Datasheet ADE7759 (Analog Devices)

a
Active Energy Metering IC with di/dt Sensor Interface ADE7759* FEATURES
can be switched off if the ADE7759 is used with conventional
High Accuracy, Supports IEC 687/1036
current sensors.
On-Chip Digital Integrator Allows Direct Interface with
The ADE7759 contains a sampled waveform register and an
Current Sensors with di/dt Output Such as Rogowski Coil
active energy register capable of holding at least 11.53 seconds
Less Than 0.1% Error over a Dynamic Range of 1000 to 1
of accumulated power at full ac load. Data is read from the
On-Chip User-Programmable Threshold for Line Voltage
ADE7759 via the serial interface. The ADE7759 also provides a
SAG Detection and PSU Supervisory
pulse output (CF) with frequency that is proportional to the
Supplies Sampled Waveform Data and Active Energy
active power.
(40 Bits) Digital Power, Phase, and Input DC Offset Calibration
In addition to active power information, the ADE7759 also
On-Chip Temperature Sensor (Typical 1 LSB/ C Resolution)
provides various system calibration features, i.e., channel offset
SPI Compatible Serial Interface
correction, phase calibration, and power offset correction. The
Pulse Output with Programmable Frequency
part also incorporates a detection circuit for short duration
Interrupt Request Pin (IRQ) and IRQ Status Register
voltage drop (SAG). The voltage threshold and the duration (in
Proprietary ADCs and DSP provide High Accuracy over
number of half-line cycles) of the drop are user programmable.
Large Variations in Environmental Conditions and Time
An open-drain logic output (SAG) goes active low when a sag
Reference 2.4 V 8% (20 ppm/ C Typical) with External
event occurs.
Overdrive Capability
A zero crossing output (ZX) produces an output that is synchro-
Single 5 V Supply, Low Power Consumption (25 mW
nized to the zero crossing point of the line voltage. This output
Typical)
can be used to extract timing or frequency information from the
GENERAL DESCRIPTION
line. The signal is also used internally to the chip in the line The ADE7759 is an accurate active power and energy measure- cycle energy accumulation mode; i.e., the number of half-line ment IC with a serial interface and a pulse output. The ADE7759 cycles in which the energy accumulation occurs can be con- incorporates two second-order Σ-∆ ADCs, a digital integrator trolled. Line cycle energy accumulation enables a faster and (on CH1), reference circuitry, temperature sensor, and all the more precise energy accumulation and is especially useful dur- signal processing required to perform active power and energy ing calibration. This signal is also useful for synchronization of measurement. relay switching with a voltage zero crossing. An on-chip digital integrator allows direct interface to di/dt The interrupt request output is an open drain, active low logic current sensors such as a Rogowski coil. The digital integrator output. The interrupt status register indicates the nature of the eliminates the need for an external analog integrator and pro- interrupt, and the interrupt enable register controls which event vides excellent long-term stability and precise phase matching produces an output on the IRQ pin. The ADE7759 is available between the current and the voltage channels. The integrator in a 20-lead SSOP package.
FUNCTIONAL BLOCK DIAGRAM AVDD RESET DVDD DGND ADE7759 INTEGRATOR ZX MULTIPLIER MULTIPLIER V1P ADC dt LPF2 SAG V1N HPF1 TEMP APGAIN[11:0] APOS[15:0] SENSOR PHCAL[7:0] V2P ADC DFC V2N CFNUM[11:0] CF 4k 2.4V REGISTERS AND CFDEN[11:0] REFERENCE SERIAL INTERFACE LPF1 AGND REF DIN DOUT SCLK CLKIN CLKOUT IN/OUT CS IRQ
*U.S. Patents 5,745,323; 5,760,617; 5,862,069; 5,872,469. 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. No license is granted by implication or otherwise
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Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS SPECIFICATIONS TIMING CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE PIN CONFIGURATION PIN FUNCTION DESCRIPTIONS TERMINOLOGY MEASUREMENT ERROR PHASE ERROR BETWEEN CHANNELS POWER SUPPLY REJECTION ADC OFFSET ERROR GAIN ERROR GAIN ERROR MATCH Typical Performance Characteristics Test Circuits ANALOG INPUTS di/dt CURRENT SENSOR AND DIGITAL INTEGRATOR ZERO CROSSING DETECTION LINE VOLTAGE SAG DETECTION Sag Level Set POWER SUPPLY MONITOR INTERRUPTS Using the ADE7759 Interrupts with an MCU Interrupt Timing TEMPERATURE MEASUREMENT ANALOG-TO-DIGITAL CONVERSION Antialias Filter ADC Transfer Function Reference Circuit CHANNEL 1 ADC Channel 1 ADC Gain Adjust Channel 1 Sampling CHANNEL 1 AND CHANNEL 2 WAVEFORM SAMPLING MODE CHANNEL 2 ADC Channel 2 Sampling PHASE COMPENSATION ACTIVE POWER CALCULATION ENERGY CALCULATION Integration Time under Steady Load POWER OFFSET CALIBRATION ENERGY-TO-FREQUENCY CONVERSION LINE CYCLE ENERGY ACCUMULATION MODE CALIBRATING THE ENERGY METER Calculating the Average Active Power Calibrating the Frequency at CF Energy Meter Display CLKIN FREQUENCY SUSPENDING THE ADE7759 FUNCTIONALITY APPLICATION INFORMATION SERIAL INTERFACE Serial Write Operation Serial Read Operation CHECKSUM REGISTER REGISTER DESCRIPTIONS Communications Register Mode Register (06H) Interrupt Status Register (04H) Reset Interrupt Status Register (05H) CH1OS Register (08H) OUTLINE DIMENSIONS Revision History