STMicroelectronics ISO808ATR

Overview

ISO808ATR from STMicroelectronics is a galvanically isolated octal high-side power solid-state relay with SPI interface, designed for driving inductive loads up to 1 A per channel (ISO808A-1 variant), featuring R_DS(on) = 0.125 Ω (TYP), V_CC operating range of 9.2–36 V, and integrated per-channel over-temperature protection. It serves as a process-stage driver in industrial PLC I/O modules where ground-referenced loads require robust fault diagnostics and fast demagnetization (V_DEMAG = V_CC − 54 V).

For engineers reviewing the ISO808ATR datasheet, ISO808ATR pinout, ISO808ATR application, or ISO808ATR equivalent, this device supports daisy-chained SPI control, provides open-drain FAULT/PGOOD diagnostics, delivers 1500 V_PEAK input-to-output isolation (PowerSO-36), and meets IEC 61000-4-2/4/5/8, UL1577, and IEC 60747-17 safety standards - critical for evaluating reliability in 24 V industrial control systems.

Technical Context

The ISO808ATR integrates two galvanically isolated voltage domains: V_CC/GND_CC (process stage, 9.2–36 V) and V_DD/GNDDD (logic stage, 2.75–5.5 V), communicating via ST's proprietary isolation protocol. Its 8-channel architecture includes independent junction thermal shutdown (T_JSD = 150–200 °C) and case over-temperature protection (T_CSD = 125–135 °C), with each channel thermally independent.

It implements an 8-bit output status register updated via SPI (up to 20 MHz), supporting daisy chaining and watchdog timeout (t_WD = 272–400 μs). Fault reporting occurs through OR-wired active-low FAULT (OVT, communication error) and PGOOD (V_CC < 14.5–16.1 V), both open-drain with ≤0.4 V low-level voltage at 5 mA.

Key Specifications

Pinout & Package

ISO808ATR is supplied in PowerSO-36 package (exposed V_CC tab), optimized for high-power dissipation and industrial board layout. The package provides 2.6 mm creepage/clearance and CTI ≥400, meeting reinforced insulation requirements for 250 V_RMS applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL9201RTJR and MAX14914ATE+T, ISO808ATR uniquely combines octal integration, active demagnetization, per-channel thermal autonomy, and reinforced 1500 V_PEAK isolation in a single PowerSO-36 package - making it optimal for space-constrained, safety-critical PLC and NC applications demanding zero external protection components.

Availability

ISO808ATR is available at Aetrix Electronics and suitable for programmable logic controller output modules, industrial PC peripheral I/O cards, numerical control machine tool I/O, and inductive load drivers requiring stable component supply, long-term lifecycle support, and certified safety compliance.

Supply support for ISO808ATR 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, specializing in intelligent power, microcontrollers, and analog/mixed-signal ICs for industrial, automotive, and IoT markets.

The ISO808A series belongs to ST's industrial-grade isolated driver product line, engineered specifically for high-reliability, high-isolation-density digital output stages in programmable automation controllers and factory equipment.

FAQ

What is the maximum continuous output current per channel for ISO808ATR?

The ISO808ATR (as part of the ISO808A-1 family) supports a minimum continuous output current of 1 A per channel under specified thermal conditions (T_A ≤ 85 °C, proper PCB copper pour). This is enforced by internal current limiting (I_LIM(MIN) = 1 A) and independent per-channel thermal shutdown (T_JSD ≥ 150 °C), ensuring safe operation without external current sense resistors.

How does the daisy-chain SPI configuration work with multiple ISO808ATR devices?

Daisy chaining uses a single SS line shared across all devices; the MCU sends 8 bits per device in sequence. On SS falling edge, the first device captures its 8-bit SDI frame and forwards remaining bits via SDO to the next device. After all bits are shifted, rising SS applies the final 8-bit state to each device's outputs - enabling synchronized control of up to 64 channels with one SPI port and three wires (SS, CLK, SDI/SDO).

Can ISO808ATR drive AC loads directly?

No - ISO808ATR is a unidirectional high-side DC switch with GND_CC-referenced outputs. It cannot commutate AC waveforms or block reverse voltage. For AC loads, it must drive an external AC-rated solid-state relay or TRIAC driver stage; its role is strictly DC process-side switching with galvanic isolation for control logic.

What happens during a loss-of-GND_CC event, and how is it detected?

When GND_CC disconnects, ISO808ATR measures reverse current from OUTx pins to V_CC and detects leakage ≥500 μA at V_OUT = −24 V. This triggers the FAULT pin and disables affected channels while maintaining isolation integrity. The condition is reported via FAULT assertion (active-low) and persists until GND_CC is restored and OUT_EN is cycled - preventing latch-up or destructive shoot-through.