STMicroelectronics ISO808QTR

Overview

ISO808QTR from STMicroelectronics is a galvanically isolated octal high-side power solid-state relay designed for driving high-inductive loads in industrial control systems. It features 8 independent channels, VCC operating range of 9.2–36 V, R_DS(on) = 0.125 Ω (typ), per-channel over-temperature protection with thermal independence, and TFQFPN32 package with 75 V isolation rating. Used in PLC I/O modules to switch solenoids and contactors.

For engineers reviewing the ISO808QTR datasheet, ISO808QTR pinout, ISO808QTR application, or ISO808QTR equivalent, key selection considerations include channel-wise thermal independence, synchronous control mode jitter reduction (6 µs typ), fault reporting via open-drain FAULT pin, and compliance with IEC 61000-4-2/4/5/8, UL1577, and IEC 60747-17 safety standards.

Technical Context

The ISO808QTR integrates two galvanically isolated voltage domains: VDD/GNDDD (logic side, 2.75–5.5 V) and VCC/GNDCC (process side, 9.2–36 V), enabling robust noise immunity in harsh industrial environments. Its dual-chip architecture supports watchdog-protected communication between logic and process stages, with refresh frequency of 15 kHz and watchdog timeout of 272–400 µs.

It supports two operational modes: Direct Control Mode (DCM), where INx directly drives OUTx when SYNC/LOAD are tied low; and Synchronous Control Mode (SCM), where independent LOAD/SYNC sequencing enables simultaneous multi-device output updates with ≤6 µs channel jitter. FAULT pin reports OR-wired junction over-temperature (TJSD = 150–200 °C) and internal communication errors.

Key Specifications

Pinout & Package

ISO808QTR uses TFQFPN32 (5 mm × 5 mm, 0.5 mm pitch) with exposed thermal pad connected to GNDCC. The package provides 75 V DC input-to-output isolation and meets IEC 60747-17 creepage/clearance (3.3 mm) and CTI ≥600 requirements.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar galvanically isolated high-side driver applications.

Compared with TLP3547A(TP,E and MAX14914AUB+, the ISO808QTR uniquely combines per-channel thermal independence, VCC−54 V demagnetization, synchronous multi-device control, and full IEC/UL safety certification - making it optimal for deterministic, high-reliability industrial I/O where channel-level fault containment and timing predictability are critical.

Availability

ISO808QTR is available at Aetrix Electronics and suitable for programmable logic controller output modules, industrial PC peripheral I/O cards, and numerical control machine tool interfaces requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for ISO808QTR 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 specializing in automotive, industrial, and power management ICs, with strong emphasis on functional safety and isolation technologies.

The ISO808QTR belongs to ST's industrial-grade galvanic isolation portfolio, engineered specifically for high-reliability programmable logic control and factory automation systems demanding robust transient immunity, thermal resilience, and safety-certified operation.

FAQ

What is the maximum continuous output current per channel for ISO808QTR?

The ISO808QTR guarantees a minimum short-circuit current limit of 0.7 A per channel under all conditions, with typical R_DS(on) of 0.125 Ω enabling up to 0.7 A continuous conduction at ≤125 °C junction temperature. Derating applies above 85 °C ambient per the TFQFPN32 thermal resistance (R_{th j-amb} = 25 °C/W).

How does the FAULT pin behave during a communication error?

During an internal communication error - defined as data corruption in the isolation barrier transfer - the FAULT pin asserts active-low immediately. Outputs retain their last valid state briefly, then transition to OFF within one refresh cycle (≤67 µs). This behavior ensures fail-safe deactivation without requiring external supervision.

Can ISO808QTR drive inductive loads without external flyback diodes?

Yes. The ISO808QTR integrates active demagnetization circuitry that clamps the output voltage to VCC−54 V (typ) during turn-off, safely dissipating stored inductive energy without external components. This eliminates need for discrete flyback diodes in most 24 V solenoid and contactor applications.

What is the difference between Direct Control Mode and Synchronous Control Mode?

In Direct Control Mode (DCM), INx pins directly control OUTx outputs when SYNC and LOAD are tied low - ideal for simple, low-jitter point-to-point control. In Synchronous Control Mode (SCM), LOAD latches inputs and SYNC triggers simultaneous output updates across all 8 channels - essential for deterministic, multi-device coordination in PLC scan cycles with ≤6 µs jitter.