критично не падение, а длина
Вот спеки usb 2.0
The maximum length of a standard USB cable (for USB 2.0 or earlier) is 5.0
metres (16.4 ft). The primary reason for this limit is the maximum allowed
round-trip delay of about 1,500 ns. If USB host commands are unanswered by
the USB device within the allowed time, the host considers the command lost.
When adding USB device response time, delays from the maximum number of hubs
added to the delays from connecting cables, the maximum acceptable delay per
cable amounts to be 26 ns.[29] The USB 2.0 specification requires cable
delay to be less than 5.2 ns per meter (192,000 km/s, which is close to the
maximum achievable bandwidth for standard copper cable).[30] This allows
for a 5 meter cable. The USB 3.0 standard does not directly specify a
maximum cable length, requiring only that all cables meet an electrical
specification. For copper wire cabling, some calculations have suggested a
maximum length of perhaps 3m. No fiber optic cable designs are known to be
under development, but they would be likely to have a much longer maximum
allowable length, and more complex construction.
usb 1 работает на ещё меньшем кабеле, именно из-за таймингов
Ну и сам кабель спецефичный -
волновое сопротивление- Дифференциальное - 90 ом +-15%, common mode - 30 ом +-30%. USB
Specification 2.0, раздел 7.3.2.
Внешняя оплетка из облуженной меди с коэффициентом экранирования не
менее 65% (для кабелей low speed рекомендована, но не обязательна). Внутренний
экран из алюминизированного пластика, с перекрытием не менее четверти оборота и
с отводящим проводом не тоньше 28AWG (обязателен для кабелей low speed). Там
же, раздел 6.6.
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