SI8751AB-ISR - Isolated FET Driver, 2.5kV, 8-SOIC | Skyworks
MPN: SI8751AB-ISR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.85 | $2.85 |
| 10 | $2.55 | $25.50 |
| 100 | $2.2 | $220.00 |
| 500 | $1.92 | $960.00 |
| 1,000 | $1.65 | $1,650.00 |
SI8751AB-ISR Overview
An isolated FET driver is a specialized gate-driver IC whose primary purpose is to drive the gate of an external power MOSFET or IGBT while maintaining galvanic isolation between the low-voltage control side and the high-voltage power stage. These devices sit hierarchically below gate drivers and optocoupler-based isolators and are widely used as solid-state relay (SSR) building blocks that replace electromechanical relays (EMRs). Capacitive coupling, used here, transmits digital signals across an isolation barrier using high-frequency on-chip RF carriers instead of LEDs, providing superior noise immunity and long-term reliability.
Key features include 2.5 kVrms withstand isolation, 20 kV/us minimum common-mode transient immunity (CMTI), 2.25 V to 5.5 V input supply range, pin-controllable gate-drive current, and integrated protection for the external FET. The 8-SOIC footprint makes the part easy to place on space-constrained SSR or half-bridge driver boards, while the wide input voltage range supports both 3.3 V and 5 V CMOS logic interfaces without level shifters.
Architecturally, the Si8751AB uses an on-chip RF oscillator and capacitive isolation barrier that reconstructs a digital signal on the secondary side, where it then controls an internal charge-pump and gate driver. Because the secondary-side supply is generated internally from the primary-side input current (programmable via the CTR pin), the part eliminates the bulky isolated DC-DC converter traditionally required for IGBT/MOSFET gate drive in solid-state relays.
Typical applications include solid-state relays (SSR) replacing electromechanical relays, PLC digital output modules, industrial process control isolation, AC line switching with back-to-back MOSFETs, and isolated gate driving for IGBTs in motor-control or inverter sections. Choose Si8752 instead of Si8751 if diode-emulation (synchronous-rectifier-style control) is preferred for DC-load switching.
When designing in the Si8751AB-ISR, ensure that the CTR resistor value is chosen to deliver sufficient gate-charge current for the chosen external FET while staying within the package thermal envelope. The IC tolerates 2.5 kVrms continuous across its barrier, but the PCB layout must maintain adequate creepage and clearance to meet end-product safety standards such as IEC 60747-17 and UL 1577.
This page synthesizes distributor pricing, drop-in alternatives, and design notes not found in the manufacturer datasheet.
Drop-in alternatives for SI8751AB-ISR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with SI8751AB-ISR (same form factor and footprint) — differing in Package, Isolation Voltage, Operating Temperature, Product Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
SI8751AB-IS
✅ Drop-In✓ In Stock
$2.84 / Unit
View Datasheet →SI8752AB-ISR
✅ Drop-In📋 Reference alternative (not in catalog)
SI8752AB-IS
✅ Drop-In📋 Reference alternative (not in catalog)
SI8271AB-ISR
✅ Drop-In✓ In Stock
$2.45 / Unit
View Datasheet →SI8751AB-ISR Maximum Ratings & Electrical Characteristics
| Product Type | Isolated FET Driver (CMOS input) |
| Technology | Capacitive (RF) Coupling |
| Number of Channels | 1 |
| Voltage - Isolation | 2500 Vrms |
| Common Mode Transient Immunity (Min) | 20 kV/us |
| Input Supply Voltage | 2.25 V to 5.5 V |
| Output Drive | External FET gate driver (self-powered secondary) |
| Input Control Interface | Digital CMOS pin control (Si8751); CTR pin adjusts drive strength |
| Operating Temperature | -40 C to +105 C |
| Package | 8-SOIC (0.154", 3.90 mm width) |
| Mounting Type | Surface Mount |
| Moisture Sensitivity Level (MSL) | 2A (4 weeks) |
| Approval Agency | CQC, CSA, UR, VDE |
| ECCN | EAR99 |
| HTSUS | 8542.39.0001 |
SI8751AB-ISR Pin Configuration
| Pin 1 | VDD — Primary-side supply voltage (2.25 V to 5.5 V) |
| Pin 2 | GND1 — Primary-side (input) ground |
| Pin 3 | IN — CMOS logic input (drive control) |
| Pin 4 | CTR — Input current program resistor - sets gate-drive strength vs quiescent input current |
| Pin 5 | NC — Not connected (per datasheet) |
| Pin 6 | NC — Not connected (per datasheet) |
| Pin 7 | GND2 — Secondary-side (FET source) ground |
| Pin 8 | GATE / OUT — Gate drive output to external FET gate |
Typical Applications
SI8751AB-ISR is suitable for 6 applications: Solid-State Relay (SSR) Replacement of Electromechanical Relays, PLC Digital Output Modules, Industrial Process Control Isolation, AC Line Switching with Back-to-Back MOSFETs, Isolated IGBT Gate Driver for Motor Control, Battery Management and Isolated Load Switching.
Solid-State Relay (SSR) Replacement of Electromechanical Relays
The SI8751AB-ISR is ideal for building AC-line solid-state relays that replace electromechanical relays in industrial control panels. With its 2500 Vrms capacitive isolation and 20 kV/us CMTI, it cleanly survives the dv/dt transients of 230 VAC mains while driving two back-to-back external MOSFETs. Compared to mechanical relays, the SSR eliminates contact bounce, arcing, and limited-cycle-life failure modes - extending system MTBF by 10x or more in high-cycle applications.
