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ADE7752A Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADE7752A
Beschreibung Polyphase Energy Metering IC
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 24 Seiten
ADE7752A Datasheet, Funktion
Polyphase Energy Metering IC
with Pulse Output
ADE7752/ADE7752A
FEATURES
High accuracy, supports 50 Hz/60 Hz IEC62053-2x
Less than 0.1% error over a dynamic range of 500 to 1
Compatible with 3-phase/3-wire delta and 3-phase/4-wire
Wye configurations
The ADE7752 supplies average real power on frequency
outputs F1 and F2
High frequency output CF is intended for calibration and
supplies instantaneous real power
Logic output REVP indicates a potential miswiring or
negative power for each phase
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
On-chip power supply monitoring
On-chip creep protection (no load threshold)
On-chip reference 2.4 V ±8% (20 ppm/°C typical) with
external overdrive capability
Single 5 V supply, low power
60 mW typical: ADE7752
30 mW typical: ADE7752A
Low cost CMOS process
GENERAL DESCRIPTION
The ADE7752 is a high accuracy polyphase electrical energy
measurement IC. The ADE7752A is a pin-to-pin compatible
low power version of ADE7752. The functions of ADE7752 and
ADE7752A are the same. Both products are referred to in the
text of this data sheet as ADE7752.
The part specifications surpass the accuracy requirements as
quoted in the IEC62053-2x standard. The only analog circuitry
used in the ADE7752 is in the analog-to-digital converters (ADCs)
and reference circuit. All other signal processing (such as multi-
plication, filtering, and summation) is carried out in the digital
domain. This approach provides superior stability and accuracy
over extremes in environmental conditions and over time.
The ADE7752 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 to
interface with an MCU. The CF logic output gives instanta-
neous real power information. This output is intended to be
used for calibration purposes.
The ADE7752 includes a power supply monitoring circuit on
the VDD pin. The ADE7752 remains inactive until the supply
voltage on VDD reaches 4 V. If the supply falls below 4 V, no
pulses are issued on F1, F2, and CF. Internal phase matching
circuitry ensures that the voltage and current channels are
phase matched. An internal no load threshold ensures the part
does not exhibit any creep when there is no load. The ADE7752
is available in a 24-lead SOIC package.
FUNCTIONAL BLOCK DIAGRAM
IAP 5
IAN 6
VAP 16
IBP 7
IBN 8
VBP 15
ICP 9
ICN 10
VCP 14
VN 13
ADC
ADC
ADC
ADC
ADC
ADC
2.4V REF
11
AGND
4kΩ
12
REFIN/OUT
HPF
Φ
PHASE
CORRECTION
HPF
Φ
PHASE
CORRECTION
HPF
Φ
PHASE
CORRECTION
ABS
17
VDD
3
X
LPF
POWER
SUPPLY
MONITOR
ADE7752/
ADE7752A
XΣ
LPF
2 DGND
19 CLKIN
20 CLKOUT
X
LPF
DIGITAL-TO-FREQUENCY CONVERTER
4 18 21 22 23 24 1
REVP SCF S0 S1 F2 F1 CF
Figure 1. 24-Lead Standard Small Outline Package [SOIC]
Rev. C
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
© 2005 Analog Devices, Inc. All rights reserved.






ADE7752A Datasheet, Funktion
ADE7752/ADE7752A
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
CF 1
24 F1
DGND 2
23 F2
VDD 3
22 S1
REVP
IAP
IAN
IBP
4 21
5 ADE7752/ 20
ADE7752A
6 TOP VIEW 19
7 (Not to Scale) 18
S0
CLKOUT
CLKIN
SCF
IBN 8
17 ABS
ICP 9
16 VAP
ICN 10
15 VBP
AGND 11
14 VCP
REFIN/OUT 12
13 VN
Figure 3. Pin Configuration
Table 4. Pin Function Descriptions
Pin No. Mnemonic
Description
1 CF
Calibration Frequency Logic Output. The CF logic output gives instantaneous real power information.
This output is intended to be used for calibration purposes. See the SCF pin description.
2 DGND
This provides the ground reference for the digital circuitry in the ADE7752: the multiplier, filters, and
digital-to-frequency converter. Because the digital return currents in the ADE7752 are small, it is
acceptable to connect this pin to the analog ground plane of the whole system.
3 VDD
Power Supply. This pin provides the supply voltage for the digital circuitry in the ADE7752. The supply
voltage should be maintained at 5 V ± 5% for specified operation. This pin should be decoupled to
DGND with a 10 μF capacitor in parallel with a 100 nF ceramic capacitor.
4 REVP
This logic output goes logic high when negative power is detected on any of the three phase inputs,
that is, when the phase angle between the voltage and the current signals is greater than 90°. This
output is not latched and is reset when positive power is once again detected. See the Negative Power
Information section.
5, 6; IAP, IAN;
7, 8; IBP, IBN;
9, 10 ICP, ICN
Analog Inputs for Current Channel. This channel is intended for use with the current transducer and is
referenced in this document as the current channel. These inputs are fully differential voltage inputs
with maximum differential input signal levels of ±0.5 V. See the Analog Inputs section. Both inputs have
internal ESD protection circuitry. In addition, an overvoltage of ±6 V can be sustained on these inputs
without risk of permanent damage.
11 AGND
This pin provides the ground reference for the analog circuitry in the ADE7752: the ADCs, temperature
sensor, and reference. This pin should be tied to the analog ground plane or the quietest ground
reference in the system. This quiet ground reference should be used for all analog circuitry, such as
antialiasing filters, current and voltage transducers, and so on. To keep ground noise around the
ADE7752 to a minimum, the quiet ground plane should connect to the digital ground plane at only
one point. It is acceptable to place the entire device on the analog ground plane.
12 REFIN/OUT This pin provides access to the on-chip voltage reference. The on-chip reference has a nominal value of
2.4 V ± 8% and a typical temperature coefficient of 20 ppm/°C. An external reference source may also be
connected at this pin. In either case, this pin should be decoupled to AGND with a 1 μF ceramic capacitor.
13–16
VN, VCP, VBP,
VAP
Analog Inputs for the Voltage Channel. This channel is intended for use with the voltage transducer and
is referenced in this document as the voltage channel. These inputs are single-ended voltage inputs with
a maximum signal level of ±0.5 V with respect to VN for specified operation. All inputs have internal ESD
protection circuitry. In addition, an overvoltage of ± 6 V can be sustained on these inputs without risk of
permanent damage.
17 ABS
This logic input is used to select the way the three active energies from the three phases are summed.
This offers the designer the capability to do the arithmetical sum of the three energies (ABS logic high)
or the sum of the absolute values (ABS logic low). See the Mode Selection of the Sum of the Three Active
Energies section.
18 SCF
Select Calibration Frequency. This logic input is used to select the frequency on the calibration output
CF. Table 7 shows how the calibration frequencies are selected.
Rev. C | Page 6 of 24

