CRD4525-Q1
2 x 15 W CS4525 Digital Amplifier Reference Design
Features
Output Filters Optimized for 8
Ω
Loads
Delivers 15 W/Ch into 8
Ω
at 0.5 % THD+N
Single-Ended 2 V
RMS
Stereo Analog Inputs
Optical and Coaxial S/PDIF Inputs
Demonstrates EMI Compliant Design per FCC
Class B Part 15 and CISPR 22 Standards
Flexible I/O Headers Provided
– PCM Input Signal Interface
– Auxiliary Serial Port Signal Interface
– Delay Port Signal Interface
– PWM Logic Level Signal Interface
Optional CRD4412A Daughter-Card for
Subwoofer Channel
– Implements a 2.1 Configuration
Demonstrates Recommended 4-Layer Layout
and Grounding Arrangements
+18 V Switching Mode Power Supply Included
Can be operated by On-Board Controls or with
Windows
®
Compatible Graphical User
Interface
Description
The CRD4525-Q1 demonstrates the CS4525 digital
PWM controller with integrated power stages. This ref-
erence design implements a two-channel amplifier that
delivers 15 W per full-bridge channel into 8
Ω
loads us-
ing a single +18 V supply. The CRD4525-Q1 is
powered by an included 80 W switching mode power
supply.
Standard RCA phono jacks are provided to easily inter-
face 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 2
nd
order low-pass filter (LPF) to re-
move high-frequency components from the output
signal, effectively converting it from digital to analog.
The Windows software provides a GUI to make config-
uration of the CRD4525-Q1 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. Additionally, control over ba-
sic functions is possible via on-board hardware controls
without the need to attach the CRD4525-Q1 to a PC.
ORDERING INFORMATION
CRD4525-Q1
CS4525 Reference Design
Stereo Analog
Inputs
Output
Filter
Speaker
Connector
8
Ω
Optical
Receiver
CS8416
S/PIDF
Receiver
Coaxial Input
PCM
Input
Header
CS4525
Output
Filter
8
Ω
Aux Port Header
CRD4412A Interface Header
USB
I/O
Status LED’s
Micro-controller
Tactile Controls
Power
Jack
Included 18 V Power Supply
Copyright
©
Cirrus Logic, Inc. 2007
(All Rights Reserved)
http://www.cirrus.com
OCTOBER '07
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CRD4525-Q1
TABLE OF CONTENTS
1. SYSTEM OVERVIEW ............................................................................................................................. 4
1.1 Power ............................................................................................................................................... 4
1.2 CS4525 Digital Amplifier .................................................................................................................. 4
1.3 CS8416 Digital Audio Receiver ........................................................................................................ 4
1.4 System Clocking .............................................................................................................................. 4
1.5 External Data Headers ..................................................................................................................... 4
1.6 Analog Inputs ................................................................................................................................... 5
1.7 Speaker Outputs .............................................................................................................................. 5
1.8 PC Control ....................................................................................................................................... 5
1.9 Stand-Alone Control ......................................................................................................................... 5
1.10 External Power Stage Interface ..................................................................................................... 6
2. PC SOFTWARE CONTROL ................................................................................................................... 7
2.1 CS4525 Main Controls Tab .............................................................................................................. 7
2.2 CS4525 Aux & Filter Controls Tab ................................................................................................... 8
2.3 S/PDIF Input Controls Tab ............................................................................................................... 9
2.4 Register Maps Tab ......................................................................................................................... 10
2.5 Pre-Configured Script Files ............................................................................................................ 11
2.5.1 Analog In ............................................................................................................................... 11
2.5.2 Optical SPDIF In .................................................................................................................... 11
2.5.3 Coaxial SPDIF In ................................................................................................................... 11
3. STAND-ALONE MODE CONTROL ..................................................................................................... 12
4. GROUNDING AND POWER SUPPLY DECOUPLING ........................................................................ 12
4.1 Power Supply Decoupling .............................................................................................................. 12
4.2 Electromagnetic Interference (EMI) ............................................................................................... 12
4.2.1 Suppression of EMI at the Source ......................................................................................... 13
5. SYSTEM CONNECTIONS & JUMPERS .............................................................................................. 14
6. CRD SCHEMATICS .............................................................................................................................. 15
7. CRD LAYOUT ...................................................................................................................................... 18
8. PERFORMANCE PLOTS ..................................................................................................................... 23
9. THERMAL DE-RATING ........................................................................................................................ 29
10. ELECTROMAGNETIC COMPLIANCE (EMC) PERFORMANCE ...................................................... 30
10.1 EMI Testing Procedures .............................................................................................................. 30
10.2 System Configuration ................................................................................................................... 31
10.3 CRD4525-Q1 Test Results .......................................................................................................... 31
11. REVISION HISTORY .......................................................................................................................... 32
LIST OF FIGURES
