ISL32601EFBZ Datasheet, PDF (11/23 Pages) Intersil Corporation – 1.8V to 3.3V, Micro-Power, ±15kV ESD, +125°C, Slew Rate Limited, RS-485/RS-422 Transceivers

ISL32600E, ISL32601E, ISL32602E, ISL32603E
Test Circuits and Waveforms (Continued)
DE
V_CC
DI
SIGNAL
GENERATOR
Z
D
Y
R_DIFF
50pF
-
V_OD
+
DI
DIFF OUT (Y - Z)
-V_OD
V_CC
0V
+V_{OD 0V}
FIGURE 6A. TEST CIRCUIT
FIGURE 6. DRIVER DATA RATE
FIGURE 6B. MEASUREMENT POINTS
GND
RE
B
A
RO
R
15pF
SIGNAL
GENERATOR
A
0V
+1V
0V
-1V
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
GND
B
RO
AR
1kΩ
15pF
V_CC
SW ^GND
PARAMETER
DE
t_HZ
X
t_LZ
X
t_ZH (Note 10)
0
t_ZL (Note 10)
0
t_ZH(SHDN) (Note 13)
0
t_ZL(SHDN) (Note 11)
0
A
+1.5V
-1.5V
+1.5V
-1.5V
+1.5V
-1.5V
SW
GND
V_CC
GND
V_CC
GND
V_CC
NOTE 11
RE
t_ZH, t_ZH(SHDN)
NOTE 11
RO
t_ZL, t_ZL(SHDN)
NOTE 11
RO
50%
50%
V_CC
0V
t_HZ
OUTPUT HIGH
1.5V
V_OH - 0.25V ^VOH
0V
t_LZ
1.5V
OUTPUT LOW
V_CC
V_OL + 0.25V _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 for use in 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 spec 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
-7V to +12V. RS-422 and RS-485 are intended for runs as long
as 4000’, so the wide CMR is necessary to handle ground
potential differences, as well as voltages induced in the cable
by external fields.
Receiver Features
These devices utilize a differential input receiver for maximum
noise immunity and common mode rejection. Input sensitivity is
better than ±200mV, as required by the RS-422 and RS-485
specifications. The symmetrical ±200mV switching thresholds
11
FN7967.0
June 22, 2012