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AD1885 Folha de dados(PDF) 10 Page - Analog Devices |
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AD1885 Folha de dados(HTML) 10 Page - Analog Devices |
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10 / 27 page  AD1885 –10– REV. 0 PRODUCT OVERVIEW The AD1885 Codec meets the Audio Codec ’97 2.1 Extensions, adding support for multiple Codecs and variable sample rates. In addition, the AD1885 SoundPort Codec is designed to meet all requirements of the Audio Codec ’97, Component Specification, Revision 1.03, © 1996, Intel Corporation, found at www.Intel.com. The AD1885 also includes other Codec enhanced features such as communicating to three Codecs on the same link, integrated headphone driver and built-in PHAT Stereo 3D enhancement. The AD1885 is an analog front end for high-performance PC audio, modem, or DSP applications. The AC’97 architecture defines a 2-chip audio solution comprising a digital audio controller, plus a high-quality analog component that includes Digital-to-Analog Converters (DACs), Analog-to-Digital Con- verters (ADCs), mixer, and I/O. The main architectural features of the AD1885 are the high quality analog mixer section, two channels of Σ∆ ADC conver- sion, two channels of Σ∆ DAC conversion and Data Direct Scrambling (D 2S) rate generators. FUNCTIONAL DESCRIPTION This section overviews the functionality of the AD1885 and is intended as a general introduction to the capabilities of the device. Detailed reference information may be found in the descriptions of the Indexed Control Registers. Analog Inputs The Codec contains a stereo pair of Σ∆ ADCs. Inputs to the ADC may be selected from the following analog signals: tele- phony (PHONE_IN), mono microphone (MIC1 or MIC2), stereo line (LINE_IN), auxiliary line input (AUX), stereo CD ROM (CD), stereo audio from a video source (VIDEO) and post-mixed stereo or mono line output (LINE_OUT). Analog Mixing PHONE_IN, MIC1 or MIC2, LINE_IN, AUX, CD, and VIDEO can be mixed in the analog domain with the stereo output from the DACs. Each channel of the stereo analog inputs may be inde- pendently gained or attenuated from +12 dB to –34.5 dB in 1.5 dB steps. The summing path for the mono inputs (PHONE_IN, MIC1, and MIC2 to LINE_OUT and HP_OUT) duplicates mono chan- nel data on both the left and right LINE_OUT and HP_OUT. Additionally, the PC attention signal (PC_BEEP) may be mixed with the line output and headphone. A switch allows the output of the DACs to bypass the PHAT Stereo 3D enhancement. Digital Audio Mode The AD1885 is designed with a Digital Audio Mode (DAM) that allows mixing of all analog inputs, independent of the DAC output signal path. Mixed analog input signals may be sent to the ADCs for processing by the DC ’97 controller or the host, and may be used during simultaneous capture and playback at different sample rates. Analog-to-Digital Signal Path The selector sends left and right channel information to the programmable gain amplifier (PGA). The PGA following the selector allows independent gain control for each channel enter- ing the ADC from 0 dB to +22.5 dB in 1.5 dB steps. Each channel of the ADC is independent, and can process left and right channel data at different sample rates. Sample Rates and D 2S The AD1885 default mode sets the Codec to operate at 48 kHz sample rates. The converter pairs may process left and right channel data at different sample rates. The AD1885 sample rate generator allows the Codec to instantaneously change and process sample rates from 7040 Hz to 48 kHz with a resolution of 1 Hz. The in-band integrated noise and distortion artifacts introduced by rate conversions are below –90 dB. The AD1885 uses a 4-bit Σ∆ structure and D2S to enhance noise immunity on mother- boards and in PC enclosures, and to suppress idle tones below the device’s quantization noise floor. The D 2S process pushes noise and distortion artifacts caused by errors in the multibit DAC to frequencies beyond the auditory response of the human ear and then filters them. Digital-to-Analog Signal Path The analog output of the DAC may be gained or attenuated from +12 dB to –34.5 dB in 1.5 dB steps, and summed with any of the analog input signals. The summed analog signal enters the Master Volume stage where each channel of the mixer out- put may be attenuated from 0 dB to –94.5 dB in 1.5 dB steps or muted. Analog Outputs The AD1885 offers a line output controlled by the Master Volume control and an integrated headphone driver with independent control. Host-Based Echo Cancellation Support The AD1885 supports time correlated I/O data format by pre- senting mic data on the left channel of the ADC and the mono summation of left and right output on the right channel. The ADC is splittable; left and right ADC data can be sampled at different rates. Telephony Modem Support The AD1885 contains a V.34-capable analog front end for sup- porting host-based and data pump modems. The modem DAC typical dynamic range is 90 dB over a 4.2 kHz analog output passband where FS = 12.8 kHz. The left channel of the ADC and DAC may be used to convert modem data at the same sample rate in the range between 7040 Hz and 48 kHz. All pro- grammed sample rates have a resolution of 1 Hz. The AD1885 supports irrational V.34 sample rates with 8/7 and 10/7 select- able multiplier coefficients. Power Management Modes The AD1885 is designed to meet notebook and ACPI power consumption requirements through flexible power management control of all internal resources. The following subsections may be independently controlled: ADCs and Input Mux Power-Down DACs Power-Down Analog Mixer Power-Down Digital Interface Power-Down Internal Clocks Disabled ADC and DAC Power-Down VREF Standby Mode Low-Power Mixer Mode—CD Mixer Alive Only Mode Mixer Bypass Mode (Digital Audio) Headphone |
Nº de peça semelhante - AD1885_15 |
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Descrição semelhante - AD1885_15 |
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