AN1348 - APPLICATION NOTE

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6. ADVICE

In order to get greater cable length and higher data rate, with a better signal quality, the following load

reduce the common mode disturbs.

Figure 7: Configuration to Improve Transmission Performance

6.2 AC Termination

loop current flowing on the load, in static conditions, the configuration shown in figure 8 is useful. The R

value depends on the line impedance, typically it is 120Ohm for twisted pair cables; C depends either on

the cable length or on the line impedance Z0 and must be calculated to result a short-circuit for data

transmission. However, this configuration limits the data rate because of the low pass filter make with R

and C, then it is useful for medium data rate.

Figure 8: Contiguration to Reduce the DC Loop Current

Note: The C capacitor breaks the DC loop current when data transmission is off and reduces the power

consumption but limits the data rate.

R

R

C

D

R

8

6

5

7

RO

3

4

2

1

__

RE

DE

DI

Vcc

B

A

GND

D

R

8

6

5

7

RO

3

4

2

1

__

RE

DE

DI

Vcc

B

A

GND

R

C