Fail-safe circuit comparisons with ST485EB

AN1690

12/15

Figure 11.

DC fail-safe characteristics

Another test was performed to verify the behavior of the different termination circuits when

an AC signal is present on the line. Figure 12 and Figure 13 show the eye patterns of the

signals driven respectively at the end of a 100 m cable and on the receiver output. The

driver was led by means of a PRBS (pseudorandom bit signalling) generator with 5 Mbit/s

data rate.