CRD-4525-Q1 Cirrus Logic Inc, CRD-4525-Q1 Datasheet - Page 12

• Manufacturer Part Number: CRD-4525-Q1
• Description: Audio Modules & Development Tools Eval Bd PWM Contrlr+ PwrStg_2Lyr 1oz Cu
• Manufacturer: Cirrus Logic Inc

Specifications of CRD-4525-Q1

• Description/function: Audio Amplifiers
• Operating Supply Voltage: 18 V
• Product: Audio Modules
• For Use With/related Products: CS4525
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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3. STAND-ALONE MODE CONTROL
The CRD4525-Q1 is capable of operation without being connected to a computer by operating in stand-alone mode.
When in this mode, the board is controlled by on-board hardware controls detailed in
volume control on the edge of the board controls the volume. Tapping the mute button mutes/un-mutes the PWM
outputs of the CS4525.
When a valid SPDIF signal is not present, the CS4525 is automatically configured to amplify the audio signal present
on the RCA analog input connectors. When a valid SPDIF signal is present, the CS4525 is automatically configured
to amplify the audio signal present in the SPDIF stream. Holding down the mute button for three seconds switches
between optical SPDIF input and coaxial SPDIF input.
4. 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.
on page 20 shows the top layout.
located as close to the CS4525 as possible. Extensive use of ground plane fill in the evaluation board yields large
reductions in radiated noise.
4.1
4.2
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.
coupling 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.
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 makes it possible for any high-frequency currents that appear on the outputs
to generate nuisance emissions.
For more detailed information regarding the EMI performance of the CRD4525-Q1, please refer to
10. “Electromagnetic Compliance” on page
Figure 13 on page 22
Figure 9 on page 18
30.
shows the bottom layout. The decoupling capacitors are
shows the component placement. Figure 11
Figure 9 on page 18
Table 2 on page
demonstrates good de-
CRD4525-Q1
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