SA9604A
1.
Power calulation
In the Application Circuit (Figure 1), the voltages from Line 1, Line 2 and Line 3, are
converted to currents and applied to the voltage sense inputs IVN1, IVN2 and IVN3.
The current levels on the voltage sense inputs are derived from the mains voltage
(3 x 230 V
AC
) being divided down through voltage dividers to 14V
RMS
. The resulting
input currents into the A/D converters are 14µA
RMS
through the resistors R
15
, R
16
and
R
17
.
For the current sense inputs, the voltages across the current transformers terminating
resistors are converted to currents of 16µA
RMS
for rated conditions, by means of
resistors R
8
, R
9
(Phase 1); R
10
, R
11
(Phase 2); and R
12
, R
13
(Phase 3).
The signals providing the current information are applied to the current sensor
inputs: IIN1; IIP1; IIN2; IIP2; IIN3; and IIP3.
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 copies of the input currents are generated for the
following analog signal processing circuitry.
V DD
II P
CURRENT
SE NS OR
INPUT S
V SS
A
V DD
I
II N
V SS
VDD
IV P
VOL T AGE
SE NS OR
INPUT
V SS
A
V
DR-0 1 3 0 8
GND
3.
Electrostatic Discharge (ESD), Protection
The SA9604A Integrated Circuits inputs/outputs are protected against ESD.
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