Complete, Isolated, 3.3V

RS-485/RS-422 Data Interface

______________________________________________________________________________________

11

_________________________________________________________________Test Circuits

Figure 3. Driver DC Test Load

Figure 4. Driver/Receiver Timing Test Circuit

Figure 5. Driver Timing Test Load

R

R

A

B

DI

´

DE

´

3.3V

A

B

A

B

RO

R3

3.3V

ISOLATION BARRIER

ISOLATION BARRIER

R

D

OUTPUT

UNDER TEST

500

Ω

S1

S2

_______________________________________________________Switching Waveforms

Figure 6. Driver Propagation Delays and Transition Times

Figure 7. Driver Enable and Disable Times

DI

´

2

2

0V

B

A

0V

10%

90%

90%

10%

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

0V

A, B

A, B

0V

2.3V

2.3V

DE

´

2

2