Revision 1.7, 22-Nov-04 Page 1 of 1
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
Σ∆-mod
VREF
Digital
Filter
Control
Power
Calculation
CAL
VS
SD
VDDD
IP
VP
Σ∆-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