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
measurementsuchastwooversamplingA/Dconvertersforthevoltageandcurrentsense
inputs, power calculation and energy integration. Internal offsets are eliminated through
the use of cancellation procedures. These devices generate pulses, the frequency of
whichisproportionaltothepowerconsumption. Thepulseratefollowstheinstantaneous
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
IntheApplicationCircuit(Figure1),thevoltagedropacrosstheshuntwillbebetween
0 and 16mVRMS (0 to 80A through a shunt resistor of 200µΩ). This voltage is
converted to a current of between 0 and 16µARMS, by means of resistors R1 and R2.
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 14VRMS . The current into the A/D converter input is set at 14µARMS 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
case1pulsewillcorrespondtoanenergyconsumptionof18.4kW/64Hz=287.5Ws.
2. Analog Input Configuration
The input circuitry of the current and voltage sensor inputs are illustrated below.
Theseinputsareprotectedagainstelectrostaticdischargethroughclampingdiodes.
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.
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