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PDF ADE7761A Data sheet ( Hoja de datos )
| Número de pieza | ADE7761A | |
| Descripción | Energy Metering IC | |
| Fabricantes | Analog Devices | |
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Energy Metering IC with On-Chip Fault and
Missing Neutral Detection
ADE7761A
FEATURES
GENERAL DESCRIPTION
High accuracy, active energy measurement IC supports
IEC 62053-21
Less than 0.1% error over a dynamic range of 500 to 1
Supplies active power on the frequency outputs, F1 and F2
High frequency output CF is intended for calibration and
supplies instantaneous active power
Continuous monitoring of the phase and neutral current
allows fault detection in 2-wire distribution systems
Current channels input level best suited for shunt and
current transformer sensors
Uses the larger of the two currents (phase or neutral) to
bill—even during a fault condition
Continuous monitoring of the voltage and current inputs
allows missing neutral detection
Uses one current input (phase or neutral) to bill when
missing neutral is detected
Two logic outputs (FAULT and REVP) can be used to indicate
a potential miswiring, fault, or missing neutral condition
Direct drive for electromechanical counters and 2-phase
stepper motors (F1 and F2)
Proprietary ADCs and DSP provide high accuracy over large
variations in environmental conditions and time
Reference 2.5 V ± 8% (drift 30 ppm/°C typical) with external
overdrive capability
Single 5 V supply, low power
The ADE7761A is a high accuracy, fault-tolerant, electrical
energy measurement IC intended for use with 2-wire distribution
systems. The part specifications surpass the accuracy requirements
as quoted in the IEC 62053-21 standard. The only analog circuitry
used on the ADE7761A is in the ADCs and reference circuit.
All other signal processing (such as multiplication 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 ADE7761A incorporates a fault
detection scheme similar to the ADE7751 by continuously
monitoring both phase and neutral currents. A fault is indicated
when the currents differ by more than 6.25%.
The ADE7761A incorporates a missing neutral detection
scheme by continuously monitoring the input voltage. When a
missing neutral condition is detected—no voltage input—the
ADE7761A continues billing based on the active current signal
(see the Missing Neutral Mode section). The missing neutral
condition is indicated when the FAULT pin goes high. The
ADE7761A supplies average active power information on the
low frequency outputs, F1 and F2. The CF logic output gives
instantaneous active power information.
The ADE7761A includes a power-supply monitoring circuit on
the VDD supply pin. Internal phase matching circuitry ensures
that the voltage and current channels are matched. An internal
no-load threshold ensures that the ADE7761A does not exhibit
any creep when there is no load.
FUNCTIONAL BLOCK DIAGRAM
PGA AGND
13 8
FAULT
15
VDD
1
V1A 2
V1N 4
V1B 3
MISCAL 7
ADC
ADC
ADC
A>B
HPF
B>A
A<>B
ZERO CROSSING
DETECTION
MISSING NEUTRAL
GAIN ADJUST
POWER
SUPPLY MONITOR
ADE7761A
SIGNAL PROCESSING
BLOCK
LPF
V2P 6
V2N 5
ADC
2.5V
3kΩ
REFERENCE
INTERNAL
OSCILLATOR
MISSING NEUTRAL
DETECTION
DIGITAL-TO-FREQUENCY CONVERTER
9
REFIN/OUT
14
RCLKIN
17
DGND
Figure 1.
10 11 12 16 18 19 20
SCF S1 S0 REVP CF F2 F1
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. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.
1 page  
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 3.
Parameter
VDD to AGND
Analog Input Voltage to AGND
V1A, V1B, V1N, V2N, V2P, MISCAL
Reference Input Voltage to AGND
Digital Input Voltage to DGND
Digital Output Voltage to DGND
Operating Temperature Range
Industrial
Storage Temperature Range
Junction Temperature
20-Lead SSOP, Power Dissipation
θJA Thermal Impedance
Lead Temperature, Soldering
Vapor Phase (60 sec)
Infrared (15 sec)
Rating
−0.3 V to +7 V
−6 V to +6 V
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
−40°C to +85°C
−65°C to +150°C
150°C
450 mW
112°C/W
215°C
220°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent 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.
ADE7761A
PERFORMANCE ISSUES THAT MAY AFFECT
BILLING ACCURACY
The ADE7761A provides pulse outputs—CF, F1, and F2—
intended to be used for the billing of active energy. Pulses
are generated at these outputs in two different situations.
Case 1: When the analog input V2P – V2N complies with the
conditions described in Figure 34, CF, F1, and F2 frequencies
are proportional to active power and can be used to bill
active energy.
