SA2002H
FUNCTIONAL DESCRIPTION
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.
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For the voltage sensor input, the mains voltage (230VAC) is
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.
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 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.
POWER CALCULATION
In the application circuit (figure 6), the voltage drop 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 16uA
RMS
, by means of resistors R1 and R2. The
current sense inputs saturates at an input current of ±25µA
peak.
VDD
N
Supply
L
GND
VSS
U1
IIN
R2
IIP
VDD
VDD
IIN
IIP
V DD
CURRENT
SENSOR
INPUTS
VSS
VDD
A
I
RSH
R1
VSS
R3
R5
R4
GND
IVP
GND
FOUT
DIR
FMO
Pulse output
Fwd/Rev. Energy
Zero crossing
IVP
VOLTA GE
SENSOR
INPUT
VDD
N
P1
L
GND
R6
VREF
VSS
SA2002H
V SS
A
V
DR-01587
VSS
GND
DR-01148
Figure 6: Application circuit
Figure 7: Internal analog input configuration
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