ADE7756 Datasheet, PDF (1/32 Pages) Analog Devices – Active Energy Metering IC with Serial Interface

a
Active Energy Metering IC
with Serial Interface
ADE7756*
FEATURES
High Accuracy, Supports IEC 687/1036
Less than 0.1% Error over a Dynamic Range of 1000 to 1
An On-Chip User Programmable Threshold for Line
Voltage SAG Detection and PSU Supervisory
The ADE7756 Supplies Sampled Waveform Data
(20 Bits) and Active Energy (40 Bits)
Digital Power, Phase and Input Offset Calibration
An On-Chip Temperature Sensor (؎3؇C Typical after
Calibration)
An SPI-Compatible Serial Interface
A Pulse Output with Programmable Frequency
An Interrupt Request Pin (IRQ) and Status Register
Provide Early Warning of Register Overflow and
Other Conditions
Proprietary ADCs and DSP Provide High Accuracy
over Large Variations in Environmental Conditions
and Time
Reference 2.4 V ؎ 8% (20 ppm/؇C Typical) with External
Overdrive Capability
Single 5 V Supply, Low Power (25 mW Typical)
GENERAL DESCRIPTION
The ADE7756 is a high-accuracy electrical power measurement
IC with a serial interface and a pulse output. The ADE7756
incorporates two second-order sigma-delta ADCs, reference
circuitry, temperature sensor, and all the signal processing
required to perform active power and energy measurement.
The ADE7756 contains a sampled Waveform register and an
Active Energy register capable of holding at least five seconds of
accumulated power at full load. Data is read from the ADE7756
via the serial interface. The ADE7756 also provides a pulse output
(CF) with a frequency that is proportional to the active power.
In addition to real power information, the ADE7756 also provides
system calibration features, i.e., channel offset correction, phase
calibration, and power calibration. The part also incorporates a
detection circuit for short duration low voltage variations or sags.
The voltage threshold level and the duration (in number of half-
line cycles) of the variation are user programmable. An open drain
logic output (SAG) goes active low when a sag event occurs.
A zero crossing output (ZX) produces an output that is synchro-
nized to the zero crossing point of the line voltage. This output can
be used to extract timing or frequency information from the line.
The signal is also used internally to the chip in the calibration
mode. This permits faster and more accurate calibration of the
real power calculation. This signal is also useful for synchronization
of relay switching with a voltage zero crossing, thus improving
the relay life by reducing the risk of arcing.
The interrupt request output is an open drain, active low logic
output. The IRQ output will become active when the accumu-
lated real power register is half-full and also when the register
overflows. A status register indicates the nature of the interrupt.
The ADE7756 is available in 20-lead DIP and 20-lead
SSOP packages.
V1P
V1N
V2P
V2N
FUNCTIONAL BLOCK DIAGRAM
AV_DD
RESET
DV_{DD DGND}
PGA
ADC
MULTIPLIER ^{HPF1 MULTIPLIER LPF2 ADE7756}
TEMP
SENSOR
ADC
APGAIN[11:0]
PHCAL[5:0]
⌽
APOS[11:0]
DFC
2.4V
4k⍀
REFERENCE
LPF1
ADE7756 REGISTERS
AND
SERIAL INTERFACE
CFDIV[11:0]
ZX
SAG
CF
AGND
REF_IN/OUT
DIN DOUT SCLK CS IRQ
CLKIN CLKOUT
*U.S. Patents 5,745,323; 5,760,617; 5,862,069; 5,872,469; other pending.
REV. 0
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© Analog Devices, Inc., 2001