SA2002D Datasheet, PDF (4/10 Pages) Sames – Single Phase Kilowatt-hour Metering IC for Mechanical Display Applications

SA2002D
sames
FUNCTIONAL DESCRIPTION
The SA2002D is a CMOS mixed signal Analog/Digital
integrated circuit, which performs power/energy calculations
across a power range of 1000:1, to an overall accuracy of
better than Class 1.
divided down through a divider (R3, R4 and P1) to 14V_RMS. The
current into the A/D converter input is set at 14µA_RMS at nominal
mains voltage, via resistor R5 (1MW). P1 may be varied for
calibration purposes.
The integrated circuit includes all the required functions for 1-
phase power and energy measurement such as two
oversampling A/D converters for the voltage and current sense
inputs, power calculation and energy integration. Internal
offsets are eliminated through the use of cancellation
procedures. The SA2002D generates pulses, the frequency of
which is proportional to the power consumption. A
complementary output (MOP and MON) is provided for the
stepper motor. One energy pulse is represented by MOP pulse
and subsequently followed by a MON pulse. This configuration
avoids the possibility that, after power up, the first energy pulse
is lost due to the stepper motor being in the wrong phase. The
pulse rate on these pins follow the instantaneous active power
consumption. The LED pulse output follows the average power
consumption measured and is intended for calibration
proposes.
The pulse rate available at the motor drive pins MOP and MON
(counter resolution) is fixed at 100 (200) impulses/kWh*. The
frequency of the LED pin is dependant on the settings of pins
R0, R1 and R2, which allow a selection of different rated
conditions. In this case (R0, R1 and R2 set to logic 0) the LED
output is 6400 impulses/kWh, with the rated conditions set to
220V/10A. This facility allows meter manufacturers to cater for
a wide range of metering applications with minimal design
changes.
ANALOG INPUT CONFIGURATION
The input circuitry of the current and voltage sensor inputs is
illustrated in figure 3.
These inputs are protected against electrostatic discharge
through clamping diodes.
POWER CALCULATION
In the Application Circuit (Figure 3), the voltage drops across
the shunt will be between 0 and 16mV_RMS (0 to 80A through a
shunt resistor of 200µW). The voltage is converted to a current
of between 0 and 16mV_RMS, by means of resistors R1 and R2.
The current sense input saturates at an input current of ±25µA
peak.
The feedback loops from the outputs of the amplifiers A_I and A_V
generate virtual shorts on the signal inputs. Exact duplications
of the input currents are generated for the analog signal
processing circuitry.
VDD
IIP
For the voltage sensor input, the mains voltage (230VAC) is
N
Supply
L
Supply
VDD
VDD
REVERSE
PULSES
CURRENT
VSS
SENSOR
AI
INPUTS
VDD
IIN
VSS
VDD
R1
R2
R3
R5
R4
VDD
IIN
IIP
DIRO DIRI
LED
IVP
SA2002
AGND
8888888
IVP
VOLTAGE
SENSOR
VSS
INPUT
A_V
P1
DR-01568
L
LOAD
N
VREF
MOP
MON
VSS TEST R0 R1 R2
Figure 3: Application Circuit
http://www.sames.co.za
DR-01288
GND
Figure 4: Analog Input Internal Configuration
*The figure not in parenthesis indicates that a MOP pulse
followed by a MON pulse is treated as one energy pulse. The
figure inside parenthesis means that a MOP pulse followed by
a MON pulse is treated as two energy pulses.
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