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CRD4525
2 x 15 W CS4525 Digital Amplifier Reference Design
Features
Output Filters Optimized for 8 Loads Delivers 15 W/Ch into 8 at 10 % THD+N Single-Ended 2 VRMS Stereo Analog Inputs Optical and Coaxial S/PDIF Inputs Flexible I/O Headers Provided - PCM Input Signal Interface - Auxiliary Serial Port Signal Interface - Delay Port Signal Interface - PWM Logic Level Signal Interface Optional CRD4412 Daughter-Card for Subwoofer Channel - Implements a 2.1 Configuration Demonstrates Recommended Layout and Grounding Arrangements +18 V Switching Mode Power Supply Included Windows(R) Compatible Software Interface - Easy and Intuitive Graphical Interface - Supports USB PC Connectivity
Description
The CRD4525 demonstrates the CS4525 digital PWM controller with integrated power stages. This reference design implements a two-channel amplifier which delivers 15 W per full-bridge channel into 8 loads using a single +18 V supply. The CRD4525 is powered by an included 80 W switching mode power supply. Standard RCA phono jacks are provided to easily interface analog input signals with the evaluation board. Optical and coaxial inputs are provided to interface with S/PDIF digital audio input signals. The PWM audio power outputs are routed through an inductor/capacitor 2nd order low-pass filter (LPF) to remove high frequency components from the output signal, effectively converting it from digital to analog. The Windows software provides a GUI to make configuration of the CRD4525 easy. The software communicates through the PC's USB port to configure the control port registers so that all features of the CS4525 can be evaluated.
ORDERING INFORMATION CRD4525 CS4525 Reference Design
Stereo Analog Inputs
Output Filter Speaker Connector
8
Optical Receiver CS8416 S/PIDF Receiver Coaxial Input PCM Input Header
CS4525
Output Filter
8
Aux Port Header CRD4412 Interface Header
USB I/O
Status LED's Micro-controller Tactile Controls Power Jack
Included 18 V Power Supply
http://www.cirrus.com
Copyright (c) Cirrus Logic, Inc. 2006 (All Rights Reserved)
SEPTEMBER '06 DS726RD1
CRD4525
TABLE OF CONTENTS
1. SYSTEM OVERVIEW ............................................................................................................................. 3 1.1 Power ............................................................................................................................................... 3 1.2 CS4525 Digital TV Amplifier ............................................................................................................ 3 1.3 CS8416 Digital Audio Receiver ........................................................................................................ 3 1.4 System Clocking .............................................................................................................................. 3 1.5 External Data Headers ..................................................................................................................... 3 1.6 Analog Inputs ................................................................................................................................... 4 1.7 Speaker Outputs .............................................................................................................................. 4 1.8 PC Interface ..................................................................................................................................... 4 1.9 Tactile Controls ................................................................................................................................ 4 1.10 CRD4412 Interface ........................................................................................................................ 4 2. PC SOFTWARE CONTROL ................................................................................................................... 6 2.1 CS4525 Main Controls Tab .............................................................................................................. 6 2.2 CS4525 Aux & Filter Controls Tab ................................................................................................... 7 2.3 S/PDIF Input Controls Tab ............................................................................................................... 8 2.4 Register Maps Tab ........................................................................................................................... 9 2.5 Pre-Configured Script Files ............................................................................................................ 10 2.5.1 Analog In ............................................................................................................................... 10 2.5.2 Optical SPDIF In .................................................................................................................... 10 2.5.3 Coaxial SPDIF In ................................................................................................................... 10 3. GROUNDING AND POWER SUPPLY DECOUPLING ........................................................................ 11 3.1 Power Supply Decoupling .............................................................................................................. 11 3.2 Electromagnetic Interference (EMI) ............................................................................................... 11 3.2.1 Suppression of EMI at the Source ......................................................................................... 11 4. SYSTEM CONNECTIONS & JUMPERS .............................................................................................. 13 5. CRD SCHEMATICS .............................................................................................................................. 14 6. CRD LAYOUT ...................................................................................................................................... 18 7. REVISION HISTORY ............................................................................................................................ 23
