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| They raised max USB output voltage from 5.25V to 5.50V. Retroactively. |
| (1/4) > >> |
| ivan747:
The USB Implementers Forum raised max USB voltage from 5.25V to 5.50V, retroactively. I took this personally. They got away with literally raising the maximum voltage of the USB port. With billions of devices in the field. Those devices were designed to receive 5.25V maximum. And now they can receive 5.5V from a new port. In manufacturing, my deviation requests used to get denied all the time. So many hours getting everyone in the plant to agree, so many hours writing good arguments on the request forms... Most of the time, if they got denied it was for good reason. But I still had to request them to make management happy. I have to laugh because the other option is to cry :scared: USB ENGINEERING CHANGE NOTICETitle: USB 2.0 VBUS Max Limit Applies to: Universal Serial Bus Specification, Revision 2.0 Summary of ECN Update the USB2.0 specification to align with the expanded VBUS voltage definition in the USB-IF Type-C specification which defines VBUS as having a Max supply voltage of 5.50 V DC. The Type-C cable and connector definition specifies a minimal current carrying capacity of 3A. This increased capacity creates a situation where losses in cables, connectors, PCB traces and power supply components will result in the VBUS level available at the consumer end of the cable that is below the minimum acceptable level for operation. As a result, in order to have an implementable Type-C specification it is necessary to boost the upper limit for VBUS at the supply side to 5.5V DC from the present spec value of 5.25 V DC. Reasons for ECN OEM’s can design products that support the higher power levels of the Type-C connector and provide VBUS levels at or above 5.25V to ensure that the VBUS voltage that is available at the far-side connection is within a suitable working range for USB products, and is also at a high enough level to charge batteries in as short a time interval as possible to ensure customer satisfaction. Impact on Existing Peripherals and Systems: The impact is difficult to assess [you don't say!? :palm:] as there is a wide range of component vendors supporting USB, and also a wide variation of design methodologies. As a result, there are certainly going to be a subset of existing USB products that may be sensitive to operation at VBUS levels of up to 5.5V. The sensitivity will be mitigated in many cases by cable losses, so the devices themselves may never experience the 5.5V. Hardware Implications: New designs adhering to this ECN will need to consider the new 5.5V VBUS max level during the component selection process. Software Implications: There are no known software implications. Compliance Testing Implications: Compliance will need to make the small modifications necessary to accommodate the new upper limit. Emphasis added by myself. Note: if anyone at the USB-IF is reading, I imagine this was not an easy decision. It's just funny how all this strict compliance is thrown out the window when the approvers are also affected and there are no other realistic solutions. |
| SiliconWizard:
That's good to know. |
| magic:
In a world without Apple there would be no reversible connectors, no USB C, none of that nonsense. Just sayin' >:D |
| DavidAlfa:
Absolutely no worries. |
| SiliconWizard:
That shouldn't cause much worries, but still something to keep in mind. Many "5V" ICs, such as regulators, are rated up to 5.5V only. So, instead of having a small margin, now we'll be running with no margin. Sure those ICs have usually an absolute max of 6V or 7V, so nothing special should happen here, but having a reduced effective margin is never that good news. They didn't bother to adjust the minimum Vbus as it didn't fit the rationale - AFAIR it was symmetric (4.75V to 5.25V), now it's going to be asymmetric. |
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