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AKM公司的 AK4955是集成了麥克風放大器，揚聲器放大器，視頻放大器，LCD和DSP的 24位立體聲CODEC，具有錄音功能，播放功能，電源管理以及主從模式，主要用在帶錄音/播放功能的手提設備。本文介紹了AK4955主要特性，方框圖以及AKD4955-A評估板方框圖，電路圖和PCB布局圖。 The AK4955 is a 24bit stereo CODEC with a microphone amplifier, speaker amplifier, video amplifier, LDO, and DSP. The input circuits include a microphone amplifier and the output circuits include a speaker amplifier. It is suitable for portable application with recording/playback function. A one channel composite In/Out video amplifier is also integrated. The internal charge pump generates a negative power eliminating the need for AC-coupling capacitors. The AK4955 is available in a small 36pin CSP (3.0mm Applications: DSCs, DVCs AK4955主要特性： Recording Functions · Stereo Single-ended input with two Selectors · MIC Amplifier (+24dB/+21dB/+18dB/+16dB/+14dB/+11dB/+8dB/+5dB/0dB) · Digital ALC (Automatic Level Control) (Setting Range: +36dB ~ -54dB, 0.375dB Step) · ADC Performance: S/(N+D): 81dB, DR, S/N: 88dB (MIC-Amp=+18dB)S/(N+D): 82dB, DR, S/N: 96dB (MIC-Amp=0dB) · 5 Band Notch Filter · Digital MIC Interface Playback Functions · Digital De-emphasis Filter (tc=50/15 · Soft Mute · Digital ALC (Automatic Level Control)(Setting Range: +36dB ~ -54dB, 0.375dB Step) · Digital Volume Control (+12dB ~ -115dB, 0.5dB Step, Mute) · Stereo Emphasis Circuit · Stereo Line Output Output Voltage: +2dBV(1.26Vrms) (LVDD = 4.8V)2.52Vpp (LVDD=3.3V) -S/(N+D): 85dB, S/N: 92dB · Mono Mixing Output · Mono Speaker-Amplifier SPK-Amp Performance: S/(N+D): 70dB@150mW, 60dB@250mW, S/N: 95dB - BTL Output - Output Power: 600mW@8 400mW@8 · Analog Mixing: Mono Input · Beep Sound Power Management · Thermal Shut-down Function Master Clock: (1) PLL Mode · Frequencies: 11.2896MHz, 12MHz, 13.5MHz, 24MHz, 27MHz (MCKI pin) 32fs or 64fs (BICK pin) (2) External Clock Mode · Frequencies: 256fs, 512fs or 1024fs (MCKI pin) Output Master Clock Frequencies: 32fs/64fs/128fs/256fs Sampling Frequency · PLL Slave Mode (BICK pin): 7.35kHz ~ 48kHz · PLL Slave Mode (MCKI pin): 8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, 48kHz · PLL Master Mode: 8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, 48kHz · EXT Master/Slave Mode: 7.35kHz ~ 48kHz (256fs, 512fs), 7.35kHz ~ 13kHz (1024fs) Master/Slave mode Audio Interface Format: MSB First, 2’s complement · ADC: 24bit MSB justified, 16/24bit I2S · DAC: 24bit MSB justified, 16bit LSB justified, 24bit LSB justified, 16/24bit I2S Video Functions · One Composite Signal Input · Capacitor-less Video Amplifier for Composite Signal Output Gain: +6 / +9 / +12 / +16.5dB · LPF · Charge Pump Circuit for Negative Power Supply Ta = -30 ~ 85℃ Power Supply: · Analog Power Supply (AVDD): 2.7 ~ 3.6V · Digital Power Supply (DVDD): 1.6 ~ 2.0V · Line Output Power Supply (LVDD): 2.7 ~ 5.5V · Speaker Power Supply (SVDD): 2.7 ~ 5.5V · Digital I/O Power Supply (TVDD): -0.2 ~ 3.6V Package: 36pin QFN (3.0 Evaluation Board: AKD4955 
圖1。AK4955方框圖 AKD4955-A評估板 The AKD4955-A is an evaluation board for AK4955, 24bit stereo CODEC with a microphone/ speaker/ video amplifiers, DSP and LDO. The AKD4955-A has the Digital Audio I/F and can achieve the interface with digital audio systems via optical connector.
圖2。AKD4955-A評估板方框圖
圖3。AKD4955-A評估板電路圖（1）
圖4。AKD4955-A評估板電路圖（2）
圖5。AKD4955-A評估板電路圖（3）
圖6。AKD4955-A評估板電路圖（4）
圖7。AKD4955-A評估板電路圖（5）
圖8。AKD4955-A評估板電路圖（6）
圖9。AKD4955-A評估板電路圖（7）
圖10。AKD4955-A評估板PCB布局圖 詳情請見： 
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