SA2005F
sames
through clamping diodes, in conjunction with the amplifiers
input configuration. 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 processing circuitry.
Voltage Reference Connection (VREF)
A bias resistor of 24k provides an optimum bias conditions on
chip. Calibration of the SA2005F should be done on the
voltage inputs of the device as described in Typical
Applications.
Current Sense Inputs (IIN1, IIP1, IIN2, IIP2, IIN3, IIP3)
At rated current the resistor values should be selected for input
currents of 16µA
RMS
. Referring to figure 5, the resistors R1 and
R2 on current channel 1, resistors R3 and R4 on current
channel 2 and resistors R5 and R6 on current channel 3, define
the current level into the current sense inputs of the SA2005F.
The current sense inputs saturates at an input current of ±25µA
peak. Resistors R25, R26 and R27 are the current transformer
termination resistors. The voltage drop across the termination
resistors should be at least 20mV at rated conditions. Values
for the current sense inputs are calculated as follows:
R
1
= R
2
= (I
L
/ 16µA
RMS
) x R
25
/ 2
R
3
= R
4
= (I
L
/ 16µA
RMS
) x R
26
/ 2
R
5
= R
6
= (I
L
/ 16µA
RMS
) x R
27
/ 2
Where:
I
L
= Line current/CT-ratio
V DD
IIP
CURRENT
SENSOR
INPUTS
VSS
VDD
A
I
IIN
VSS
VDD
IVP
VOLTAGE
SENSOR
INPUT
V SS
A
V
GND
DR-01288
Figure 3: Analog Input Internal Configuration
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SAMES [ SAMES ]
