Skyworks Solutions Inc. SI8751AB-ISR

Overview

SI8751AB-ISR from Skyworks Solutions is a digital-input isolated FET driver IC designed to replace mechanical relays and optocoupler-based SSRs in high-reliability industrial and automotive systems. It integrates 2.5 kV_RMS CMOS isolation, self-contained secondary-side gate drive (10 V output), Active Miller Clamp, and TT pin-controlled turn-on speed optimization - enabling robust AC/DC load switching with external FETs in motor control, HVAC, and battery monitoring applications.

For engineers reviewing the SI8751AB-ISR datasheet, SI8751AB-ISR pinout, SI8751AB-ISR application, or SI8751AB-ISR equivalent, this page delivers verified technical context, SOIC-8 package mapping, real-world timing specs (e.g., 42–650 µs turn-on), AEC-Q100 qualification, and precise input voltage (2.25–5.5 V) and isolation compliance (UL/CSA/VDE/CQC).

Technical Context

The SI8751AB-ISR uses RF-based on/off keying across a semiconductor isolation barrier to transmit both signal and power - eliminating need for external isolated supplies. Its input side accepts CMOS logic (2.25–5.5 V), while the output side generates a regulated 10 V gate drive referenced to SOURCE, supporting both single-FET DC and dual-FET AC switch topologies.

It implements an Active Miller Clamp via two optional MCAP pins (MCAP1/MCAP2), activated by dV/dt-induced current through external 10–100 pF capacitors connected to FET drains. The TT pin enables dynamic trade-off between input current (1.5–17 mA) and turn-on time (42–650 µs at 50% VG(ON)), without requiring firmware or configuration registers.

Key Specifications

Pinout & Package

SI8751AB-ISR is housed in a ROHS-compliant narrow-body SOIC-8 package (5.00 × 4.00 mm, 1.27 mm pitch), offering 4.7 mm clearance and 3.9 mm creepage - exceeding IEC 60664-1 requirements for 600 V_RMS basic insulation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar isolated FET driver applications.

Compared with SI8751BB-ISR, SI8751AB-ISR trades higher isolation for lower cost and broader industrial availability; compared with TLP3547, it replaces aging LED technology with stable RF isolation, enabling automotive-grade reliability and programmable switching behavior without optical degradation.

Availability

SI8751AB-ISR is available at Aetrix Electronics and suitable for motor controls, HVAC relay replacement, and HEV/EV charging systems requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.

Supply support for SI8751AB-ISR 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

Skyworks Solutions is a global leader in analog and mixed-signal semiconductors, specializing in RF, isolation, timing, and power management solutions for communications, automotive, and industrial markets.

The Si875x product line was engineered specifically to replace electromechanical relays and optocoupler-based SSRs - delivering higher reliability, longer lifetime, wider temperature range, and integrated Miller clamping for solid-state switching in harsh environments.

FAQ

What is the maximum recommended input voltage for SI8751AB-ISR?

The absolute maximum input supply voltage (VDD) for SI8751AB-ISR is 6.0 V, but the functional operating range is strictly 2.25 V to 5.5 V per the datasheet. Operating above 5.5 V risks permanent damage; below 2.25 V may cause unreliable logic recognition. SI8751AB-ISR must be used within this window to guarantee specified timing, isolation, and drive performance across its full temperature range.

Does SI8751AB-ISR require an external isolated power supply?

No, SI8751AB-ISR does not require an external isolated power supply. It uses internal RF energy transfer across its CMOS isolation barrier to generate a self-contained 10 V gate drive output referenced to the SOURCE pin. This eliminates the need for isolated DC/DC converters or charge pumps - reducing bill-of-materials cost and PCB area while improving system reliability. SI8751AB-ISR only needs a single 2.25–5.5 V input supply on the primary side.

How does the TT pin affect switching performance in SI8751AB-ISR?

The TT pin on SI8751AB-ISR controls input-side current draw and directly determines turn-on speed: connecting TT to GND draws ~17 mA and achieves minimum 42 µs turn-on (50% VG(ON)), while leaving TT unconnected reduces current to ~1.5 mA and increases turn-on to 650 µs. A series resistor (e.g., 10 kΩ) provides intermediate settings. SI8751AB-ISR's TT pin thus enables hardware-based optimization of switching loss versus EMI without software or external components beyond the resistor/capacitor network.

Can SI8751AB-ISR drive AC loads directly?

Yes, SI8751AB-ISR can drive AC loads when paired with two external N-channel FETs in a back-to-back configuration. Its GATE output drives both FET gates simultaneously, while SOURCE serves as the common reference. The dual MCAP1/MCAP2 pins allow independent Miller clamping of each FET's drain - critical for suppressing false turn-on during AC zero-crossing transitions. SI8751AB-ISR supports full-cycle AC switching without additional level-shifting or floating supply circuitry.

Is SI8751AB-ISR qualified for automotive applications?

Yes, SI8751AB-ISR is AEC-Q100 Grade 1 qualified (–40 °C to +125 °C ambient), with full test reports covering HTOL, temperature cycling, ESD, and latch-up. It meets automotive safety requirements for under-hood and cabin applications including battery monitoring, contactor control, and charging systems. Its 2.5 kV_RMS isolation and UL/CSA/VDE/CQC certifications further validate suitability for ASIL-B–level functions in HEV/EV platforms.