Case 2: When the analog input V2P – V2N does not comply with
the conditions described in Figure 34, the ADE7761A does not
measure active energy but a quantity proportional to kAh. This
quantity is used to generate pulses on the same CF, F1, and F2.
This situation is indicated when the FAULT pin is high.
Analog Devices, Inc. cautions users of the ADE7761A about the
following:
• Billing active energy in Case 1 is consistent with the
understanding of the quantity represented by pulses on CF,
F1, and F2 outputs (watt-hour).
• Billing active energy while the ADE7761A is in Case 2 must
be decided knowing that the entity measured by the
ADE7761A in this case is ampere-hour and not watt-hour.
Users should be aware of this limitation and decide if the
ADE7761A is appropriate for their application.
ESD 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 this product 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.
Rev. 0 | Page 5 of 24
5 Page 
OPERATION
POWER SUPPLY MONITOR
The ADE7761A continuously monitors the power supply (VDD)
with its on-chip, power supply monitor. If the supply is less than
4 V ± 5%, the ADE7761A goes into an inactive state, that is, no
energy is accumulated and the CF, F1, and F2 outputs are
disabled. This is useful to ensure correct device operation at
power-up and during power-down. The power supply monitor
has built-in hysteresis and filtering, which provides a high
degree of immunity to false triggering due to noisy supplies.
The power supply and decoupling for the part should be such
that the ripple at VDD does not exceed 5 V ± 5% as specified for
normal operation.
VDD
5V
4V
0V
TIME
ADE7761A
REVP - FAULT - CF - INACTIVE
F1 - F2 OUTPUTS
ACTIVE
INACTIVE
Figure 11. On-Chip, Power Supply Monitoring
ANALOG INPUTS
Channel V1 (Current Channel)
The voltage outputs from the current transducers are connected
to the ADE7761A at Channel V1. It has two voltage inputs, V1A
and V1B. These inputs are fully differential with respect to V1N.
However, at any one time, only one is selected to perform the
power calculation (see the Fault Detection section).
The maximum peak differential signal on V1A − V1N and V1B − V1N
is ±660 mV. However, Channel 1 has a programmable gain
amplifier (PGA) with user-selectable gains of 1 or 16 (see
Table 5). This gain facilitates easy transducer interfacing.
Table 5. Channel 1 Dynamic Range
PGA
Gain
Maximum Differential Signal (mV)
0 1 660
1 16 41
Figure 12 shows the maximum signal levels on V1A, V1B, and
V1N. The maximum differential voltage is ±660 mV divided by
the gain selection. The differential voltage signal on the inputs
must be referenced to a common mode (usually AGND).
ADE7761A
V1A, V1B
+660mV
GAIN
+
VCM
VCM
–660mV
GAIN
+ VCM
DIFFERENTIAL INPUT A
±660mV MAX PEAK
COMMON MODE
±100mV MAX
VCM
AGND
DIFFERENTIAL INPUT B
±660mV MAX PEAK
V1A
V1
V1N
V1
V1B
Figure 12. Maximum Signal Levels, Channel 1
Channel V2 (Voltage Channel)
The output of the line voltage transducer is connected to the
ADE7761A at this analog input. Channel V2 is a single-ended,
voltage input. The maximum peak differential signal on Channel 2
is ±660 mV with respect to V2N. Figure 13 shows the maximum
signal levels that can be connected to Channel 2.
V2
+660mV + VCM
VCM
DIFFERENTIAL INPUT
±660mV MAX PEAK
V2P
V2
V2N
–660mV + VCM
COMMON MODE
±100mV MAX
VCM
Figure 13. Maximum Signal Levels, Channel 2
The differential voltage V2P − V2N must be referenced to a
common mode (usually AGND). The analog inputs of the
ADE7761A can be driven with common-mode voltages of up
to 100 mV with respect to AGND. However, the best results
are achieved using a common mode equal to AGND.
MISCAL Input
The input for the power calibration in missing neutral mode
is connected to the ADE7761A at this analog input. MISCAL is
a single-ended, voltage input. It is recommended to use a dc
signal derived from the voltage reference to drive this pin. The
maximum peak differential signal on MISCAL is 660 mV with
respect to V2N. Figure 14 shows the maximum signal levels that
can be connected to the MISCAL pin.
MISCAL
+660mV + VCM
VCM
DIFFERENTIAL INPUT
±660mV MAX PEAK
COMMON MODE
±100mV MAX
MISCAL
MISCAL
V2N
VCM
AGND
Figure 14. Maximum Signal Levels, MISCAL
Rev. 0 | Page 11 of 24
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet ADE7761A.PDF ] | |
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