6 Page









ADE7752A pdf, datenblatt
ADE7752/ADE7752A
THEORY OF OPERATION
The six voltage signals from the current and voltage transducers
are digitized with ADCs. These ADCs are 16-bit second-order
∑-Δ with an oversampling rate of 833 kHz. This analog input
structure greatly simplifies transducer interface by providing a
wide dynamic range for direct connection to the transducer and
also by simplifying the antialiasing filter design. A high-pass
filter in the current channel removes the dc component from
the current signal. This eliminates any inaccuracies in the real
power calculation due to offsets in the voltage or current
signals. See the HPF and Offset Effects section.
The real power calculation is derived from the instantaneous
power signal. The instantaneous power signal is generated by a
direct multiplication of the current and voltage signals of each
phase. In order to extract the real power component (the dc
component), the instantaneous power signal is low-pass filtered
on each phase. Figure 15 illustrates the instantaneous real
power signal and shows how the real power information can be
extracted by low-pass filtering the instantaneous power signal.
This method is used to extract the real power information on
each phase of the polyphase system. The total real power
information is then obtained by adding the individual phase
real power. This scheme correctly calculates real power for
nonsinusoidal current and voltage waveforms at all power
factors. All signal processing is carried out in the digital domain
for superior stability over temperature and time.
The low frequency output of the ADE7752 is generated by
accumulating the total real power information. This low
frequency inherently means a long accumulation time between
output pulses. The output frequency is therefore proportional to
the average real power. This average real power information
can, in turn, be accumulated (by a counter, for example) to
generate real energy information. Because of its high output
frequency and therefore shorter integration time, the CF output
is proportional to the instantaneous real power. This pulse is
useful for system calibration purposes that would take place
under steady load conditions.
POWER FACTOR CONSIDERATIONS
Low-pass filtering, the method used to extract the real power
information from the individual instantaneous power signal, is
still valid when the voltage and current signals of each phase are
not in phase. Figure 16 displays the unity power factor
condition and a DPF (displacement power factor) = 0.5, or
current signal lagging the voltage by 60°, for one phase of the
polyphase. Assuming that the voltage and current waveforms
are sinusoidal, the real power component of the instantaneous
power signal, or the dc term, is given by
⎜⎝⎛
V×
2
1
⎟⎠⎞
×
cos
(60°)
V×I
V×I
2
TIME
IAP
IAN
VAP
IBP
IBN
VBP
ICP
ICN
VCP
VN
p(t) = i(t) × v(t)
WHERE:
v(t) = V × cos (ωt)
i(t) = I × cos (ωt)
p(t) = V × I {1+ cos (2ωt)}
2
INSTANTANEOUS
POWER SIGNAL - p(t)
V×I
2
INSTANTANEOUS
REAL POWER SIGNAL
VA × IA + VB × IB +
VC×IC
2
ADC
HPF
MULTIPLIER
ADC
ADC
HPF
MULTIPLIER
ADC
ADC
HPF
MULTIPLIER
ADC
ABS
LPF
|X|
LPF
|X|
Σ
LPF
|X|
INSTANTANEOUS
TOTAL
POWER SIGNAL
DIGITAL-TO-
FREQUENCY
Σ
F1
F2
DIGITAL-TO-
FREQUENCY
Σ CF
Figure 15. Signal Processing Block Diagram
Rev. C | Page 12 of 24

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