Intersil ISL32740EVAL1Z User Manual
User’s Manual
ISL32740EVAL1Z
User’s Manual: Evaluation Board
Industrial Precision
Rev 1.00 Aug 2017
USER’S MANUAL
LOGIC
I/O
RS-485
I/O
3.3V
SUPPLY
J5J2
J1
ISL32740EIBZ
ISOLA TED
RS-485
TRANSCEIVER
ISOLA TED
DC-DC
CONVERTER
5V
3
ISL32740EVAL1Z
Evaluation Board
Aug 24, 2017
1. Overview
The ISL32740EVAL1Z board enables the evaluation of the ISL32740EIBZ isolated, half-duplex RS-485 transceiver in
a typical bus node application, used in isolated industrial networks.
1.1 Features
• Drive capability of up to 160x1/5UL-transceivers
• Isolated 3.3V to 5V DC/DC converter with regulated output
1.2 Specifications
This board has been configured and optimized for the following operating conditions:
• Up to 40Mbps data rate
•V
= 3.3V
CC
1.3 Related Literature
• For a full list of related documents, visit our website
• ISL32740E
product page
UG119
Rev.1.00
1.4 Ordering information
Part Number Description
ISL32740EVAL1Z ISL32740EIBZ evaluation board
1.5 Block Diagram
UG119 Rev.1.00 Page 2 of 10
Aug 24, 2017
Figure 1. Block Diagram
ISL32740EVAL1Z 2. Functional Description
2. Functional Description
The ISL32740EIBZ is an isolated, 40Mbps, half-duplex RS-485 transceiver. The device incorporates a patented
refresh circuit to maintain the correct output state with respect to data input. At power-up, the bus outputs follow the
truth tables shown in Tables 1
The DE input should be held low during power-up to prevent false drive data pulses on the bus. This is accomplished by
connecting DE using a 10kΩ pull-down resistor to GND1.
This transceiver uses a differential input receiver for maximum noise immunity and common-mode rejection. Input
sensitivity is ±200mV, as required by the RS-485 specification.
The receiver input resistance is 54kΩ minimum. The receiver includes a “fail-safe if open” function that ensures a
high-level receiver output if the receiver inputs are unconnected (floating). The receiver output is tri-statable through
the active low RE
input.
The RS-485 driver is a differential output device that delivers at least 2.1V across a 54Ω purely differential load. The
driver features low propagation delay skew to maximize bit width and to minimize EMI.
The driver in the ISL32740E is tri-statable through the active high DE input. The outputs of the ISL32740E driver are
not slew rate limited, so faster output transition times allow data rates of at least 40Mbps.
Important Notice:
For convenience, an isolated DC/DC converter is used to provide the power supply across the isolation barrier. Its
isolation ratings however, are lower than those of the transceiver. Therefore, it must be ensured that the ground
potential difference between the left side (GND1, GND2) and the right side (GND3, GND4) of the board remain below
50VAC (see Figure 2.1 on page 4
and 2.
).
2.1 Truth Tables
RE
00 V
0 0 -0.05V > V
00 V
0 0 Inputs Open/Shorted 1
1 1 X High-Z
10 X High-Z*
RE
X11101
X10110
0 0 X 0 High-Z High-Z
1 0 X 0 High-Z* High-Z*
Note: *Transceiver shutdown mode.
Table 1. Truth Table - Receiving
Receiving
Inputs Output
DE A-B RO
≥ -0.05V 1
AB
> -0.2V Undetermined
AB
≤ -0.2V 0
AB
Table 2. Truth Table - Transmitting
Transmitting
Inputs Outputs
DE D ISODE B A
UG119 Rev.1.00 Page 3 of 10
Aug 24, 2017
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