FS7755

Rev. 1.1

14/22

4.2 Channel V2 (Voltage Channel)

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.

V2P

V2N

AGND

VCM

V2

Differential Input

660mV Max

Common Mode

100mV Max

±

±

V2

VCM

-660mV

+660mV

Fig8

Maximum Signal Levels (Channel 2)

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.

4.3 Typical Connection Diagrams

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

voltage of ±470mV/Gain at maximum load.

Neutral

Phase

I

ph

R

f

R

f

CT

C

f

C

f

V1P

V1N

±

470mV

Gain

Fig9

Typical Connection for Channel 1

Ne u t r a l

P has e

R

f

R

f

PT

C

f

C

f

V2 P

V2 N

±

660 m V

R

f

C

f

V2 P

V2 N

R

a

*

C

f

R

b

*

±

6 60m V

No t e :

* R

* R

Fig10

Typical Connection for Channel 2