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ADE7759 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADE7759
Beschreibung Active Energy Metering IC with di/dt Sensor Interface
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 30 Seiten
ADE7759 Datasheet, Funktion
a
Active Energy Metering IC with
di/dt Sensor Interface
ADE7759*
FEATURES
High Accuracy, Supports IEC 687/1036
On-Chip Digital Integrator Allows Direct Interface with
Current Sensors with di/dt Output Such as Rogowski Coil
Less Than 0.1% Error over a Dynamic Range of 1000 to 1
On-Chip User-Programmable Threshold for Line Voltage
SAG Detection and PSU Supervisory
The ADE7759 Supplies Sampled Waveform Data and
Active Energy (40 Bits)
Digital Power, Phase and Input DC Offset Calibration
On-Chip Temperature Sensor (Typical 1 LSB/؇C Resolution)
SPI-Compatible Serial Interface
Pulse Output with Programmable Frequency
Interrupt Request Pin (IRQ) and IRQ Status Register
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 Consumption (25 mW
Typical)
GENERAL DESCRIPTION
The ADE7759 is an accurate active power and energy measurement
IC with a serial interface and a pulse output. The ADE7759 incor-
porates two second order Σ-ADCs, a digital integrator (on CH1),
reference circuitry, temperature sensor, and all the signal processing
required to perform active power and energy measurement.
An on-chip digital integrator allows direct interface to di/dt
current sensors such as a Rogowski coil. The digital integrator
eliminates the need for an external analog integrator and pro-
vides excellent long-term stability and precise phase matching
between the current and the voltage channels. The integrator
can be switched off if the ADE7759 is used with conventional
current sensors.
The ADE7759 contains a sampled Waveform register and an Active
Energy register capable of holding at least 11.53 seconds of accumu-
lated power at full ac load. Data is read from the ADE7759 via the
serial interface. The ADE7759 also provides a pulse output (CF)
with frequency that is proportional to the active power.
In addition to active power information, the ADE7759 also
provides various system calibration features, i.e., channel offset
correction, phase calibration, and power offset correction. The
part also incorporates a detection circuit for short duration
voltage drop (SAG). The voltage threshold and the duration (in
number of half-line cycles) of the drop 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 line
cycle energy accumulation mode; i.e., the number of half-line
cycles in which the energy accumulation occurs can be con-
trolled. Line cycle energy accumulation enables a faster and
more precise energy accumulation and is especially useful dur-
ing calibration. This signal is also useful for synchronization of
relay switching with a voltage zero crossing.
The interrupt request output is an open drain, active low logic
output. The Interrupt Status Register indicates the nature of the
interrupt, and the Interrupt Enable Register controls which
event produces an output on the IRQ pin. The ADE7759 is
available in a 20-lead SSOP package.
AVDD
FUNCTIONAL BLOCK DIAGRAM
RESET
DVDD DGND
MULTIPLIER
INTEGRATOR MULTIPLIER
ADE7759
ZX
V1P ADC
V1N
dt
LPF2
SAG
HPF1
TEMP
SENSOR
APGAIN[11:0]
PHCAL[7:0]
APOS[15:0]
V2P
ADC
V2N
DFC
2.4V
4k
REFERENCE
LPF1
REGISTERS AND
SERIAL INTERFACE
CFNUM[11:0]
CFDEN[11:0]
CF
AGND
REFIN/OUT
DIN DOUT SCLK CS IRQ
*U.S. Patents 5,745,323; 5,760,617; 5,862,069; 5,872,469; others pending.
REV. 0
CLKIN CLKOUT
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
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2001






ADE7759 Datasheet, Funktion
ADE7759
ABSOLUTE MAXIMUM RATINGS*
(TA = 25°C unless otherwise noted)
AVDD to AGND . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
DVDD to DGND . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
DVDD to AVDD . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +0.3 V
Analog Input Voltage to AGND
V1P, V1N, V2P, and V2N . . . . . . . . . . . . . . . . . –6 V to +6 V
Reference Input Voltage to AGND . . –0.3 V to AVDD + 0.3 V
Digital Input Voltage to DGND . . . . –0.3 V to DVDD + 0.3 V
Digital Output Voltage to DGND . . . –0.3 V to DVDD + 0.3 V
Operating Temperature Range
Industrial (A, B Versions) . . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150°C
20-Lead SSOP, Power Dissipation . . . . . . . . . . . . . . . 450 mW
θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 112°C/W
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
ORDERING GUIDE
Model
Package Option*
ADE7759ARS
ADE7759ARSRL
EVAL-ADE7759E
RS-20
RS-20
ADE7759 Evaluation Board
*RS = Shrink Small Outline Package in tubes; RSRL = Shrink Small
Outline Package in reel.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the ADE7759 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
–6– REV. 0

