fs7755 Fortune Semiconductor Corporation, fs7755 Datasheet - Page 14

• Manufacturer Part Number: fs7755
• Description: Energy Metering Ic With Impulse Output
• Manufacturer: Fortune Semiconductor Corporation

Rev. 1.0
4.2 Channel V2 (Voltage Channel)
4.3 Typical Connection Diagrams
The output of the line voltage transducer is connected to the FS7755 at this analog input. Channel V2 is a
fully differential voltage input. The maximum peak differential signal on Channel 2 is ± 660mV.
Fig8 illustrates the maximum signal levels that can be connected to the FS7755 Channel 2.
Channel 2 must be driven from a common-mode voltage, i.e., the differential voltage signal on
the input must be referenced to a common mode (usually AGND). The analog inputs of the
FS7755 can be driven with common-mode voltages of up to 100mV with respect to AGND.
However, best results are achieved using a common mode equal to AGND.
Fig9 shows a typical connection diagram for Channel V1. A CT (Current Transformer) is the current
transducer selected for this example. Notice the common-mode voltage for Channel 1 is AGND and is
derived by center tapping the burden resistor to AGND. This provides the complementary analog input
signals for V1P and V1N. The CT turns ratio and burden resistor R
voltage of ±470mV/Gain at maximum load.
+660mV
-660mV
Phase
I
P h a s e
VCM
p h
N o t e : * R
V2
Fig8
Neutral
Fig9
Fig10
* R
N e u t r a l
a
b
> > R
+ V R = R
CT
R
b
PT
Maximum Signal Levels (Channel 2)
a
+ V R
*
Typical Connection for Channel 1
Typical Connection for Channel 2
V R
R
f
Differential Input
b
*
*
±
Common Mode
±
660mV Max
100mV Max
± 6 6 0 m V
± 6 6 0 m V
C
f
R
R
R
AGND
R
R
f
f
f
f
f
V2
VCM
±470mV
Gain
V2P
V2N
b
C
C
C
are selected to give a peak differential
C
C
f
f
f
f
f
V 2 P
V 2 N
V 2 P
V 2 N
V1P
V1N
FS7755
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