USERS MANUAL ISL32704EVAL1Z UG104 Rev 0.00 Evaluation Board User Guide January 3, 2017 Description Key Features The ISL32704EVAL1Z board enables the evaluation of the Industrys smallest isolated RS-485 transceiver ISL32704E isolated, half-duplex RS-485 transceiver in a Drive capability of up to 32 x 1UL-transceivers typical bus node application, used in isolated industrial Isolated 3.3V to 5V DC/DC converter with regulated output networks. 2 Small total device footprint of 183mm Specifications Related Literature This board has been configured and optimized for the following For a full list of related documents, visit our website operating conditions: - ISL32704E product page Up to 4Mbps data rate V = 3.3V CC Ordering Information PART NUMBER DESCRIPTION ISL32704EVAL1Z ISL32704E evaluation board J1 5V ISOLATED 3.3V DC-DC SUPPLY CONVERTER J2 J5 ISL32704EIAZ LOGIC ISOLATED RS-485 I/O 3 RS-485 I/O TRANSCEIVER FIGURE 1. BLOCK DIAGRAM UG104 Rev 0.00 Page 1 of 8 January 3, 2017ISL32704EVAL1Z Functional Description Truth Table The ISL32704EIAZ is an isolated, 4Mbps, half-duplex RS-485 RECEIVING transceiver. The device incorporates a patented refresh circuit to INPUTS OUTPUT maintain the correct output state with respect to data input. At power-up, the bus outputs follow the truth tables on the right. RE DE A-B R The DE input should be held low during power-up to prevent false 00 0.2V 1 drive data pulses on the bus. This is accomplished by connecting 00 -0.2V 0 DE via a 10k pull-down resistor to GND1. 0 0 Inputs Open/Shorted 1 This transceiver utilizes a differential input receiver for maximum noise immunity and common-mode rejection. Input sensitivity is 11 X High-Z 200mV, as required by the RS-485 specification. 10 X High-Z The receiver input resistance meets the RS-485 Unit Load (UL) requirement of 12k minimum. The receiver includes a fail-safe Truth Table if open function that ensures a high-level receiver output if the receiver inputs are unconnected (floating). The receiver output is TRANSMITTING tri-statable via the active low RE input. INPUTS OUTPUTS The RS-485 driver is a differential output device that delivers at RE DE D ISODE B A least 1.5V across a 54 purely differential load. The driver features low propagation delay skew to maximize bit width and X 1 110 1 to minimize EMI. X 1 011 0 The driver in the ISL32704E is tri-statable via the active high DE 0 0 X 0 High-Z High-Z input. The outputs of the ISL32704E driver are not slew rate 1 0 X 0 High-Z High-Z limited, so faster output transition times allow data rates of at least 4Mbps. PCB Layout Guidelines Important Notice: Both supplies, V and V , must be bypassed with 100nF DD1 DD2 For convenience, an isolated DC/DC converter is used to provide ceramic capacitors. These should be placed as close as possible the power supply across the isolation barrier. Its isolation ratings to the supply pins for proper operation. 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). UG104 Rev 0.00 Page 2 of 8 January 3, 2017