The AS8218 and AS8228 1-phase energy metering ICs from austriamicrosystems offer the meter manufacturer highly integrated LCD meter system solutions. These ICs enable cost effective system implemen-tations, while also accommodating all utility anti-tamper requirements. The AS8218 and AS8228 ICs incorporate all the required functional blocks for 1-phase metering, including a precision energy measurement front-end, microcontroller, real-time clock, LCD driver and programmable multi-purpose inputs/outputs. The AS8218 IC drives a liquid crystal display (LCD) of up to 80 segments and has 9 independently programmable inputs/outputs, while the AS8228 IC drives a 96 segment LCD display and has 12 programmable inputs/outputs. The ICs require a minimum of external components, inherently improving meter reliability, reducing meter cost and thus providing the meter manufacturer with a fast time-to-market metering solution.

The anti-tamper features are provided by the precision, two-current input analog front-end (AFE) and the user-configurable digital signal processor (DSP). The two current inputs each have digital phase correction and allow the use of current transformers (CTs) or a combination of shunt resistor and CT. The DSP accommodates all meter anti-tamper conditions, including the many meter connection variations and a missing mains voltage. The DSP calculates active energy, mains voltage and mains current, which are directly accessible by the microcontroller. Reactive power and apparent power can also be calculated.

CALIBRATION

A programmable energy LED pulse output is generated by the DSP and can be accessed and displayed through one of the multi-purpose input/outputs. This precision output is used for calibration, which ensures a reduction in programme size and the required memory capacity.

Figure 1

An on-chip real-time clock/calendar (RTC) with two alarm registers is provided. The 1Hz input clock to the RTC can also be accessed externally, allowing for on-chip digital calibration of the low-power RTC to an accuracy of better than ±1.4ppm. A battery back-up facility ensures RTC time retention during power-down.

A fully programmable industry standard 8-bit 8051 compatible microcontroller (MCU) is integrated and includes 24kBytes of programme RAM and 1kByte of data RAM. Two universal asynchronous receiver transmitters (UARTs) provide external communication for functions such as programme download and programme debugging. Low power operating modes are provided by the programmable MCU clock divider.

FURTHER FEATURES

The liquid crystal display driver (LCDD) has 2 display data registers for simplified display data scrolling, and is capable of driving up to 96 segments. The LCD contrast is also digitally programmable.

Up to 12 multi-purpose inputs/outputs (MPIO) are fully programmable for data direction, pull-up or pull-down resistors and for drive strength. An on-chip pulse counter is accessible through the MPIOs, which allows for fast on-chip automatic digital calibration of the meter by simply providing a reference meter input to the IC.

A 4-wire Serial Peripheral Interface (SPI) ensures direct connection of most standard external EEProm devices. The memory size is selectable in binary steps up to 32kBytes.

The AS8218 and AS8228 ICs provide meter manufacturers with a cost competitive LCD meter system design, by providing most required metering system functions on-chip, including fast digital calibration.

All metering ICs from austriamicrosystems far surpass the utility specification requirements laid out in the IEC and ANSI standards.