The most common specification error in this category is to state the wattage and assume the adjustable mode comes with it. The protocol support is an option, the range is a parameter, and the current limit is a third item. An RFQ that names all three gets comparable answers; one that names the wattage gets three different products.
USB PD PPS: what to specify
Four items: whether the adjustable mode is required, the voltage range it has to cover, the current available within that range, and the evidence that proves the behaviour.
Each is a parameter rather than a marketing term, and each can be verified against a reference device. The four are ordered because they build on each other: the range only matters if the mode is supported, the current only matters inside the range, and the evidence is what turns the claim into a specification.
The reason this matters commercially is that devices using fast-charging implementations negotiate an adjustable level rather than a fixed one, so a charger without the mode charges them at a lower rate while still meeting its wattage claim.
Decision 1: is the mode required at all
Decide from the device list, not from the wattage tier.
The mode is useful for devices that use an adjustable profile and unnecessary for devices that charge at fixed levels. A range aimed at laptops that take fixed voltages may not need it at all, while a phone-focused range almost certainly does. Stating the decision explicitly in the RFQ prevents a supplier from adding the capability speculatively and pricing it into every unit.
Decision 2: the voltage range
State the range as a parameter with the current that goes with it.
A range without a current limit describes half of the behaviour: the same voltage band can carry different currents depending on the design, and the device will settle where the negotiation permits. The RFQ should state the lowest and highest level required, the current available across that band, and whether the current has to be held at the top of the range or may taper. Those three items define what the charger has to do.
Decision 3: the interaction with the other ports
The sharing rule belongs in the same paragraph.
On a multi-port product the adjustable range is available only while the power budget allows it, so the sharing rule decides whether the mode survives when a second device is connected. The specification should state the conditions: the range at full availability, the reduced condition when another port is active, and the behaviour when the input adapter cannot supply the total.
Decision 4: the evidence
Four documents or measurements, and each answers a different question.
The negotiated profile list against a named reference device; the measured voltage accuracy and ripple across the band; the load-step response; and the production test positions that exercise the behaviour. With those four, the claim is a specification; without them, it is a feature description that the first support query will test.
| Item | What to state in the RFQ | Evidence to request | Common omission |
|---|---|---|---|
| Mode required | Yes or no, from the device list | A statement in the specification response | Assuming it comes with the wattage |
| Voltage range | The lowest and highest level required | Measured accuracy across the band | A range with no current limit |
| Current in the band | The current available, and whether it tapers | Load-step measurements | Only the headline current |
| Sharing rule | The condition when other ports are active | The multi-port test positions | The rule left to the datasheet |
| Evidence | The four items as deliverables | Profile list, ripple, response, test plan | A claim with no measurement |
How the parameters interact
Three relationships that decide whether the design is straightforward.
The wider the voltage band, the more the control loop and the thermal path have to do; the higher the current inside the band, the more the connector and cable rating matter; and the more ports that share the budget, the more conditions the firmware has to handle. Reading the three together explains why two chargers with the same wattage can differ in cost by more than the component difference suggests.
Reading the responses
Three answers, and one of them is the useful one.
A response that repeats the wattage has not engaged with the specification. A response that states the mode is supported without the range and the current is a partial answer. The response that names the range, the current, the sharing condition and the evidence is the one that can be compared with another supplier and priced. That comparison is what the RFQ was for.
FAQ
Does every USB PD charger support the adjustable mode?
No. The mode is an optional part of the specification, so a charger can meet its wattage claim and still charge an adjustable-mode device at a lower rate. Support has to be specified and evidenced. The adjustable mode is an optional part of the specification, so a charger can meet its wattage claim and still charge an adjustable-mode device at a lower rate.
How should the range be written in an RFQ?
As a lowest and highest level with the current available across the band and the taper condition. Those three items define the behaviour; a voltage range alone does not. Write the lowest and highest level with the current available across the band and the taper condition, because those three define the behaviour and a voltage range alone does not define it.
Does the mode affect the certification scope?
It affects the protocol behaviour that is tested, and it changes the thermal position because the output can sit near the top of the range for longer. The construction evidence still follows the safety and electromagnetic requirements for the product. The mode affects the protocol behaviour that is tested and the thermal position, because the output can sit near the top of the range for longer.
What if the supplier cannot provide the evidence?
Then the claim is an intention rather than a specification. The practical options are to request a sample measured against a reference device, to narrow the claim to what is evidenced, or to choose a platform whose behaviour is documented. The options are to request a sample measured against a reference device, to narrow the claim to what is evidenced, or to choose a platform whose behaviour is documented.
Next step
Send the device list, the required range and the port configuration to Wecent Group through the contact page. The reply states whether the mode is supported on the platform, the measured behaviour across the band, the sharing rule and the production test positions that exercise it. Related reading: GaN charger applications, OEM and ODM charger manufacturing and charger quality control. External references: USB Power Delivery specification, USB-IF documentation, USB-IF compliance programme, IEC standards, UL standards and certification and TUV testing services.
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