LIST OF FIGURES
Figure 1.Speaker Terminal Configuration ................................................................................................... 4 Figure 2.CS4525 Main Controls Tab ........................................................................................................... 6 Figure 3.CS4525 Aux & Filter Controls Tab ................................................................................................ 7 Figure 4.S/PDIF Input Controls Tab ............................................................................................................ 8 Figure 5.Register Maps Tab ........................................................................................................................ 9 Figure 6.CS4525 - Schematic Page 1 ....................................................................................................... 14 Figure 7.Power Outputs - Schematic Page 2 ............................................................................................ 15 Figure 8.S/PDIF Digital Audio Input - Schematic Page 3 .......................................................................... 16 Figure 9.Serial Control / Power - Schematic Page 4 ................................................................................. 17 Figure 10.Silkscreen Top .......................................................................................................................... 18 Figure 11.Topside Copper Layer .............................................................................................................. 19 Figure 12.Inner Copper Layer 1 ................................................................................................................ 20 Figure 13.Inner Copper Layer 2 ................................................................................................................ 21 Figure 14.Bottomside Copper Layer ......................................................................................................... 22
LIST OF TABLES
Table 1. System Connections ................................................................................................................... 13 Table 2. On-Board Tactile Controls ........................................................................................................... 13 Table 3. System Headers .......................................................................................................................... 13
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CRD4525 1. SYSTEM OVERVIEW
The CRD4525 reference design is an excellent means for evaluating the CS4525 30 W digital TV amplifier with integrated ADC. Analog and digital audio input signal interfaces are provided, an on-board microcontroller and USB PC interface is used for easily configuring the CS4525's internal registers, and a USB cable is included for use with the FlexGUI Windows configuration software. The CRD4525 schematic set is shown in Figure 6 through Figure 9.
1.1
Power
A 80 W OEM switching-mode power supply is included to power the CRD4525. The power supply provides +18 V to the CS4525 power stages, and an on-board buck-converter and regulator provide power to the logic-level digital circuitry. Power must be supplied from the included power supply to the CRD4525 via the power connector J3 (see the System Connections table on page 13).
1.2
CS4525 Digital TV Amplifier
A complete description of the CS4525 is included in the CS4525 product data sheet. The required configuration settings of the CS4525 are achieved via its control port registers, accessible through the CS4525 tab of the Cirrus Logic FlexGUI software. A register-level configuration interface is provided on the Register Maps tab. See the "PC Software Control" section on page 6 for more information.
1.3
CS8416 Digital Audio Receiver
A complete description of the CS8416 receiver (Figure 8 on page 16) and a discussion of the digital audio interface are included in the CS8416 data sheet. The CS8416 converts the input S/PDIF data stream into PCM data and clocks for the CS4525. The CS8416 operates in master mode and can provide PCM data in Left-Justified, IS, Right-Justified 16-bit, and RightJustified 24-bit interface formats. The most common operations of the CS8416 may be controlled via the S/PDIF Input Controls tab in the GUI software application. Advanced options are accessible through the CS8416 sub-tab on the Register Maps tab of the Cirrus Logic FlexGUI software.
1.4
System Clocking
A 24.576 MHz parallel resonant crystal, Y1, is available to provide a clock source to the CS4525. The crystal is mounted in pin sockets, allowing easy removal or replacement. Alternatively, an input SYS_CLK signal can be provided on pin 3 of the serial audio input header (J2).
1.5
External Data Headers
The evaluation board has been designed to allow interfacing with external systems via the headers J2, J4, and J11. Figure 6 shows the headers' electrical connections. The 12-pin, 3 column header, J2, provides access to the CS4525's serial audio input and SYS_CLK input signals. Place shunts across the SCLK, LRCK, and SDIN pins located in the columns labeled "S/PDIF" to connect to the on-board S/PDIF digital interface receiver circuitry. To use an external digital audio source, simply remove the shunts and connect a ribbon across the SCLK, LRCK, and SDIN pins located in the columns labeled "EXT SAI". A single ground column for the ribbon cable's ground connection is provided to maintain signal integrity.
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The 8-pin, 2 column header, J11, provides access to the CS4525's auxiliary serial audio port output signals, as well as the SYS_CLK output signal. A single ground column is provided to maintain signal integrity. The 20-pin, 2 column header, J4, is included to interface with a CRD4412 card. Various signals, power, and ground are presented on this header. Notably, this header includes the DLY_SDOUT and DLY_SDIN signals which can be used to interface with an external delay device or DSP. See Figure 6 for complete connectivity information.
