AS3501 Active Noise Cancellation IC

Description

The AS3501/2 combine a high quality (0.1% THD, >100dB SNR), true ground, audio headphone amplifier with all the necessary circuitry to enable superior performance Active Noise Cancellation, all at very low power consumption.

The AS3501 is ideally suited for feed-forward topology, whereas AS3502 is better suited for feedback topology.

The speakers can be configured in single ended mode (2x 34mW @1.5V, 16Ω) or Bridge Tied Load (1x 109mW @1.5V, 16Ω) and the line-in gain is adjustable to allow for locally controlled volume setting.

The device contains an OTP-ROM to store calibration settings for the noise cancelling microphones, removing the need for the manually trimmed pots typically used. The OTP can also be used to store device configuration settings, allowing flexibility and differentiation for a broad end-product portfolio.

The device is designed to operate in both stand-alone mode, ideal for accessories, and embedded mode targeting MP3 players and other portable multimedia equipment.

The AS3501/2 also contains a monitor mode, allowing the user to attenuate Line-in, while amplifying the ambient noise. This is typically used to hear announcements in airports, without the need to remove the headset.

Typically powered directly off a AAA battery, the AS3501/2 tolerates 1.0V to 1.8V supply, and contains the necessary charge pumps to enable true ground operation, as well as providing a supply voltage for the microphones.

Key Features

• ANC processing
  • Feed-forward and feedback topology
  • Calibration and configuration programmable on prod line without manual intervention
  • Typically up to 20dB noise reduction depending on headset
• High Performance true ground Headphone Amplifier
  • 2x34mW, THD <0.1% @ 16Ω with 1.5V supply, SNR >100dB
  • Click and pop less start-up/shutdown
• Line-In gain programmable or User adjustable
• 2-wire serial control
• Low quiescent current of 0.6µA (typ)
• Single Cell (AA/AAA) or 1.0V to 1.8V supply
• Short circuit protection
• High PSRR, 80dB at 1KHz and 217Hz
• Package:
  • AS3501 : 4x4mm QFN24 0.5mm pitch
  • AS3502 : 5x5mm QFN32 0.4mm pitch

Applications

• Headsets (Over-ear, On-ear and In-ear)
• Hands-Free Kits
• Mobile Phones
• Portable Media Players
• Portable DVD players

Block diagram for AS3501 Active Noise Cancellation IC