RS485 Isolator 2 Click Board™

Product Code: MIKROE-3863

How Does The RS485 Isolator 2 Click Board™ Work? The RS485 Isolator 2 Click Board™ is based on ADM2867E from Analog Devices. It includes a flexible integrated dc-to-dc converter optimized for low radiated emissions (EMI). The isolated dc-to-dc converter is constructed of a set of chip scale coplanar coils that are separated by an insulating material. By exciting the upper coil with an ac signal, power is magnetically coupled across the isolation barrier where it is rectified and regulated. Because no direct electrical connection exists between the top and bottom coil, the primary and secondary side of the device remain galvanically isolated. The integrated dc-to-dc converter is optimized to minimize radiated electromagnetic interference (EMI), and allows designers to meet the CISPR22/EN55022 Class B requirements on a 2-layer PCB. The ADM2867E features a proprietary transmitter architecture with a low driver output impedance, resulting in an increased differential output voltage. This architecture is particularly useful when operating the device at lower data rates over long cable runs, where the dc resistance of the transmission line dominates signal attenuation.

In these applications, the increased differential voltage extends the reach of the device to longer cable lengths. The RS485 Isolator 2 features separate digital logic pins, IND and INR, to correct cases where the driver and/or receiver are wired incorrectly. Use the IND pin to correct driver functionality when Y and Z are wired incorrectly. Use the INR pin to correct receiver functionality when A and B are wired incorrectly. When the receiver is inverted, the device maintains a Logic 1 receiver output with a 30 mV noise margin when inputs are shorted together or open circuit. The standard RS-485 receiver input impedance is 12 kΩ (1 unit load), and the standard driver can drive up to 32 unit loads. The ADM2867E transceiver has a 1/6 unit load receiver input impedance (72 kΩ), allowing up to 196 transceivers to be connected in parallel on one communication line. Any combination of these devices and other RS-485 transceivers with a total of 32 unit loads or fewer can be connected to the line. The integrated isoPower isolated dc-to-dc converter requires up to 10 ms to power up to its set point of 3.3 V or 5 V. During this start-up time, it is not recommended to assert the DE driver enable signal. The RS485 Isolator 2 Click Board™ can be supplied and interfaced with both 3.3V and 5V without the need for any external components. The onboard SMD jumper labelled as VCC SEL allows voltage selection for interfacing with both 3.3V and 5V MCUs. SPECIFICATIONS Type RS485,Isolators Applications Heating, ventilation, and air-conditioning (HVAC) networks, Industrial field buses, Building automation, Utility networks On-board modules ADM2867E Power Isolated RS-485 Transceiver from Analog Devices Key Features 5.7 kV rms isolated full duplex RS-485/RS-422 transceiver, Cable invert smart feature, High speed 25 Mbps data rate, Supports 196 bus nodes, Full hot swap support Interface GPIO,UART Compatibility mikroBUS Click Board™ size L (57.15 x 25.4 mm) Input Voltage 3.3V or 5V PINOUT DIAGRAM This table shows how the pinout on RS485 Isolator 2 Click Board™ corresponds to the pinout on the mikroBUS socket (the latter shown in the two middle columns). Notes Pin Pin Notes NC 1 AN PWM 16 INR Receiver Inversion Receiver Enable RE 2 RST INT 15 IND Driver Inversion Driver Enable DE 3 CS RX 14 TX UART Transmit NC 4 SCK TX 13 RX UART Receive NC 5 MISO SCL 12 NC NC 6 MOSI SDA 11 NC Power Supply 3.3V 7 3.3V 5V 10 5V Power supply Ground GND 8 GND GND 9