Overview of ON Semiconductor solutions for various functional modules of smart meters

Smart meters play a key role in the emerging smart grid applications. As the leading high-performance silicon solution supplier for energy-efficient green electronic products, ON Semiconductor has rich experience and a long history in providing solutions for smart meters. Our power line carrier (PLC) modems and power management products for smart meters have a successful application record in Europe. We also provide a wide range of memories (EEPROM and SRAM), clocks, interfaces, protection/filtering products, etc., which constitute our complete solutions for smart meters. This article will introduce the solutions for each functional module.

Figure 1: Simplified block diagram of a smart meter.

Communication module: PLC modem and line driver solution

In smart grid applications, the network connection from smart meters to data concentrators usually does not require high communication rates, and the most important consideration is to reduce costs. Power line carrier (PLC) technology is very suitable for such systems because it does not require additional wiring and has relatively low costs. In terms of PLC modulation technology, S-FSK modulation technology is undoubtedly a suitable choice because it has low complexity, greater commercial application potential, and a reliable field application record.

Figure 2: PLC modem and line driver solution for smart meter communication module.

ON Semiconductor has a long history of developing PLC modems. The 1.2 kb AMIS-30585 was introduced earlier and was originally developed to comply with the IEC 61334 standard (S-FSK specification). It has been field tested for 8 years. This device is packaged in PLCC-28.

In response to customers' requirements for higher data rates, ON Semiconductor has launched the AMIS-49587 highly integrated, low-power PLC modem solution. This device supports a higher half-duplex adjustable communication rate of 2.4 kb, provides different packages such as PLCC-28 and QFN-52, complies with the IEC61334-5-1 standard, and provides customers with many application advantages, such as based on the ARM7TDMI processor core, and includes both the physical interface transceiver (PHY) and the media access controller (MAC) layer, so that it combines the analog modem front-end and digital post-processing functions in a single-chip solution. Using the AMIS-49587 modem, designers can simplify the design, develop a full set of interoperable PLC solutions faster, and reduce development costs.

Line driving in PLC communication is also very important, and it is necessary to select a suitable PLC line driver for the application. Such a line driver requires large output current capability, low voltage drop, low harmonic distortion, wide operating temperature range and easy heat dissipation. ON Semiconductor has launched a highly energy-efficient Class A/B low-distortion line driver, the NCS5650, for PLC line drive applications. The design of the NCS5650 has been optimized to receive signals transmitted by the PLC modem, and the output stage is designed to drive up to 2 A of current, which is coupled to the AC main power supply through an isolation transformer or a simple coil. The unique 2 A driving capability of the NCS5650 ensures effective communication even at very low power line impedance. In addition to power amplifying the signal, the integrated two-stage operational amplifier structure of the device also forms a 4th-order low-pass filter with a very steep attenuation characteristic. In addition to helping reduce the number of components and thus save costs, it can also ensure that the system's high-frequency interference injection into the power line meets the requirements of the EN-50065 specification.

Power management modules: AC-DC, DC-DC and LDO

ON Semiconductor provides a variety of options for smart meter power supply/power management modules, including AC-DC converters/regulators, DC-DC switching regulators/controllers and low dropout (LDO) linear regulators (see Figure 3 and Table 1), making it easy for users to choose a suitable power solution.

Figure 3: Schematic diagram of the PLC smart meter power supply/power management module.

In the AC-DC part, a series of monolithic high-voltage switching regulators from ON Semiconductor can be used, such as NCP1014, NCP1027, NCP1051, etc. Take NCP1014 as an example, this is a self-powered high-voltage monolithic switching regulator for low-power offline power supply, integrating a fixed-frequency current mode controller and a 700 V MOSFET, and its main functional features include soft start, frequency jitter, short-circuit protection, cycle skipping and maximum peak current setting point.

Table 1: List of devices suitable for smart meter power supply/power management modules (*Expected to be available in Q4 2010)

In the DC-DC part, there are also many options, including switching regulators that support different current levels and pulse width modulation (PWM) controllers. Take the NCP1034 as an example. This is a flexible synchronous high-voltage PWM controller designed to operate with a wide input power supply voltage range of up to 100 V. This device also provides 1 A gate drive capability and can generate an output voltage as low as 1.25 V. Its synchronization feature allows an external source to set the switching frequency or output a synchronization signal to multiple NCP1034 controllers. In addition to switching regulators such as the NCP1034, designers can also choose a variety of DC-DC low-dropout (LDO) linear regulators from ON Semiconductor, such as the NCP562, NCP4640, etc.

