With the growing pressure on the world’s mineral and energy resources, and the inevitable increase in the cost of energy – along with the growing environmental pressures on ‘clean’ energy generation – the demand for advanced metering systems is surely set to grow. The pressure is thus on meter designers and manufacturers to produce sophisticated metering instruments that provide a host of consumption data that is useful for both the consumer and utility alike and automatically transfers the information. Yet the meters must still provide a cost-effective system solution to utilities.
Such stringent system design criteria would certainly require the highest levels of system integration, which in turn would provide a more compact meter through the reduction in the number of external electronic components. Improved reliability would inherently result through the reduction in solder joints and the elimination of passive components that may be vulnerable to long-term drift.
The highly integrated AS8267 and AS8268 single-phase systemon- chip metering integrated circuits (ICs) from austriamicrosystems provide such system solutions that are capable of meeting these system demands and are complimented by the extremely reliable on-chip Flash memory technology that ensures programme and data retention performance over the extended operating temperature range of -40OC to +125OC.
The AS8267 and AS8268 ICs incorporate all the required functional blocks for single-phase metering, including a precision energy measurement front-end, an 8-bit microcontroller, 32kBytes of on-chip Flash memory for secure programme and data, a real-time clock/calendar, up to 96-segment liquid crystal display (LCD) driver, up to 12 programmable multi-purpose inputs/outputs for all possible customer-specified interfaces and display requirements, as well as an on-chip temperature sensor. Furthermore, the AS8267 and AS8268 ICs offer the option of implementing all meter anti-tamper features.
The AS8267 and AS8268 ICs measurement front-end provide outstanding measurement accuracy performance, which is demonstrated by the consistent repeatability of measurements. Active energy, MAINS voltage and MAINS current is calculated directly within the on-chip digital signal processor (DSP). Reactive power and apparent power can also be calculated through user configurable application software.
In addition to the two universal asynchronous receiver transmitters (UARTs), the AS8267 and AS8268 ICs also provide a serial peripheral interface (SPI) for full duplex data transfer. The SPI can also be used for the option of adding an additional external EEProm of 2 to 32kBytes in size for data retention, in conjunction with the fully programmable industry standard 8-bit 8051 compatible microcontroller (MCU) and 32kBytes on-chip Flash memory.
The fully programmable multi-purpose inputs/outputs (MPIO) allow for a programmable energy LED pulse output to be displayed through any one of the MPIO. This precision output, along with an on-chip pulse counter, allows for the option of fast automatic digital calibration. The MPIO also offers the option of implementing an I2C interface if required. An on-chip ±1.4ppm real-time clock/calendar (RTC) with two alarm registers and battery back-up is available for complex tariff applications, with the option of added precision through the on-chip temperature sensor.
The AS8268 has a dedicated 96 segment LCD driver and 12 programmable inputs/outputs, while the AS8267 offers a lower-cost solution with its dedicated 80 segment LCD driver and 9 programmable inputs/outputs. The AS8267 and AS8268 ICs are pin compatible devices and are available in LQFP-64 packages.