Using a STUSB4500 to negotiate sinking. Source has the following PDOs; 5V3A, 9V3A, 12V3A, 15V3A, 20V3A, 20V5A. How do I get 20V5A? No matter what I try the most I seem to be able to get is 20V3A

[s_]

You need a cable which is "electronically tagged as being capable of handling 5A.

The power source will query the cable for its power capability. If it doesn't get an answer (because the cable is just a simple one), it will assume 3A.

I think the STUSB4500 evaluation board comes with a "5A tagged" cable - at least the one I have does.

[DTola.1]

Thanks for your response @s​ ! And of course you are completely right, however I am already using a eMarked cable that is 5A capable. I believe the problem has to do with the STUSB4500 being limited to 3PDOs and the source having 2 20V PDOs. I'm guessing the STUSB4500 just sees the 'first' 20V PDO(at 3A) and just chooses that one unaware there is another 20v PDO(at 5A) with more power available.

[s_]

What have you set the STUSB PDO1, PDO2, and PDO3 to (by writing to its non-vol memory) ?

With the default configuration is will attempt to negotiate PDO3 first (20V 1A).

If that fails, it will then try PDO2 (15V 1.5A)

and if that also fails, it will fall back to PDO1 (5V1.5A)

Are you sure the cable is tagged? (I bought one which claimed to be, but doesn't seem to be)

[DTola.1]

PDO1=5V1A, PDO2=15V1A, PDO3=20V1A (though I've also tried different combinations including setting PDO2 and 3 to 20V).

I also have the REQ_SRC_CURRENT bit set high. So I would think it would select 20V5A if available.

It works fine with sources that have only one 20V PDO the problem is just with this source that has two 20V PDOs, again I think it for some reason always picks the 3A one instead of the 5A one.

[Winfred LU]

Could you try to configure PDO3 as 20V5A?