Energy Metering IC with Integrated
Oscillator and Reverse Polarity Indication
AD71056
FEATURES
On-chip oscillator as clock source
High accuracy, supports 50 Hz/60 Hz IEC62053-21
Less than 0.1% error over a dynamic range of 500 to 1
Supplies average real power on frequency outputs (F1, F2)
High frequency output (CF) calibrates and supplies
instantaneous real power
Logic output (REVP) indicates potential miswiring or
negative power
Direct drive for electromechanical counters and 2-phase
stepper motors (F1, 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 2.45 V (20 ppm/°C typical) with external
overdrive capability
Single 5 V supply, low power (20 mW typical)
Low cost CMOS process
The AD71056 specifications surpass the accuracy requirements
as quoted in the IEC62053-21 standard.
The only analog circuitry used in the AD71056 is in the Σ-Δ
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
time and in extreme environmental conditions.
The AD71056 supplies average real power information on F1
and F2, the low frequency outputs. These outputs either directly
drive an electromechanical counter or interface with an MCU.
The high frequency CF logic output, ideal for calibration
purposes, provides instantaneous real power information.
The AD71056 includes a power supply monitoring circuit on
the V
DD
supply pin. The AD71056 remains inactive until the
supply voltage on V
DD
reaches approximately 4 V. If the supply
falls below 4 V, the AD71056 also remains inactive and the F1,
F2, and CF outputs are in their nonactive modes.
Internal phase matching circuitry ensures that the voltage and
current channels are phase matched, and the HPF in the current
channel eliminates dc offsets. An internal no load threshold
ensures that the AD71056 does not exhibit creep when no load
is present.
The part is available in a 16-lead, narrow body SOIC package.
GENERAL DESCRIPTION
The AD71056
1
is a high accuracy, electrical energy metering IC
with a precise oscillator circuit that serves as a clock source to
the chip. The AD71056 eliminates the need for an external
crystal or resonator, thus reducing the overall cost of building a
meter with this IC. The chip directly interfaces with the shunt
resistor.
FUNCTIONAL BLOCK DIAGRAM
V
DD
1
AGND
6
DGND
13
AD71056
POWER
SUPPLY MONITOR
V2P
2
V2N
3
+
Σ-Δ
ADC
...110101...
MULTIPLIER
PHASE
CORRECTION
V1N
4
V1P
5
+
Σ-Δ
ADC
...11011001...
Ф
HPF
DIGITAL-TO-FREQUENCY
CONVERTER
05636-001
SIGNAL
PROCESSING
BLOCK
LPF
2.5V
REFERENCE
4kΩ
INTERNAL
OSCILLATOR
7
11
8
10
9
12
14
16
15
REF
IN/OUT
RCLKIN
SCF
S0
S1 REVP CF
F1
F2
Figure 1.
1
U.S. Patents 5,745,323; 5,760,617; 5,862,069; 5,872,469; others pending.
Rev. A
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.
Trademarks and registered trademarks are the property of their respective owners.
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.
AD71056
TABLE OF CONTENTS
Features .............................................................................................. 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Timing Characteristics ................................................................ 4
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Terminology ...................................................................................... 6
Pin Configuration and Function Descriptions............................. 7
Typical Performance Characteristics ............................................. 8
Theory of Operation ...................................................................... 10
Power Factor Considerations.................................................... 10
Nonsinusoidal Voltage and Current........................................ 10
Applications..................................................................................... 12
Analog Inputs ............................................................................. 12
Power Supply Monitor............................................................... 13
Internal Oscillator (OSC).......................................................... 15
Transfer Function....................................................................... 15
Selecting a Frequency for an Energy Meter Application...... 16
No Load Threshold .................................................................... 17
Negative Power Information..................................................... 17
Outline Dimensions ....................................................................... 18
Ordering Guide .......................................................................... 18
REVISION HISTORY
8/06—Revision A: Initial Version
Rev. A | Page 2 of 20
AD71056
SPECIFICATIONS
V
DD
= 5 V ± 5%, AGND = DGND = 0 V, on-chip reference, RCLKIN = 6.2 kΩ, 0.5% ± 50 ppm/°C, T
MIN
to T
MAX
= −40°C to +85°C, unless
otherwise noted.
Table 1.
