Tuesday, December 9, 2014

Modern MEMS technology for clock and timing applications – all-electronics.de

                 12.08.2014 09:11 |

                Journal article
 Gareth Williams

With Micro-electro-mechanical systems, or MEMS, can be traditional mechanical function with high space replaced by tiny silicon structures. This also applies to oscillators: MEMS variants are increasingly replacing the quartz oscillators. Micrel reached with his models even comparable Genaugkeiten.

Figure 1: MEMS devices are already being used in a variety of applications. (Image: Micrel)

MEMS oscillators can be found today in most electronic devices (image 1 ) and are increasingly replacing traditional quartz crystals. Micrel expects this market penetration in the future accelerated. Clock and Timing Devices MEMS-based help developers to avoid the disadvantages of quartz devices, such as manufacturing, quality improvement, lack of stability in a wide temperature range, low scalability and sensitivity to shock and vibration. Basically MEMS timing solutions, when operating at high temperatures reliable than their counterparts on quartz crystal base and they can be divided into smaller size and high-volume manufacture.

At a glance

If you need very accurate, low-jitter clock sources, has had to rely on quartz oscillators , Micrel sees himself now in a position to meet the required properties with MEMS products. The corresponding components are more robust than traditional technologies.

Micrel his offer in terms of the rapidly growing MEMS manufacturing business to the ultra-modern SPTS Pegasus DRIE extended machine. It offers the highest currently available Tiefenätzgeschwindigkeiten for silicon as well as a very good sidewall smoothness and uniformity of the wafer. The Pegasus is the tool of choice for the high axial ratios and high demands on the cavity size of today’s MEMS products. MEMS customers also have the option of monolithically integrating MEMS structures in CMOS to get on the housing-level access to all IC products from Micrel. Fabless customers may direct the production of an entire MEMS sensor system in a single work Micrel.

Growth through acquisition

Over a year ago bought Micrel the company Discera on, a leading provider of silicon timing solutions and inventor of the first MEMS resonator. This acquisition completed the product range of Micrel of high-performance clock and timing products and extended its MEMS abilities. The combination of technologies and products from both companies provides strategic synergies and opens up broader markets and a global customer base. With this new addition and the acquisition of phase-Link and its own “Flex and Fusion” products want Micrel serve as a comprehensive point of contact for all high-performance clock and -Timinglösungen.

Micrel for 15 years has been developing MEMS devices for business customers, the new Discera MEMS product line, however, greatly expanded Micrel’s market presence and capabilities in MEMS area. In addition, the technical team from Discera Micrel gives a solid technical knowledge and associated intellectual property to produce not only timing devices based on MEMS, but also other kinds of MEMS devices.

Three families

The clock and timing solutions Micrel include a three product lines: the Clock and Data Link product families Flex, Fusion and Precision Edge. Flex and Fusion include oscillators and clock generators with extremely low jitter (less than 200 fs), which were developed for high-speed communications, and LTE wireless and wireline communications applications. The Precision Edge family includes clock and data transmission solutions with innovative features such as internal termination, crosstalk noise insulation and lowest jitter for optimal signal integrity.

MEMS devices have become in recent years become a central component of electronic systems , A suite of MEMS devices is nowadays used in all kinds of mobile devices and allows applications such as screen rotation, gesture recognition, games, pedometer and personalized navigation. Regarding the progressive concentration of the mobile market in MEMS integration, the improvement of products through the constant development of MEMS gyroscopes, microphones, and -Beschleunigungs- -Magnetsensoren is a good example for the dissemination of MEMS technologies.

Figure 2: MEMS resonators are microscopic small, mechanically movable structures on a silicon wafer. (Image: Micrel) reach

MEMS resonators

MEMS timing devices high reliability because traditional mechanical steps are required: a microscopic structure as a resonator (Figure 2) will be held crystals on the frequency you want to crop suitable for MEMS etched into the silicon wafer. The same methods are used that are used to etched and mass-produced silicon chips – so it is mature, reliable and repeatable method

Table 1: The advantages of MEMS oscillators with respect to quartz crystals. (Image: Micrel)