1.6
Analog Inputs
RCA connectors supply the CS4525 analog inputs through single-ended passive circuits with one pole of input filtering. A resistive attenuation network is implemented to allow 2 VRMS input levels to be supplied to the CRD4525. Refer to the CS4525 data sheet for the maximum input signal level at the analog input pins.
1.7
Speaker Outputs
The CS4525 power outputs are configured for stereo parallel full-bridge operation. The outputs are routed through a 2nd order low-pass filter to remove high-frequency content from the output signals and then presented at the speaker wire crimp terminals (J5). The output filters are optimized for 8 speaker loads. The speaker terminal connections are shown below.
R
L
Figure 1. Speaker Terminal Configuration
1.8
PC Interface
A USB connection is provided to facilitate software control of the CS4525's internal registers. A graphical user interface is available for the CRD4525 to allow easy manipulation of the CS4525's internal registers. See the CS4525 datasheet for complete internal register descriptions. To enable the CRD4525, simply connect the supplied USB cable from an available USB port on a PC to the USB connector (J37) and launch the Cirrus Logic FlexGUI software. Refer to "PC Software Control" on page 6 for a description of the Graphical User Interface (GUI).
1.9
Tactile Controls
A volume control knob (S1), reset button (S2), and mute button (S3) are included for stand-alone operation of the CRD4525. These controls are currently unsupported by the firmware running on the CRD4525, and the PC interface must be used in order to operate the board. The CRD4525 firmware is field-upgradable through the Cirrus Logic FlexGUI application. When available, a new version of the FlexGUI (downloadable at www.cirrus.com/msasoftware) will automatically upgrade the firmware upon its first launch.
1.10
CRD4412 Interface
A keyed connector (J4) is included to interface with the CRD4412. The CRD4525 can be used with or without a CRD4412 attached.
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Without the CRD4412 attached, the CRD4525 configures itself for 2-channel stereo full-bridge operation. When the CRD4412 is attached, the CS4525 enables its bass manager and routes the LFE channel to the CRD4412 which amplifies the signal in mono parallel full-bridge mode. Together, the CRD4525 and CRD4412 implement a 2.1 configuration. The CRD4412 must be inserted and removed while power is not applied to the CRD4525.
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CRD4525 2. PC SOFTWARE CONTROL
The CRD4525 is designed for use with the Microsoft Windows based FlexGUI graphical user interface. This interface provides comprehensive control over the CS4525's internal registers via a PC's USB port. The FlexGUI software may be downloaded and installed from www.cirrus.com/msasoftware. Step-by-step instructions for using the FlexGUI are provided as follows: 1. Download and install the FlexGUI software from www.cirrus.com/msasoftware. 2. Connect the CRD4525 to a host PC using the supplied USB cable. 3. Connect load speakers to the speaker output terminals. 4. Connect an input source to the S/PDIF or analog input connectors. 5. Plug the input to the included +18 V power supply into an available power outlet. 6. Plug the output of the included +18 V power supply into the power input connector on the CRD4525. 7. Launch the FlexGUI software. The GUI will load and be displayed. 8. Un-check the "Power Down CS4525" check box to power-up the device. In this state, the CRD4525 will convert and amplify the content present on the optical S/PDIF input.
2.1
CS4525 Main Controls Tab
The CS4525 Main Controls tab provides a high-level intuitive interface to many of the basic configuration options of the CS4525. Use this tab to access functions such as power-down, input source, and volume control.
Figure 2. CS4525 Main Controls Tab
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2.2 CS4525 Aux & Filter Controls Tab
The CS4525 Aux & Filter Controls tab provides a high-level intuitive interface to many of the advanced configuration options of the CS4525. Use this tab to configure the auxiliary port, the internal filters, and advanced PWM adjustments. Control over device and board resets is also provided.
Figure 3. CS4525 Aux & Filter Controls Tab
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2.3 S/PDIF Input Controls Tab
When the CRD4525 is configured to make use of the CS8416 S/PDIF receiver, the devices must be configured for proper operation. The S/PDIF Input Controls tab provides a high-level intuitive interface to the most common configuration options of the CS8416.
Figure 4. S/PDIF Input Controls Tab
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2.4 Register Maps Tab
The Register Maps tab provides an easy register-level interface to the on-board devices. Register values can be modified on a bit-wise or byte-wise basis. To modify a single bit, first select the register by clicking its position in the register matrix, then click the appropriate push-button for the desired bit. To modify an entire register, simply enter the register's new value directly into the register matrix. Within the Register Maps tab, the CS4525 tab is used to access the CS4525's internal registers, and the CS8416 tab is used to access the CS8416's internal registers.
