5/8

AN589

Figure 7. Ve/VR with DRIVER 2 voltage = 0 V

Figure 8. Ve/VR with DRIVER 2 voltage = 12 V

The waveforms of figure 6, 7 and 8 show parasitic overvoltages lower than in the simulation. This is largely

due to the presence of line capacitance and a finite input impedance. The duration of the spikes is similar,

so again they would be removed by the RS232 input sampling.

The expanded view of Figure 7 given by Figure 9 quantifies the duration of the phenomenon.

Chanel 1

20

s 5V

Chanel 2

20

s 5V

Ch 1

5 V ~

T/div20

Trig

1.28 div+CHAN 1 =

100

0

5V/Div

0

5V/Div

Ve

Vr

20

s/div

Chanel 1

20

s 5V

Chanel 2

20

s 5V

Ch 1

5 V ~

T/div20

Trig

1.28 div+CHAN 1 =

100

0

5V/Div

0

5V/Div

Ve

Vr

20

s/div