The USB standard 3.1 with a Type C connector promises data rates of 10 GB / s, power supply with up to 100 W, external signaling by means of Alternate Mode and a uniform, twistable connector. However, USB 3.1 still raises questions. Lindy knows answers.
The connectivity expert Lindy USB-3.1 / Type C products has been around for a year and has had enough time to gain experience with both the technology and the market with the new standard. However, the situation is not as simple as it could be, because the initially highly praised standard has come into the criticism and there are accumulated negative headlines. Dr. Rainer Bachmann, Senior Product Manager at Lindy, was responsible for USB 3.1 at Lindy right from the beginning and knows many questions.
Is USB 3.1 actually faster than USB 3.0?
USB 3.1 promises data rates of up to 10 GBit / s. However, this is only the case if manufacturers explicitly advertise a “USB 3.1 Gen 2 product”. Otherwise, the transfer speed of USB 3.1 is the same as for USB 3.0. Anyway, these 10 GBit / s today are still rather theoretical. With Lindy, the 10 GBit / s could not be reached even under laboratory conditions. However, this is not a problem of the cables, but the chipsets and the available hardware. Because even a very fast SSD hard drive via USB 3.1 would come maximum to the SATA 6 GBit / s. Of course, a vendor of this product would then call as USB 3.1 Gen 2, even if it does not exhaust the 10 GBit / s. For a provider of connectivity solutions like Lindy, it is therefore hardly possible to make binding statements on maximum transmission rates, as long as market sources and receivers do not yet standardize the standard.
Can USB 3.1 transfer up to 100 watts of power?
The 100 watts are a promise of the power delivery specification (PD), which was introduced strictly before USB 3.1, but is now finally to become reality. Whether and to what extent PD is really implemented, is somewhat more complicated to answer.
To this end, a retrospect: Up to now, USB was set to 5 V and only the power was raised in moderate steps from USB 1.1 with 100 mA to 900 mA at USB 3.0. Basically, little has changed on the power supply via USB. In addition to the classic 5V, PD also offers 12V and even 20V. It is also possible to transmit significantly higher current intensities up to 5000 mA. Which power and voltage are used effectively, make the devices under itself. Unlike the step-by-step increase from 100 mA to 900 mA, the USB ports as well as the connected devices have to be completely redesigned for PD. Even the cables require more than just a new plug for 5000 mA. Additional passive components, such as resistors, must be installed in PD-compatible cables. Previously, cables of any quality, even under optimal conditions, can be loaded with 3000 mA at best. The new development on all sides should also be the reason why PD has not yet gained a foothold in the market.
In order to help PD to breakthrough, the PD specification for cables with Type C connectors was made mandatory. However, this is hardly more than a pious wish, which many no-name manufacturers will not hold on cables with type C connectors. Because USB Type C requires a completely new cable design and can not be reduced to the new connector. More than twice as many cores as USB 3.0, additional resistors built into the cable and lower manufacturing tolerances make PD-compatible USB type C cables considerably more expensive than conventional USB cables. But the few customers currently use PD components, also do not use data rates over 5 GBit / s and would need in principle actually only a normal USB cable with a type C plug. These customers are therefore also not willing to pay the additional prices for fully wired Type C cables with resistor network. At Lindy, therefore, type C cables with different levels of PD support are offered and marked and described accordingly. There are, however, many other providers, which simply speak of “type C cable” or “USB 3.1 cable” and do not go into detail. Consumers must therefore pay close attention to whether and at what level their USB cable really supports PD. Otherwise connected devices could be destroyed by overvoltages.
Even if there are almost no PD devices available in the market, the possibilities that PD does not provide can be ignored. For example, printers could be directly connected via USB and simultaneously powered, or 100-watt smartphones could be fully loaded within a short time. Since the flow direction of the current can also be reversed at PD, there are other scenarios: it is possible to connect a notebook via a USB cable to a docking station, which is itself plugged into an electrical outlet. Then at the same time via the USB cable in the direction of the notebook load while the notebook communicates with the docking station. In view of the possibilities, it is therefore still to be expected that PD will play a greater role than is currently the case.
How does the transmission of strange signals (Alternate Mode) work?
In principle, the idea is quite simple. A USB 3.1 type C cable has 16 wires plus shielding as per specification. Four wire pairs, eight wires, are used for the USB-typical SuperSpeed data transmission standards TX1 / 2 and RX1 / 2. Of these four pairs of conductors, one, two or all four can be used to transmit other signals. If, for example, a DisplayPort signal with 4K resolution is transmitted, this requires two pairs of wires. There are two wire pairs for USB, which means that the full USB 3.1 standard can still be transmitted at 10 GB / s in parallel. If all four wire pairs are used for Alternate Mode (necessary for example with DP 5K or Thunderbolt 3), only USB 2.0 can be transmitted in parallel via a fifth wire pair.
As with PD, Alternate Mode is still at the beginning of his career. The possibilities are also tempting. On the side of the PC, for example, graphic signals can be natively passed through the USB Type C cable and tapped from the monitor. Combined with PD, for example, one could hang a monitor on the notebook’s USB port and load the notebook from the monitor. Currently, it is mainly Apple devices connected to DisplayPort adapters, where this possibility is used real. Apart from that, the market is still sluggish here and offers only a few components that support the Alternate Mode.
