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AD1819B Arkusz danych(PDF) 2 Page - Analog Devices |
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AD1819B Arkusz danych(HTML) 2 Page - Analog Devices |
2 / 28 page AD1819B –2– REV. 0 PRODUCT OVERVIEW The AD1819B SoundPort Codec is designed to meet all require- ments of the Audio Codec ’97, Component Specification, Revision 1.03, © 1996, Intel Corporation, found at www.Intel.com. In addition, the AD1819B supports multiple codec configurations (up to three per AC-Link), a DSP serial mode, variable sample rates, modem sample rates and filtering, and built-in Phat Ste- reo 3D enhancement. The AD1819B 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 con- troller, 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 AD1819B 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. The AD1819B’s left channel ADC and DAC are compatible for modem applications support- ing irrational sample rates and modem filtering requirements. FUNCTIONAL DESCRIPTION This section overviews the functionality of the AD1819B 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 in- puts may be independently 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) dupli- cates mono channel data on both the left and right LINE_OUT. Additionally, the PC attention signal (PC_BEEP) may be mixed with the line output. A switch allows the output of the DACs to bypass the Phat Stereo 3D enhancement. Analog-to-Digital Signal Path The selector sends left and right channel signals to the program- mable gain amplifier (PGA). The PGA following the selector allows independent gain for each channel entering 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. All pro- grammed sample rates from 7 kHz to 48 kHz have a resolution of 1 Hz. The AD1819B also supports irrational V.34 sample rates. Sample Rates and D 2S The AD1819B 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 AD1819B sample rate generator allows the codec to instantaneously change and process sample rates from 7 kHz to 48 kHz with a resolution of 1 Hz. The in-band integrated noise and distortion artifacts in- troduced by rate conversions are below –90 dB. The AD1819B uses a 4-bit D/A structure and Data Directed Scrambling (D 2S) to enhance noise immunity on motherboards and in PC enclo- sures, and to suppress idle tones below the device’s quantization noise floor. The D 2S process pushes noise and distortion arti- facts caused by errors in the multibit D/A conversion process to frequencies beyond the audible range 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 –46.5 dB in 1.5 dB steps or muted. Host-Based Echo Cancellation Support The AD1819B supports time correlated I/O data format by presenting 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 AD1819B contains a V.34-capable analog front end for supporting 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 7 kHz and 48 kHz. All pro- grammed sample rates have a resolution of 1 Hz. The AD1819B supports irrational V.34 sample rates with 8/7 and 10/7 select- able sample rate multiplier coefficients. Differences Between the AD1819A and AD1819B The voltage reference (VREF) of the AD1819B remains active while RESET is asserted. This eliminates the audible artifacts associated with the RESET LO to HI transitions that can occur during a Windows boot (power-up) or Windows warm restart (reset). |
Podobny numer części - AD1819B_15 |
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Podobny opis - AD1819B_15 |
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