STMicroelectronics ST490ABN

Overview

ST490ABN from STMicroelectronics is a low-power, high-speed RS-485/RS-422 transceiver in full-duplex configuration with one driver and one receiver. It operates from a single 5 V supply, draws ≤5 mA supply current, supports up to 25 Mbps data rate, and features ±4 kV ESD protection and fail-safe receiver logic for open-circuit inputs - deployed in industrial serial backbones and point-to-point fieldbus links.

For engineers reviewing the ST490ABN datasheet, ST490ABN pinout, ST490ABN application, or ST490ABN equivalent, key selection criteria include common-mode range (–7 V to +12 V), input hysteresis (70 mV typ.), thermal shutdown behavior, driver short-circuit current limits (±35 to ±250 mA), and receiver input resistance (12–24 kΩ).

Technical Context

The ST490ABN implements differential line driving and receiving using complementary TTL/CMOS-compatible logic interfaces. Its driver incorporates current limiting and thermal shutdown that forces outputs into high-impedance state during overload, while the receiver includes internal fail-safe biasing ensuring logic-high output when A and B inputs are floating or shorted.

It meets RS-485 and RS-422 electrical standards with guaranteed differential output voltage ≥1.5 V (RL = 54 Ω), common-mode input range spanning –7 V to +12 V, and 70 mV typical input hysteresis to reject noise near switching thresholds - enabling robust operation in electrically noisy factory-floor environments.

Key Specifications

Pinout & Package

DIP-8 package: 0.3-inch wide dual in-line plastic package with through-hole mounting; RoHS-compliant ECOPACK® construction.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RS-485/RS-422 transceiver applications.

Compared with MAX485CPA+ and SN65HVD72DR, the ST490ABN uniquely balances 25 Mbps speed, 5 V single-supply operation, thermal fault protection, and industrial-grade common-mode tolerance - making it optimal for cost-sensitive, medium-speed, self-protected fieldbus nodes.

Availability

ST490ABN is available at Aetrix Electronics and suitable for industrial PLC backplanes, motor drive feedback links, and building automation gateways requiring stable component supply and long-term manufacturing continuity.

Supply support for ST490ABN 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The ST490ABN belongs to ST's legacy RS-485/RS-422 transceiver portfolio, engineered specifically for robust, low-power, full-duplex serial communication in harsh industrial environments where reliability and electromagnetic resilience are critical.

FAQ

What is the maximum cable length supported by ST490ABN at 25 Mbps?

At 25 Mbps, ST490ABN supports ≤10 m of properly terminated twisted-pair cable per the RS-422 standard. Longer distances require reducing data rate - e.g., 1200 m is achievable at 100 kbps. Signal integrity depends on characteristic impedance matching (100–120 Ω), termination resistors, and noise environment.

Does ST490ABN support automatic direction control like some half-duplex RS-485 transceivers?

No, ST490ABN is a full-duplex transceiver with separate DI (driver input) and RO (receiver output) pins and does not integrate direction control logic. It requires external GPIO or hardware handshaking to manage transmit/receive timing in half-duplex configurations.

Can ST490ABN be used with 3.3 V microcontrollers without level shifting?

Yes - its DI input accepts 3.3 V logic levels (VIH = 2.0 V min, VIL = 0.8 V max), and RO output drives 3.3 V–compatible loads (VOH ≥ 3.5 V at –8 mA). However, VCC must remain at 5 V; the device has no 3.3 V supply option.

How does the fail-safe feature behave when both A and B inputs are shorted together?

When A and B are shorted, the differential input voltage is 0 V, falling within the receiver's indeterminate region (–0.2 V to +0.2 V). The internal fail-safe biasing still forces RO high, preventing bus-induced false start bits - confirmed in Table 4 of the datasheet under "OPEN" and "between –0.2 V to 0.2 V" conditions.