SN65HVD21D - Extended Common-Mode RS-485 | Texas Instruments
料号： SN65HVD21D ✓ 量产中SN65HVD21D 概述
An RS-485 transceiver is an interface IC that converts logic-level signals into a balanced differential bus and receives differential bus signals back into logic-level outputs. This class of device belongs to the interface IC hierarchy and ultimately supports the broader semiconductor and industrial communication ecosystem. Balanced signaling improves noise immunity by referencing the signal to differential line pairs rather than a single conductor, while extended common-mode capability helps a node remain functional when bus voltages exceed the common-mode range of a conventional transceiver.
The SN65HVD21 family's verified features include high ESD protection, wide receiver hysteresis, and failsafe operation. High ESD protection is valuable in industrial environments where cables may be connected or disconnected during installation. Wide receiver hysteresis improves decision margin between logic states when a valid differential signal is present. Failsafe operation provides a defined receiver behavior for an inactive or undriven bus, helping system designers avoid ambiguous states in multi-node networks.
The D-package suffix identifies an 8-pin SOIC implementation, while the P option is offered as a plastic through-hole package in the same family. This distinction matters to PCB designers: the SN65HVD21D uses a surface-mount footprint and cannot replace a through-hole SN65HVD21P without board changes. Although the SN65HVD21D and SN65HVD21DR may share the same electrical device and SOIC footprint, the latter is a packaging or orderable variant rather than a distinct engineering alternative.
Typical uses include industrial RS-485 control links, factory automation equipment, remote sensor interfaces, building controls, and instrumentation networks. In a half-duplex arrangement, the transceiver's driver and receiver share the same differential pair, so system firmware and bus hardware must manage transmit and receive intervals without allowing multiple drivers to contend. Termination, biasing, grounding, and common-mode limits remain system-level constraints that cannot be selected from the limited values published in the supplied search results.
Design with the manufacturer datasheet as the controlling authority for supply voltage, driver output current, receiver thresholds, propagation delay, maximum data rate, operating temperature, ESD ratings, and recommended external components. Keep bus-side traces away from sensitive signals, provide a solid ground reference, and verify that every attached node supports the same logic and baud rate. Confirm the exact pinout and exposed-pad requirements for the selected package rather than relying on generic SOIC drawings.
This page consolidates the verified distributor and manufacturer information, distinguishes a true bus-interface alternative from packaging variants, and identifies missing electrical data explicitly. It provides selection and design guidance beyond a distributor listing while preserving the distinction between verified facts and parameters that require datasheet confirmation.
直接替换替代料： SN65HVD21D ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
ISL43485IBZ-T
✅ 直接替换📋 参考替代料（不在目录中）
SN65HVD21D 规格参数
| Product Type | RS-422/RS-485 bus-line transceiver |
| Channel Configuration | 1 transmitter / 1 receiver |
| Duplex Operation | Half duplex |
| Supported Interfaces | RS-422 and RS-485 |
| Common-Mode Capability | Extended common-mode range |
| Receiver Hysteresis | Wide receiver hysteresis |
| Fail-Safe Behavior | Failsafe operation |
| ESD Protection | High ESD protection; rating not stated in supplied data |
| Compliance Reference | TIA/EIA-485-A |
| 封装 | 8-pin SOIC (D package) |
| Package Family | SOIC family, surface mount |
| 安装类型 | Surface mount |
SN65HVD21D soic family, surface mount 引脚配置指南
SN65HVD21D（soic family, surface mount 封装）的引脚配置。 引脚编号、功能和连接图在制造商数据手册中定义。请参阅该手册以了解确切的封装尺寸和焊接指南。
暂无详细引脚数据： SN65HVD21D.
请参阅 数据手册 以查看完整引脚配置。
典型应用
SN65HVD21D 适用于 6 应用s: Industrial Automation Bus Interface, Remote Sensor and Instrumentation Network, Building Controls and HVAC Equipment, Data Acquisition and Test Equipment, Gateways and Serial-to-RS-485 Conversion, Long-Distance Robust Serial Communication.
Industrial Automation Bus Interface
The SN65HVD21D fits industrial automation links that need one half-duplex differential bus channel in an 8-pin SOIC footprint. Its verified extended common-mode operation and high ESD protection are valuable on factory equipment where bus nodes may experience ground offsets or connector-borne ESD events. The device also provides wide receiver hysteresis and failsafe operation, improving the defined state of a valid differential signal and an undriven bus. Engineers should use the driver for outbound data, enable it only during transmission, and follow the manufacturer circuit for termination, fail-safe biasing, and protection. Exact supply voltage, maximum data rate, common-mode limits, and temperature ratings must be confirmed in the TI datasheet before industrial qualification.