Figure 1.Speaker Terminal Configuration ................................................................................................... 5
Figure 2.CS4525 Main Controls Tab ........................................................................................................... 7
Figure 3.CS4525 Aux & Filter Controls Tab ................................................................................................ 8
Figure 4.S/PDIF Input Controls Tab ............................................................................................................ 9
Figure 5.Register Maps Tab ...................................................................................................................... 10
Figure 6.CS4525 - Schematic Page 1 ....................................................................................................... 15
Figure 7.USB Microcontroller & Tactile Control - Schematic Page 2 ........................................................ 16
Figure 8.Power & I/O Connections - Schematic Page 3 ........................................................................... 17
Figure 9.Component Map ......................................................................................................................... 18
Figure 10.Top-Side Copper Layer ............................................................................................................. 19
Figure 11.Inner Copper Layer 1 ................................................................................................................ 20
Figure 12.Inner Copper Layer 2 ................................................................................................................ 21
Figure 13.Bottom-Side Copper Layer ....................................................................................................... 22
Figure 14.Frequency Response ................................................................................................................ 23
Figure 15.THD+N vs. Power ..................................................................................................................... 24
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CRD4525-Q1
Figure 16.THD+N vs. Frequency .............................................................................................................. 25
Figure 17.FFT at -60 dB Input ................................................................................................................... 26
Figure 18.FFT at 0 dB Input ...................................................................................................................... 27
Figure 19.Inter-Modulation Distortion of 19 kHz + 20 kHz ........................................................................ 28
Figure 20.Thermal De-Rating Curve for a Typical CRD4525-Q1 .............................................................. 29
Figure 21.Test Facility Setup .................................................................................................................... 30
Figure 22.Vertical Peak Scan Data for the CRD4525-Q1 ......................................................................... 31
Figure 23.Horizontal Peak Scan Data for the CRD4525-Q1 ..................................................................... 31
LIST OF TABLES
Table 1. System Connections ................................................................................................................... 14
Table 2. On-Board Tactile Controls ........................................................................................................... 14
Table 3. System Headers .......................................................................................................................... 14
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CRD4525-Q1
1. SYSTEM OVERVIEW
The CRD4525-Q1 reference design is an excellent means for evaluating the CS4525 30 W digital amplifier with in-
tegrated 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 stand-alone mode is supported
through on-board tactile controls.
The CRD4525-Q1 schematic set is shown in
Figure 6
through
Figure 8.
1.1
Power
A 80 W OEM switching-mode power supply is included to power the CRD4525-Q1. The power supply pro-
vides +18 V to the CS4525 power stages, and an on-board buck-converter and regulator provide power to
the logic-level digital circuitry.
Power may be supplied from the included power supply or any 12-18 VDC power supply capable of deliv-
ering sufficient current for the intended power output. Connection for the power supply is provided in J3 (see
the
System Connections
table on
page 14).
1.2
CS4525 Digital Amplifier
A complete description of the CS4525 is included in the CS4525 product data sheet.
Optional user configuration settings of the CS4525 are provided through its control port registers, accessible
through the CS4525 tab of the Cirrus Logic FlexGUI software. A register-level configuration interface is pro-
vided on the Register Maps tab. See the
“PC Software Control” section on page 7
for more information.
1.3
CS8416 Digital Audio Receiver
A complete description of the CS8416 receiver (Figure
8 on page 17)
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, I²S, Right-Justified 16-bit, and Right-
Justified 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 col-
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CRD4525-Q1
umns labeled “EXT SAI”. A single ground column for the ribbon cable’s ground connection is provided to
maintain signal integrity.
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 CRD4412A 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 con-
nectivity 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 V
RMS
input levels to be supplied to
the CRD4525-Q1. 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 full-bridge operation. The outputs are routed through
a 2
nd
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
Ω
speaker loads. The speaker
terminal connections are shown below.
R
L
Figure 1. Speaker Terminal Configuration
1.8
PC Control
A USB connection is provided to facilitate software control of the CS4525’s internal registers.
A graphical user interface is available for the CRD4525-Q1 to allow easy manipulation of the CS4525’s in-
ternal registers. See the CS4525 data sheet for complete internal register descriptions.
To enable the CRD4525-Q1, 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.
A visual indicator is provided by an on-board LED (D12) that illuminates when the board is being operated
under PC control. When operating under PC Control, the stand-alone controls on the board should not be
manipulated.
Refer to
“PC Software Control” on page 7
for a description of the Graphical User Interface (GUI).
1.9
Stand-Alone Control
A volume control knob (S1), reset button (S2), and mute button (S3) are included for stand-alone operation
of the CRD4525-Q1. These controls were not supported by early versions of firmware running on the
CRD4525-Q1, so it may be necessary to upgrade older firmware versions to enable their functionality.
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Analogue and Mixed Signal
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