you use as power source for the STUSB4761 and VBUS? If this is the case, what is the purpose of the STUSB4761?

[EThom.3]

Now, if you don't intend to use the STUSC4761 for regulating the VBUS voltage, then I assume that you aren't going to connect Opto_DRV to anything either, and the device will not have any influence on the supply voltage. In this case, I don't think that you need to connect FB to anything.

The question is if the device will accept that the 5 V supply is good, or if will shut down the output because it finds the voltage (that it cannot regulate) to be wrong for some reason. That I don't know the answer to.

One thing you need to keep in mind is that the STUSB4761 is becoming obsolete. So if you are designing something that is to go in production, the STUSB4761 may be an impractical choice.

[JPZ]

I tryed for more the 80 hours to make this stusb4761 work.
Even programming with nucleo board is not posible.
I will have to focus on chinese chips. 
This chip is very unstable. 
i will go for sw3516 or sw3518 this looks much more easy.
I also changed from st chip to esp32 works much better and easyer.
sorry to tell you this.
But I think the future is in china if usa and europe do not change.

[JPZ]

hi,
we only need max 1000 devices.
yes i will use sw3561 thank you

[EThom.3]

Any suggestions as to what exactly we need to change?

[JPZ]

The programming is too complicated.

The manual is incomplete.

More information would be helpful.

Good, short YouTube videos would be helpful.

Test circuits and better explanations about the chip would also be helpful.

[JPZ]

Hi 

i will tray to make a pcb with stusb4761 just for testing.
I can not unterstand why it is not working.
this is my schematic. And ist is not working.

Now a made a testing pcb

i hope this will work