Texas Instruments DS89C21TMX

Overview

DS89C21TMX from Texas Instruments is a differential CMOS line driver and receiver pair compliant with TIA/EIA-422-A (RS-422) and CCITT V.11 standards, operating at up to 20 Mbps with 2.2 ns driver transition time, 2.0 ns max driver skew, and −40°C to +85°C temperature range in an 8-pin SOIC package for industrial serial communication interfaces.

For engineers reviewing the DS89C21TMX datasheet, DS89C21TMX pinout, DS89C21TMX application, or DS89C21TMX equivalent, this device supports high-speed point-to-point differential signaling in noise-prone environments, requires no external biasing for failsafe open-input receiver operation, and delivers low-power performance at 6 mA typical supply current under load.

Technical Context

The DS89C21TMX integrates one RS-422-compliant driver and one receiver in a single SOIC-8 package, with TTL/CMOS-compatible inputs (DI, RO) and differential outputs (DO, DO*, RI, RI*). Its driver delivers 2.0–3.0 V differential output voltage into 100 Ω, while the receiver features 200 mV minimum detectable differential input threshold and built-in hysteresis of 20–50 mV for noise immunity.

It operates from a single 4.5 V to 5.5 V supply, supports open-circuit receiver input failsafe (RO = HIGH), and guarantees AC timing with ≤10 ns propagation delay (driver), ≤30 ns (receiver), and ≤4.0 ns receiver skew - all specified across the full −40°C to +85°C industrial temperature range.

Key Specifications

Pinout & Package

DS89C21TMX is housed in an 8-pin SOIC package (Package Drawing D, JEDEC MS-012), with 1.27 mm pitch, 3.9 mm body width, and RoHS-compliant matte tin (CuSn) lead finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar differential line driver/receiver applications.

Compared with MAX3041ESA+ and SN65LBC179DR, DS89C21TMX uniquely combines 20 Mbps operation, failsafe open-input, and 6 mA ultra-low ICC in a minimal SOIC-8 footprint - making it optimal for high-speed, low-power, point-to-point industrial serial links where simplicity and robustness are prioritized.

Availability

DS89C21TMX is available at Aetrix Electronics and suitable for industrial PLC serial interfaces, test equipment digital I/O, point-to-point data acquisition, and metering communication interfaces requiring stable component supply and long-term design continuity.

Supply support for DS89C21TMX 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 company headquartered in Dallas, Texas, delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and consumer markets.

The DS89C21TMX belongs to TI's legacy RS-422 line driver/receiver portfolio, engineered specifically for noise-immune, low-power, high-speed point-to-point serial communication in industrial control and instrumentation systems.

FAQ

What is the maximum data rate supported by the DS89C21TMX?

The DS89C21TMX supports a maximum data rate of 20 Mbps, as guaranteed by its AC electrical specifications including propagation delay (≤10 ns driver, ≤30 ns receiver) and transition time (2.2 ns driver LOW-to-HIGH). This performance is validated across the full −40°C to +85°C operating temperature range and with 100 Ω differential load, making DS89C21TMX suitable for high-speed industrial serial links where timing margin is critical.

Does the DS89C21TMX require external biasing for receiver input termination?

No, the DS89C21TMX does not require external biasing for receiver input termination because it features a built-in failsafe function: when both RI and RI* inputs are left open (unterminated), the receiver output RO defaults to a logic HIGH state. This eliminates the need for external pull-up/down resistors and improves system reliability during cable disconnect or bus idle conditions - a key advantage confirmed in the DS89C21TMX truth table and Electrical Characteristics section.

What supply voltage range is valid for DS89C21TMX operation?

The DS89C21TMX operates over a supply voltage range of 4.5 V to 5.5 V, as specified in the Recommended Operating Conditions table. Operation outside this range - including below 4.5 V or above 5.5 V - risks violating absolute maximum ratings (e.g., VCC ≤7 V) and may cause undefined behavior, increased ICC, or permanent damage. The DS89C21TMX is not rated for 3.3 V operation, and interfacing with 3.3 V logic requires level-shifting circuitry.

How does the DS89C21TMX handle noise on differential inputs?

The DS89C21TMX handles noise on differential inputs through two integrated mechanisms: a 20–50 mV receiver hysteresis band that prevents chatter during slow or noisy transitions, and a ±14 V common-mode input voltage tolerance that rejects ground potential differences and coupled EMI. These features - explicitly documented in the DS89C21TMX Electrical Characteristics table - ensure stable RO output even in electrically hostile environments such as factory floors or utility substations.

Is the DS89C21TMX pin-compatible with other TI RS-422 transceivers like the DS8921?

No, the DS89C21TMX is not pin-compatible with DS8921 or other members of TI's DS89xx family. While DS8921 shares functional similarity, its pinout differs - notably assigning VCC to Pin 8 and GND to Pin 1, whereas DS89C21TMX places GND at Pin 2 and VCC at Pin 8. This inversion invalidates direct PCB replacement. Always verify pin mapping using the official DS89C21TMX connection diagram (Package D) before board-level integration.