Recommended
PLC Digital Output Modules
Programmable logic controller (PLC) digital output cards benefit from the SI8751AB-ISR's compact 8-SOIC footprint and integrated isolation, reducing component count versus opto-isolator-plus-driver solutions. The 2.25 V to 5.5 V CMOS input range directly interfaces to 24 V-to-5 V PLC logic via simple resistor dividers, while the 2500 Vrms isolation meets IEC 61131-2 field-side requirements. The CTR pin lets the PLC firmware tune switching speed versus quiescent current to balance thermal load in 32-channel modules.
Recommended
Industrial Process Control Isolation
Process-control loops in chemical plants and factories require robust isolation between 4-20 mA HART field instrumentation and the controller's analog front end. The SI8751AB-ISR provides 2500 Vrms isolation between the controller MCU and the high-side FET switch controlling the loop, with 20 kV/us CMTI to reject the fast transients of nearby variable-frequency drives. The capacitive (RF) isolation technology delivers 50+ year service life versus the LED-aging concerns of optocouplers in continuous-on instrumentation.
Recommended
AC Line Switching with Back-to-Back MOSFETs
For AC line-voltage switching applications (110/230 VAC), the SI8751AB-ISR drives a pair of back-to-back N-channel MOSFETs to form a bidirectional solid-state switch. The integrated gate-driver output stage is self-powered from the primary-side input current, so no isolated DC supply is needed - dramatically reducing PCB area versus discrete gate-driver-plus-DC-DC designs. The 8-SOIC package keeps the driver footprint small enough to fit alongside standard TO-220 or TO-252 power MOSFETs.
Recommended
Isolated IGBT Gate Driver for Motor Control
Variable-frequency motor drives and small inverter sections benefit from the SI8751AB-ISR's isolated gate-drive capability for IGBTs or high-voltage MOSFETs in half-bridge or H-bridge topologies. The 2500 Vrms isolation safely separates the low-voltage MCU PWM outputs from the 400-600 V DC bus, while the self-powered secondary side eliminates the costly isolated DC-DC brick typically required. Designers pair this driver with the MCU's hardware PWM peripherals to achieve sub-microsecond dead-time control.
Recommended
Battery Management and Isolated Load Switching
Battery management systems (BMS) in industrial or backup-power applications use the SI8751AB-ISR to provide isolated control of high-side disconnect MOSFETs or pre-charge circuits. The 2500 Vrms isolation meets the 1500 V DC transient requirements of large lithium battery packs, while the 2.25 V to 5.5 V supply range simplifies 3.3 V BMS-controller interfacing. Pin-controlled turn-on avoids the surge currents of always-on gate drivers during cold-crank events.
Recommended
Recommended Products Summary
Engineering reference data for SI8751AB-ISR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SI8751AB-IS | SI8752AB-ISR | SI8752AB-IS | SI8271AB-ISR |
|---|---|---|---|---|---|
| Package | 8-SOIC (0.154" / 3.90 mm) | 8-SOIC - same | 8-SOIC - same | 8-SOIC - same | 8-SOIC - same |
| Brand | Skyworks Solutions | Skyworks Solutions | Skyworks Solutions | Skyworks Solutions | Skyworks Solutions |
| Isolation Voltage | 2500 Vrms | 2500 Vrms | 2500 Vrms | 2500 Vrms | 2500 Vrms |
| Technology / Coupling | Capacitive (RF) | Capacitive (RF) | Capacitive (RF) | Capacitive (RF) | RF (capacitive) |
| Input Protocol | CMOS pin-control (CTR adjustable) | CMOS pin-control (CTR adjustable) | Diode-emulation | Diode-emulation | CMOS pin-control |
| CMTI (min) | 20 kV/us | 20 kV/us | 20 kV/us | 20 kV/us | 20 kV/us |
| Input Supply Voltage | 2.25 V to 5.5 V | 2.25 V to 5.5 V | 2.25 V to 5.5 V | 2.25 V to 5.5 V | 2.25 V to 5.5 V |
| Automotive Grade (AEC-Q100) | No (industrial) | No (industrial) | No (industrial) | No (industrial) | Yes (Si827x automotive family) |
Key Differentiators
- Self-powered secondary gate drive - no isolated DC-DC needed (vs Traditional opto-isolator + discrete gate driver designs)
- CTR pin allows programming gate-drive strength vs quiescent current (vs SI8752AB-ISR (fixed diode-emulation input))
- Capacitive (RF) isolation with 50+ year service life (vs Photo-MOSFET optocouplers with LED aging)
Design Notes
The CTR pin resistor value directly programs the gate-drive strength and the primary-side input current. A too-small CTR resistor pulls excessive input current during FET turn-on, potentially exceeding the controller's source/sink capability. A too-large CTR resistor slows FET turn-on, increasing switching loss in the external MOSFET. Per the Si875x datasheet, choose the CTR value based on the external FET's total gate charge (Qg) and target switching time.
Maintain adequate creepage and clearance between the primary-side and secondary-side copper pours to meet the 2500 Vrms isolation rating. Use slotting in the PCB or remove copper beneath the isolation barrier to maximize clearance in compact 8-SOIC layouts. Reference UL 1577 and IEC 60747-17 for end-product safety spacing.
The 8-SOIC package dissipates the input current plus secondary drive losses into a small copper area. At sustained 10 mA primary current, junction-to-ambient thermal resistance becomes significant. Provide at least 0.5 square inches of copper on the primary-side ground pin and consider airflow in multi-channel SSR modules.
Compliance Information
RoHS compliant per Skyworks product page. VDE, UL, CSA, and CQC safety-agency certified for reinforced insulation. For AEC-Q100 automotive qualification, choose Si8271AB-ISR instead.
