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PDF CRD4525 Data sheet ( Hoja de datos )
| Número de pieza | CRD4525 | |
| Descripción | 2 x 15 W Digital Amplifier Reference Design | |
| Fabricantes | Cirrus Logic | |
| Logotipo |  |
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CRD4525
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 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® 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 deliv-
ers 15 W per full-bridge channel into 8 Ω loads using a
single +18 V supply. The CRD4525 is powered by an in-
cluded 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 2nd 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 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
Optical
Receiver
Coaxial Input
CS8416
S/PIDF
Receiver
PCM
Input
Header
CS4525
Output
Filter
Output
Filter
Speaker
Connector
Aux Port Header
CRD4412 Interface Header
8Ω
8Ω
USB
I/O
http://www.cirrus.com
Micro-controller
Status LED’s
Tactile Controls
Power
Jack
Included 18 V Power Supply
Copyright © Cirrus Logic, Inc. 2006
(All Rights Reserved)
SEPTEMBER '06
DS726RD1
1 page  
CRD4525
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.
DS726RD1
5
5 Page 
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 µF electrolytic capacitors are also lo-
cated 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 prob-
lems and available solutions. They should be considered a resource - most makers of switch mode equip-
ment 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 sup-
pressing 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 emis-
sions 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 mini-
mizing 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 Ω) 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.
DS726RD1
11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet CRD4525.PDF ] | |
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