ISL32173EIVZ-T Datasheet, PDF (11/22 Pages) Intersil Corporation – QUAD, 16.5kV ESD Protected, 3.0V to 5.5V, RS-485/RS-422 Receivers

ISL32173E, ISL32175E, ISL32177E, ISL32273E, ISL32275E, ISL32277E
Test Circuits and Waveforms
+1.5V
EN
B
A
RO
R
15pF
3V
A
1.5V
1.5V
0V
t_PLH
t_PHL
SIGNAL
GENERATOR
V_CC OR V_L
RO
50% 50%
0V
FIGURE 1A. TEST CIRCUIT
FIGURE 1B. MEASUREMENT POINTS
FIGURE 1. RECEIVER PROPAGATION DELAY
SIGNAL
GENERATOR
EN
B
GND
A
RO
R
1kΩ
V_CC
OR V_L
15pF
SW ^GND
PARAMETER
t_HZ
t_LZ
t_ZH (Notes 15, 21)
t_ZL (Notes 15, 21)
t_ZH(SHDN) (Notes 16, 20)
t_ZL(SHDN) (Notes 16, 20)
A
+1.5V
-1.5V
+1.5V
-1.5V
+1.5V
-1.5V
SW
GND
V_CC
GND
V_CC
GND
V_CC
EN
t_ZH, t_ZH(SHDN)
RO
t_ZL, t_ZL(SHDN)
RO
1.5V
1.5V
3V OR V_L
0V
t_HZ
OUTPUT HIGH
LOWER OF
1.5V OR V_L/2
V_OH - 0.5V ^VOH
0V
t_LZ
LOWER OF
1.5V OR V_L/2
OUTPUT LOW
V_CC OR V_L
V_OL + 0.5VV_OL
FIGURE 2A. TEST CIRCUIT
FIGURE 2B. MEASUREMENT POINTS
FIGURE 2. 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.
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’, 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 differential receivers for maximum
noise immunity and common mode rejection. Input
sensitivity is better than ±200mV, as required by the
RS-422 and RS-485 specifications.
Receiver input resistance of 48kΩ surpasses the RS-422
specification of 4kΩ and is four times the RS-485 “Unit
Load (UL)” requirement of 12kΩ minimum. Thus, these
products are known as “one-quarter UL” receivers and
there can be up to 128 of these devices on a network
while still complying with the RS-485 loading
specification.
Receiver inputs function with common mode voltages as
great as +9V/-7V outside the power supplies (i.e., +12V
and -7V with V_CC = 3.0V), making them ideal for long
networks where induced voltages, and ground potential
differences are realistic concerns.
All the receivers include a “fail-safe open” function that
guarantees a high level receiver output if the receiver
inputs are unconnected (floating).
All receivers easily support a 20Mbps data rate, and the
ISL32173E, ISL32175E, and ISL32177E support data
rates up to 80Mbps. All receiver outputs are tri-statable,
with the enable scheme varying by part type (see next
section).
Receiver Enable Functions
All product types include functionality to allow disabling
of the Rx outputs. The ISL32X73E types feature group
(all four Rx) enable functions that are active high (EN) or
active low (EN). Receivers enable when EN = 1, or when
EN = 0, and they disable only when EN = 0 and EN = 1.
ISL32X75E versions use active high paired enable
11
FN7529.1
March 14, 2013