Memory: Serial EEPROM, Parallel EEPROM, Serial SRAM and NVRAM

Smart meters involve data storage issues, so safe and reliable memory is required. ON Semiconductor provides serial electrically erasable programmable read-only memory (EEPROM), parallel EEPROM, serial static random access memory (SRAM) and non-volatile random access memory (NVRAM), etc. For details, please refer to the ON Semiconductor Memory Product Selection Guide (login to www.onsemi.cn, enter SGD530-D in the search box and click search). As for the serial EEPROM, it also includes products with different interface types such as I2C, SPI or MicroWire. Among them, the I2C interface products also involve different types such as full array write protection, partial array write protection and special use, with density ranging from 1 kb to 1 Mb.

Clock: NLRTC1220 real-time clock

ON Semiconductor provides a variety of clock products for smart meter applications, including PureEdge™ series crystal oscillator modules, zero delay buffers, etc. In addition, ON Semiconductor also plans to launch the NLRTC1220 real-time clock in the fourth quarter of 2010, which can be used in smart meters with ON Semiconductor's NCT66 temperature sensor (see Figure 4).

Figure 4: NLRTC1220 real-time clock application in smart meters.

Temperature sensor: A series of digital temperature sensors based on I2C interface

ON Semiconductor offers a wide range of digital temperature sensors for smart meter designs with increasing heat density. These digital temperature sensors convert temperature data into digital format and transmit the information through the I2C interface bus. Temperature set points and limits can also be designed through the bus. This information can be used to dynamically calibrate the real-time clock to improve system accuracy, performance and reliability.

Take NCT1008 as an example, this is a dual-channel digital temperature sensor with an accuracy of ±1°C, suitable for applications such as smart meters. This device has a series resistance reduction function, which can automatically reduce up to 1.5 kΩ in series with the temperature monitoring diode based on the temperature measurement results, thereby helping to filter out noise. This device also provides a configurable warning (ALERT) output and an expandable and convertible temperature measurement range (from the default 0°C to +127°C to -64°C to +191°C).

Figure 5: The NCT1008 digital temperature sensor for smart meters.

In addition to the NCT1008, ON Semiconductor also offers the NCT66 and NCT124 digital temperature sensors. These two products are planned to be launched in the fourth quarter of 2010. Both use an I2C interface and provide a temperature accuracy of ±1°C in WDFN-6 and WDFN-10 packages, respectively.

Interface: Smart card interface and SIM card interface that conforms to the standards

ON Semiconductor offers the NCN6001 smart card interface for smart meter applications. The device complies with ISO7816-3, EMV and GSM11.11 standards and is compatible with both synchronous and asynchronous cards. The device handles any type of smart card through a simple and flexible microcontroller interface, especially due to the built-in chip select pin, which allows several couplers to be connected in parallel. The device is particularly suitable for low-cost and low-power applications. The NCN6001 is available in TSSOP-20 or LLGA-20 packages.

Figure 6: Application circuit diagram of NCN6001 in smart meter.

In addition, ON Semiconductor's NCN4555 1.8 V/3.0 V SIM card interface in QFN16 package complies with the IMT-2000 (i.e. 3G) standard and the ISO7816 smart card standard, making it suitable for smart meter applications that require data transmission using mobile communication technology.

Protection and filtering: Transient voltage suppressor series

ON Semiconductor is a leading supplier of circuit protection and filtering solutions. Its protection and filtering products for smart meters include the P6SMB series Zener transient voltage suppressors (TVS), 1SMB series Zener TVS, ESD5Z series TVS and ESD9X series TVS. Among them, the P6SMB and 1SMB series both provide unidirectional and bidirectional protection, can withstand a rated surge peak power of 600 W, and are packaged in SMB. The ESD5Z and ESD9X series are used for ESD protection and comply with the IEC61000-4-2 Level 4 ESD protection standard (contact discharge ±30 kW; air discharge ±30 kW). They are packaged in SOD-523 and SOD-923 respectively. The SOD-923 package is only 1.0 x 0.6 x 0.37 mm in size, which is very suitable for space-constrained applications.

Summarize:

As the leading high-performance silicon solution supplier for energy-efficient green electronic products, ON Semiconductor provides a wide range of solutions for smart meter applications, including PLC modem solutions with a successful application record in Europe and high-efficiency power and power management solutions in which ON Semiconductor has expertise, as well as various memory, clock, interface, protection and filtering products. Engineers can use these complete solutions from ON Semiconductor to design reliable and cost-effective smart meter products and gain an advantage in market competition.