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Texas Instruments ISO35TDWR
- Part No.:
- ISO35TDWR
- Manufacturer:
- Texas Instruments
- Category:
- Digital Isolators
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
ISO35TDWR.pdf
- Description:
- ISO RS485 W/ TRANSFORMER DRIVER
- Quantity:
- Payment:
- Shipping:
Inventory:3,233
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Product details
Overview
ISO35TDWR from Texas Instruments is an isolated 3.3V RS-485/RS-422 transceiver with integrated transformer driver, providing galvanic isolation up to 4242 VPK and supporting signaling rates up to 1 Mbps. It features fail-safe receiver operation, 1/8 unit load (256-node bus), and 50-kV/µs CMTI for noise immunity in industrial networks.
For engineers reviewing the ISO35TDWR datasheet, ISO35TDWR pinout, ISO35TDWR application, or ISO35TDWR equivalent, this device serves as a full-duplex isolated interface for factory automation, motor control, and building automation systems requiring robust common-mode transient immunity and integrated isolated power delivery.
Technical Context
The ISO35TDWR integrates a dual-channel open-drain transformer driver (D1/D2) operating at 300–550 kHz to energize an external isolation transformer, enabling isolated secondary-side power (VCC2) generation. Its symmetrical isolation barrier meets VDE 0884-17 (4242 VPK) and UL 1577 (2500 VRMS) standards.
It implements full-duplex RS-485/RS-422 communication with independent driver (Y/Z) and receiver (A/B) channels, configurable for half-duplex via pin strapping (pins 11–14 and 12–13). Logic inputs tolerate 5 V, and the receiver includes fail-safe biasing for open/short/idle bus conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Isolation Voltage | 4242 VPK per VDE 0884-17 (60 s); enables safe operation across high common-mode voltage domains in industrial environments. |
| Signaling Rate | Up to 1 Mbps; supports high-speed deterministic communication in motion control and real-time networks. |
| Bus Node Count | 1/8 unit load (≤256 nodes); allows large-scale daisy-chained RS-485 networks without signal degradation. |
| CMTI | 25–50 kV/µs minimum; ensures reliable data integrity in electrically noisy settings like motor drives and HVAC systems. |
| Operating Temperature | –40°C to +85°C ambient; qualified for deployment in uncontrolled industrial enclosures and outdoor building automation nodes. |
| Transformer Driver Frequency | 300–550 kHz typical; provides stable, efficient primary-side excitation for compact external isolation transformers. |
| ESD Protection | ±16 kV HBM (bus-to-GND2), ±6 kV HBM (bus-to-GND1); reduces risk of field failure due to handling or cable discharge events. |
Pinout & Package
ISO35TDWR is housed in a 16-pin SOIC (DW) package measuring 10.30 mm × 7.50 mm, with creepage and clearance ≥8 mm and internal DTI ≥8 µm to meet reinforced insulation requirements.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A | Non-inverting receiver input | Connects to RS-485 bus non-inverting line; used with B for differential reception under fail-safe biasing. |
| B | Inverting receiver input | Connects to RS-485 bus inverting line; forms differential pair with A for noise-rejecting data recovery. |
| D | Driver input | Logic-level data input controlling Y/Z outputs; accepts 3.3V CMOS levels with 5-V tolerance. |
| DE | Driver enable input | Active-high control for Y/Z driver output; enables half-duplex operation when tied to RE. |
| RE | Receiver enable input | Active-low control for R output; complements DE logic for direction control in half-duplex mode. |
| R | Receiver output | CMOS-compatible logic output reflecting bus state on A/B; high-impedance when RE = high. |
| VCC1 | Logic-side supply | 3.3V ±10% input powering digital interface and transformer driver circuitry. |
| VCC2 | Bus-side supply | 3.3V ±10% input powering isolated transceiver stage; derived externally or via transformer secondary. |
| GND1 | Logic-side ground | Reference for VCC1 and all logic pins (D, DE, RE, R); galvanically separated from GND2. |
| GND2 | Bus-side ground | Reference for VCC2 and bus pins (A, B, Y, Z); internally connected between pins 9 and 15. |
| Y | Non-inverting driver output | Drives RS-485 bus non-inverting line; differential output with Z defines bus polarity. |
| Z | Inverting driver output | Drives RS-485 bus inverting line; complements Y for balanced differential signaling. |
| D1, D2 | Transformer driver outputs | Open-drain outputs generating square-wave excitation for external isolation transformer primary. |