6 Page









ADE7759 pdf, datenblatt
ADE7759
It is also possible to adjust offset errors on Channel 1 and Channel 2
by writing to the Offset Correction registers (CH1OS and CH2OS
respectively). These registers allow channel offsets in the range
±24 mV to ±50 mV (depending on the gain setting) to be removed.
Note that it is not necessary to perform an offset correction in an
energy measurement application if HPF1 Channel 1 is switched
on. Figure 6 shows the effect of offsets on the real power calcula-
tion. As seen in Figure 6, an offset on Channel 1 and Channel 2
will contribute a dc component after multiplication. Since this
dc component is extracted by LPF2 to generate the Active (Real)
Power information, the offsets will have contributed an error to
the Active Power calculation. This problem is easily avoided by
enabling HPF1 in Channel 1. By removing the offset from at
least one channel, no error component is generated at dc by the
multiplication. Error terms at cos(ω t) are removed by LPF2 and
by integration of the Active Power signal in the Active Energy
register (AENERGY[39:0])—see Energy Calculation section.
CH1OS[5:0]
1Fh 01,1111b SIGN + 5 BITS
50mV
00h
0mV
+50mV
OFFSET
ADJUST
3Fh 11,1111b SIGN + 5 BITS
Figure 7. Channel Offset Correction Range (Gain = 1)
di/dt CURRENT SENSOR AND DIGITAL INTEGRATOR
di/dt sensor detects changes in magnetic field caused by ac
current. Figure 8 shows the principle of a di/dt current sensor.
VOS ؋ IOS
V؋I
2
DC COMPONENT (INCLUDING ERROR TERM)
IS EXTRACTED BY THE LPF FOR REAL
POWER CALCULATION
MAGNETIC FIELD CREATED BY CURRENT
(DIRECTLY PROPORTIONAL TO CURRENT)
IOS ؋ V
VOS ؋ I
0 2
Figure 6. Effect of Channel Offsets on the Real
Power Calculation
The contents of the Offset Correction registers are 6-bit, sign,
and magnitude coded. The weighting of the LSB size depends
on the gain setting, i.e., 1, 2, 4, 8, or 16. Table II shows the
correctable offset span for each of the gain settings and the LSB
weight (mV) for the Offset Correction registers. The maximum
value that can be written to the offset correction registers is ± 31
decimal—see Figure 7.
Gain
1
2
4
8
16
Table II. Offset Correction Range
Correctable Span
± 50 mV
± 37 mV
± 30 mV
± 26 mV
± 24 mV
LSB Size
1.61 mV/LSB
1.19 mV/LSB
0.97 mV/LSB
0.84 mV/LSB
0.77 mV/LSB
+ EMF (ELECTROMOTIVE FORCE)
INDUCED BY CHANGES IN
MAGNETIC FLUX DENSITY (di/dt)
Figure 8. Principle of a di/dt Current Sensor
The flux density of a magnetic field induced by a current is directly
proportional to the magnitude of the current. The changes in
the magnetic flux density passing through a conductor loop
generate an electromotive force (EMF) between the two ends of
the loop. The EMF is a voltage signal that is proportional to the
di/dt of the current. The voltage output from the di/dt current
sensor is determined by the mutual inductance between the
current-carrying conductor and the di/dt sensor. Figure 9 shows
the mutual inductance produces a di/dt signal at the output of
the sensor.
MUTUAL INDUCTANCE M
+
i(t)
v
=
M
؋
di(t)
dt
Figure 7 shows the relationship between the Offset Correction
register contents and the offset (mV) on the analog inputs for a
gain setting of one. In order to perform an offset adjustment, the
analog inputs should be first connected to AGND, and there
should be no signal on either Channel 1 or Channel 2. A read
from Channel 1 or Channel 2 using the Waveform register will
give an indication of the offset in the channel. This offset can be
canceled by writing an equal but opposite offset value to the
relevant offset register. The offset correction can be confirmed by
performing another read. Note that when adjusting the offset of
Channel 1, the digital integrator and the HPF1 should be disabled.
Figure 9. Mutual Inductance Between the di/dt
Sensor and the Current Carrying Conductor
The current signal needs to be recovered from the di/dt signal
before it can be used for active power calculation. An integrator
is therefore necessary to restore the signal to its original form.
The ADE7759 has a built-in digital integrator to recover the
current signal from the di/dt sensor. The digital integrator on
Channel 1 is switched on by default when the ADE7759 is
powered up. Setting the MSB of the CH1OS register to 0 will
turn off the integrator. Figures 10 to 13 show the magnitude and
phase response of the digital integrator.
–12–
REV. 0

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