Automotive Infotainment Systems: Connecting High Bandwidth Data
The following article is an edited reprint, courtesy of Tyco Electronics.

The demands on the automotive industry to accommodate the growing requirements for the integration of consumer products, as well as responding to the drivers capabilities of processing higher data content, remains a significant challenge for the industry. Tyco Electronics is the only connector supplier who can offer solutions based on all connectivity mediums, such as electrical, optical, coaxial, and wireless.

Optical-Based Solutions

Tyco Electronics was the first connector company to support the launch of an optical-based automotive network with the D2B system. This network was later replaced by the MOST 25 standard, which is now available on all high-end automotive platforms covering the multi-media networking solutions, mainly focused on digital audio streaming.

Tyco Electronics was the connector representative on the MOST physical layer development team, and offers a wide product portfolio for all the physical layer components. Picture 1 shows an example of the MOST network. Picture 2 is an example of a recently launched MOST pigtail. The MOST 25 micro pigtail 180° is focused on applications where the optic cable routing is not compatible to the form of the existing micro pigtail 90°. Common applications include the instrument cluster connections. This pigtail is fully compatible to the MOST 25 optical requirements, as well as the MOST 2+0 mechanical requirements. It also includes a reflow soldering option when combined with a reflow-compatible FOT (Fiber Optic Transmitter), and delivered in a two-piece format.

The MOST 25 standard includes data rates up to 25 Mb/s. The growing requirements for digital video streaming, as well as the added functional requirements of an Ethernet channel to transmit Internet protocols within the automobile, necessitated the widening of the bandwidth of the MOST protocol. This update will be accomplished with the introduction of the MOST 150 specification.

The MOST 150 connectors will increase the data rate transmission to 150 Mb/s while maintaining the existing Plastic Optical Fibre (POF) physical layer currently used on the MOST 25 connector system. This limits the overall impact of the change and the existing wiring harness logistics channel will remain unaffected by the upgrade. What will change is the light source and, optionally, the method how the light source and photo diode should be packaged.

This would result in the traditional flexible pigtail being split in two separate components. The SMD (surface mount device) houses the light source (RCLED), the photo diode, and the POF assembly, which will make the connection to the MOST interface. This concept has the advantage of removing the thermal-sensitive POF from the soldering process, but could prove costly from a material and a manual assembly aspect.

Another option is the side-looker form that is already available for MOST 25 and can be expanded to cover the MOST 150 requirements. The present MOST 25 device has four pins, with MOST 150 devices; this will increase to seven pins to accommodate the additional functionality. To safeguard the higher data rates, the shielding concept will also be upgraded with the addition of shielding pins to the PCB. It is the philosophy of Tyco Electronics (TE) to build on the positive building blocks of previous generations. So TE will offer the existing product concept for the micro pigtail, fulfill the MOST 150 requirements, and upgrade the product to be compatible with reflow (pin-in-paste) process requirements of the tier 1 manufacturers.

The MOST 150 Micro Pigtail can be seen in picture 3. The advancements made on the existing MOST 25 Micro Pigtail, which has been successfully used by all MOST OEM car makers, can be summarized in two ways: To accommodate the new packing form of the MOST 150 side-looker FOTs, the connector has been extended by 2.4mm to accommodate the second row of pinning. Also, the new features built upon the success of the MOST 25 version, including a fully shielded connector body, extra grounding pins to the board, the shielding option to the device casing, and an option of pin-in-paste/reflow soldering compatibility. This is achieved by removing the heat-sensitive POF currently used in the MOST interface, and replacing it with a glass optical fibre (GOF). This product is also fully compatible to automatic pick-and-place processing.

In comparison to the SMD version, a number of critical advantages are present. There is a cost saving because of material savings. Fewer parts are required and processing costs are lower compared to the manual assembly of the pigtail to the SMD housing. Also, there is less space used on the PCB, as only one element is required. And, quality is improved as the part is processed within a fully controlled, automatic operation—from-pick-and-place to potentially pin-in-paste/reflow processing.

The focus is now on the next generation optical system, as bandwidth increases because of additional connectivity requirements in the automobile, and the growing number of sources that create interference, such as high current/voltage networks due to alternative power systems. Then the future demand for an interference-immune data signaling system, such as an optical-based solution, will become more attractive.