Remote Sensor and Instrumentation Network
The SN65HVD21D can connect a controller to remote sensors or instrumentation over a balanced RS-485 pair, providing one receiver and one transmitter in a compact 8-pin SOIC package. Extended common-mode range helps maintain operation when voltage differences develop across a long cable network, while wide receiver hysteresis supports cleaner switching decisions. Failsafe operation gives the receiver a defined condition when the bus is inactive, reducing ambiguity in supervisory software. The design should preserve the recommended differential routing, provide a stable reference ground, and avoid long unprotected stubs. Because the supplied data does not state the maximum data rate or input sensitivity, verify cable length, baud rate, termination topology, and noise margin using the official Texas Instruments datasheet.
Building Controls and HVAC Equipment
The SN65HVD21D is appropriate for building-control modules that exchange commands and status over an RS-485 backbone. Its single half-duplex channel limits bus contention when firmware controls the transmit-enable state, while the 8-pin SOIC package simplifies compact control-board assembly. Extended common-mode operation can improve tolerance to voltage offsets among controllers connected over building wiring, and the verified failsafe behavior supports predictable diagnostics when a remote node stops communicating. Designers should still evaluate isolation, surge protection, grounding, and cable routing for the installation environment. Verify the exact receiver thresholds, logic levels, supply range, and operating temperature from the manufacturer datasheet before deploying the device across floors or between dissimilar building systems.
Data Acquisition and Test Equipment
The SN65HVD21D can serve as the physical-layer interface between a data-acquisition controller and external measurement equipment communicating over RS-485. The integrated receiver and transmitter reduce the number of separate bus components, and wide receiver hysteresis improves transition reliability in systems with imperfect cable termination. Extended common-mode capability is valuable when connected instruments do not share exactly the same ground potential. The transceiver should be paired with disciplined termination and biasing, while test engineers should verify skew, propagation delay, and maximum supported baud rate against the official datasheet. Those timing values are not stated in the supplied results, so they must not be inferred from the broader SN65HVD2x family description.
Gateways and Serial-to-RS-485 Conversion
The SN65HVD21D is suitable for compact serial gateways that expose an RS-485 downstream connection and require a deterministic half-duplex control interface. One driver and one receiver in an 8-pin SOIC package allow a processor or communications controller to connect directly to a balanced bus while firmware manages direction control. The verified failsafe operation and wide receiver hysteresis support robust supervision of idle or noisy links, and high ESD protection is useful around external connectors. Board layout should keep the transceiver close to the connector, use a controlled ground reference, and include protection appropriate to the cable environment. Confirm supply voltage, bus-common-mode limits, logic thresholds, data rate, and thermal performance from the TI manufacturer datasheet before production.
Long-Distance Robust Serial Communication
The SN65HVD21D supports long-distance differential serial communication by combining an RS-485 transmitter and receiver with extended common-mode operation. The balanced bus reduces susceptibility to externally coupled noise, while the verified wide receiver hysteresis improves margin when signal amplitude is reduced or degraded. Failsafe operation makes an undriven line easier for the host controller to diagnose, and the high ESD protection provides a useful margin in physically accessible systems. Actual cable reach depends on baud rate, topology, termination, shielding, and environmental noise, so those variables should be evaluated rather than inferred from the transceiver name. The manufacturer datasheet remains authoritative for data rate, input sensitivity, common-mode range, supply limits, and operating temperature.
工程参考数据： SN65HVD21D ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | ISL43485IBZ-T |
|---|---|---|
| Package | 8-pin SOIC (D package) | 8-pin SOIC |
| Brand | Texas Instruments | Renesas Electronics |
| Supported Interfaces | RS-422 and RS-485 | RS-422 and RS-485 |
关键差异点
- Extended common-mode operation （对比 ISL43485IBZ-T)
- Verified fail-safe and hysteresis features （对比 ISL43485IBZ-T)
- Established family compliance （对比 ISL43485IBZ-T)
设计说明
Place the SN65HVD21D close to the RS-485 connector and route the differential pair as a tightly coupled pair over a continuous reference plane. Keep the driver outputs and receiver inputs free from stubs, test pads, and unrelated high-current paths. The supplied data confirms an 8-pin SOIC package but does not provide the detailed pinout, so verify every connection against the official D-package drawing before routing.
Do not assume SN65HVD21DR is a different electrical transceiver: the cross-reference result describes it as completely interchangeable with the same terminals and package characteristics. It is an orderable packaging variant rather than a distinct drop-in engineering alternative. Conversely, do not assume ISL43485IBZ-T is equivalent merely because both parts use an 8-SOIC package and support a similar data rate; verify supply, thresholds, timing, enable logic, and protection ratings.
Use the manufacturer-recommended termination and fail-safe bias network because the bus impedance, node count, cable length, and topology determine whether ringing or an undefined idle state occurs. Keep protection devices away from the transceiver's sensitive receive path and account for their capacitance and leakage. Extended common-mode capability helps with ground offsets but does not replace proper grounding, shielding, or surge protection.
合规信息
The verified Texas Instruments family material states that the SN65HVD2x devices meet all requirements of the TIA/EIA-485-A standard. RoHS, REACH, lead-free, halogen-free, conflict-minerals, and AEC-Q100 status were not included in the supplied data. AEC-Q100 is marked not_applicable because this is an industrial interface transceiver rather than an automotive-qualified device.
