REV. PrC.

Preliminary Technical Data

PRELIMINARY TECHNICAL DATA

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

a

ADE7757*

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, USA.

Tel: 781/329-4700

World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., February 2002

Energy Metering IC

with Integrated Oscillator

FEATURES

On Chip Oscillator as clock source

High Accuracy, Supports 50 Hz/60 Hz IEC 521/1036

Less than 0.1% Error Over a Dynamic Range of

500 to 1

The ADE7757 Supplies

Average Real Power on the

Frequency Outputs F1 and F2

The High Frequency Output CF Is Intended for

Calibration and Supplies

Instantaneous Real Power

Direct Drive for Electromechanical Counters and

Two Phase Stepper Motors (F1 and F2)

Proprietary ADCs and DSP Provide High Accuracy over

Large Variations in Environmental Conditions and

Time

On-Chip Power Supply Monitoring

On-Chip Creep Protection (No Load Threshold)

On-Chip Reference 2.5 V

8% (30 ppm/ C Typical)

with External Overdrive Capability

Single 5 V Supply, Low Power (15 mW Typical)

Low Cost CMOS Process

AC Input only

GENERAL DESCRIPTION

The ADE7757 is a high accuracy electrical energy mea-

surement IC. It is a pin reduction version of AD7755

with an enhancement of a precise oscillator circuit that

serves as a clock source to the chip. The ADE7757

eliminates the cost of an external crystal or resonator,

thus reducing the overall cost of a meter built with this

IC. The chip directly interfaces with shunt resistor and

only operates with AC input.

*U.S. Patents 5,745,323, 5,760,617, 5,862,069, 5,872,469; other pending.

FUNCTIONAL BLOCK DIAGRAM

The ADE7757 specifications surpass the accuracy require-

ments as quoted in the IEC1036 standard. Due to the

similarity between the ADE7757 and AD7755, the Appli-

cation Note AN-559 can be used as a basis for a descrip-

tion of an IEC1036 low cost watt-hour meter reference

design.

The only analog circuitry used in the ADE7757 is in the

sigma-delta ADCs and reference circuit. All other signal

processing (e.g., multiplication and filtering) is carried

out in the digital domain. This approach provides superior

stability and accuracy over time and extreme environmen-

tal conditions.

The ADE7757 supplies average real power information on

the low frequency outputs F1 and F2. These outputs may

be used to directly drive an electromechanical counter or

interface with an MCU. The high frequency CF logic

output, ideal for calibration purposes, provides instanta-

neous real power information.

The ADE7757 includes a power supply monitoring circuit

mately 4 V. If the supply falls below 4 V, the ADE7757

will also reset and the F1, F2 and CF outputs will be in

their non-active modes.

Internal phase matching circuitry ensures that the voltage

and current channels are phase matched while the HPF in

the current channel eliminates dc offsets. An internal no-

load threshold ensures that the ADE7757 does not exhibit

creep when no load is present.

The ADE7757 is available in 16-lead SOIC narrow-body

package.

MULTIPLIER

RESERVED

V2P

V2N

V1P

HPF

RCLKIN

F1

F2

CF

SCF

S0 S1

PHASE

CORRECTION

4kV

SIGNAL

PROCESSING

BLOCK

ADC

POWER

SUPPLY MONITOR

ADC

V1N

ADE7757

LPF

2.5V

REFERENCE

DIGITAL-TO-FREQUENCY

CONVERTER

AGND

DGND

∆

∑

∆

∑

INTERNAL

OSCILLATOR

Φ