For many applications such as enterprise storage and networking are the highest accuracy in jitter specification in the MEMS and the control ASIC required. With its leading technology position Micrel could reduce by the PLL (Phase Locked Loop) and the buffer circuit jitter generated and thus compete with existing crystal solutions (Table 1). In these applications, the resonator must be so structured that it generates higher frequencies, lower jitter and a higher Q-factor. For the ASIC a differential input is required

Fusion. Oscillators with low jitter

Micrel recently introduced the Fusion XOs (crystal oscillators) MX55 / 57 a, the industry-leading phase jitter performance exhibit of 170 fs RMS (12 kHz to 20 MHz) in a standard 5 × 7 mm 2 , or 3.2 × 5 mm 2 , These XOs are focused on a wide range of frequencies up to 840 MHz and support standard frequencies for applications and including 10/40/100 Gigabit Ethernet, optical communication, SAS and XAUI.

Figure 3: The MX55 / 57 family is designed to maximum performance for network, storage, server and telecommunications equipment to offer. (Image: Micrel)

The MX55 / 57 family is designed for maximum performance networking, storage, server and telecommunications equipment to offer. Due to the extremely low jitter design tolerances are improved, increasing the signal-to-noise ratios and bit error minimized. These products offer numerous programmable options for all development requirements. The family is very insensitive to high voltage noise. On-chip regulator improve the overall performance in environments with strong interference. The devices support a supply of 3.3 V or 2.5 V and the output logic formats LVPECL, LVDS, CMOS and HCSL. You achieve an overall stability of +50 ppm including aging and temperature drift with an operating temperature range of -40 to +85 ° C.

Through the use of proven plastic casting module, the long-term reliability is improved and the aging drift in the minimized compared to traditional XO enclosures. All options for the MX55 family are in a compact package of 3.2 × 5 mm 2 available to save valuable board space. This is a significant advantage in applications with high channel density. The MX57 family of solutions comes in a 5 × 7 mm 2 large housing.

For the fusion-family and the oscillator product MX85 heard five-generated outputs that the developer integration and savings on board space is available.

Quartz Loose clock generator

The DSC400 Micrel is a Crystal-Less clock generator with four outputs, which claims to be the most comprehensive level of integration in the timing industry represents. It is the first product to have Micrel timing based on the proven Pure Silicon MEMS technology of Micrel, the excellent jitter and exceptional stability while additional equipment functions integrated. The device is designed for numerous applications, including communication and networks, 1Gb Ethernet, 10GBASE-T / KR / LR / SR and FCoE SAN, FC, SATA, SAS, FTTH EPON, 10G EPON, GPON and 10-G-PON, video and surveillance in HD / SD / SDI, automotive, media and video as well as embedded systems and industrial applications.

Figure 4: The DSC400 is a Crystal-Less-clock with multiple outputs, requiring no external crystal for operation , (Image: Micrel)

The DSC400 (Figure 4) is a Crystal-Less-clock with multiple outputs which requires no external quartz crystal for operation. Instead, it is based on an integrated MEMS resonator is connected to internal PLLs. This technology provides a higher performance and reliability by strict frequency stability over a wide temperature range. He is also highly resistant to shock and vibration and thus has a slower aging and thus a higher product life cycle in the system.

The unit offers a low RMS phase jitter of less than 1 ps (typical) and a high stability with options of ± 25 ppm and ± 50 ppm. In addition, the DSC400 provides a high supply noise suppression of -50 dBc and generates four outputs. Each output can be specified for the formats LVPECL, LVDS, or LVCMOS HCSL configure. In addition to the wide frequency range from 2.3 to 460 MHz, the device is very sensitive to shocks and vibrations (qualified to MIL-STD-88), very reliable and suitable for a wide supply range from 2.24 to 3.6 V. solution is RoHS compliant and qualified for MIL-STD-883 and AEC-Q100 automotive. It offers a wide temperature range from -20 to +70 ° C for the advanced commercial and -40 to +85 ° C for industrial use. The block is supplied in a 20-QFN package with 5 × 3.2 mm 2 .

Concluding Remarks

The MEMS technology requires extensive research and development. This concerns the implementation and development, but especially the back-end process and production. The overall experience of Micrel in all of these requirements includes decades. As a result, (lei) faces the manufacturer in an ideal position to establish itself in this area.

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