AD7755 Datasheet, PDF (1/16 Pages) Analog Devices – Energy Metering IC with Pulse Output

a
Energy Metering IC
with Pulse Output
AD7755*
FEATURES
High Accuracy, Supports 50 Hz/60 Hz IEC 687/1036
Less than 0.1% Error Over a Dynamic Range of
500 to 1
The AD7755 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
Two Phase Stepper Motors (F1 and F2)
A PGA in the Current Channel Allows the Use of Small
Values of Shunt and Burden Resistance
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 6 8% (30 ppm/8C Typical)
with External Overdrive Capability
Single 5 V Supply, Low Power (15 mW Typical)
Low Cost CMOS Process
GENERAL DESCRIPTION
The AD7755 is a high accuracy electrical energy measurement
IC. The part specifications surpass the accuracy requirements
as quoted in the IEC1036 standard. See Analog Devices’
Application Note AN-559 for a description of an IEC1036
watt-hour meter reference design.
The only analog circuitry used in the AD7755 is in the ADCs
and reference circuit. All other signal processing (e.g., multipli-
cation 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 AD7755 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 interface
to an MCU. The CF logic output gives instantaneous real power
information. This output is intended to be used for calibration
purposes, or interfacing to an MCU.
The AD7755 includes a power supply monitoring circuit on the
AV_DD supply pin. The AD7755 will remain in a reset condition
until the supply voltage on AV_DD reaches 4 V. If the supply falls
below 4 V, the AD7755 will also be reset and no pulses will be
issued on F1, F2 and CF.
Internal phase matching circuitry ensures that the voltage and
current channels are phase matched whether the HPF in Chan-
nel 1 is on or off. An internal no-load threshold ensures that the
AD7755 does not exhibit any creep when there is no load.
The AD7755 is available in 24-lead DIP and SSOP packages.
G0 G1
FUNCTIONAL BLOCK DIAGRAM
AV_DD AGND
AC/DC
DV_DD DGND
AD7755
POWER
SUPPLY MONITOR
PHASE
CORRECTION
V1P
. . .110101. . .
ADC
⌽
V1N
PGA
x1, x2, x8, x16
HPF
MULTIPLIER
SIGNAL
PROCESSING
BLOCK
LPF
V2P
. . .11011001. . .
ADC
V2N
2.5V
4k⍀
REFERENCE
DIGITAL-TO-FREQUENCY
CONVERTER
RESET
REF_IN/OUT CLKIN CLKOUT SCF S0 S1 REVP CF F1 F2
*U.S. Patents 5,745,323, 5,760,617, 5,862,069, 5,872,469.
REV. B
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use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
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© Analog Devices, Inc., 2000