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PDF ( 数据手册 , 数据表 ) ADE7751

零件编号 ADE7751
描述 Energy Metering IC with On-Chip Fault Detection
制造商 Analog Devices
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ADE7751 数据手册, 描述, 功能
a
Energy Metering IC
with On-Chip Fault Detection
ADE7751*
FEATURES
High Accuracy, Surpasses 50 Hz/60 Hz IEC 687/1036
Less than 0.1% Error over a Dynamic Range of 500 to 1
Supplies Average Real Power on the Frequency
Outputs F1 and F2
High-Frequency Output CF Is Intended for Calibration
and Supplies Instantaneous Real Power
Continuous Monitoring of the Phase and Neutral
Current Allows Fault Detection in 2-Wire
Distribution Systems
ADE7751 Uses the Larger of the Two Currents (Phase
or Neutral) to Bill—Even During a Fault Condition
Two Logic Outputs (FAULT and REVP) Can Be Used to
Indicate a Potential Miswiring or Fault Condition
Direct Drive for Electromechanical Counters and
2-Phase Stepper Motors (F1 and F2)
A PGA in the Current Channel Allows the Use of Small
Values of Shunt and Burden Resistance
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
GENERAL DESCRIPTION
The ADE7751 is a high-accuracy, fault-tolerant electrical energy
measurement IC that is intended for use with 2-wire distribution
systems. The part specifications surpass the accuracy require-
ments as quoted in the IEC1036 standard.
The only analog circuitry used in the ADE7751 is in the ADCs
and reference circuit. All other signal processing (e.g., multipli-
cation and filtering) is carried out in the digital domain. This
approach provides superior stability and accuracy over extremes
in environmental conditions and over time.
The ADE7751 incorporates a novel fault detection scheme that
warns of fault conditions and allows the ADE7751 to continue
accurate billing during a fault event. The ADE7751 does this
by continuously monitoring both the phase and neutral (return)
currents. A fault is indicated when these currents differ by more
than 12.5%. Billing is continued using the larger of the two currents.
The ADE7751 supplies average real power information on the
low-frequency outputs F1 and F2. These logic outputs may be
used to directly drive an electromechanical counter or interface
to an MCU. The CF logic output gives instantaneous real power
information. This output is intended to be used for calibration purposes.
The ADE7751 includes a power supply monitoring circuit on the
AVDD supply pin. The ADE7751 will remain in a reset condition
until the supply voltage on AVDD reaches 4 V. If the supply falls
below 4 V, the ADE7751 will also be reset and no pulses will be
issued on F1, F2, and CF.
Internal phase matching circuitry ensures that the voltage and
current channels are matched whether the HPF in Channel 1 is
on or off. The ADE7751 also has anticreep protection.
The ADE7751 is available in 24-lead DIP and SSOP packages.
FUNCTIONAL BLOCK DIAGRAM
G0 G1
AVDD AGND
FAULT
AC/DC DVDD DGND
V1A
V1N
V1B
V2P
V2N
ADE7751
POWER
SUPPLY MONITOR
SIGNAL
A< >B
...110101... A
PROCESSING
BLOCK
ADC
HPF
PGA
A >B
؋1, ؋2, ؋8, ؋16
ADC
PGA
؋1, ؋2, ؋8, ؋16
...110101... B
B>A
PHASE
CORRECTION
MULTIPLIER
LPF
. . .11011001. . .
ADC
2.5V
4k
REFERENCE
DIGITAL-TO-FREQUENCY
CONVERTER
REFIN/OUT CLKIN CLKOUT SCF S0 S1 REVP CF F1 F2 RESET
*US Patent 5,745,323; 5,760,617; 5,862,069; 5,872,469.
REV. 0
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., 2002







ADE7751 pdf, 数据表
ADE7751
0.20
0.10
+25؇C PF=1
0.00
+85؇C PF=0.5
–0.10
–0.20
–0.30
+25؇C PF=0.5
–0.40
–0.50 PF = 0.5
GAIN = 8
–0.60 ON-CHIP REFERENCE
0.01
0.1
1
AMPS
–40؇C PF=0.5
10 100
TPC 7. Error as a % of Reading (PF = 0.5, Gain = 8)
0.30
PF = 1
GAIN = 8
0.20 EXTERNAL REFERENCE
0.10
0.00
–0.10
+85؇C
+25؇C
–0.20
–0.30
–40؇C
–0.40
0.01
0.1
1
AMPS
10
100
TPC 10. Error as a % of Reading over Temperature with
an External Reference (Gain = 8)
0.60
PF = 0.5
GAIN = 16
0.40 ON-CHIP REFERENCE
+85؇C PF = 0.5
0.20
0.00
–0.20
+25؇C PF = 1
+25؇C PF = 0.5
–0.40
–0.60
–0.80
–40؇C PF = 0.5
–1.00
0.01
0.1
1
AMPS
10
100
TPC 8. Error as a % of Reading (Gain = 16)
0.20
PF = 1
0.15 GAIN = 2
EXTERNAL REFERENCE
0.10
+85؇C
0.05
0.00
–0.05
–0.10
+25؇C
–0.15
–0.20
–40؇C
–0.25
–0.30
0.01
0.1
1
AMPS
10
100
TPC 9. Error as a % of Reading over Temperature with
an External Reference (Gain = 2)
0.60
PF = 1
GAIN = 16
0.40 EXTERNAL REFERENCE
0.20
0.00
+85؇C PF = 0.5
+25؇C PF = 1
–0.20
–0.40
–0.60
–40؇C PF = 1
–0.80
0.01
0.1
1
AMPS
10
100
TPC 11. Error as a % of Reading over Temperature with
an External Reference (Gain = 16)
DISTRIBUTION
16
CHARACTERISTICS
NUMBER OF PTS: 138
MINIMUM: –11.1367
14 MAXIMUM: +10.1775
MEAN: –1.44576
STD DEV: 4.6670
12 GAIN = 1
TEMP = 25؇C
10
8
6
4
2
0
؊15 ؊10 ؊5 0 5 10 15
TPC 12. Channel 1 Offset Distribution (Gain = 1)
–8– REV. 0