Copper-Based Solutions

Not all OEMs are comfortable with the fiber optic solution. Due to the increased data rates for applications such as real-time visual data transmission for safety-relevant camera applications, high resolution displays, or high-speed USB applications, the current automotive grade POF and LED-based FOTs do not offer an adequate solution. Even though significant development has occurred with polymer cladding silica (PCS) and laser (VCSEL) technology, the many applications are based on an electrical medium, and in the case of camera and display links, utilize the LVDS protocol.

Tyco Electronics is the main supplier of the automotive grade, four-channel LVDS, based on the 10-way MQS connection system. Improved IC technology and increased bandwidth capabilities allows high-speed links in automotive applications to increase. TE has developed a four-way LVDS interface, high-speed data (HSD).

This product family is completely compatible with the planned German “Facharbeitskreis Automotive” Specification for one channel LVDS communication based on the Shielded Star Quad connection system. Picture 4 demonstrates an overview of the TE HSD product portfolio. This is a complete range of terminals, connectors, PCB headers, and cable assemblies. Picture 5 shows the new HSD 4-way header from TE. The fully shielded header is optimized for two channel differential signal transmission, with target system impedance of about 100Ω for each channel. The header was developed with excellent RF performance and mechanical robustness, as well as low cost.

These three opposing parameters can be unified when modern methods of simulation are adopted and applied at the initial phase of the mechanical design. A simple measurement can give us an indication of the RF performance related to the mechanical and material attributes. It is a time domain measurement method that shows the impedance over the propagation path (picture 6). If there are ripples with high dynamic and large widths, we can imagine that the signal will be reflected at those areas. A typical connector system has many of these areas, including different diameters of pin and socket contacts, the crimping zone, the area between the twisted cable and the contacts, and the difference of the grid dimension of the cable and the connector. Typical standards specify measurement signal rise times at about 100 ps and more for time domain measurements. In that case, the corresponding fundamental wave is about 3.5 GHz. The graph shows the same PCB header before and after fine tuning (the two red colored lines show the impedance limits).

The impedance is measured by means of a signal rise time of 27 ps. This represents a fundamental frequency of 12 GHz. The TE HSD (high-speed data) PCB header fulfils even the impedance limits at a signal rise time of 27 ps. This behavior predestines the header for high-speed data transfer up to more than 1 GB/s. Measurements of other RF parameters will confirm this.

An important aspect for the HSD connector is the system performance, but just as important is the compatibility to the processing requirements further down the logistics chain, which can have a significant impact on the overall system cost. The TE HSD header system has taken into account the requirements of the tier 1 (device) manufacturers during the development process, and is fully pick-and-place, as well as reflow pin-in-paste compatible. The shielding connection to the device casing is achieved through the integration of the shielding lock into the coding cover cap. This eliminates the use of extra tooling and significantly reduces the assembly effort.

Picture 7 shows header forms based on a 180° connection direction, as well as incorporating the HSD interface, which has the same electrical performance as the 90° version. The 90° version is also available in a one-piece design with a shielded connection. A USB connection combined with a HSD header allows the consumer interface to be introduced into the car and accommodates the automotive requirements. As the USB interface was originally developed for consumer applications, it is not ideally suited to the automotive environment. This issue is overcome by TE’s HSD, because the USB devices will be connected to the automobile’s electrical infrastructure through the automotive-based HSD connection. This consumer port concept can be developed further to incorporate Aux-In connections, as well as SD card reader slots on one side, which is then coupled to automotive grade connectors, such as HSD on the opposite side. In the event of any damage, the consumer hub can be easily replaced.

Coax-Based Solutions

The German “Facharbeitskreis Automobil” (Fakra) Council is widely accepted as the standard for coaxial connections within the automotive industry. This standard covers the design of the connector interface for the mechanical and electrical characteristics, and also encompasses testing methods.

Over the last 10 years, this standard has gained worldwide acceptance for the distribution of coaxial-based connections in application areas such as antenna-to-head units for GPS, GSM, and AM/FM signals. TE offers a wide portfolio of products based on the Fakra standard.

Not all car manufacturers want to use the RF Fakra standard, so for these applications, an alternative, such as TE’s RF Stripline, is required.



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For more information about TE’s infotainment products, contact Peter McCarthy at peter.mccarthy@te.com, or phone +49 6251 133 1181.