Focus AMPLIFIERS & OSCILLATORS

SILICON OSCILLATORS OFFER

ALTERNATIVE TO

QUARTZ By ASHOK BINDRA, Technical Writer

Q

uartz oscillators and ceramic resonators have met the timing needs of electronic circuits for decades. Lately, however, silicon oscillators have made strides toward providing an alternative for applications that require the attributes of traditional timing devices in smaller packages and at a lower cost. Silicon oscillators also promise immunity to shock, vibration, and electromagnetic interference (EMI). In addition, silicon simplifies their use within integrated circuits (ICs) while minimizing component count. Over the last few years, several makers have begun challenging the arena that was previously dominated by quartzcrystal oscillators. Among the key silicon vendors are Discera, Inc., Ecliptek, Silicon Labs, STMicroelectronics, SiTime Corp., Linear Technology Corp., Mobius Microsystems, and Vectron International (see the table). Ecliptek (www.ecliptek. com), for example, has improved the long-term frequency stability and ther-

mal hysteresis of microelectromechanical-systems (MEMS) resonators. Those resonators can achieve reliable performance comparable to quartz. Specifically, Ecliptek’s EMO product family of programmable oscillators encompasses four industry-standard package sizes and three supply voltages (1.8, 2.5, and 3.3 V). The oscillators provide frequency stabilities of ±50 PPM maximum over an operating temperature range of –40º to +85ºC. The EMO family features frequencies ranging from 1 to 125 MHz. Any frequency in this

1. The MEMS-based SiT8002XT is one-third the height of quartz-based oscillators.

range can be ordered with as much as six-significant-digit precision (for example, 100.123456 MHz). Another proponent to tap the benefits of MEMS resonator technology is Vectron International (www.vectron. com). By implementing Discera’s (www. discera.com) MEMS-based PureSilicon resonator, Vectron has readied a new silicon oscillator for military precisionguided munitions. Such munitions require rugged and high-shock-resistance timing components. For instance, the VMEM5Q is designed to withstand up to 100,000g shock. It is available from 1 to 130 MHz with ±100-and ±50-PPM stabilities and a –40º-to- +85ºC temperature range. The VMEM5Q uses a 3.3-V supply. It offers an enable/disable feature to allow the clock output to be disabled for board testing. The MEMS resonators from Discera also are at the heart of silicon oscillators from ABRACON (www.abracon.com). Distributor Digi-Key (www.digikey.com) has joined this partnership to distribute ABRACON’s MEMS-based oscillators to engineers worldwide. According to Digi-Key, the collaboration with Discera and ABRACON provides its customers with a proven and scalable silicon alternative to quartz. The ASFML1 is the the first product in the ABRACON MEMS oscillator series to offer a standard 0º to –70ºC temperature-range option across the entire 1-to-125-MHz frequency range with power consumption under 10 mA, 30k G shock resis-

SILICON OSCILLATOR SUPPLIERS and their recent offerings Frequency Frequency Phase Jitter Resonator Range (MHz) Accuracy/ Stability (ppm) (ps)

Suppliers

Part #

Discera Inc.

MOS series

MEMS

Ecliptek

EMO

MEMS

Linear Technology

LT6930

RC

MM8511

LC

SiT8102 Si500

Mobius Microsystems SiTime Corp. Silicon Labs

10 - 20 (p-p) 100 (p-p)

1.8 - 3.3

QFN

3.3, 2.5 or 1.8

SMD

10,000

<0.15%

1.7 to 5.5

DFN,MSOP

10 to 66

±500

<0.5 (rms*)

3.3

DFN, TSSOP

MEMS

1 to 200

±50 or ±100

<1 (rms)

3.3, 2.5 or 1.8

QFN

LC

0.9 to 200

±100 to ±150

1.5 (rms)

3.3, 2.5 or 1.8

DFN

10, 12, 16

±1.5%

±150 (p-p)

4.5 to 5.5

SOT23-5L

1 to 130

±50 or ±100

7 (rms)

2.7 to 3.6

QFN

STMicroelectroncs STLC1120 Vectron International

VMEM5Q

Package

±50

MEMS

1 to 150 1 to 125 32.768 kHz to 8.192

±50

Supply Voltage (V)