| NC | No connect | Pin 10 is unconnected internally; must be left floating or tied to GND1 per layout guidelines. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated transformer driver | Eliminates need for external oscillator or gate driver IC, reducing BOM count and PCB area in isolated power architectures. |
| Fail-safe receiver | Guarantees known logic state (R = high) during bus open, short, or idle - prevents spurious UART framing errors. |
| 5-V tolerant logic inputs | Allows direct interfacing with legacy 5V microcontrollers or FPGAs without level-shifting components. |
| Low bus capacitance (16 pF) | Minimizes signal distortion and timing skew on long cables, preserving signal integrity at 1 Mbps over 1200 m. |
| Thermal shutdown protection | Prevents permanent damage during sustained short-circuit or overload conditions on Y/Z outputs. |
| High ESD robustness | ±16 kV HBM on bus pins relative to GND2 enables reliable operation in electrostatic-prone factory floors. |
Applications
| Factory Automation | Motor/Motion Control |
|---|---|
Use Scenario: PLC-to-I/O module communication over extended RS-485 daisy chains in metal-rich plant environments. IC Role / Device Role / Timing Role: Isolated transceiver bridging controller logic domain and noisy fieldbus domain while delivering isolated power to remote nodes. Use Value: Breaks ground loops to suppress >10 kV common-mode transients induced by variable-frequency drives, preventing communication dropouts. |
Use Scenario: Real-time position feedback and command transmission between servo drive and motion controller. IC Role / Device Role / Timing Role: Full-duplex isolated interface ensuring sub-microsecond propagation delay symmetry (<1.5 ns pulse skew) for synchronized axis control. Use Value: Maintains deterministic latency (tPHL/tPLH ≤340 ns) and 50 kV/µs CMTI to avoid jitter-induced positioning errors in closed-loop systems. |
| HVAC and Building Automation | Networked Security Stations |
Use Scenario: Interconnecting thermostats, dampers, and controllers across multi-floor commercial buildings using shared RS-485 trunk lines. IC Role / Device Role / Timing Role: 1/8-unit-load transceiver enabling 256-node scalability with fail-safe receiver preventing false alarms during bus disconnection. Use Value: Supports long-distance (≥1000 m) communication at 100 kbps with low bus capacitance (16 pF), minimizing repeater count and installation cost. |
Use Scenario: Secure alarm panel interconnection with door sensors, cameras, and access controllers over outdoor-rated cabling. IC Role / Device Role / Timing Role: Galvanically isolated RS-485 node protecting central panel from lightning-induced surges on perimeter wiring. Use Value: 4242 VPK isolation rating and 16-kV HBM bus-pin ESD withstand capability prevent field failures during thunderstorms or ESD events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated RS-485 transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ISO3082DWR | Half-duplex only; no integrated transformer driver; lower CMTI (25 kV/µs min); 500-kbps max rate. | Suitable for cost-sensitive, lower-speed point-to-point links where external isolated power is already available. | Select ISO3082DWR only if full-duplex operation and transformer driver integration are unnecessary. |
| ADM2483BRWZ | Integrated isolated DC-DC converter (no external transformer required); 500-kbps max rate; 2.5 kV RMS isolation. | Better for space-constrained designs needing self-contained isolation, but lacks 1-Mbps capability and VDE 0884-17 certification. | Choose ADM2483BRWZ when board area is critical and 1-Mbps performance is not required. |
Compared with ISO35TDWR, ISO3082DWR omits full-duplex and transformer driver functionality, limiting system flexibility, while ADM2483BRWZ trades off speed and regulatory compliance for integrated power conversion - making ISO35TDWR optimal for high-speed, standards-compliant industrial networks requiring external transformer-based isolation.
Availability
ISO35TDWR is available at Aetrix Electronics and suitable for factory automation, motor/motion control, and HVAC and building automation networks requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for ISO35TDWR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies for industrial, automotive, and communications markets.
The ISO35T product line delivers isolated RS-485/RS-422 interfaces with integrated transformer drivers, designed specifically for industrial networks demanding high noise immunity, regulatory-certified isolation, and scalable multi-node communication.
