RS485 Isolator 3 Click Board™

How Does The RS485 Isolator 3 Click Board™ Work?

The RS485 Isolator 3 Click Board™ is based on the ADM2763E, a 5.7kV RMS signal-isolated RS-485 transceiver from Analog Devices. The ADM2763E is optimized for low speed over long cable runs and has a maximum data rate of 500kbps. It is protected against ≥±12 kV contact and ≥±15 kV air IEC 61000-4-2 electrostatic discharge (ESD) events on the RS485 receiver and driver terminal pins, easily accessible via the screw terminal blocks. The ADM2763E has four bus signals: signal A for the noninverting input signal, signal B for the inverting input signal, signal Y for the noninverting output signal, and signal Z for the inverting output signal, alongside a common ground connection.

Using coplanar transformer coils with an ON or OFF keying modulation scheme allows a high data throughput across the isolation barrier of the ADM2763E while minimizing radiation emissions. Architecture like this provides a digital isolator with immunity to common-mode transients >250 kV/μs across the device's full temperature and supply range. The ADM2763E also features a proprietary transmitter architecture with a low driver output impedance that increases the differential output voltage. The high differential output voltage extends the reach of the ADM2763E to longer cable lengths and makes this board suitable for PROFIBUS® nodes when powered with 5V on the isolated side of a supply (isolated-side provides the possibility of a supply voltage in the range from 3V to 5.5V).

Besides commonly used UART TX and RX pins on the mikroBUS™ socket, this board also has receiver and driver enable pins routed to the RE and DE pins of the mikroBUS™ socket. It also features a receiver cable invert pin, routed to the INV pin of the mikroBUS™ socket, to quickly correct the reversed cable connection on the A and B receiver bus pins while maintaining complete receiver fail-safe performance.

In addition, the ADM2763E has a built-in receiver fail-safe for the bus idle condition, accessible through some of the unpopulated onboard jumpers (the R4 and R5 pull-up resistors to the VDD2 isolated-side supply on the ADM2763E pins A and Y, as well as the R14 and R15 pull-down resistors to the GND2 common ground connection on pins B and Z). These resistors can be fitted if the user connects this board to other devices that require external biasing resistors on the bus. The ADM2763E also has a jumper that allows adding a 120Ω load to the RS485 receiver by placing the jumper cap on it.

The RS485 Isolator 3 Click Board™ can operate with either 3.3V or 5V logic voltage levels selected via the VDD1 SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

SPECIFICATIONS

PINOUT DIAGRAM

This table shows how the RS485 Isolator 3 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	DE	Driver Enable
Receiver Enable	RE	2	RST	INT	15	INV	Receiver Cable Invert
NC	3	CS	RX	14	TX	UART TX
NC	4	SCK	TX	13	RX	UART RX
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	GND	Ground

ONBOARD SETTINGS AND INDICATORS

RS485 ISOLATOR 3 CLICK ELECTRICAL SPECIFICATIONS