SI8921AD-AS4R

Special Purpose Amplifiers Overview

The SI8921AD-AS4R is an automotive-grade, galvanically isolated analog amplifier from Skyworks Solutions. It features a specified linear differential input range of ±62.5 mV and provides a differential output amplified by a gain of 32.8x. The device utilizes CMOS isolation technology to support up to 5.0 kVRMS withstand voltage per UL1577. Key electrical specifications include a typical signal delay of 0.8 µs, a bandwidth of 600 kHz, and a typical input offset voltage of ±0.04 mV. It operates within a supply voltage range of 3.0 V to 5.5 V and supports an ambient temperature range of -40 °C to +125 °C.

Special Purpose Amplifiers Feature Summary

• Automotive-grade qualification with AEC-Q100 certification and AIAG-compliant PPAP documentation support.
• Galvanic isolation barrier supporting up to 5.0 kVRMS withstand voltage using proprietary CMOS technology.
• High common-mode transient immunity rated at 75 kV/µs for accurate measurement in high-power switching environments.
• Fail-safe output mode that activates upon loss of the primary-side supply voltage (VDDA).

Special Purpose Amplifiers Applications

• Current shunt measurement in industrial inverters
• Electric vehicle (HEV) and renewable energy inverter systems
• AC, brushless, and DC motor controls and drives
• Automotive onboard chargers and battery management systems

Special Purpose Amplifiers Procurement Notes

Verify the specific suffix 'AS4R' corresponds to the wide-body SOIC-8 package and reel packaging format. Confirm that the 'D' designation indicates the 5.0 kVRMS insulation rating and the 'A' designation specifies the ±62.5 mV input range. Ensure compliance with automotive quality standards such as AEC-Q100 and PPAP requirements if applicable to the target application.

Special Purpose Amplifiers Selection Notes

Select this component when a differential output is required for current sensing applications involving low-voltage signals across shunt resistors. The ±62.5 mV input range is suitable for low-resistance shunts where higher gain is necessary. Consider the 5.0 kVRMS isolation rating for high-voltage side monitoring. Verify that the system requires an automotive-grade part with documented failure rates and manufacturing process controls.

Special Purpose Amplifiers Part Context

This device belongs to the Si8921/Si8922 family of isolated amplifiers designed for current shunt measurement. The Si8921 variant specifically provides a differential output, whereas the Si8922 offers a single-ended output. Both share similar isolation characteristics and input options, but differ in output topology and pin configurations.

Special Purpose Amplifiers Replacement Considerations

SI8921BD-AS4R: Offers a wider ±250 mV input range with lower gain (8.2x).

Special Purpose Amplifiers FAQ

What is the fail-safe output voltage when the VDDA supply is removed?

When VDDA is removed, the Si8921 outputs a nominal fail-safe voltage of approximately -2.8 V.

How does the device handle common-mode noise on the input pins?

The device rejects common-mode signals applied to AIP and AIN, provided the common-mode voltage remains between -0.2 V and 1 V relative to GNDA.