AD71056_15 Datasheet, PDF (1/20 Pages) Analog Devices – Energy Metering IC with Integrated Oscillator and Reverse Polarity Indication

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
GENERAL DESCRIPTION
The AD71056¹ 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.
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 VDD supply pin. The AD71056 remains inactive until the
supply voltage on VDD 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.
V2P 2
V2N 3
V1N 4
V1P 5
FUNCTIONAL BLOCK DIAGRAM
V_DD
1
AGND
6
POWER
SUPPLY MONITOR
+
Σ-Δ ^...110101...
ADC
AD71056
DGND
13
MULTIPLIER
SIGNAL
PROCESSING
BLOCK
+
2.5V
REFERENCE
Σ-Δ
ADC
4kΩ
PHASE
CORRECTION
LPF
...11011001...
Ф
HPF
INTERNAL
OSCILLATOR
DIGITAL-TO-FREQUENCY
CONVERTER
7
REF_IN/OUT
11
8 10 9 12 14 16 15
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
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