SA9602M
FUNCTIONAL DESCRIPTION
The SA9602M is a CMOS mixed signal Analog/Digital integrated circuit, which performs
power/energy calculations across a power range of 1000:1, to an overall accurancy 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 SA9602M generates pulses, the
frequency of which is proportional to the power consumption. Two frequency outputs
(MOTOR and LED) are available. The pulse rate follows the instantaneous power
consumption measured.
The motor drive pin can be configured as a unipolar or bipolar output using input MD. This
choice allows the manufacturer to use either an impulse counter (unipolar) or stepper
motor (bipolar).
1.
Power Calculation
In the Application Circuit (Figure 1), the voltage drop across the shunt will be
between 0 and 16mV
RMS
(0 to 80A through a shunt resistor of 200µΩ). This voltage
is converted to a current of between 0 and 16µA
RMS
, by means of resistors R
1
and
R
2
.
The current sense input saturates at an input current of ±25µA peak.
For the voltage sensor input, the mains voltage (230VAC) is divided down through
a divider to 14V
RMS
. The current into the A/D converter input is set at 14µA
RMS
at
nominal mains voltage, via resistor R4 (1MΩ).
Different pulse rates are available at the motor drive pin. The device may be
programmed for a 1 pulse/kWh, 10 pulses/kWh or 100 pulses/kWh output,
depending on the status of the motor pulse rate select pins MPD and MP1.
The LED pulse rate is fixed at 1000 pulses/kWh. The frequency of the motor drive
and LED pin is dependant on the settings of R0 and R1 which allow selection of
different rated conditions. Rated conditions such as 230V/40A, 230V/60A, 230V/
80A and 230V/100A may be chosen. 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 are illustrated below.
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.
2.
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