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AD1843JS Scheda tecnica(PDF) 11 Page - Analog Devices |
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AD1843JS Scheda tecnica(HTML) 11 Page - Analog Devices |
11 / 64 page AD1843 REV. 0 –11– POWER SUPPLIES Pin Name PQFP TQFP I/O Description VCC 20, 41, 44 25, 51, 55 I Analog Supply Voltage (+5 V). GNDA 21, 37, 40, 48 27, 46, 49, 59 O Analog Ground. VDD 4, 8, 50, 53, 5, 10, 62, 66, I Digital Supply Voltage (+5/3 V). 63, 64, 68, 72, 79, 80, 85, 90, 77 96 GNDD 3, 7, 54, 60, 4, 9, 67, 75, I Digital Ground. 65, 69, 73, 78 81, 86, 91, 97 NC 3, 8, 13, 14, No Connect. May be left floating. 24, 26, 32, 37, 42, 50, 52, 60, 63, 68, 73, 78, 83, 88, 93, 98 (continued from page 1) The versatility of the device is shown by the following examples of functions it can perform: • Stereo audio input and/or quad output, simultaneously at dif- ferent sample rates • Stereo audio output with simultaneous full duplex modem or fax operation with frequency and phase resampling • Mono audio input and stereo audio output with simultaneous modem receive and transmit for simultaneous voice and data communications • Dual independent audio inputs with audio output for echo- cancelling speakerphones Audio Functional Description The AD1843 SoundComm codec provides a complete audio so- lution with very few external components required. Dynamic range of the device exceeds 80 dB over the 20 kHz audio band and sample rates from 4 kHz to 49 kHz are supported (up to 54 kHz for a single channel if other channels are powered down). The audio functionality of this device is a superset of that found in the Analog Devices AD1848 SoundPort ® device which has set the business audio standard throughout the com- puter industry. Inputs to the device include a stereo microphone pair, a stereo line pair, a stereo CD input pair (AUX1), a stereo synthesized music input pair (AUX2), a dual phone line input (AUX3), a mono input, and a stereo input from an FM synthesizer (SUM). All of these inputs (except SUM) are multiplexed to the two ∑∆ A/D converters and are mixable directly as analog signals with the outputs of the D/A converters. All analog input signals (ex- cept SUM) can be amplified, attenuated or muted before mix- ing with the outputs of the D/A converters. The device has two pairs of ∑∆ DACs which accept 8- or 16-bit digital data from the serial port. Each DAC pair’s independent sampling rate can either be programmed by Control Register (with 1 Hz resolution) or synchronized to an external input. The second pair of DACs can be used to replace the music syn- thesis DAC pair found on many audio products for PCs. Out- puts from the AD1843 include a line output, a mono output, a stereo headphone output with its own current return path, and a SoundPort is a registered trademark of Analog Devices, Inc. differential stereo output for connection to a DAA. The line and differential outputs are looped back to the ADC input selector. The AD1843’s mixing and routing capabilities are extensive. The digital data from both DAC channels after interpolation can be routed back to the ADC decimators, to support digital- to-digital sample rate conversion (digital resampling). Digital data from the ADC can also be routed to the two stereo DAC pairs, for a digital loopback mode which is helpful for device- level and board-level test. Digital data from either stereo DAC can be mixed with the digital data feeding the other DAC, and the analog signal from DAC2 can be mixed with the analog out- put from DAC1. Sample rates are independently programmable in the range of 4 kHz to 54 kHz to a 1 Hz resolution or sample rates can be synchronized to an external source. Up to three different signals can be applied to the device’s three digital phase lock loop SYNC inputs for external synchronization. These SYNC inputs can also be used in a special mode for au- dio/video synchronization. In this mode, an NTSC or PAL de- rived clock signal (approximately 15 kHz) is applied to the SYNC inputs and the device produces one of a variety of stan- dard audio sample rates (32 kHz, 44.056 kHz, 44.1 kHz and 48 kHz, and most of these divided by the integers 1 through 8). In this manner, video and audio sample rates which are math- ematically unrelated can be locked together. Data Communications/Telephony Functional Description The AD1843 includes all data conversion, filtering, and clock generation circuitry needed to implement an echo-cancelling modem with a companion digital signal processor. Software- programmable sample rates and clocking modes support all established modem standards including those for the V.34 standard. The AD1843 utilizes advanced ∑∆ technology to move the entire echo-cancelling modem implementation into the digital domain. The device maintains 90 dB typical dynamic range throughout all filtering and data conversion across a 9.6 kHz passband. Purely DSP-based echo cancellation algorithms can maintain robust bit error rates under worst-case signal attenua- tion and echo amplitude conditions. The AD1843’s on-chip interpolation filter resamples (both frequency and phase) the re- ceived signal after echo cancellation in the DSP, freeing the pro- cessor for other voice or data communications tasks. |
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