What are the problems with the new connector type C?
A standard plug, which is no longer available as a standard, mini and micro version, but only a format similar to the current USB Micro or Apple Lightning; This is a practical plus on the user side, which should increase the acceptance of Type C connectors. On the technical side, however, this has considerable disadvantages. A high signal quality is achieved mainly by a higher wire cross-section and a large contact area. The pins in the type C connector are then 0.28 mm wide to the bottle neck. Even if the wires are soldered against each other to the contact pins and the depth of the plug is increased, the contact area is considerably smaller than for a type A plug. As a result, even small manufacturing tolerances can lead to significant differences in the quality of the connection. In addition, current is to be transmitted over the 0.28 mm wide contact pin, which is almost 0.08 mm² in size, in the case of PD up to 5 A. According to the VDE standard for current carrying conductors, however, the conductor cross-section should then be at least 0.15 mm², rather 0.3 mm². This has been solved with Type C plugs, as the current is transmitted in parallel via 4 pins (and another 4 pins for the ground). A total cross-section of approximately 0.31 mm 2 then results. To avoid short circuits, opposing pins are used. For Plus these are A4 / B4 and A9 / B9, for mass A1 / B1 and A12 / B12.
What lengths are possible with a USB 3.1 / Type C cable?
The question can only be answered reliably when USB 3.1 has established itself on the market. Reizen manufacturers the 10 GBit / s really off or is the realistic mean transmission value rather at 5 to 8 GBit / s? This question will also determine the maximum possible cable lengths. To date, Lindy is limited to cables up to a maximum of 1.5 meters to ensure that the full specification is met at this distance.
If maximum cable lengths are concerned, shielding, copper quality and wire cross section are the decisive criteria. However, for USB 3.0 cables, the limits of physics have already been quite advanced. The shielding is already almost perfect to increase the cross-section of the wire, does not make much more since the pins in the new type C connectors themselves form the throat, and to use cleaner copper grades with lower resistance is also difficult. Lindy has been using a 100% copper cable for a long time. Times where copper-coated wires with cheap aluminum or steel core could be used in USB cables have long since passed. As a result, in the early summer of 2016, every statement about the maximum possible cable lengths is either guessed or a blind promise, in which one can not actually assess the fulfillability.
Where do the many negative headlines for USB Type C come from?
The main problem is that you wanted to force the big USB revolution with one step. However, complete implementation requires new motherboards, new plug-in cards, new cables, new hubs, and finally, new devices. It is understandable that both manufacturers and customers react to behavior. For who starts the revolution? A new, more expensive motherboard that supports PD, allows for Alternate Mode, and delivers a full 10 GBit / s and costs significantly more will be sold only if there are already hubs, docking stations, monitors, active boxes and printers USB ports. Conversely, there are no monitors connected via USB and supplied with power if they can not be connected anywhere.
What is however, however, the spread is the new plug type C. This is mainly due to Apple and Google and meanwhile also many smartphone manufacturers. However, only rarely PD, Alternate Mode or 10 GBit / s SuperSpeed have been implemented. Up to now, USB Type C is usually only “old wine in new hoses”, and up to the new type C plug has remained with USB 3.0. On the cable side, many no-name manufacturers have simply equipped conventional USB cables with Type C connectors in order to have fast-priced USB Type C equipment in their assortment. Unfortunately one has to concede that this is currently sufficient for many new devices with a type C socket. The actual advantages of USB 3.1 can not be used with such a cable however. If these USB 3.0 cables with Type C connectors are used to use certain functions of USB 3.1, which were not already available in USB 3.0, the problems begin.
Most of the negative headlines come from Type C cables that do not support PD but have been connected to PD components. There are already numerous documented cases, in which hardware has been irreparably damaged.
What should consumers consider?
“USB 3.1 Gen 2 Type C”, as one has to say correctly, will be pretty secure. The advantages and too much is the market power of Apple and Google, which both push this standard to tempting. How long it will take, however, until all new features have become normality, can hardly be estimated. Currently, the situation is that many specifications are disregarded because they are not needed and would cause additional costs in the highly competitive market. This will cause frustration on the user’s side and start USB 3.1 with a delivery charge. Because the new features do not work, can be at the host, the cable or the terminal. For all three components, the consumer must look very closely at what he actually buys.
But even if you look at the correct designations, you can easily be disappointed by current USB 3.1 equipment. Most of the available hardware and chipsets are currently at best at the Betaphase and for manufacturers is not yet foreseeable, which chipsets in a few years the actual existing De-facto standard will form. Manufacturers such as Lindy design their products not only on the cutting board according to a standard and its specification, but above all in connection with components available in the market. But right here, it is currently difficult with USB 3.1 to assess which components should be tested for compatibility and reliability. However, the situation is still comparatively comfortable for connectivity specialists like Lindy. Cables and adapters have to meet physical requirements that are independent of future chipsets. As a result, it is already possible to produce fully compatible USB-type C cables for which there is hardly any use. Consequently, there are currently many online providers with pseudo-type C cables. For hardware, the only feature of which are the new type C connectors, these cables may work, but at the latest when PD and SuperSpeed are established, these cables are at best unreliable and at worst risky.