SA2002H
sames
FUNCTIONAL DESCRIPTION
For the voltage sensor input, the mains voltage (230VAC) is
divided down through a divider (R3, R4 and P1) to 14VRMS. The
current into the A/D converter input is set at 14µARMS at nominal
mains voltage, via resistor R5 (1MW). P1 may be varied for
calibration purposes.
The SA2002H 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.
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 SA2002H generates pulses, the frequency of
which is proportional to the measured power consumption.
One frequency output (FOUT) is available. The pulse rate
follows the instantaneous power consumption measured.
In this configuration, with a mains voltage of 230V and a
current of 80A, the output frequency measured on the FOUT
pin is 1360Hz. In this case one pulse on FOUT correspond to
an energy consumption of 18.4kW/1360Hz = 13.53Ws.
ANALOG INPUT CONFIGURATION
The input circuitry of the current and voltage sensor inputs is
illustrated in figure 7. These inputs are protected against
electrostatic discharge through clamping diodes. The
feedback loops from the outputs of the amplifiers AI and AV
generate virtual shorts on the signal inputs. Exact duplications
of the input currents are generated for the analog signal
processing circuitry.
POWER CALCULATION
In the application circuit (figure 6), the voltage drop across the
shunt will be between 0 and 16mVRMS (0 to 80A through a shunt
resistor of 200µW) The voltage is converted to a current of
between 0 and 16uARMS, by means of resistors R1 and R2. The
current sense inputs saturates at an input current of 25µA
peak.
V
DD
VDD
N
IIP
Supply
L
V
V
SS
DD
CURRENT
SENSOR
INPUTS
AI
GND
VSS
U1
IIN
VDD
R1
R2
RSH
VDD
IIN
IIP
V
SS
R3
R5
V
DD
Pulse output
IVP
FOUT
Fwd/Rev. Energy
Zero crossing
GND
DIR
R4
GND
IVP
FMO
VREF
VSS
VOLTAGE
SENSOR
INPUT
N
L
V
SS
SA2002H
A V
R6
P1
DR-01587
VSS
GND
GND
DR-01148
Figure 7: Internal analog input configuration
Figure 6: Application circuit
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