Datasheet ADE7768 (Analog Devices)

Energy Metering IC with Integrated Oscillator and Positive Power Accumulation ADE7768 FEATURES
The ADE7768 specifications surpass the accuracy require-
On-chip oscillator as clock source
ments of the IEC62053-21 standard. The AN-679 Application
High accuracy, supports 50 Hz/60 Hz IEC62053-21
Note can be used as a basis for a description of an IEC61036
Less than 0.1% error over a dynamic range of 500 to 1
(equivalent to IEC62053-21) low cost, watt-hour meter reference design.
Supplies positive-only average real power on frequency outputs F1 and F2
The only analog circuitry used in the ADE7768 is in the Σ-Δ
High frequency output CF calibrates and supplies
ADCs and reference circuit. All other signal processing, such as
instantaneous, positive-only real power
multiplication and filtering, is carried out in the digital domain.
Logic output REVP indicates potential miswiring or negative power
This approach provides superior stability and accuracy over
Direct drive for electromechanical counters and 2-phase
time and extreme environmental conditions.
stepper motors (F1 and F2)
The ADE7768 supplies positive-only average real power
Proprietary ADCs and DSPs provide high accuracy over
information on the low frequency outputs, F1 and F2. These
large variations in environmental conditions and time
outputs can be used to directly drive an electromechanical
On-chip power supply monitoring
counter or interface with an MCU. The high frequency CF logic
On-chip creep protection (no-load threshold)
output, ideal for calibration purposes, provides instantaneous
On-chip reference 2.45 V (20 ppm/°C typical) with external overdrive capability
positive-only, real power information.
Single 5 V supply, low power (20 mW typical)
The ADE7768 includes a power supply monitoring circuit on
Low cost CMOS process
the VDD supply pin. The ADE7768 remains inactive until the
GENERAL DESCRIPTION
supply voltage on VDD reaches approximately 4 V. If the supply falls below 4 V, the ADE7768 also remains inactive and the F1, The ADE77681 is a high accuracy, electrical energy metering IC. F2, and CF outputs are in their nonactive modes. It is a pin reduction version of the ADE7755, enhanced with a precise oscillator circuit that serves as a clock source to the chip. Internal phase matching circuitry ensures that the voltage and The ADE7768 eliminates the cost of an external crystal or current channels are phase matched, while the HPF in the resonator, thus reducing the overall cost of a meter built with current channel eliminates dc offsets. An internal no-load this IC. The chip directly interfaces with the shunt resistor. threshold ensures that the ADE7768 does not exhibit creep when no load is present. When REVP is logic high, the ADE7768 does not generate any pulse on F1, F2, and CF. 1U.S. Patents 5,745,323; 5,760,617; 5,862,069; 5,872,469; others pending. The ADE7768 comes in a 16-lead, narrow body SOIC package.
FUNCTIONAL BLOCK DIAGRAM VDD AGND DGND 1 6 13 ADE7768 POWER SUPPLY MONITOR SIGNAL PROCESSING BLOCK V2P 2 + ...110101...
Σ
-
Δ
ADC V2N 3 MULTIPLIER PHASE LPF CORRECTION V1N 4 ...11011001...
Σ
-
Δ Φ
ADC HPF V1P 5 + INTERNAL DIGITAL-TO-FREQUENCY OSCILLATOR CONVERTER 2.5V 4k
Ω
REFERENCE
001
7 11 8 10 9 12 14 16 15
05331-
REF RCLKIN SCF S0 S1 REVP IN/OUT CF F1 F2
Figure 1.
Rev. A 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 that may result from its use. Specifications subject to change without notice. No license is granted by implication One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. or otherwise under any patent or patent rights of Analog Devices. Trademarks and Tel: 781.329.4700 www.analog.com registered trademarks are the property of their respective owners. Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved.
Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM SPECIFICATIONS TIMING CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ESD CAUTION TERMINOLOGY PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS FUNCTIONAL DESCRIPTION THEORY OF OPERATION Power Factor Considerations Nonsinusoidal Voltage and Current ANALOG INPUTS Channel V1 (Current Channel) Channel V2 (Voltage Channel) Typical Connection Diagrams POWER SUPPLY MONITOR HPF and Offset Effects Digital-to-Frequency Conversion Connecting to a Microcontroller for Energy Measurement Power Measurement Considerations INTERNAL OSCILLATOR (OSC) TRANSFER FUNCTION Frequency Outputs F1 and F2 Example Frequency Output CF SELECTING A FREQUENCY FOR AN ENERGY METER APPLICATION Frequency Outputs NO-LOAD THRESHOLD NEGATIVE POWER INFORMATION EVALUATION BOARD AND REFERENCE DESIGN BOARD OUTLINE DIMENSIONS ORDERING GUIDE