*Bandwidth limited S12

focus / October/2008

Focus AMPLIFIERS & OSCILLATORS

tance, and low-cost, compact QFN plastic packaging. Aside from enabling others, Discera also is a supplier of silicon oscillators. The firm continues to refurbish its MEMS capability for a line of MOS oscillators that combines the latest advances in CMOS technology with CMOS-compatible MEMS-resonator technology. The maker has extended the frequency range for its MOS oscillator line to 150 MHz. Along with very low current consumption of about 4.5 mA, it has managed to keep the standby current consumption to less than 1 μA. Startup SiTime Corp. (www.sitime. com) has begun sampling a family of low-jitter programmable oscillators targeting the high-speed serial-communication and storage markets. The SiT8102 combines a MEMS resonator with a CMOS chip that controls, drives, and frequency-multiplies the resonator. As a result, this oscillator is one-time factory programmable over a frequency range of 1 to 200 MHz. It offers sub-1-ps rms jitter performance over an integrated bandwidth. The SiT8102 is rated to deliver ±50- or ±100-PPM frequency stability. Both commercial and industrial temperature ranges are available. The unit can operate from 1.8-, 2.5-, or 3.3-V supplies. For lower power consumption, it offers a power-down or output-disable mode. For high-volume portable electronics, SiTime also has readied a MEMS-based silicon timing solution that is one-third the height of quartz-based oscillators (Fig. 1). Labeled the SiT8002XT, it measures 3.5 x 3.0 mm with a typical height of 0.25 mm. It is packaged in a four-pad XLLGA package. The SiT8002XT is fully factory-programmable, allowing samples to be delivered in 24 to 48 hours. This is significantly faster than the 8- to16-week lead times for quartz oscillators, states Piyush Sevalia, SiTime’s Vice President of Marketing. CMOS Oscillators Leveraging its expertise in low-jitter, frequency-flexible timing products, Silicon Laboratories (www.silabs.com) has entered the consumer timing market A Supplement to Microwaves & RF / focus

2. The Si500 has no moving parts and is highly immune to shock and vibration. It also is housed in a plastic package and is not susceptible to contamination.

with a high-stability, 100-percent CMOS oscillator (Fig. 2). Unlike the quartz resonator, which must be cut and tuned for each frequency, the low-phase-noise Si500 is manufactured using a standard, high-volume IC manufacturing process that is capable of generating any output frequency from 0.9 to 200.0 MHz, says James Wilson, senior marketing manager at Silicon Labs. While providing high immunity to shock and vibration, the devices support differential clock outputs (LVPECL, LVDS, HCSL) in addition to CMOS and SSTL formats. The Si500 is designed to offer dualoutput CMOS format mode, whereby it can produce two output clocks at the same frequency. Other highlights of the device include temperature stability on par with crystal oscillators and frequency-stability options ranging from ±100 to ±150 PPM. The silicon oscillator uses low-voltage operation of 3.3, 2.5, or 1.8 V. Jitter is 1.5 ps (rms) and maximum period jitter is 2 ps (rms). Meanwhile, Linear Technology (www. linear.com) has released a family of lowpower, precision silicon oscillators with fixed frequencies from 32.768 kHz to 8.192 MHz and 99.91-percent accuracy. Labeled the LTC6930 series, it consists of five devices. Each one has a unique master frequency as well as digitally controlled frequency dividers that provide eight different frequencies per device. Operating on a single 1.7-to-5.5-V supply, each unit draws only 105 μA at 32 kHz. The LTC6930 also claims to have a guaranteed startup time of less than 110

μs. Other features include 0.09-percent frequency tolerance and –40°-to- +125°C operating-temperature range. A family of silicon oscillators from STMicroelectronics (www.st.com) targets microprocessor clock applications, display drivers, or other systems in which tighter clock accuracy is not critical. These oscillators combine fast startup and high immunity to shock, vibration, and EMI with lower operating current. In addition, chip-select control enables easier and more efficient power management. The first members of STCL1120 family are 10-, 12- and 16-MHz devices with startup times of 50 μs and a 0.65-mA operating current. With standby-mode current consumption of less than 3 μA, the company states that the STCL1120’s push-pull, CMOS-compatible output produces a fixed operating frequency that is accurate to within ±1.5 percent throughout all operating conditions. The oscillator operates directly from a 5-V supply. It is specified for operation from -20° to +85°C. To address system-level EMI issues, Mobius Microsystems, Inc. (www.mobiusmicro.com) is exploiting its patented CMOS harmonic oscillator (CHO) technology to deliver an accurate, stable frequency source with spread-spectrum capability in a miniature package. The MM8511 is architected to generate output frequencies from the hundreds of kilohertz to the hundreds of megahertz. The initial version will be factory programmed to offer a 10-to-66-MHz range with spread-spectrum modulation from 0.25 to 6 percent. The MM8511 operates from a 3.3-V supply.

