STMicroelectronics STR485ELVQT

Overview

STR485ELVQT from STMicroelectronics is a half-duplex RS-485 transceiver with dual supply domains (VL = 1.65–3.6 V for logic, VCC = 3.0–3.6 V for bus), 20 Mbps high-speed or 250 kbps low-slew-rate operation selectable via SLR pin, ±16 kV IEC61000-4-2 air discharge ESD protection on bus pins, and thermal shutdown at 165 °C - deployed in industrial automation networks requiring robust multi-drop communication over long cables.

For engineers reviewing the STR485ELVQT datasheet, STR485ELVQT pinout, STR485ELVQT application, or STR485ELVQT equivalent, key selection criteria include dual-voltage domain compatibility (1.8 V/3.3 V I/O), fail-safe receiver behavior under open/short/idle bus conditions, slew-rate programmability, DFN10 package thermal performance, and compliance with RS-485 unit load requirements up to 128 nodes.

Technical Context

The device implements a half-duplex differential driver/receiver compliant with ISO/IEC 8482 (RS-485), featuring independent logic (VL) and bus (VCC) supplies - VL must be ≤ VCC, enabling low-power 1.8 V I/O interfacing while maintaining 3.3 V bus drive strength. The SLR pin selects between two discrete signaling modes: 20 Mbps (tr/tf ≈ 7 ns) for short-haul high-throughput links or 250 kbps (tr/tf ≈ 200 ns) for noise-immune long-distance transmission.

Receiver fail-safe operation guarantees high output when A–B differential voltage is outside ±200 mV (VIT− = −200 mV, VIT+ = −60 mV), covering open-circuit, shorted, and terminated-idle bus states. Thermal shutdown disables driver outputs above 165 °C with 15 °C hysteresis, and internal 48 kΩ input impedance supports ≥128 unit loads at 125 °C per RS-485 standard.

Key Specifications

Pinout & Package

STR485ELVQT uses a thermally enhanced 3 mm × 3 mm DFN10 (VFDFPN) package with exposed thermal pad (A = 0.90 mm height, e = 0.50 mm pitch), optimized for PCB heat dissipation in high-density industrial modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX13487EESA+ and SN65HVD72DR, STR485ELVQT uniquely supports 1.8 V logic interfacing, user-selectable 20 Mbps/250 kbps rates, and guaranteed 128-node bus loading at 125 °C - making it optimal for next-generation industrial edge controllers requiring voltage scalability and EMI resilience.

Availability

STR485ELVQT is available at Aetrix Electronics and suitable for industrial automation, smart metering infrastructure, and building management systems requiring stable component supply across extended temperature and ESD stress conditions.

Supply support for STR485ELVQT 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 silicon solutions for automotive, industrial, and power applications since 1987.

The STR485E series targets ruggedized RS-485 physical layer implementation in harsh environments, emphasizing dual-supply flexibility, fail-safe reliability, and high-temperature node density - directly addressing industrial IoT connectivity challenges.

FAQ

Can STR485ELVQT operate with VL = 1.8 V and VCC = 3.3 V simultaneously?

Yes. The datasheet explicitly specifies VL = 1.65–3.6 V and VCC = 3.0–3.6 V with VCC ≥ VL. At VL = 1.8 V and VCC = 3.3 V, all logic inputs (D, DE, RE, SLR) meet VIH/VIL thresholds, and driver output voltage exceeds 1.5 V into 54 Ω - satisfying RS-485 electrical requirements while minimizing MCU-side power consumption.

What happens if the SLR pin is left unconnected?

SLR floats high internally due to weak pull-up, defaulting to 20 Mbps mode. However, STMicroelectronics recommends explicit connection to GND (for 20 Mbps) or VL (for 250 kbps) to avoid noise-induced transitions. Floating SLR may cause unintended speed changes in high-EMI environments, risking timing violations on long cables.

Does the fail-safe receiver guarantee logic-high output under all fault conditions?

Yes - the receiver outputs high when VA−VB is > −60 mV (VIT+) or < −200 mV (VIT−), covering open-circuit (infinite impedance), shorted (0 V differential), and terminated-idle (≈0 V) bus states. This behavior is verified across −40 °C to +125 °C and eliminates need for external bias resistors in most topologies.

How does thermal shutdown affect bus communication during overload?

When junction temperature reaches 165 °C, thermal shutdown forces driver outputs (A/B) into high-impedance state, halting bus transmission but preserving receiver functionality. Communication resumes automatically after cooldown to 150 °C (15 °C hysteresis), preventing permanent damage during sustained bus contention or short circuits.