Revision 1.7, 22-Nov-04
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Features
-
Extremely accurate, surpassing the accuracy
requirements of the IEC 1036 Specification less than
0.1% error over a 600 : 1 dynamic range
-
On-chip programmable current input gain suitable for
use with low-resistance shunt resistor or current
transformer
-
On-chip programming for output pulse rate selection
-
On-chip calibration eliminates the need for an external
resistor network or trim-potentiometer
-
Programmable on-chip creep prevention under no-
load condition
-
All on-chip programmable functions may be
reprogrammed a second time
-
Outputs directly drive an electromechanical counter or
counters with a two phase stepper motor and
consumption LED indicator
-
Fast calibration pulse output for high speed manual or
automated calibration
-
On-chip voltage reference and power supply
monitoring
-
Bi-directional or unidirectional energy measurement,
with direction indication output available
Description
The AS8118 is a very accurate single-phase bi-directional
instantaneous energy measurement integrated circuit,
which surpasses all the accuracy requirements for
IEC1036 alternating current static watt-hour meters. The
measured energy is converted into pulses with the
number of output pulses being proportional to the
measured energy.
The AS8118 is ideal for use in `stand alone' kWh meter
applications, where the IC directly drives an
electromechanical counter with a two-phase stepper
motor, or for more complex meter applications, the
AS8118 interfaces directly to a micro-controller.
The highly integrated AS8118 design includes all the
required functional blocks. The blocks comprise of analog
to digital converters (ADC) for the voltage and current
channels, digital filters, a digital signal processing block, a
control block and non-volatile calibration memory for the
on-chip programming. The on-chip programming enables
the setting of the current input gain, the anti-creep
threshold, the output pulse rates and the system
calibration. The high level of integration ensures a
minimum number of non-critical external components are
required.
The on-chip anti-creep circuit ensures that the AS8118
does not output pulses when the meter is in a no-load
condition and that the IEC1036 anti-creep test
requirements are fully complied with, for both direct or
transformer connection meters.
The AS8118 offers three different pulse outputs. A
stepper motor drive output for directly driving a stepper
motor display, a LED output for energy consumption
indication and a dedicated high frequency output for fast
single point system calibration.
The AS8118 is available in either surface mount SOIC-18
or dual-in-line DIP-18 packages.
Block Diagram
-mod
VREF
Digital
Filter
Control
Power
Calculation
CAL
VS
SD
VDDD
IP
VP
-mod
Crystal
Osc
Non-volatile
Calibration
PRO
G
VS
SA
V
DDA
TM
XIN
XOUT
DIRI
DI
RO
POR
AGND
Buffer
IN
LED
Digital
Filter
MON
MOP
VN
Figure 1
Block diagram of the AS8118
AS8118
Single Phase Instantaneous Energy Metering IC
with On-Chip Calibration, Stepper Motor Drive and LED Output
FEATURES
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