Parameter
ACCURACY
1
,
2
Measurement Error
1
on Channel V1
Phase Error
1
Between Channels
V1 Phase Lead 37°
V1 Phase Lag 60°
AC Power Supply Rejection
1
Output Frequency Variation (CF)
DC Power Supply Rejection
1
Output Frequency Variation (CF)
ANALOG INPUTS
3
Channel V1 Maximum Signal Level
Channel V2 Maximum Signal Level
Input Impedance (DC)
Bandwidth (–3 dB)
ADC Offset Error
1, 2
Gain Error
1
OSCILLATOR FREQUENCY (OSC)
Oscillator Frequency Tolerance
1
Oscillator Frequency Stability
1
REFERENCE INPUT
REF
IN/OUT
Input Voltage Range
Input Capacitance
ON-CHIP REFERENCE
Reference Error
Temperature Coefficient
LOGIC INPUTS
4
SCF, S0, S1
Input High Voltage, V
INH
Input Low Voltage, V
INL
Input Current, I
IN
Input Capacitance, C
IN
LOGIC OUTPUTS
4
F1 and F2
Output High Voltage, V
OH
Output Low Voltage, V
OL
CF
Output High Voltage, V
OH
Output Low Voltage, V
OL
Frequency Output Error
1, 2
(CF)
Value
0.1
Unit
% reading typ
Test Conditions/Comments
Channel V2 with full-scale signal (±165 mV), 25°C over a
dynamic range 500 to 1, line frequency = 45 Hz to 65 Hz
Power factor (PF) = 0.8 capacitive
PF = 0.5 inductive
S0 = S1 = 1, V1 = 21.2 mV rms, V2 = 116.7 mV rms @
50 Hz, ripple on V
DD
of 200 mV rms @ 100 Hz
S0 = S1 = 1, V1 = 21.2 mV rms, V2 = 116.7 mV rms,
V
DD
= 5 V ± 250 mV
V1P and V1N to AGND
V2P and V2N to AGND
OSC = 450 kHz, RCLKIN = 6.2 kΩ, 0.5% ± 50 ppm/°C
OSC = 450 kHz, RCLKIN = 6.2 kΩ, 0.5% ± 50 ppm/°C
External 2.5 V reference, V1 = 21.2 mV rms,
V2 = 116.7 mV rms
RCLKIN = 6.2 kΩ, 0.5% ± 50 ppm/°C
±0.1
±0.1
0.2
degrees max
degrees max
% reading typ
±0.3
% reading typ
±30
±165
320
7
±18
±4
450
±12
±30
2.65
2.25
10
±200
±20
mV max
mV max
kΩ min
kHz nominal
mV max
% ideal typ
kHz nominal
% reading typ
ppm/°C typ
V max
V min
pF max
mV max
ppm/°C typ
2.45 V nominal
2.45 V nominal
2.45 V nominal
2.4
0.8
±1
10
V min
V max
μA max
pF max
V
DD
= 5 V ± 5%
V
DD
= 5 V ± 5%
Typically 10 nA, V
IN
= 0 V to V
DD
4.5
0.5
4
0.5
±10
V min
V max
V min
V max
% ideal typ
I
SOURCE
= 10 mA, V
DD
= 5 V, I
SINK
= 10 mA, V
DD
= 5 V
I
SOURCE
= 5 mA, V
DD
= 5 V, I
SINK
= 5 mA, V
DD
= 5 V
External 2.5 V reference, V1 = 21.2 mV rms,
V2 = 116.7 mV rms
Rev. A | Page 3 of 20
AD71056
Parameter
POWER SUPPLY
V
DD
I
DD
1
2
Value
4.75
5.25
5
Unit
V min
V max
mA max
Test Conditions/Comments
For specified performance
5 V − 5%
5 V + 5%
Typically 4 mA
See the Terminology section for an explanation of specifications.
See plots in the Typical Performance Characteristics section.
3
See the Analog Inputs section.
4
Sample tested during initial release and after any redesign or process change that may affect this parameter.
TIMING CHARACTERISTICS
V
DD
= 5 V ± 5%, AGND = DGND = 0 V, on-chip reference, RCLKIN = 6.2 kΩ, 0.5% ± 50 ppm/°C, T
MIN
to T
MAX
= −40°C to +85°C, unless
otherwise noted.
Sample tested during initial release and after any redesign or process change that may affect this parameter. See Figure 2.
Table 2.
Parameter
t
1 1
t
2
t
3
t
41, 2
t
5
t
6
1
2
Specifications
120
See Table 6
1/2 t
2
90
See Table 7
2
Unit
ms
sec
sec
ms
sec
μs
Test Conditions/Comments
F1 and F2 pulse width (logic low).
Output pulse period. See the Transfer Function section.
Time between F1 falling edge and F2 falling edge.
CF pulse width (logic high).
CF pulse period. See the Transfer Function section.
Minimum time between F1 and F2 pulses.
The pulse widths of F1, F2, and CF are not fixed for higher output frequencies. See the Frequency Outputs section.
The CF pulse is always 35 μs in high frequency mode. See the Frequency Outputs section and Table 7.
Timing Diagram
t
1
F1
t
6
t
2
F2
t
3
t
4
t
5
05636-002
CF
Figure 2. Timing Diagram for Frequency Outputs
Rev. A | Page 4 of 20
AD71056
ABSOLUTE MAXIMUM RATINGS
T
A
= 25°C, unless otherwise noted.
Table 3.
Parameter
V
DD
to AGND
V
DD
to DGND
Analog Input Voltage to AGND
V1P, V1N, V2P, and V2N
Reference Input Voltage to AGND
Digital Input Voltage to DGND
Digital Output Voltage to DGND
Operating Temperature Range
Storage Temperature Range
Junction Temperature
16-Lead Plastic SOIC, Power Dissipation
θ
JA
Thermal Impedance
1
Package Temperature Soldering
1
Rating
−0.3 V to +7 V
−0.3 V to +7 V
−6 V to +6 V
−0.3 V to V
DD
+ 0.3 V
−0.3 V to V
DD
+ 0.3 V
−0.3 V to V
DD
+ 0.3 V
−40°C to +85°C
−65°C to +150°C
150°C
350 mW
124.9°C/W
See J-STD-20
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 indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
JEDEC 1S standard (2-layer) board data.
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. A | Page 5 of 20
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