100Base-T1 Ethernet PHY Simplifies Space-Constrained Automotive Design

The 100-Mb/s single-pair PHY transceiver with SGMII support lets designers pack more capability and intelligence into automotive networks


By Murray Slovick, Contributing Editor

As automotive electrical systems grow in complexity, with more electronic control units (ECUs) being packed into vehicles, the need to share real-time data has boosted demand for increased network bandwidth. To address this issue, Texas Instruments (TI) has introduced a PHY transceiver with a serial gigabit media-independent interface (SGMII).

SGMII is the interface with the lowest pin count available for connecting compatible Ethernet MAC blocks to a PHY. SGMII uses only four pins instead of the 12 required for the reduced gigabit media independent interface (RGMII), trimming board size and the number of traces and in turn simplifying the design layout. SGMII can be used for Gigabit Ethernet, but here it will provide 100-Mb/s transmit and receive capability. The device is optimized for automotive use cases.

Designated DP83TC811S-Q1, the transceiver cuts external component count and board space in half, according to TI, and consumes as little as half the power of competitive solutions. It enables designers to bring greater intelligence via Ethernet connectivity to space-constrained automotive body electronics, infotainment and cluster instrumentation, as well as advanced driver-assistance systems (ADAS) applications.

Figure 1: Here’s a simplified schematic of TI’s DP83TC811S-Q1 automotive Ethernet physical-layer transceiver.

In addition to requiring fewer external components, the part comes in a 6- by 6-mm wettable flank package, which can reduce solution size by 50%, again according to TI. In addition, the device is compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.3bw standard and OPEN Alliance qualification, enabling the use of unshielded single twisted-pair copper cable, which reduces overall cable weight and cost.

Transceiver is a First

As the first 100Base-T1 device to support SGMII, the DP83TC811S-Q1 transceiver improves design flexibility by enabling connections to multiple switches and interfaces. To help the system monitor and detect cable breaks, temperature and voltage variations, and electrostatic-discharge (ESD) events, the DP83TC811S-Q1 features a diagnostic toolkit that incorporates cable diagnostics, temperature and voltage sensors, and a patent-pending ESD monitor.

The DP83TC811S-Q1 provides up to 8 kV of ESD protection, helping shield the device against high-voltage faults. As a result, engineers can create designs that withstand ESD and voltage events. It’s able to provide real-time monitoring via a programmable interrupt. The diagnostic features enable designers to continually monitor the integrity of the Ethernet link.

Developed using low-power process technologies, the DP83TC811S-Q1 minimizes thermal dissipation and enables components to be placed closer together. The device also includes power-saving features such as standby, disable, and wake-on local-area network (LAN).

Integration of a physical medium dependent (PMD) filter, MII series terminators, PMD termination, and power-supply filtering components reduce the need for external discrete circuitry, leaving more board space for designers to add features. The DP83TC811S-Q1 has a latency as low as 140 ns, allowing latency-critical systems like automotive ADAS to respond and communicate more quickly.

Designers can evaluate the device and its SGMII support with the DP83TC811SEVM evaluation module. Those who need only the RGMII can use the DP83TC811EVM evaluation module. Both are available for $299.00 through TI and authorized distributors. The DP83TC811S-Q1 is now available in a 36-pin wettable flank, thin quad flat no-lead package (VQFNP) starting at $2.25 in 1,000-unit quantities.

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