WM9708 WM9709 MC78L05ACD - Datasheet Archive

 

WM9708 WM9708 Low Power AC'97 Audio CODEC AMR Card Reference Design DESCRIPTION The WM9708 AMR is an audio only daughter card

 

w WM9708 WM9708 WM9708 WM9708 Low Power AC'97 Audio CODEC AMR Card Reference Design DESCRIPTION The WM9708 WM9708 AMR is an audio only daughter card implementation of the Intel Audio Modem Riser (AMR) Rev 1.01 specification. This card can also be used in systems supporting the ACR 1.0 specification. The design supports the connectivity requirements of a typical sound card. Inputs include Line, CD (Mitsumi and Sony types) and Mic. Outputs include Line Out and Mono. The Audio CODEC used in the design is the WM9708 WM9708 Rev 2.1 Stereo Audio CODEC. The WM9708 WM9708 is compliant with the Intel 2.1 AC'97 CODEC specification and supports split supplies and variable audio sample rates. FEATURES · · · · Reference design for WM9708 WM9708 Revision 2.1 Low Power Audio CODEC AMR audio only add-in card conforming to Intel AMR card specifications May be used in systems supporting the ACR (Advanced Communications Riser) 1.0 specification Analogue connections for Line In, Line Out and MIC-In · Design kit available including schematics (PADS) layout and Gerber files and bill of materials · Meets Microsoft's PC'97, PC'98 and PC'99 requirements and advanced audio performance requirements BLOCK DIAGRAM CD IN MIC IN LINE IN LINE OUT WM9708 WM9708 MONO OUT WOLFSON MICROELECTRONICS LTD www.wolfsonmicro.com November 2002, Rev 1.1 Copyright 2002 Wolfson Microelectronics Ltd. WM9708 WM9708_AMR_EV1M INTRODUCTION The WM9708 WM9708 AMR is an audio only daughter card implementation of the Intel Audio Modem Riser (AMR) Rev 1.01 specification. A block diagram of the card is shown above and in Figure 1. MOTHERBOARD AUDIO/MODEM RISER PCBEEP RESETB BIT_CLK SYNC SDATA_IN0 SDATA_OUT WM9708 WM9708 AC'97 REV 2.1 CODEC AC-LINK +12V MAIN +5.0V MAIN +3.3V MAIN TO I/O BRACKET AUDIO MINIJACKS POWER Figure 1 Block Diagram of WM9708 WM9708 AMR The card is designed to fully utilise the performance of the WM9708 WM9708 Stereo Audio CODEC and achieves signal-to-noise ratios of better than 95dB on playback and 92dB for the record path. The board performance is comparable to a typical PCI soundcard. WM9708 WM9708 AC'97 AUDIO CODEC The WM9708 WM9708 is compliant with Rev 2.1 of the AC'97 specification. The WM9708 WM9708 comprises a stereo 18-bit CODEC, plus a comprehensive analogue mixer with 2 sets of stereo inputs, plus 2 microphone and PC-beep inputs. Additionally, a bi-directional serial interface allows transfer of control data and DAC and ADC words to and from the AC'97 controller. The WM9708 WM9708 incorporates a 5-pin digital serial interface that links it to the motherboard based AC'97 controller via the AMR bus. The AC-link is a bi-directional, fixed rate, serial PCM digital stream. It handles multiple input and output audio streams, as well as control register access employing a time division multiplexed (TDM) scheme. The DACs and ADCs on this device support all the recommended audio sample rates specified in the Intel AC'97 Rev 2.1 specification. Default rate is 48ks/s. If alternative rates are selected, the AC'97 interface continues to run at 48k words per second, but data is transferred across the link in bursts such that the net sample rate selected is achieved. It is up to the AC'97 Rev 2.1 compliant controller to ensure that data is supplied to the AC link, and received from the AC link, at the appropriate rate. AUDIO MODEM RISER SPECIFICATION The Audio Modem Riser Specification, originally defined by Intel Corporation, is an open industry standard specification that defines a motherboard riser board and interface. The specification supports various configurations for audio and modem partitioning within the PC. The riser module can include audio only, modem only, or audio and modem functions depending on the need of the manufacturing OEM. The backbone of the AMR interface is an AC'97 compliant link, power signals and digital IO for defining for example, the status of the CODEC on the riser module. The AMR specification has been superseded by the Advanced Communications Riser (ACR). This card is fully compliant with this specification and can be used without modification in systems designed to the ACR 1.0 specification. w Rev 1.1 November 2002 2 WM9708 WM9708_AMR_EV1M DESIGN IMPLEMENTATION The WM9708 WM9708 AMR reference design is implemented using a hierarchical design methodology. This allows the design to be split into logical parts that are easy to explain and follow. Note: The PCB shown was designed for dual population by either the WM9708 WM9708 or WM9709 WM9709. Both are AC'97 CODECS with some functional differences. Due to this, some of the circuitry shown in the attached schematic is not applicable to the WM9708 WM9708 CODEC. All relevant circuitry will be explained. FUNCTIONAL DIAGRAM The Functional Diagram on Sheet 1 of the schematic depicts the interconnectivity of the other five sheets. The flow of data can easily be seen from this. Sheet 1 Functional Diagram w Rev 1.1 November 2002 3 WM9708 WM9708_AMR_EV1M AMR_BUS Signal flow in and out of the AMR bus is shown on Sheet 2. The ground references defined in the AMR specification have