AS3421

Overview

The AS3421 is a low-power ambient noise cancelling speaker driver designed for headsets, headphones, and earpieces. It features a fully analog implementation to reduce background noise while maintaining natural voice enhancement. The device includes a differential microphone amplifier with AGC, a high-efficiency headphone amplifier delivering up to 2x23mW at 0.1% THD+N into 32Ω loads, and a stereo line input. It supports feed-forward topology for frequencies up to 3kHz and utilizes an internal OTP-ROM for gain calibration settings.

Feature Summary

• Fully analog ambient noise cancellation using feed-forward topology to effectively reduce background noise without DSP complexity.
• Integrated differential microphone amplifier with automatic gain control and programmable gain steps for optimized signal capture.
• High-efficiency headphone amplifier capable of bridged mode operation for higher impedance loads with minimized startup artifacts.
• Internal OTP-ROM storage for microphone gain calibration and application-specific configuration settings.

Applications

• Stereo Bluetooth headsets
• Stereo wireless headsets
• Headphones with active noise reduction

Procurement Notes

Verify the specific package variant required, as the AS3421 uses a QFN24 package with a 0.5mm pitch. Confirm that the exposed pad connection aligns with the design requirement to connect to VNEG or leave it unconnected, strictly avoiding GND connections. Ensure the system architecture supports the necessary external passive components for the charge pump and filter networks.

Selection Notes

Select this component for applications prioritizing low power consumption and minimal bill-of-materials cost through analog processing. It is suitable for designs requiring simple production calibration via serial interface or line-in. Consider the feed-forward topology limitations when designing for very low-frequency attenuation compared to feedback systems.

Part Context

This device belongs to a family of audio processors from AMS (now ams-OSRAM) designed for battery-powered portable devices. It combines audio processing capabilities with system power management options. The AS3421 represents the feed-forward variant within this series, distinct from the AS3422 which supports feedback topologies.

Replacement Considerations

The AS3422 is a related model in the same product family offering feedback topology support. Verify pin compatibility and functional requirements before substitution, as the AS3422 utilizes a QFN32 package compared to the AS3421's QFN24.