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1 x 1.7 W CS35L01 Amplifier Reference Design Kit
Features
Four boards provided in the CS35L01 Amplifier
Reference Design Kit
Separate boards for each mode configuration
– SD, FSD, HD, and FHD
CS35L01 produces a default +6-dB Gain
Delivers 1.4 W/Ch into 8 at 1% THD+N
Delivers 1.7 W/Ch into 8 at 10% THD+N
Differential mono analog inputs
Demonstrates recommended 4-layer layout
and grounding arrangements
– Optional output filter connections
– Optional gain adjustment resistors
Powered by a sing le 2.5- to 5.5-V power supply
Device shutdown control
Description
The CRD35L01 demonstrates the CS35L01 high-effi-
ciency Hybrid Class-D audio amplifier. This reference
design implements a singl e-channel amplifier that deliv-
ers 1.7 W p er full-brid ge channel into 8- loads using a
single +5-V supply.
Differential audio inputs can easily be connected
through the J1 header. If desired, the gain can be ad-
justed through the optional input resistors.
The -SD, -FSD, -HD, or -FHD suffix designates the
CS35L01’s operational mode. Each of the four boards
is configured to operate in each of the four correspond-
ing modes of the CS35L01 device.
Device shutdown control is available through the J2
header.
ORDERING INFORMATION
CRD35L01 CS35L01 Reference Design
Shutdown
Control (J2)
Speaker
Outp u t (J3)
Optional
Gain
Adjustment
Analog
In p u t (J 1 ) CS35L01
(SD Mode)
Optional
Output
Filter
VBATT
Power (J4)
Shutdown
Control (J2)
Speaker
Outp u t (J3)
Optional
Gain
Adjustment
Analog
In p u t (J 1 ) CS35L01
(FSD Mode)
Optional
Output
Filter
VBATT
Powe r (J4)
Shutdown
Control (J2)
Speaker
Outp u t (J3)
Optional
Gain
Adjustment
Analog
In p u t (J 1 ) CS35L01
(HD Mo d e)
Optional
Output
Filter
VBATT
Powe r (J4)
Shutdown
Control (J2)
Speaker
Outp u t (J3)
Optional
Gain
Adjustment
Analog
In p u t (J 1 ) CS35L01
(FHD M o d e)
Optional
Output
Filter
VBATT
Powe r (J4)
CRD35L01
APR '10
DS914RD2
2DS914RD2
CRD35L01
TABLE OF CONTENTS
1. SYSTEM OVERVIEW ............................................................................................................................. 4
1.1 CS35L01 Hybrid Class-D Amplifier .................................................................................................. 4
1.2 Power Supply ................................................................................................................................... 4
1.3 Operational Modes ........................................................................................................................... 4
1.4 Shutdown Control ............................................................................................................................ 4
1.5 Amplifier Gain .................................................................................................................................. 4
1.5.1 Optional Input Gain Adjustment Resistors ......................... ................... .... ... ... ... ... .... .............. 4
1.6 Differential Analog Inputs ................................................................................................................. 5
1.7 Speaker Outputs .............................................................................................................................. 5
1.7.1 Optional Speaker Output EMI Filter Components ................................................................... 5
2. GROUNDING AND POWER SUPPLY DECOUPLING .......................................................................... 6
2.1 Power Supply Decoupling ................................................................................................................ 6
2.2 Electromagnetic Interference (EMI) ................................................................................................. 6
2.2.1 Suppression of EMI at the Source .. .... ... ... ... .................... ... ... ... .................... ... ... ... .... .............. 6
3. SYSTEM CONNECTORS AND JU MP ERS ....... ... ... ... .... ................... ... ... .... ... ... ... .................... ... ... ... .... . 7
4. CRD SCHEMATIC .................................................................................................................................. 8
4.1 Bill of Materials ................................................................................................................................. 9
5. CRD LAYOUT ....................................................................................................................................... 10
6. REVISION HISTORY ............................................................................................................................ 14
LIST OF FIGURES
Figure 1.Optional Bypass Trace Cut Locations ........................................................................................... 5
Figure 2.CRD35L01-SD Schematic ................... .... ... ... ... .... ... ... ... .... ... ................... ... .... ... ... ... ... .... .. ............ 8
Figure 3.CRD35L01-FSD Schematic ........................ ... ... .... ... ... ... .... ... ... ... .................... ... ... ... ... .... ... ........... 8
Figure 4.CRD35L01-HD Schematic .......... ... ... ... .... ... ... ... .... ... ................... ... .... ... ... ... .... ... ... ... ... .................. 8
Figure 5.CRD35L01-FHD Schematic ..... ... ... ... ... .... ... ... ... .................... ... ... ... .... ... ... ... .... ... ... ... ... .... ... ........... 8