been partitioned on the reference design to provide a separate "clean" analogue ground (AGND) from that used for the digital signals (GND). Sheet 2 AMR BUS w Rev 1.1 November 2002 4 WM9708 WM9708_AMR_EV1M WM9708 WM9708 Connection to the WM9708 WM9708 CODEC is shown on Sheet 3. Sheet 3 WM9708 WM9708 CODEC w Rev 1.1 November 2002 5 WM9708 WM9708_AMR_EV1M AUDIO_IN All the external audio input signals to the board are shown on Sheet 4. To prevent damage to the WM9708 WM9708 and to allow for the full 2Vrms input signal defined in the PC'99 specification, all the audio input signals of the reference design (apart from MIC) have been potted down by a simple resistor divider. This provides approximately 7dB of attenuation to the input signal. The microphone input circuits to the reference design provide support for 3-pin electret (bias on ring), 2-pin electret (tip and ring shorted together) and 2-pin dynamic microphones. The bias circuits for the microphone inputs provide the required drive characteristics stipulated in the PC'99 System Design Guide, Chapter 17, "Audio Components". The WM9708 WM9708 can be programmed to give a +20dB gain on the microphone input path if required ­ refer to the datasheet. Sheet 4 Audio In w Rev 1.1 November 2002 6 WM9708 WM9708_AMR_EV1M AUDIO_OUT The audio outputs from the reference design are shown on Sheet 5. The Mono and Line Out signals are passed to the output connectors via passive high-pass filters. This enables the signals to meet the bandwidth suggested in the PC'97 Hardware Design Guide FAQ and AC couple the outputs. These outputs are capable of driving a 10Kohm load. Sheet 5 Audio Out w Rev 1.1 November 2002 7 WM9708 WM9708_AMR_EV1M POWER The power supply circuitry for the reference design is shown on Sheet 6. The analogue +5V supply to the CODEC is provided from the regulated down +12V AMR Bus supply. An MC78L05ACD MC78L05ACD regulator with suitable bypassing is used for this purpose. If the +12V system supply proves to be excessively noisy, LINK L2 can be replaced with a suitable inductor. The digital supply is taken directly from the AMR Bus +5VD and +3.3VD power signals. This is jumper selectable on the board. In order to allow for possible EMC compliance testing issues with the board, the connections to the PC bracket have been left as unpopulated sites (L1 and L3). These can easily be linked out or populated with suitable components at test time. Sheet 6 Power w Rev 1.1 November 2002 8 WM9708 WM9708_AMR_EV1M GROUNDING AND LAYOUT CONSIDERATIONS The pin-out of the WM9708 WM9708 allows the simple partitioning of the analogue and digital ground planes on the board. Returning ground currents can then flow in their respective ground planes, and the crosstalk between them is minimised. A connection between the two ground planes is made with a 1.27mm track close to the CODEC to maintain the proper reference potential for each ground plane. In order to allow for possible EMC compliance testing issues with the board, the connections to the PC bracket have been left as unpopulated sites (L1 and L3). These can easily be linked out or populated with suitable components at test time. All the front panel 3.5mm jack connections have 220pF capacitors connected to ground to guard against high frequency noise which may cause the board to fail EMC tests. Figure 2 Top Layer Silkscreen w Rev 1.1 November 2002 9 WM9708 WM9708_AMR_EV1M Figure 3 Top Layer w Rev 1.1 November 2002 10 WM9708 WM9708_AMR_EV1M Figure 4 Bottom Layer w Rev 1.1 November 2002 11 WM9708 WM9708_AMR_EV1M Figure 5 Bottom Layer Silkscreen REFERENCES 1. 2. 3. Intel Audio Modem Riser Specification, Rev 1.01. September 10, 1998 - No longer available from Intel, superceded by CNR specification Advanced Communications Riser (ACR) specification http://www.acrsig.com Wolfson Microelectronics, WM9708 WM9708 AC'97 Rev 2.1 Low Power Audio CODEC Datasheet, 4. Intel Audio CODEC AC'97 Component Specification, Rev 2.1 5. Intel and Microsoft, PC'99 System Design Guide http://www.microsoft.com/HWDEV/PC99.htm w Rev 1.1 November 2002 12 WM9708 WM9708_AMR_EV1M EVALUATION SUPPORT The aim of this evaluation kit is to help you to become familiar with the functionality and performance of the WM9708 WM9708 AC'97 Audio CODEC. If you require more information or require technical support please contact Wolfson Microelectronics Applications group through the following channels: Email: apps@wolfsonmicro.com Telephone Apps: Fax: Mail: (+44) 131 272 7070 (+44) 131 272 7001 Applications Department at address on last page. or contact your local Wolfson representative. Additional information may be made available from time to time on our web site at http://www.wolfsonmicro.com w Rev 1.1 November 2002 13 WM9708 WM9708_AMR_EV1M IMPORTANT NOTICE Wolfson Microelectronics Ltd (WM) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current. All products are sold subject to the WM terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. WM warrants performance of its products to the specifications applicable at the time of sale in accordance with WM's standard warranty. Testing and other quality control techniques are utilized to the extent WM deems necessary to support this warranty. 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