Si875x Isolated FET Drivers​​

The Silicon Labs Si8751/52 FET driver offers a simple way for customers to replace solid-state relays (SSRs) or electromechanical relays (EMRs). The Si875x combines robust CMOS isolation technology with a FET driver to form a complete, isolated switch.  

Versatile inputs provide digital CMOS pin control (Si8751) or diode emulation (Si8752) to best suit the application, plus flexible outputs to support driving AC or DC load configurations. A floating secondary side DC voltage source is unnecessary as the self-contained product generates its own gate drive output voltage, reducing cost, size, and complexity. The Si875x eliminates the need for bulky mechanical relays, which can be difficult to assemble onto PCBs and add switching noise to the system. Further, with the customer selecting their own flexible FET switch, the design can be completely optimized for the application’s power, cost, and performance requirements. Unlike traditional SSRs, which integrate optocoupler-style LED inputs and limit the operating temperature range of the solution, the Si875x can support full industrial and automotive temperature ranges with increased stability and longer life-time.  

The Si875x drives FET gates with a nominal 10.3 V using as low as 1 mA input current. Increasing the input current to 10 mA enables ultra-fast turn-on time as fast as 94 µs. A unique power optimization option delivers maximum turn-on current for fast speed, then lowers to static holding current once the optional external cap is discharged. Input side voltages are flexible from 2.25 V to 5.5 V and support seamless connection to low-power controllers. The Si875x devices provide a clamping device to prevent unintended turn on of the external FET when a high dV/dt is present on the FET’s drain. Further, its 2.5 kVrms isolation rating forms the basis for full certification to UL, CSA, VDE, and CQC.  


  • Digital CMOS or diode emulation control inputs
  • 10.3 V gate drive output with <100 µs turn-on time
  • Internally-generated secondary side power supply
  • Miller clamp cap support for reducing inductive chatter
  • DC or AC load switching support
  • Drives user-selected external FETs
  • 2.5 kVrms isolation rating
  • UL, CSA, VDE, and CQC certifications (pending)
  • Industrial -40 to +105°C or Automotive -40 to 125 °C temperature ranges
  • ROHS-compliant SOIC-8 Package

Si875x Product Matrix

Part Number Data Sheet Evaluation Kit Isolation Rating (kVrms) Input Type Input Supply (V) Peak Output Current Max Propagation Delay (µs) Driver Supply Range (V) Driver Supply Feature Temperature Range (°C) 10 Kv Surge Package Type Overlap Protection and Dead Time Control AEC-Q100
Si8751-KIT 2.5 Digital CMOS 2.25 5.5 External FET Specific 41 8 13 Internally generated driver supply -40 105 No NB SOIC8 No Yes
Si8752-KIT 2.5 Diode Emulation 2.25 5.5 External FET Specific 41 8 13 Internally generated driver supply -40 105 No NB SOIC8 No Yes
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