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Did you Know

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Voltage-Controlled Oscillator Operates From 5340 To 5390 MHz A voltage-controlled oscillator (VCO) serves digital radio equipment, fixed wireless access, satellite-communications systems, and base stations. The CVCO55CXT-5340-5390 VCO operates from 5340 to 5390 MHz with a control voltage range of 0.5 to 4.5 V. Typical phase noise is -102 dBc/ Hz at 10-kHz offset while output power is typically +3.0 dBm. Input voltage is 5 V with a maximum current consumption of 25 mA. Pulling and pushing are minimized to 0.50 MHz and 1.50 MHz/V, respectively. Second harmonic suppression is typically -30 dBc. Model CVCO55CXT-5340-5390 is packaged in an industry-standard 0.5-x-0.5-in. SMD package. Pricing starts at $21.43 each in volume. Crystek Corp.; 12730 Commonwealth Dr., Fort Myers, FL 33913; (239) 561-3311; Fax: (239) 561-1025; Internet: www.crystek.com.

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What’s New

VCSO Performs At 622.08 MHz With Very Low Jitter

Even at high frequencies, the VSO9900A series voltage-controlled, SAW-device-based oscillator (VCSO) suffers very low jitter. By using a high-frequency SAW resonator, the VSO9900A bypasses the many multiplication stages needed to attain a high frequency with standard crystal-based designs. It operates directly at 622.08 MHz or higher. These oscillators are particularly suitable for applications like SONET/SDH, base stations, high-speed data transfer, optical transmission, and many types of phase-locked loops (PLLs). The family has been designed for use from 400 MHz to 1 GHz with particular emphasis on typical frequencies used in the optical transmission domain (622.08 MHz, 644.531 MHz, 669.327 MHz, and so on). The VCSO operates on a 3.3-V supply voltage and features LVDS or LVPECL complementary outputs. It produces jitter as low as 0.100 ps-rms within a bandwidth of 12 kHz to 20 MHz; phase noise of -150 dBc/Hz offset 10 kHz from the carrier; and an absolute pull range (APR) of ±100 PPM. The VSO9900A series is offered in a 5-x-7-x-2.5mm package. It includes an enable/disable function. Pricing is set at $28.00 each for 1000 pieces. Delivery is eight weeks ARO for production quantities. Samples are available in two to four weeks ARO. Raltron Electronics Corp.; 10651 Northwest 19th St., Miami, FL 33172; (305) 593-6033; Fax: (305) 594-3973; Internet: www.raltron.com.

Quartz SAW Oscillators Remain Stable To 2.5 GHz Applications like wireless communications and measurement instrumentation require high-accuracy clocks at microwave and higher frequencies. Conventional technology commonly uses surface-transverse-wave (STW) quartz material to achieve high fundamental frequencies. However, the frequency-temperature characteristics are dependent on the electrode material and its film thickness. As a result, it is extremely difficult to create a high-accuracy resonator that is also stable with temperature. To achieve the high frequency and high accuracy required by current designs, Epson Toyocom has developed the NS-34R surface-acoustic-wave (SAW) resonator. A SAW resonator is a crystal unit that uses surface acoustic waves to provide high-frequency signals, at the same frequency as the carrier wave, through fundamental oscillation. The NS-34R combines SAW resonator design and microfabrication technology to achieve a high frequency stability of ±200 PPM at a 2.5-GHz S14

fundamental frequency. The oscillation circuit designed for use with the NS-34R provides superior loaded quality factor (Q) of 1000 and insertion loss of 6 dB and can achieve +10 dBm outputs and more. An oscillator built with the NS-34R is able to take advantage of the high frequency stability to provide low phase noise and low jitter in addition to low power consumption and high-speed startup of a superior oscillation signal. This contributes to dramatic performance gains in applications like wireless communication and measuring instruments, which require high-accuracy clocks and frequencies in the microwave range and higher. Epson Toyocom’s newly developed SAW resonator boasts frequencytemperature characteristics that are three times better than a conventional STW resonator. This improvement was achieved by applying manufacturing technologies, such as interdigital

transducer (IDT) miniaturization and stabilization, to the company’s current volume-production quartz SAW resonator technology. IDT structures are made of comb-shaped electrodes formed on a quartz substrate. The center frequency and filter range of the resonator is determined by the periodic structure of the IDT and the physical properties of the electrode. Epson Toyocom plans to use the NS-34R to develop and commercialize quartz SAW oscillators and voltage-controlled SAW oscillators (VCSO) that can generate fundamental oscillation frequencies in the gigahertz range. Products with frequency stability of ±100 PPM are also under development. The external dimensions are 3.8 × 3.8 × 0.98 mm. Commercial development is scheduled for completion sometime this year. Epson Toyocom Corp.; 2580 Orchard Pkwy., San Jose, CA 95131; (800) 228-3964; Fax: (408) 922-0238; Internet: www.epsontoyocom.co.jp/english. focus / October/2008

