Application Note

Murata’s IC Matching Service for Resonators Contributes to Miniaturization and Performance Enhancement of Assembled Products

Murata has been providing the IC matching service of its ceramic resonators for IC manufacturers and the manufacturers of home appliances and automotive onboard electronic components that use ICs in their products for more than 30 years. We receive hundreds of evaluation requests from our customers every month. Our service contributes to reducing the evaluation man-hours for the assembled products of our customers. We also started providing the IC matching service for our quartz crystals in 2008, catering to the need in the telecommunication equipment market where much higher precision of frequency control is required.

Required IC matching varies by the market where resonators are used. In this article, we present the details of our IC matching service.

1. IC Matching for Resonators

Resonators are coupled with ICs that have built-in oscillator circuits in practical use. The oscillator circuits have built-in inverting amplifier circuits such as inverters. The characteristics of these built-in inverters vary by IC. In addition, there are factors contributing to the variation such as the conditions of user-designed circuit boards, resonator characteristics, and the voltage applied to ICs. These variables sometimes cause abnormal oscillations as shown in Fig.1. When abnormal oscillations occur, the assembled products start to operate in an abnormal manner. To prevent this kind of problem from occurring, Murata borrows the IC-mounted circuit boards from its customers to evaluate the IC matching.

Another important goal of the IC matching is the calibration of oscillation frequency. Wired communication such as USB and CAN and wireless communication such as BLE and Wi-Fi® designate the required frequency precision for each standard to ensure the quality of communication. Table 1 shows the required frequency precision for typical telecommunication standards. We borrow evaluation boards under development from our customers, check the accuracy of oscillation frequencies for each model, and determine the optimum parameters of oscillator circuit and product specifications. This evaluation service is called IC matching.

Fig. 1. Examples of Abnormal Oscillation

Communication standards	Required frequency precision
CAN	± 3000 ppm
USB2.0	± 500 ppm
USB3.0	± 300 ppm
SATA	± 350 ppm
NFC	± 500 ppm
BLE	± 50 ppm
Wi-Fi	± 20 ppm

Table 1. Required Frequency Precision by Various Communication Standards

2. IC Matching Policy by Product and Market

There are two kinds of resonators: ceramic resonators and quartz crystals. Murata has been marketing ceramic resonators under the trade name of CERALOCK for more than 30 years. The product still covers 70% of the world market. In particular, the product dominates the automotive onboard electronic component market, covering 90% of the world market. Figure 2 shows the evaluation circuit diagram of a ceramic resonator. The optimum resistance and capacitance are determined by varying the voltage and temperature applied to the IC while checking the amplitude, waveform, and margin of the oscillation. Figure 3 presents a summary of the evaluation of various ceramic resonators. Since Murata considers it necessary to ensure the normal operation of oscillator circuits as well as the stable operation of ICs, it has established the minimum amplitude of oscillation for the low-end products that may be used as the quality standards for resonators used in the automotive electronic market, whose measurements have been reported to the customers.

Next, we present three examples of the services that we have been providing for our customers. In these services, we measure not only the stability of oscillator circuits but also the performance and electronic characteristics of assembled products. The first example is the test result of the USB communication quality of a quartz crystal used in PCs such as the one used in HDDs and optical disk drives (Fig. 4). Equipment adapted for the communication protocol for USB and SATA must undergo a signal quality test to obtain authentication for communication. Murata usually obtains data that verify the signal quality in the communication for USB and SATA, in addition to the IC matching data, and submits them to its customers. This service has been contributing to reducing the evaluation man-hours in the customers’ work.

The second example is the IC matching service dedicated for devices requiring total frequency precision to be no more than ±20 ppm, which was started since volume production of the precision quartz crystals for the RF market such as Wi-Fi^® started in 2014. In the RF market, the mainstream products are battery-driven assembled products such as smartphones. Manufacturers of assembled products and ICs have been trying to develop low-power devices that feature short operating periods at a time to extend a battery life. Figure 5 shows the measurement of the current consumed in the BLE module in μs timescale. Using these data for reference, manufacturers of BLE modules and ICs determine the frequency of the quartz crystals to be installed in their products and the size of their products.

The third example is the EVM measurement service for Wi-Fi^® equipment. The EVM is the parameter of the precision of wireless-signal modulation. The better the EVM value, the better the quality of wireless communication. Figure 6 shows the measurement of the EVM of a Wi-Fi^® module. We have been studying the possibility of the improvement of EVM by manipulating the parameters of resonator; in particular, we have been investigating the possibility of mitigating the EVM by manipulating the parameters of oscillator circuit. Recent research has revealed the parameters of resonator that improve the EVM, which have been reflected in the specification of our new products.

Fig. 2. The Evaluation Circuit for a Ceramic Resonator

Fig. 4. Test Result of the USB Communication Signal Quality of a Quartz Crystal

Characteristics		Value		Criterion Criterion
Oscillating Voltage (Vset=13.5V, 25deg. C) (Vcel=2.1V) Vcel is driving voltage of oscillation circuit Vcel	Typical sample	VIH	2.2 [V]	≤2.4V
		VIL	-0.2 [V]	≥-0.3V
		VOH	2.1 [V]
		VOL	-0.3 [V]
	R1 limit sample	Vlp-p	1.9 [V]	≥0.4 x Vcel ( ≥0.84V)
	R1 limit sample	VOp-p	1.9 [V]	≥0.4 x Vcel ( ≥0.84V)
Starting Voltage (-40 to +85deg. C)	Typical sample	3.7 [V]		≤8.0 [V]
Starting Voltage (-40 to +85deg. C)	R1 limit sample	3.7 [V]		≤8.0 [V]
Oscillation Start up Time (Typical sample at Vset=13.5V,25deg. C)		3.06 [ms]
Frequency Correlation (Reference) (Typical sample at Vset=13.5V,25deg. C)		No Frequency Shift
Negative Resistance Analysis (at Vset=13.5V,25deg. C))		Rs_max [ Ω ]	Calculated Rs [ Ω ]	Ratio [Times]
Negative Resistance Analysis (at Vset=13.5V,25deg. C))		240	62	3.9

