It seems like we’ll be using wireless technologies everywhere. But we’ll never be completely wireless. Hard connections offer too many speed and reliability advantages to ever be displaced completely. In fact, some technologies will use the best of both worlds. This year, Greenvity Communications and Micrel both offered the best innovations in wired networking in home and automotive technologies alike.
Wired Meets Wireless In The HAN
Home-area networks (HANs) can make life so convenient. But sometimes, wireless technology can’t cover the whole house, making the ac power line the best choice for high-speed applications. Yet power lines also can be very noisy. Greenvity Communications integrates a ZigBee wireless radio and a HomePlug Green PHY power-line transceiver in the Hybrii-XL GV7011, combining both technologies for the best communications under all possible conditions.
ZigBee and HomePlug Green PHY are competitors in the HAN market. Both can be used in smart meters and other HAN equipment, but neither technology fits all potential uses. With both on board, the Hybrii-XL GV7011 can reduce the cost of HAN equipment and speed up product design. It also uses less power than the multiple separate chips and boards that would be required to support both standards.
The chip integrates the full analog front end, RF, baseband, media access controller (MAC), and embedded memory. An 8051 microcontroller implements low-power energy management (Fig.1). The ZigBee radio achieves its standard 250-kbit/s rate with a power level to +13 dBm. The HomePlug power-line communications (PLC) device uses robust orthogonal frequency-division multiplexing (OFDM) from 2 to 28 MHz to achieve rates to 9.8 Mbits/s. The chip also has multiple interfaces like SPI, UART, I2C, Serial Flash, 23 GPIO connections, and even Ethernet.
1. The Greenvity Hybrii-XL GV7011 combines a ZigBee radio and a HomePlug Green PHY power-line communications modem to significantly reduce HAN equipment cost and power consumption. It comes in a 12- by 12-mm GFN-148.
The Hybrii chip automatically selects the best medium to transmit data, wirelessly or on the power line. If the power line is too noisy, the wireless nodes will be enabled and vice versa, ensuring reliable communications under most circumstances. Potential uses in home and industrial environments include smart meters, smart appliances, HVAC systems and thermostats, home energy monitors, home gateways, routers, solar inverters, and smart lighting control. It’s ideal for multi-dwelling units such as condos and apartments where power-line communications are often more reliable than wireless.
Greenvity’s similar Hybrii-PLC GV7012 only offers HomePlug Green PHY connectivity. It’s designed for use in electric vehicles (EVs), EV support equipment, and battery chargers. Samples of both chips are now available. Evaluation kits also are available.
Cars Get Caught In The Ethernet
The electronic content of automobiles continues to increase as manufacturers add more sensors, controllers, and entertainment equipment. These electronic components need to communicate with one another, leading to a variety of communications buses to network the electronics. Now the most widely used and well-known networking technology, Ethernet, is coming to the automotive space.
Multiple buses have been developed to handle these communications. The Controller Area Network (CAN) bus came along in the 1980s, and it’s still widely used. It is a shared bus, and the CAN bus is a standard interface on many embedded controllers. However, its speed tops out at 1 Mbit/s over a range up to 40 meters. For many applications, more speed is needed.
The cheaper Local Interconnect Network (LIN) was introduced in the late 1990s to meet the need for slower sensors and actuators. It can achieve 19.2 kbits/s up to 40 meters. The Media Oriented Systems Transport (MOST) bus then emerged in the early 2000s for high-speed applications. MOST is mainly a protocol, and it can use both copper and plastic fiber media for transport. Data rates up to 50 Mbits/s are possible.
Newer vehicles require even higher data rates, as the need to transport more video has increased. New applications like backseat video monitors and backup cameras demand more bandwidth and less latency. One almost obvious solution is to use everyone’s favorite networking standard, Ethernet.
Ethernet, the IEEE 802.3 standard, has been around for many years. Well over 80% of all wired networking is Ethernet. Virtually every computer and communications device has at least one Ethernet port for networking or Internet access. Furthermore, the standard is highly developed and fine-tuned. It offers low power consumption with its Energy Efficient version as well as dc power delivery over the cable.
In its basic forms, Ethernet delivers speeds of 10/100 Mbits/s. The 1-Gbit/s and 10-Gbit/s versions also are widely adopted. While fiber optic versions are available, most of the world still uses the popular 100Base-TX standard with unshielded twisted pair (UTP) CAT5 or CAT6 cable. Finally, many interoperable parts are available to implement interfaces, switches, and other portions of the network, keeping Ethernet’s costs low with many second sources.
Ethernet offers some major benefits to the automotive environment. First, it boosts data rates to 100 Mbits/s in both directions on each link. In addition, it offers power delivery and power savings over other options. The 802.3az Energy Efficient Ethernet (EEE) version has idle modes that save power in both directions on a link. The 802.3at/af Power over Ethernet (PoE) standards provide dc power delivery over the cable to external nodes.
However, Ethernet was not developed for the harsh automotive environment. By itself, it doesn’t meet the stringent electromagnetic compatibility (EMC) requirements as spelled out in the CISPR25, ISO11452-2, and ISO11452-4 testing standards. While a shielded UTP cable can help, it is heavy and expensive, two factors that auto engineers want to avoid. The challenge lies in finding a way to meet EMC standards with standard UTP.
Using its standard Ethernet physical-layer (PHY) chips, Micrel added a clever low pass filter on the transmit front end in its KSZ8061MHL 10BaseT/100BaseTX PHY transceiver. The combination meets the IEC 61967-1/4 RF emissions tests in addition to the direct power injection immunity test, the CISPR35 stripline emissions standard, and the ISO 11452-4 bulk current immunity test.
The KSZ8061MHL is designed for reliable transmission and reception over UTP cable. It incorporates Micrel’s Quiet-WIRE internal filtering to reduce line emissions where stringent radiated emission limits must be met. The I/O is a standard Media Independent Interface (MII) for direct connection with MMI Ethernet MAC processors and switches.
The transceiver can exceed Automotive AEC-Q100 and EMC requirements and interoperate with any other IEEE 802.3 Ethernet PHY. The chip also has the standard MDC/MDIO management Interface for PHY register configuration. The internal Quiet-WIRE filter that allows the chip to meet all EMC requirements is on chip, along with termination resistors for the differential pairs.
The KSZ8061MHL supports the IEEE 802.3az Energy Efficient Ethernet standard. It also offers on-chip diagnostics and an extended temperature range from –40°C to 105°C. It operates from a 3.3-V supply with I/O options of 1.8, 2.5, or 3.3 V. The package is a 48-pin, 7- by 7-mm quad flat no-lead (QFN). An evaluation board for the chip is available as well (Fig. 2).
