ISL32496EIUZ Datasheet, PDF (11/22 Pages) Intersil Corporation – ±60V Fault Protected, 5V, RS-485/RS-422 Transceivers with ±25V CMR and ESD Protection

ISL32490E, ISL32492E, ISL32493E, ISL32495E, ISL32496E, ISL32498E
Test Circuits and Waveforms (Continued)
DE
V_CC
DI
SIGNAL
GENERATOR
Z
D
Y
54Ω
C_D
+
V_OD
-
DI
DIFF OUT (Y - Z)
-V_OD
3V
0V
+V_{OD 0V}
FIGURE 6A. TEST CIRCUIT
FIGURE 6B. MEASUREMENT POINTS
FIGURE 6. DRIVER DATA RATE
SIGNAL
GENERATOR
V_CM
RE
B
A
RO
R
15pF
SIGNAL
GENERATOR
B
V_CM + 750mV
V_CM
V_CM
A
V_CM - 750mV
t_PLH
t_PHL
V_CC
RO
50%
50%
0V
FIGURE 7A. TEST CIRCUIT
FIGURE 7B. MEASUREMENT POINTS
FIGURE 7. RECEIVER PROPAGATION DELAY AND DATA RATE
SIGNAL
GENERATOR
RE
B
A
RO
R
1kΩ
15pF
V_CC
SW ^GND
(Note 11)
RE
1.5V
3V
1.5V
0V
PARAMETER
DE
t_HZ
0
t_LZ
0
t_ZH (Note 10)
0
t_ZL (Note 10)
0
t_ZH(SHDN) (Note 13)
0
t_ZL(SHDN) (Note 13)
0
A
+1.5V
-1.5V
+1.5V
-1.5V
+1.5V
-1.5V
SW
GND
V_CC
GND
V_CC
GND
V_CC
t_ZH, t_ZH(SHDN)
(Note 11)
RO
t_ZL, t_ZL(SHDN)
(Note 11)
RO
t_HZ
OUTPUT HIGH
1.5V
V_OH - 0.5V
V_OH
0V
t_LZ
1.5V
OUTPUT LOW
V_CC
V_OL + 0.5V _VOL
FIGURE 8A. TEST CIRCUIT
FIGURE 8B. MEASUREMENT POINTS
FIGURE 8. RECEIVER ENABLE AND DISABLE TIMES
Application Information
RS-485 and RS-422 are differential (balanced) data
transmission standards used for long haul or noisy environments.
RS-422 is a subset of RS-485, so RS-485 transceivers are also
RS-422 compliant. RS-422 is a point-to-multipoint (multidrop)
standard, which allows only one driver and up to 10 (assuming
one-unit load devices) receivers on each bus. RS-485 is a true
multipoint standard, which allows up to 32 one-unit load devices
(any combination of drivers and receivers) on each bus. To allow
for multipoint operation, the RS-485 specification requires that
drivers must handle bus contention without sustaining any
damage.
Another important advantage of RS-485 is the extended
common mode range (CMR), which specifies that the driver
outputs and receiver inputs withstand signals that range from
+12V to -7V. RS-422 and RS-485 are intended for runs as long as
4000 feet; thus, the wide CMR is necessary to handle ground
potential differences, as well as voltages induced in the cable by
external fields.
The ISL3249xE is a family of ruggedized RS-485 transceivers
that improves on the RS-485 basic requirements and thereby
11
FN7786.2
March 16, 2012