Summary of ISOLATED FULL-DUPLEX RS-485 TRANSCEIVERS
This article describes an isolated full-duplex differential line driver and receiver module for TIA/EIA RS485/RS422 applications. It features a 2500Vrms isolation barrier, operates on a single 3.3V supply, and uses an SN6505 chip with a Wurth transformer to generate 5V DC for the isolated side. The design incorporates an ISO35 IC as the transceiver and an LM1117-5V regulator. This module protects against electrical noise in industrial settings like factory automation and HVAC networks by breaking ground loops.
Parts used in the Isolated Full-Duplex RS485 Module:
- ISO35 IC
- SN6505 Chip
- Wurth Elektronik 760390015 Transformer
- LM1117-5V IC
- CN2 6 Pin Header Connector
- CN3 Connector
- CN1 Connector
This module is an isolated full-duplex differential line driver and receiver for TIA/EIA RS485/RS422 applications. The module is ideal for long transmission lines because the ground loop is broken to allow for a much larger common-mode voltage range. The symmetrical barrier of the device is tested to provide isolation of 2500Vrms between bus line Trans-receiver and the logic-level interface. The circuit works with a single supply 3.3V input. SN6505 Chip and Wurth Elekronics 760390015 transformer help to generate 5V DC to power up isolated circuitry. Module has been designed using ISO35 IC which is an isolated full-duplex RS485 trans-receiver, SN6505 IC used to form isolated DC-DC converter to power up the bus side of isolated circuitry of ISO35, LM1117-5V IC regulates the output of DC-DC converter and provides 5V DC. CN2 6 Pin header connector provided to power up the board and micro-controller interface, CN3 for Full-Duplex communication. CN1 is for AUX power 5V DC.
Any cables I/O can be subjected to electrical noise transients that can cause damage to the transceiver and/or nearby sensitive circuitry if they are of sufficient magnitude and duration. This module can significantly increase protection and reduce the risk of damage to an expensive control circuit. The device can be used for applications like security systems, chemical production, factory automation, motor control circuit, networked security stations, HVAC and building automation networks.
When the driver enable pin, DE, is logic high, the differential outputs Y and Z follow the logic states at data input D. A logic high at D causes Y to turn high and Z to turn low. In this case, the differential output voltage defined as VOD = V(Y) – V (Z) is positive. When D is low, the output states reverse, Z turns high, Y becomes low, and VOD is negative. When DE is low, both outputs turn high-impedance. In this condition the logic state at D is irrelevant. The DE pin has an internal pull-down resistor to ground, thus when left open the driver is disabled (high impedance) by default. The D pin has an internal pull up resistor to VCC, thus, when left open while the driver is enabled, output Y turns high and Z turns low.
Read more: ISOLATED FULL-DUPLEX RS-485 TRANSCEIVERS
- What is the primary function of this module?
It is an isolated full-duplex differential line driver and receiver for TIA/EIA RS485/RS422 applications. - How much isolation voltage does the device provide?
The symmetrical barrier provides an isolation of 2500Vrms between the bus line Trans-receiver and the logic-level interface. - What components are used to generate 5V DC for the isolated circuitry?
An SN6505 Chip and a Wurth Elektronik 760390015 transformer help generate 5V DC to power up the isolated circuitry. - Which IC regulates the output of the DC-DC converter?
The LM1117-5V IC regulates the output of the DC-DC converter and provides 5V DC. - What happens when the driver enable pin DE is logic high?
When DE is logic high, the differential outputs Y and Z follow the logic states at data input D. - How is the driver disabled by default?
The DE pin has an internal pull-down resistor to ground, so when left open the driver is disabled. - What is the effect of leaving the D pin open while the driver is enabled?
Since the D pin has an internal pull-up resistor to VCC, leaving it open causes output Y to turn high and Z to turn low. - Can this module be used in motor control circuits?
Yes, the device can be used for applications like motor control circuit among others.
