Comment on Dell PSU is “PD3” but cannot do PPS. WTF? Isn’t that non-conformant? OTOH, no USB-PD indicator to begin with.

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daveyOsborn@infosec.pub ⁨4⁩ ⁨days⁩ ago

I appreciate the link. I wanted to see what you saw, so I opened the ZIP file and it expands to 27 files. I believe the relevant file is USB_PD_R3.2_V1.2_2026_05_20.pdf, page 42, which states:

3.2.5.2. SPR Programmable Power Supply (PPS) Programmable Power Supply (PPS) is Optional. When included, the voltages and currents a PPS Shall support are as defined in Table 3.4.

If it’s optional in rev. 3.2, I assume it’s optional in rev 3.0. I’m a bit astonished because PPS is probably the most signficant feature of rev.3. The industry is not competent enough to even tell consumers which rev a device conforms to. But if it did, typical Wikipedia-informed consumers who see PD “rev.3” advertised would naturally expect PPS. As you are correct that PPS is indeed optional, many consumers will get burnt by the misunderstanding.

A potentially interesting follow-up question would be whether the laptop’s mainboard PDO tells you the laptop supports PPS even though its power brick doesn’t.

What’s PDO?

The problem seems to be that a laptop could be designed to /need/ PPS, e.g. if the voltage it needs is well below 20v. While most PSUs do not advertise USB-PD 3(+) compliance, much less PPS.

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