Revision 2.1, 06-Oct-05

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1. Key Features

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Precision single-phase, one or two current input

energy measurement front-end including Sigma-

Delta modulators for A/D-conversion and digital

signal processor (DSP).

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Low current consumption of 5mA, depending on

MCU activity.

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Digital phase correction and selectable gain on

both current channels for use with two current

transformers (CT) or one CT and one shunt.

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Power-supply monitor (PSM) for power-on reset

and reset when the supply voltage falls below a

defined threshold.

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Customer programmable 8-bit 8051 compatible

microcontroller (MCU).

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Programmable MCU clock with optional low

power operating conditions.

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2 x Universal Asynchronous Receiver /

Transmitters (UART) for external

communications such as programme download

and debugging.

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Real-time clock/calendar (RTC) with on-chip

digital calibration and separate battery backup

pin.

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On-chip voltage reference (VREF) with small

temperature coefficient.

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Low power 3.0 – 4.0MHz crystal oscillator.

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SPI compatible interface for external EEPROM

memory.

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Standard on-chip LCD driver (LCDD) interface.

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Programmable multi-purpose I/Os (MPIO) with

selectable data direction, pull-up or pull-down

resistors and drive strength.

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Low power battery operating mode for meter

reading when Mains voltage is not present.

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The difference between the AS8218 and

AS8228 ICs are:

AS8218: 20 x 4 segment LCDD

9 x multi-purpose I/O (MPIO)

AS8228: 24 x 4 segment LCDD

12 x multi-purpose I/O (MPIO)

2. General Description

The AS8218 / AS8228 are highly integrated CMOS

single-phase energy metering devices for fully

electronic LCD meter systems. The AS8218 /

AS8228 have been designed to ensure that meters

can fully comply with the international Standards

IEC1036 and ANSI.

The AS8218 / AS8228 ICs include all the functions

required for conventional 1 current or 2-current

anti-tamper meters. The functions include precision

energy measurement, an 8-bit microcontroller unit

(MCU), an on-chip Liquid Crystal Display driver

(LCDD), programmable and selectable multi-

purpose Inputs/Outputs (MPIO), a real time

clock/calendar (RTC) for complex tariff functions

such as time-of-use or maximum demand billing

and a Serial Peripheral Interface (SPI) for reading

data from and writing data to an external non-

volatile memory (EEPROM).

The AS8218 / AS8228 ICs have a dedicated energy

measurement front-end, which include an analog

front-end and programmable Digital Signal

Processor (DSP) from which active energy, mains

voltage and mains current are provided. Reactive

and apparent energy can also be calculated.

The on-chip 8-bit 8051 compatible microcontroller

is freely programmable and provides user access to

the various functional blocks. The dedicated

Universal Asynchronous Receiver / Transmitter

(UART1) in the System Control block provides

access to various system functions and blocks. A

second UART (UART2) is also provided, which may

for example be used for debugging. The on-chip

memory includes 24kByte program memory and

1kByte data memory.

Due to the large diversity of non-volatile memory

requirements for fully electronic single-phase

metering systems, the AS8218 / AS8228 ICs allow

the system designer to select the size of the

external EEPROM memory, 1kByte to 32kByte (in

binary steps).

The system timing and real time clock (RTC) has a

dedicated supply pin (VDD_BAT), which is separate

from the rest of the IC, enabling the oscillator to be

supplied with an external battery during ‘power-

AS8218 / AS8228

Highly Integrated Single Phase 2-Current Energy

Metering Integrated Circuits with Microcontroller, RTC,

Programmable Multi-Purpose I/Os and LCD Driver

FEATURES