This part is a kind of semiconductor called AK4537.

Function of this product has 16-Bit Stereo CODEC.

Manufacturers : Asahi Kasei Microsystems

Image and pinout :

Some of the text within the PDF file :

ASAHI KASEI [AK4537] AK4537 16-Bit ∆Σ Stereo CODEC with MIC/HP/SPK-AMP GENERAL DESCRIPTION The AK4537 targeted at PDA and other low-power, small size applications. It features a 16-bit stereo CODEC with a built-in Microphone-Amplifier, Headphone-Amplifier and Speaker-Amplifier. Input circuits include a Microphone-Amplifier and an ALC (Auto Level Control) circuit. The AK4537 is available in a 52-QFN, utilizing less board space than competitive offerings. FEATURES 1. Resolution : 16bits 2. Recording Function • Stereo Mic Input • Stereo Line Input • 1st MIC Amplifier : +20dB or 0dB • 2nd Amplifier with ALC -8dB ∼ +27.5dB, 0.5dB Step (MIC input) -23.5dB ∼ +12dB, 0.5dB Step (LINE input) • ADC Performance : S/(N+D) : 79dB, DR, S/N : 83dB (MIC input) S/(N+D) : 88dB, DR, S/N : [ ... ]

AK4537 PDF Datasheet Download