FAQ
What is the maximum signaling rate supported by the ISO35TDWR?
The ISO35TDWR supports signaling rates up to 1 Mbps under recommended operating conditions. This performance is validated across the full temperature range (–40°C to +85°C) with proper termination and cable length matching, making it suitable for time-critical industrial protocols such as Modbus RTU at high baud rates. The ISO35TDWR achieves this with low propagation delay skew (<1.5 ns) and fast rise/fall times (120–180 ns).
Does the ISO35TDWR require an external transformer, and what are its driver specifications?
Yes, the ISO35TDWR requires an external isolation transformer driven by its integrated D1/D2 open-drain outputs. These outputs operate at 300–550 kHz with <2.5 Ω on-resistance and 70/80 ns rise/fall times, supporting efficient energy transfer to the transformer primary. The ISO35TDWR does not include an integrated DC-DC converter - transformer selection must match the oscillator frequency and load requirements specified in TI's SLUU470 application note.
How does the fail-safe receiver in the ISO35TDWR function, and what conditions does it cover?
The ISO35TDWR's fail-safe receiver guarantees a logic-high output (R = high) when the A–B differential voltage falls outside the valid range (±200 mV), including bus open, shorted, or idle states. This behavior prevents undefined UART framing and avoids false interrupts in host microcontrollers. The ISO35TDWR implements internal biasing to achieve this without external resistors, simplifying design and improving reliability in disconnected or faulted network segments.
What safety certifications apply to the ISO35TDWR, and what do they cover?
The ISO35TDWR is certified to DIN EN IEC 60747-17 (VDE 0884-17) for 4242 VPK transient isolation voltage, UL 1577 for 2500 VRMS withstand voltage (1 minute), and CSA Component Acceptance Notice 5A per IEC 60950-1 and IEC 61010-1. These certifications validate its suitability for basic insulation in industrial equipment with working voltages up to 600 VRMS, and confirm compliance with international safety standards for end-equipment approval.
Can the ISO35TDWR be configured for half-duplex operation, and how is this achieved?
Yes, the ISO35TDWR can be configured for half-duplex RS-485 operation by connecting pin 11 (Y) to pin 14 (DE) and pin 12 (Z) to pin 13 (RE). This configuration synchronizes driver enable and receiver enable, allowing bidirectional single-wire communication on a two-wire bus. The ISO35TDWR retains full electrical performance in this mode, including 1/8 unit load and fail-safe receiver functionality, with no change to isolation or timing specifications.
ISO35TDWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Technology:
- Capacitive Coupling
- Type:
- RS422, RS485
- Isolated Power:
- No
- Number of Channels:
- 3
- Inputs - Side 1/Side 2:
- 2/1
- Channel Type:
- Unidirectional
- Voltage - Isolation:
- 2500Vrms
- Common Mode Transient Immunity (Min):
- 25kV/µs
- Data Rate:
- 1Mbps
- Propagation Delay tpLH / tpHL (Max):
- -
- Pulse Width Distortion (Max):
- -
- Rise / Fall Time (Typ):
- -
- Voltage - Supply:
- 3V ~ 3.6V
- Grade:
- -
- Qualification:
- -
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
ISO35TDWR FAQ
1.How can I place an order for ISO35TDWR through Aetrix?
Please submit a Request for Quotation (RFQ) for ISO35TDWR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for ISO35TDWR reliable?
The price and inventory of ISO35TDWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ISO35TDWR is usually 5 days.
3.What payment methods are accepted for ISO35TDWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ISO35TDWR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ISO35TDWR?
ISO35TDWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ISO35TDWR order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for ISO35TDWR?
For technical support, including ISO35TDWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ISO35TDWR requirements.
6.How does Aetrix verify that ISO35TDWR is sourced from the original manufacturer or authorized distributors?
All ISO35TDWR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that ISO35TDWR meets industry standards.
7.What is the process for return or replacement of ISO35TDWR?
All ISO35TDWR units undergo pre-shipment inspection (PSI). If there is an issue with ISO35TDWR, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The ISO35TDWR part is unused and in its original packaging.
Return procedure for ISO35TDWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
ISO35TDWR Tags
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