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uC lowcost variant: 5V Sensor Regulator - Feedback Voltage Divider correct Resistance values? #41

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FriedrichUthe opened this issue May 10, 2022 · 1 comment

FriedrichUthe commented May 10, 2022 •

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Just checking your designs I came accross this part:

According to the datasheet I would expect the regulator to return 5.5V instead of 5V with the two resistor values
(https://datasheet.lcsc.com/lcsc/1810182113_Feeling-Tech-FP6291LR-G1_C18701.pdf)

180/22+1*0,6 = 5,5?

Am I right here?
And if so: Why not 5V with 12k and 88k as suggested in the datasheet?

Please forgive me my ignorance - I am a non-engineer-noob-hobbyist trying to design my first PCB :)

TMillesich commented May 11, 2022

Your Voltage Divider gets the voltage AFTER the schotty diode. So depending what diode you use there the voltage drop varies.

The D4 diode populated with a SM340A has a max forward voltage of 0.52V, what are the values of your diode?

(That's a good example why the typical applications & values from the datasheets don't always work in real live as expected)

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