Figure 5. Register Maps Tab
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2.5 Pre-Configured Script Files
Pre-configured script files are provided with the CRD4525 to allow easy initial board bring-up. The board configurations stored within these files are described in sections 2.5.1 - 2.5.3.
2.5.1
Analog In
Using the pre-configured script file named "Analog In.fgs", an analog input signal applied to the analog inputs of the CRD4525 will be used as the CS4525's input source. The device will be powered up with no internal processing active and the master volume control set to -20 dB.
2.5.2
Optical SPDIF In
Using the pre-configured script file named "Optical SPDIF In.fgs", the optical S/PDIF input signal will be received by the CS8416 S/PDIF receiver. The CS8416 PCM output signals will be used as the CS4525's input source. The device will be powered up with no internal processing active and the master volume control set to -20 dB.
2.5.3
Coaxial SPDIF In
Using the pre-configured script file named "Coaxial SPDIF In.fgs", the coaxial S/PDIF input signal will be received by the CS8416 S/PDIF receiver. The CS8416 PCM output signals will be used as the CS4525's input source. The device will be powered up with no internal processing active and the master volume control set to -20 dB.
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CRD4525 3. GROUNDING AND POWER SUPPLY DECOUPLING
The CS4525 requires careful attention to power supply and grounding arrangements to optimize performance and heat dissipation and minimize radiated emissions. Figure 10 on page 18 shows the component placement. Figure 11 on page 19 shows the top layout. Figure 14 on page 22 shows the bottom layout. The decoupling capacitors are located as close to the CS4525 as possible. Extensive use of ground plane fill in the evaluation board yields large reductions in radiated noise.
3.1
Power Supply Decoupling
Proper power supply decoupling is one key to maximizing the performance of a Class-D amplifier. Because the design uses an open loop output stage, noise on the power supply rail will be coupled to the output. Careful decoupling of the power stage supply rails is essential. Figure 10 on page 18 demonstrates good decoupling capacitor placement. Notice that the small value decoupling capacitors are placed as close as physically possible to the power pins of the CS4525. The ground side of the capacitors is connected directly to top side ground plane, which is also used by the power supply return pins. This keeps the high frequency current loop small to minimize power supply variations and EMI. 470 F electrolytic capacitors are also located in close proximity to the power supply pins to supply the current locally for each channel. These are not required to be expensive low ESR capacitors. General purpose electrolytic capacitors that are specified to handle the ripple current can be used.
3.2
Electromagnetic Interference (EMI)
The EMI challenges that face a maker of Class-D amplifiers are largely the same challenges that have been faced by the switch mode power supply industry for many years. The numerous EMI consulting firms that have arisen and the many books that have been written on the subject indicate the scope of potential problems and available solutions. They should be considered a resource - most makers of switch mode equipment would benefit from developing a working relationship with a qualified EMI lab and from bringing their experience to bear on design issues, preferably early in the design process. This reference design is a board level solution which is meant to control emissions by minimizing and suppressing them at the source in contrast to containing them in an enclosure. The EMI requirements for an amplifier have added dimensions beyond those imposed on power supplies. Audio amplifiers are usually located in close proximity to radio receivers, particularly AM receivers which are notoriously sensitive to interference. Amplifiers also need to operate with speaker leads of unpredictable length and construction which make it possible for any high frequency currents that appear on the outputs to generate nuisance emissions. The criteria for judging successful EMI control is not as well defined for amplifier design as it is for power supplies. While the techniques of measuring conducted and radiated emissions are similar for both types of products, power supplies have a number of clearly defined (and legally imposed) thresholds that are useful mainly as guidelines when testing amplifiers.
3.2.1
Suppression of EMI at the Source
Several techniques are used in the circuit design and board layout to minimize high frequency fields in the immediate vicinity of the high power components. Specific techniques include the following: * As mentioned in Section 3.1, effective power supply decoupling of high frequency currents, and minimizing the loop area of the decoupling loop is one aspect of minimizing EMI. * Each output of the CS4525 includes "snubbing" components. For example, OUT1 and OUT2 include snubber components R24 (20 ) and C23 (330 pF). These components serve to damp ringing on the switching outputs in the 30-50 MHz range. The snubbing components should be as close as practical to the output pins to maximize their effectiveness.