ADE7751 equivalent, schematic
ADE7751
When selecting a suitable F1–4 frequency for a meter design, the
frequency output at IMAX (maximum load) with a meter constant
of 100 imp/kWhr should be compared with Column 4 of Table VI.
The frequency that is closest in Table VI will determine the best
choice of frequency (F1–4). For example, if a meter with a maxi-
mum current of 25 A is being designed, the output frequency on F1
and F2, with a meter constant of 100 imp/kWhr, is 0.153 Hz at 25 A
and 220 V (from Table V). Looking at Table VI, the closest
frequency to 0.153 Hz in column four is 0.17 Hz. Therefore F2
(3.4 Hz—see Table II) is selected for this design.
Frequency Outputs
Figure 1 shows a timing diagram for the various frequency
outputs. The outputs F1 and F2 are the low-frequency outputs
that can be used to directly drive a stepper motor or electrome-
chanical impulse counter. The F1 and F2 outputs provide two
alternating low-going pulses. The pulsewidth (t1) is set at 275 ms
and the time between the falling edges of F1 and F2 (t3) is
approximately half the period of F1 (t2).
If, however, the period of F1 and F2 falls below 550 ms (1.81 Hz),
the pulsewidth of F1 and F2 is set to half of their period. The maxi-
mum output frequencies for F1 and F2 are shown in Table III.
The high-frequency CF output is intended to be used for
communications and calibration purposes. CF produces a
90 ms wide active high pulse (t4) at a frequency that is propor-
tional to active power. The CF output frequencies are given in
Table IV. As in the case of F1 and F2, if the period of CF (t5)
falls below 180 ms, the CF pulsewidth is set to half the period.
For example, if the CF frequency is 20 Hz, the CF pulse-
width is 25 ms.
NO LOAD THRESHOLD
The ADE7751 also includes a “no load threshold” and “start-
up current” feature that will eliminate any creep effects in the
meter. The ADE7751 is designed to issue a minimum output
frequency. Any load generating a frequency lower than this
minimum frequency will not cause a pulse to be issued on F1,
F2, or CF. The minimum output frequency is given as 0.0014%
of the full-scale output frequency for each of the F1–4 frequency
selections (see Table II). For example, for an energy meter with
a meter constant of 100 imp/kWhr on F1, F2 using F2 (3.4 Hz),
the maximum output frequency at F1 or F2 would be 0.0014%
of 3.4 Hz or 4.76 × 10–5 Hz. This would be 3.05 × 10–3 Hz at
CF (64 × F1 Hz). In this example, the no load threshold would be
equivalent to 1.7 W of load or a start-up current of 8 mA at 220 V.
Compare this value to the IEC1036 specification, which states
that the meter must start up with a load equal to or less than
0.4% Ib. For a 5 A(Ib) meter, 0.4% of Ib is equivalent to 20 mA.
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
24-Lead Plastic DIP
(N-24)
1.275 (32.30)
1.125 (28.60)
24
1
PIN 1
0.210
(5.33)
MAX
0.200 (5.05)
0.125 (3.18)
0.022 (0.558)
0.014 (0.356)
0.100
(2.54)
BSC
13 0.280 (7.11)
12 0.240 (6.10)
0.325 (8.25)
0.300 (7.62)
0.060 (1.52)
0.015 (0.38)
0.195 (4.95)
0.150
(3.81)
MIN
0.070 (1.77) SEATING
0.045 (1.15) PLANE
0.115 (2.93)
0.015 (0.381)
0.008 (0.204)
24-Shrink Small Outline Package
(RS-24)
24
0.311 (7.9)
0.301 (7.64)
1
0.328 (8.33)
0.318 (8.08)
13
0.212 (5.38)
0.205 (5.207)
12
0.078 (1.98) PIN 1
0.068 (1.73)
0.07 (1.78)
0.066 (1.67)
0.008 (0.203)
0.0256
(0.65)
0.002 (0.050) BSC
0.015 (0.38) SEATING 0.009 (0.229)
0.010 (0.25) PLANE 0.005 (0.127)
0.037 (0.94)
0.022 (0.559)
–16–
REV. 0










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