Focus AMPLIFIERS & OSCILLATORS

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What’s New Programmable Gain Amplifier Is Tailored For DOCSIS 3.0 CableLabs’ Data-Over-Cable Service Interface Specifications (DOCSIS) standard is an important facilitator for innovation in the cable broadband industry. The latest version, DOCSIS 3.0, allows cable operators to provide data rates in the hundreds of megabits and potentially gigabits per second. Designers looking to implement the standard can turn to the ARA2017 programmable gain amplifier, which is optimized for DOCSIS 3.0 cable modem and E-MTA applications. This new device supports high linearity and power levels, which enable channel bonding and therefore higher data rates in the cable system upstream (return) path. The ARA2017, which can be vital to the performance of DOCSIS 3.0 terminal products, is used by multiple vendors in cable modems that were certified for DOCSIS 3.0 based on recent testing at CableLabs. Operating in the 5-to-85-MHz frequency range, the ARA2017 supports DOCSIS 3.0-specified signal levels of +64 dBmV while decreasing harmonic distortion and output noise levels. At minimum attenuation, the ARA2017 has 33 dB gain. An integrated, digitally controlled, multistage precision step attenuator provides as much as 58 dB attenuation in 2-dB increments. Requiring a single 5-V supply, the device is offered in a 28-pin, 5-x-5-x-1-mm QFN package. The ARA2017 is available now for $3.60 in 5000-unit quantities. ANADIGICS, Inc.; 141 Mount Bethel Rd., Warren, NJ 07059; (908) 668-5000; Fax: (908) 668-5132; Internet: www.anadigics.com.

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Customizable OCXOs Serve Phase-Locked Signal Sources

Bandwidth and resolution continue to become increasingly critical in communications, military, and test systems. As a result, frequency-generation components must keep up with the needs of these demanding applications. The NV26AJ line of low-phase-noise, oven-controlled crystal oscillators (OCXOs) are well suited for radar, communications, and test-system applications. The oscillators provide compact packaging and a frequency output covering 30 to 130 MHz. Because engineers can specify exact output frequencies and a host of other variables, the NV26AJ OCXO oscillator can be accurately customized for particular applications. All oscillators in the NV26AJ series operate at fundamental output frequencies in order to maintain superior phase-noise performance. Special attention was given to the crystal design and manufacturing process to optimize phase-noise performance under heavy vibration. Notable features of the NV26AJ OCXO series include a frequency range of 30 to 130 MHz, power output up to +15 dBm, low-profile packaging, superior long-term aging, and low power consumption. Bliley Technologies, Inc.; 2545 W. Grandview Blvd., P.O. Box 3428, Erie, PA 16508-0428; (814) 838-3571; Fax: (814) 833-2712; Internet: www.bliley.com.

Broadband LNAs Offer High IP3 Headroom System designers are increasingly challenged to provide broadband performance without sacrificing key parameters like noise figure, linearity, or return loss. Meeting that challenge head-on are three high-linearity broadband low-noise amplifiers (LNAs), which preserve signal purity by minimizing the nonlinear contributions. These amplifiers simultaneously achieve several high-performance characteristics in a unique wideband design. They are available in three frequency bands of 0.5 to 2 GHz (JCA02-4000), 2 to 4 GHz (JCA24-4001), and 4 to 8 GHz (JCA48-4000). The LNAs feature noise figures of under 2 dB through the C-band, +24-dBm output power at 1-dB compression, and +15 dBm or greater output third-orderintercept-point headroom levels. In addition, units deliver saturated output power levels approaching +27 dBm, have excellent input/output (I/O) return loss of at least 11 dB across the entire operating bandwidth, and provide signal gain of 35 dB or more. They deliver stable performance over a temperature range of –54º to +85 ºC and draw just 425 mA of current from a standard 12-V supply. With the addition of a low-drop-out (LDO) voltage regulator, customers may run these components on as little as +8 VDC for lower-power applications. These amplifiers are available in gain/phase matched sets, making them a good choice for applications that require unit-to-unit repeatability like phased-array radar. They’re available with a variety of options including variable gain control, I/O isolators, input limiters, limiting amplifiers, TTL switches, phase tracking, low phase noise, temperature compensation, detector outputs, and bias-T outputs. They are available in hermetic packages with a variety of connector options. Endwave Corp.; 130 Baytech Dr., San Jose, CA 95134; (408) 522-3100; Fax: (408) 522-3197; Internet: www.endwave.com.

Advertiser Index

Coilcraft ....................................... S3 DigiKey .................................Cover 2 DucommTechnologies ............... S15 Lansdale Semiconductor, Inc. ..... S5

Microlambda Wireless ................ S9 Narda West ............................... S11 NoiseWave Corp. ................Cover 3 Tusonix .................................Cover 4

focus / October/2008