SA9602F/SA9602J
FUNCTIONAL DESCRIPTION
The SA9602F and SA9602J are CMOS mixed signal Analog/Digital integrated circuits,
which perform power/energy calculations across a power range of 1000:1, to an overall
accurancy of better than Class 1.
The integrated circuits include 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. These devices generate pulses, the frequency of
which is proportional to the power consumption. The pulse rate follows the instantaneous
power consumption measured. Direction information is also provided.
A voltage zero crossover signal, relevant to the positive going half cycle, is available on
pin FMO. This signal can be used to sychronise circuit breaker switching.
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).
In this configuration, with a mains voltage of 230V and a current of 80A, the output
frequency of the SA9602F and SA9602J power meter chip at FOUT is 64Hz. In this
case 1 pulse will correspond to an energy consumption of 18.4kW/64Hz = 287.5Ws.
2.
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.
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