SA9122E
1.
Power calculation
In the Application Circuit (Figure 1), the voltage drop across the shunt will be
between 0 and 16mV (0 to 80A through a shunt resistor of 200µΩ). This voltage is
converted to a current of between 0 and 16µA, 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. 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 SA9122E power meter chip at FOUT1 is 1.16kHz. In this case, 1
pulse will correspond to an energy consumption of 18.4kW/1160Hz = 15.9Ws.
The output frequency at FOUT2 is FOUT1 /290 (i.e. The frequency ouput at FOUT1
divided by 290).
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.
V DD
2.
IIN
CURRENT
SENSOR
INPUTS
V SS
V DD
A
I
IIP
V SS
VDD
IVN
VOLTAGE
SENSOR
INPUT
V SS
A
V
DR-00935
GND
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sames
SAMES [ SAMES ]
