How could I reduce 5v to 0.6v? Maybe something like a LM317 but capable of lower outputs?

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steveastrouk8 months ago

For the doubters out there

Here's the simplest thing I can think of to get roughly 600mV, you'll have to play with the resistor a bit probably. I want to get enough drive off 5V to get 600mV, but not toast the diode if the supply jumps to 20V

diode reg.png
Will2MakesStuff (author)  steveastrouk7 months ago

Sorry for the late reply, thank you for your answer.

steveastrouk8 months ago

What for ? Making a regulator do it isn't too hard, but knowing why might let us give you a better answer

Will2MakesStuff (author)  steveastrouk8 months ago

I'm looking to convince a qualcom usb quick charge device to output 12v, to do this it needs to sense 0.6v on the plus and minus data lines

I want to build a circuit which will take power from the normal 5v usb socket and output 0.6v to the data lines

Well, if you use wrong information to solve a problem that does not exist you might end up running around in circles.
According to the USB specifications the resistors provided in a conform charger provide either the voltages required for Apple products or those for all other (normal) devices.
If a conform phone and conform charger won't be able to provide the specified charging current than in 99.95% of cases the USB is to blame.
But no matter what you mess up on the data lines the charger will always and only output 5V.
To make it provide 12V you need to modify the electronics inside - those responsible to drive the output circuit.
If you need 12V then do yourself a favour and buy a 12V adapter/charger.

Will2MakesStuff (author)  Downunder35m8 months ago

If you read the spec of qualcomm quick charge you will find it can output up to 20V over usb its not limited to 5V at all

Then check the USB 3 specifications to work out how to get the 20V.

The Vbus is used to determine the charging current on all USB2 systems, as per USB 3 specification all fast charge enabled devices communicate over Vbus with the charger to set the charging voltage.
So it is not as simpla as with USB2 where you just put the correct resistors onto the unused datalines.

You'd do that with resistors ! Or a resistor and a single forward biased diode.

Will2MakesStuff (author)  steveastrouk8 months ago

Thanks Steve!

Could you point me to some circuit examples maybe something explaining what components values I would need and how to wire them up?


Yonatan248 months ago

Step down voltage converter. Search for one on eBay.

Will2MakesStuff (author)  Yonatan248 months ago

Hi Yonantan,

I have looked I can't find any which go down to 0.6V I think.

Read what everything says, I didn't make sure...