Fig. 3. Measurement of a Ceramic Resonator

Fig. 5. Measurement of Current Consumed in a Short Period

Fig. 6. EVM Measurement in a Wi-Fi^® Module

3. Promotion of the IC Matching Service Overseas

At present, the IC matching evaluation for overseas manufacturers of assembled products accounts for about 40% of our orders. When the matching evaluation for precision quartz crystals increases in the future, we expect a further increase in the percentage of overseas orders.

Meanwhile, when overseas customers want to send their evaluation boards to Murata in Japan, they have to go through export procedures. These procedures would require at least two days for customs clearance and the transportation in Japan and overseas. Some customers therefore give up requesting Murata to conduct the IC matching for their products or just choose local manufacturers providing similar services. As a strategy to increase the number of IC matching requests, we have been promoting the IC matching evaluation service at our overseas offices. To begin with, we started the IC matching evaluation service for ceramic resonators and quartz crystals at our Shanghai laboratory in China in 2012. In cooperation with relevant divisions in Murata, our evaluation staff in China communicates directly with customers’ design personnel in Chinese to find out their needs while ensuring a shorter delivery time.

Launching our IC matching laboratories in other regions has been under consideration. We will continue providing the IC matching service for those who cannot send us their evaluation boards by dispatching our staff from Japan.

4. Referencing Service for IC Manufacturers

Murata has been providing the referencing service of its resonators for IC manufacturers since it started to market the ceramic resonators more than 30 years ago. The service determines the optimum parameters of oscillator circuit by coupling the ICs under development at IC manufacturers, which we borrow from them, with our resonators; the checked data are then fed back to the IC manufacturers. Using the feedback data, the IC manufacturers can check the integrity of the oscillator circuits of their ICs. The IC manufacturers also use the data to guarantee their customers stability of oscillation in their products. Through this service over the years, the BOM of many ICs now includes the part numbers of Murata’s resonators. The websites of IC manufacturers make the information about the IC matching data that Murata has found available to the public. We have provided the matching result for more than 50 IC manufacturers. The number of IC types we have checked has reached more than 3,000 and the number of matching results per frequency we have checked has reached more than 20,000. The huge amount of these checked data have been posted on Murata’s website, which is easily accessible to anyone. Use our resources. Find the necessary information through the search portal “IC-Timing Devices Search” on our website (Fig. 7).

Fig. 7. IC Matching Search Result by Murata

5. Our Philosophy for the Oscillation Margin of Compact Products

Murata has been promoting the miniaturization of quartz crystals. When you try to miniaturize a quartz crystal, you have to miniaturize the built-in crystal blank as well. In such cases, the vibration leakage of the crystal blank always increases, predisposing the equivalent series resistance (ESR) of the resonator to deteriorate. Particles have been a lingering problem for the crystal industry. To avoid the particle problem, the manufacturers of quartz crystals have conventionally taken the oscillation margin more than fivefold in the products for the general consumer market and more than tenfold in the products for the automotive onboard electronic equipment market. On the other hand, IC manufacturers have had a tendency to suppress the output of the inverters built in the oscillator circuits of their ICs to accomplish low power consumption; consequently, in an increasing number of cases, these ICs cannot satisfy the standards for the above-mentioned conventional oscillation margin. Using the characteristics of HCR, Murata affirms the satisfactory usability of the products, even if their oscillation margins are below the standards. Murata's HCR series has adopted the resin-sealed structure, where the metal cap is sealed onto the ceramic substrate with epoxy resin. Characteristic of the resin-sealed structure is moderate permeability of moisture across the seal. For Murata’s HCR series, the particle screening (Murata’s patented technology) under a high-temperature and high-humidity environment has been implemented in the volume production process since its commercial production started. Presently, we have been preparing the new HCR-specific standards for oscillation margin based on this characteristic feature of HCR.

6. Conclusion

The trend toward miniaturization of the module of Wi-Fi® equipment and tuners, which Murata considers a major general consumer market for quartz crystals, is expected to strengthen further, and the development of miniature 1210-size resonators has been under study. This trend will lead to an even more increasing demand for the matching service catering to the need for even greater oscillation margin and reliable characteristics in assembled products. Furthermore, the size of resistors and capacitors used in the oscillator circuits has been becoming below the 0402 size, requiring a specialized skill in packaging miniature components for the matching evaluation. Our goal is for our customers to say that Murata’s support is irreplaceable for improving the performance of miniature modules in the near future. To accomplish this goal, we strive to strengthen our support for enhancing the performance of assembled products, and furthermore, to build up the corporate organization to support this service worldwide.

Glossary

*1 SATA:

An abbreviation of serial ATA. One of the expansion features of the connection standards between a computer and storage devices such as hard disk drives and optical disk drives.

*2 BLE:

An abbreviation of Bluetooth low energy. A wireless network technology that uses the low-power electromagnetic wave of the license-free 2.4 GHz band.

*3 EVM:

An abbreviation of error vector magnitude. A measure for the precision of digital-signal modulation.

*4 BOM:

An abbreviation of bill of materials. A format for tables of components used in the manufacturing industry. A list of the components from which products are assembled.

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