ADE7757_15 Datasheet, PDF (1/16 Pages) Analog Devices – Energy Metering IC with Integrated Oscillator

Energy Metering IC
with Integrated Oscillator
ADE7757^*
FEATURES
On-Chip Oscillator as Clock Source
High Accuracy, Supposes 50 Hz/60 Hz IEC 521/IEC 61036
Less than 0.1% Error over a Dynamic Range of 500 to 1
The ADE7757 Supplies Average Real Power on the
Frequency Outputs F1 and F2
The High Frequency Output CF Is Intended for
Calibration and Supplies Instantaneous Real Power
The Logic Output REVP Can Be Used to Indicate a
Potential Miswiring or Negative Power
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 2.5 V (20 ppm/؇C Typical)
with External Overdrive Capability
Single 5 V Supply, Low Power (20 mW Typical)
Low Cost CMOS Process
AC Input Only
GENERAL DESCRIPTION
The ADE7757 is a high accuracy electrical energy measurement
IC. It is a pin reduction version of the ADE7755 with an enhance-
ment of a precise oscillator circuit that serves as a clock source
to the chip. The ADE7757 eliminates the cost of an external
crystal or resonator, thus reducing the overall cost of a meter
built with this IC. The chip directly interfaces with the shunt
resistor and operates only with ac input.
The ADE7757 specifications surpass the accuracy requirements
as quoted in the IEC 61036 standard. The AN-679 Application
Note can be used as a basis for a description of an IEC 61036
low cost watt-hour meter reference design.
The only analog circuitry used in the ADE7757 is in the ⌺-⌬
ADCs and reference circuit. All other signal processing (e.g.,
multiplication and filtering) is carried out in the digital domain.
This approach provides superior stability and accuracy over
time and extreme environmental conditions.
The ADE7757 supplies average real power information on the
low frequency outputs F1 and F2. These outputs may be used
to directly drive an electromechanical counter or interface with
an MCU. The high frequency CF logic output, ideal for calibra-
tion purposes, provides instantaneous real power information.
The ADE7757 includes a power supply monitoring circuit on
the V_DD supply pin. The ADE7757 will remain inactive until
the supply voltage on V_DD reaches approximately 4 V. If the
supply falls below 4 V, the ADE7757 will also remain inactive
and the F1, F2, and CF outputs will be in their nonactive modes.
Internal phase matching circuitry ensures that the voltage and
current channels are phase matched while the HPF in the cur-
rent channel eliminates dc offsets. An internal no-load threshold
ensures that the ADE7757 does not exhibit creep when no load
is present.
The ADE7757 is available in a 16-lead SOIC narrow-body package.
FUNCTIONAL BLOCK DIAGRAM
V_DD
AGND
DGND
ADE7757
POWER
SUPPLY MONITOR
SIGNAL
PROCESSING
V2P
⌺-⌬ ^...110101...
BLOCK
V2N
ADC
MULTIPLIER
LPF
PHASE
CORRECTION _HPF
V1N
V1P
⌺-⌬ ^{...11011001...}
ADC
⌽
2.5V
4k⍀
REFERENCE
INTERNAL
OSCILLATOR
DIGITAL-TO-FREQUENCY
CONVERTER
REF_IN/OUT RCLKIN
*U.S. Patents 5,745,323; 5,760,617; 5,862,069; 5,872,469.
REV. A
SCF S0 S1 REVP CF F1 F2
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