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* A separate ground plane with a solid electrical connection to the chassis and which surrounds the speaker output connector should be implemented. This allows the speaker outputs to be RF decoupled to the chassis just before they exit the chassis from the speaker connector. * Make use of source termination resistors on all digital signals whose traces are longer than about 25 mm. It is extremely critical that the layout of the power amplifier section of the CRD4525 be copied as exactly as possible to assure best RF/EMI performance.
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CRD4525 4. SYSTEM CONNECTIONS & JUMPERS
Connector Name
Power In Left In Right In S/PIDF Input S/PIDF Input Speaker Connector USB C2
Reference Designator
J3 J1 J10 J6 J7 J5 J8 J9
Signal Direction
Input Input Input Input Output Input/Output Input/Output Power connector. +18V. Analog input to CS4525.
Connector Function
Coaxial digital input to CS8416 Optical digital input to CS8416 Analog output from CS4525. USB connection to PC for software control. Connection for programming the on-board microcontroller (U3). Table 1. System Connections
Control Name
Master Volume Board Reset Mute
Reference Designator
S1 S2 S3
Tactile Control Function
Tactile controls not currently supported. See "Tactile Controls" on page 4. Table 2. On-Board Tactile Controls
Connector Name
DSP IN DSP OUT CRD4412 I/F
Reference Designator
J2 J11 J4
Header Function
When shunts are placed across column 1 and 2, the CS4525 serial audio input data is sourced by the CS8416. To use external serial audio input data, connect the PCM source cable across column 2 and 3. Auxiliary serial audio data from the CS4525. Connection to CRD4412 daughter card. Table 3. System Headers
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5. CRD SCHEMATICS
CRD4525
Figure 6. CS4525 - Schematic Page 1
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Figure 7. Power Outputs - Schematic Page 2
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Figure 8. S/PDIF Digital Audio Input - Schematic Page 3
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Figure 9. Serial Control / Power - Schematic Page 4
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6. CRD LAYOUT
4.5"
2.65"
CRD4525
Figure 10. Silkscreen Top
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Figure 11. Topside Copper Layer
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20
CRD4525
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Figure 12. Inner Copper Layer 1
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Figure 13. Inner Copper Layer 2
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22
CRD4525
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Figure 14. Bottomside Copper Layer
CRD4525 7. REVISION HISTORY
Release
RD1 Initial Release
Changes
Contacting Cirrus Logic Support
For all product questions and inquiries, contact a Cirrus Logic Sales Representative. To find the one nearest to you, go to www.cirrus.com.
IMPORTANT NOTICE Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third parties. This document is the property of Cirrus and by furnishing this information, Cirrus grants no license, express or implied under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual property rights. Cirrus owns the copyrights associated with the information contained herein and gives consent for copies to be made of the information only for use within your organization with respect to Cirrus integrated circuits or other products of Cirrus. This consent does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale. CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE ("CRITICAL APPLICATIONS"). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED FOR USE IN AIRCRAFT SYSTEMS, MILITARY APPLICATIONS, PRODUCTS SURGICALLY IMPLANTED INTO THE BODY, AUTOMOTIVE SAFETY OR SECURITY DEVICES, LIFE SUPPORT PRODUCTS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF CIRRUS PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER'S RISK AND CIRRUS DISCLAIMS AND MAKES NO WARRANTY, EXPRESS, STATUTORY OR IMPLIED, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR PARTICULAR PURPOSE, WITH REGARD TO ANY CIRRUS PRODUCT THAT IS USED IN SUCH A MANNER. IF THE CUSTOMER OR CUSTOMER'S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES, BY SUCH USE, TO FULLY INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND OTHER AGENTS FROM ANY AND ALL LIABILITY, INCLUDING ATTORNEYS' FEES AND COSTS, THAT MAY RESULT FROM OR ARISE IN CONNECTION WITH THESE USES. Cirrus Logic, Cirrus, and the Cirrus Logic logo designs are trademarks of Cirrus Logic, Inc. All other brand and product names in this document may be trademarks or service marks of their respective owners. IC is a registered trademark of Philips Semiconductor. Windows is a registered trademark of Microsoft Corporation.
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