AS3422

Overview

The AS3422 is a low power ambient noise-canceling speaker driver designed for headsets, headphones, and earpieces. It features a fully analog implementation to minimize power consumption and system BOM cost while enhancing voice quality. The device supports feed-forward and feedback topologies with filter loops defined by external RC components. It includes a high-efficiency headphone amplifier delivering up to 2x23mW at 1.5V supply into 32Ω loads with 100dB SNR. The unit operates on a fixed 1.0-1.8V supply with an internal charge pump and utilizes a 2-wire serial interface for control.

Feature Summary

• Fully analog ambient noise cancellation supporting both feed-forward and feedback topologies with external RC-defined filter loops
• High-efficiency stereo headphone amplifier with bridged mode capability for high impedance loads and pop-free startup
• Integrated microphone input stage with programmable gain, AGC, and dedicated bias supply via internal charge pump
• Low power operation with automatic block shutdown in music playback mode and OTP ROM for calibration storage

Applications

• Stereo Bluetooth headsets
• Stereo wireless headsets
• On-ear and over-ear headset designs requiring active noise reduction

Procurement Notes

Verify the specific package variant, as the AS3422 utilizes a QFN32 package with 0.5mm pitch distinct from the AS3421. Confirm that the design accommodates the exposed pad connection requirements specified in the datasheet. Ensure the application circuit supports the 1.0V to 1.8V supply range and integrates the necessary external passive components for the charge pump and ANC filter loops.

Selection Notes

Select the AS3422 when a feedback topology is required for low-frequency noise attenuation or when additional filtering stages are needed beyond the single op-amp provided in the AS3421. This component is suitable for designs prioritizing low power consumption through analog processing rather than DSP implementations. Consider the QFN32 footprint availability and the need for external RC networks to define the specific filter transfer functions for the target headset mechanical design.

Part Context

The AS3422 belongs to a family of low-power audio drivers developed by ams-OSRAM USA INC. (formerly austriamicrosystems). It serves as the feedback-capable counterpart to the AS3421, which is limited to feed-forward configurations. Both devices share similar core functionalities including microphone amplification and headphone driving but differ in package count and operational amplifier availability to support different ANC architectural needs.

Replacement Considerations

The AS3421 is a related part within the same product family but lacks the second operational amplifier required for feedback topology. Substitution requires verifying if the application strictly requires feedback ANC or if feed-forward is sufficient. Pinout differences between the QFN24 (AS3421) and QFN32 (AS3422) packages necessitate PCB layout modifications.