Texas Instruments ISO35TDWR

The ISO35TDWR is an isolated 3.3V RS-485 transceiver produced by Texas Instruments. This device is designed for full-duplex differential line communication and is particularly suited for applications requiring high isolation and robustness against electrical noise and transients. The ISO35TDWR features integrated oscillator outputs and a transformer driver, enabling the generation of isolated power for the secondary side when only a single primary-side power supply is available. It operates over a wide temperature range from -40°C to 85°C, making it versatile for various industrial and automotive environments.

• Designed for RS-485 and RS-422 applications with signaling rates up to 1 Mbps.
• Full-duplex differential line transceiver with integrated oscillator outputs and transformer driver.
• Galvanic isolation up to 4242 V PK per VDE and 2500 V RMS per UL, providing robust protection against electrical noise and transients.
• Active-high driver enable and active-low receiver enable for controlling data flow.
• Internal pullup and pulldown resistors for driver and receiver enable pins.
• Thermal shutdown and output current-limiting features for short-circuit fault protection.
• Supports up to 256 nodes on a bus due to 1/8 unit load.
• Failsafe receiver output when the transceiver is disconnected from the bus or the bus is not actively driven.

• Industrial automation and control systems requiring reliable and isolated communication.
• Automotive systems where high isolation and robustness against electrical noise are critical.
• Long-distance networking and data transmission in harsh environments.
• Medical devices and equipment that require high isolation for safety and reliability.
• Any application needing full-duplex RS-485 communication with high isolation and protection against transients.

1. What is the primary application of the ISO35TDWR?

   The ISO35TDWR is primarily used for RS-485 and RS-422 applications, particularly in environments requiring high isolation and robustness against electrical noise and transients.

2. What is the maximum signaling rate supported by the ISO35TDWR?

   The ISO35TDWR supports signaling rates up to 1 Mbps.

3. What level of galvanic isolation does the ISO35TDWR provide?

   The ISO35TDWR provides galvanic isolation up to 4242 V PK per VDE and 2500 V RMS per UL.

4. What are the operating temperature ranges for the ISO35TDWR?

   The device operates over a temperature range from -40°C to 85°C.

5. Does the ISO35TDWR have built-in protection features?

   Yes, the ISO35TDWR includes thermal shutdown and output current-limiting features to protect against short-circuit faults.

6. How many nodes can be supported on a bus using the ISO35TDWR?

   The device supports up to 256 nodes on a bus due to its 1/8 unit load.

7. What type of package is the ISO35TDWR available in?

   The ISO35TDWR is available in a SOIC-16 package.

8. What is the recommended layout for PCB design to minimize EMI?

   A minimum of four layers is recommended, with the high-speed signal layer, ground plane, power plane, and low-frequency signal layer stacked in that order. High-frequency layout techniques and the use of bypass capacitors are also advised.

9. How should the enable pins be managed to avoid noise currents?

   The enable pins should be managed using 1-kΩ to 10-kΩ pullup and pulldown resistors to limit noise currents during transient events.

10. What additional protection components are recommended for high transient voltages?

    For higher transients, metal-oxide varistors (MOVs) and transient blocking units (TBUs) are recommended to reduce and limit transient currents.