Complete, Isolated RS-485/RS-422
Data Interface
____________________________________________________Test Circuits (continued)
ISO V
_
CC
S1
S2
500Ω
OUTPUT
UNDER TEST
C
L
Figure 6. Driver Timing Test Load
Switching Waveforms
V
- 0.4V
V
CC_
- 0.4V
CC_
V
-0.4V
0V
V
- 0.4V
0V
CC_
CC_
2
2
V
CC_
- 0.4V
V
CC_
- 0.4V
2
2
DE´
DI´
t
t
PHL
PLH
1/2 V
O
t
t
LZ
ZL
B
A
A, B
V
O
2.3V
V
V
+ 0.5V
- 0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
OL
V
OL
1/2 V
O
V
= V (A) - V (B)
DIFF
V
O
A, B
0V
V
DIFF
90%
90%
0V
-V
2.3V
OH
10%
10%
O
t
R
t
F
t
ZH
t
HZ
t
t - t
SKEW = PLH PHL
Figure 7. Driver Propagation Delays and Transition Times
Figure 8. Driver Enable and Disable Times
INPUT
V
ID
2.4V
0V
0V
-V
ID
SD
0.8V
1.6V
1.6V
V - V
A
B
MAX1490A/B
OUTPUT
t
t
SHDN
ZL(SHDN)
A, B
RO V
OH
t
t
PHL
2.3V
V
V
+ 0.5V
- 0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
OL
1.5V
t
1.5V
1.5V
V
OL
V
OL
PLH
A, B
0V
V
OH
2.3V
OH
MAX1480A/B/C
OUTPUT
RO
1.5V
V
OL
t
t
SHDN
ZH(SHDN)
t
PHL
PLH
t
= t
t
SKEW
PLH - PHL
Figure 10. Receiver Propagation Delays
______________________________________________________________________________________ 15
Figure 9. Times to/from Shutdown
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
