ISO1176TDWR

The ISO1176TDWR is a galvanically isolated RS-485/RS-422 transceiver with integrated transformer driver from Texas Instruments. Designed for high-speed industrial communication applications, this device provides both signal isolation and integrated power isolation, simplifying the design of isolated RS-485 and Profibus interfaces. The ISO1176T combines a high-speed differential line transceiver with a capacitive isolation barrier and an integrated DC-DC oscillator/transformer driver. When paired with an external transformer, the device generates its own isolated secondary supply, eliminating the need for a separate isolated power module. Supporting data rates up to 40 Mbps, the transceiver is well-suited for Profibus DP and other high-speed industrial fieldbus protocols. The device features basic isolation with 2500 Vrms withstand voltage (UL 1577, 1 minute) and 4242 Vpk transient isolation voltage (VDE V 0884-10, 60 seconds). Common-mode transient immunity (CMTI) is guaranteed at a minimum of 25 kV/µs, with a typical value of 50 kV/µs, ensuring robust operation in electrically noisy industrial environments. The receiver includes a failsafe feature that outputs a logic high when the bus is open, shorted, or idle. With a 1/8 unit load input impedance, up to 256 transceivers can be connected to a single bus segment. The ISO1176TDWR is supplied in a 16-pin wide-body SOIC (DW) package that provides sufficient creepage and clearance distances for safety isolation requirements.

The ISO1176TDWR operates as a fully integrated isolated RS-485 transceiver with built-in power isolation. Its functional architecture includes: 1) Primary-Side Circuitry: The primary side (low-voltage side) interfaces with the host microcontroller via UART-style signals (DI – data in, RO – receiver output, DE – driver enable, RE# – receiver enable). This side also contains the integrated oscillator and MOSFET driver for the external isolation transformer. The device operates from a single 3.3V supply on the primary side. 2) Capacitive Isolation Barrier: High-voltage silicon dioxide capacitors form the isolation barrier, transmitting digital data and control signals across the galvanic boundary while blocking high voltages and common-mode noise. This capacitive isolation technology provides high CMTI (common-mode transient immunity) and long-term reliability. 3) Secondary-Side RS-485 Transceiver: The isolated secondary side contains a full-featured RS-485 transceiver with differential A and B bus pins. The driver and receiver are independently controlled through the isolated DE and RE# signals. The receiver features a failsafe input stage that ensures a high output level when the bus is open-circuited, short-circuited, or idle with all drivers disabled. 4) Integrated Power Isolation: A DC-DC controller on the primary side drives an external center-tapped transformer primary winding. The transformer secondary provides the isolated supply for the secondary-side circuitry. This integrated approach significantly reduces system cost and board space compared to using a separate digital isolator and isolated power module.

• Profibus DP and RS-485 industrial fieldbus networks
• Industrial PLC communication interfaces and I/O modules
• Building automation systems (HVAC, lighting, security)
• Smart grid and substation automation communication
• Motor drive, VFD, and servo control communication ports
• Isolated sensor networks and data acquisition
• Telecommunications and networking equipment requiring isolation