Figure 6.CRD35L01-SD Top Side Component Placement .......... .... ... ... ... ... .... ... ... ... .... ... ... ... ... .... ... ... ... ... 10
Figure 7.CRD35L01-SD Bottom Side Component Placem ent .................................................................. 10
Figure 8.CRD35L01-SD Layer 1 Copper ..................... ... .... ... ... ... .... ... ... ... ... .... ... ... ... .... ... ... ... ... .... ... ......... 10
Figure 9.CRD35L01-SD Layer 2 Copper ..................... ... .... ... ... ... .... ... ... ... ... .... ... ... ... .... ... ... ... ... .... ... ......... 10
Figure 10.CRD35L01-SD Layer 3 Copper ................................................................................................ 10
Figure 11.CRD35L01-SD Layer 4 Copper ................................................................................................ 10
Figure 12.CRD35L01-FSD Top Side Component Placement ................................................................... 11
Figure 13.CRD35L01-FSD Bottom Side Component Placement . .... ... ... ... ... .... ... ... ... .................... ... ... ... ... 11
Figure 14.CRD35L01-FSD Layer 1 Copper .............................................................................................. 11
Figure 15.CRD35L01-FSD Layer 2 Copper .............................................................................................. 11
Figure 16.CRD35L01-FSD Layer 3 Copper .............................................................................................. 11
Figure 17.CRD35L01-FSD Layer 4 Copper .............................................................................................. 11
Figure 18.CRD35L01-HD Top Side Component Placement .................. ... .................... ... ... ... ... .... ... ... ... ... 12
Figure 19.CRD35L01-HD Bottom Side Component Placement ....... ................... ................ ................ ...... 12
Figure 20.CRD35L01-HD Layer 1 Copper ................................................................................................ 12
Figure 21.CRD35L01-HD Layer 2 Copper ................................................................................................ 12
Figure 22.CRD35L01-HD Layer 3 Copper ................................................................................................ 12
Figure 23.CRD35L01-HD Layer 4 Copper ................................................................................................ 12
Figure 24.CRD35L01-FHD Top Side Component Placement ... ................ ................ ................ ................ 13
Figure 25.CRD35L01-FHD Bottom Side Component Placement ............................................................. 13
Figure 26.CRD35L01-FHD Layer 1 Copper .............................................................................................. 13
Figure 27.CRD35L01-FHD Layer 2 Copper .............................................................................................. 13
Figure 28.CRD35L01-FHD Layer 3 Copper .............................................................................................. 13
Figure 29.CRD35L01-FHD Layer 4 Copper .............................................................................................. 13
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CRD35L01
LIST OF TABLES
Table 1. System Input and Output Connections .... ..................................................................................... 7
Table 2. J2 Shutdown Control Settings ....................................................................................................... 7
Table 3. Bill of Materials Listing .................................................................................................................. 9
4DS914RD2
CRD35L01
1. SYSTEM OVERVIEW
The CRD35L01 reference design is a practical means for evaluating the CS35L01 high-efficiency Class-D audio am-
plifier with idle current consumption. A diffe rential mono analog input signal interface is provided. Optional input g ain
and output filtering comp onent placehol ders are provide d for easy modifica tion to custom tune the CS35L01 for the
user’s specific system requirements.
1.1 CS35L01 Hybrid Class-D Amplifier
The CS35L01 Hybrid Class-D amplifier is a mono, full-bridge, closed-loop, +6-dB gain, audio amplifier avail-
able in a 9-ball, WLCSP package. A complete description of the CS35L01 device is included in the CS35L01
product data sheet.
1.2 Power Supply
A single +2.5 to +5.5 VDC powe r su pp ly is required to power the CRD35L01. The supply must be capable
of delivering sufficient current for the intended power output. The supply provides power to the CS35L01.
The power supply connection to the board is provided by the header J4. The positive terminal is labeled
VBATT. The ground ter m ina l is labe led GND.
1.3 Operational Modes
The CS35L01 device has fou r operational modes, each o f which require sl ightly different hardware conn ec-
tions. Four boards are available to illustrate the hardware design differences between each of the four
modes. More information on the specifics of each op erationa l mode can be found in the CS3 5L01/03 prod-
uct datasheet. The CRD names listed below are populated with a CS35L01 device.
• CRD35L01-SD: Standard Class-D Mode
• CRD35L01-FSD: Reduced-Frequency Standard Class-D Mode
• CRD35L01-HD: Hybrid Class-D Mode
• CRD35L01-FHD: Reduced-Frequency Hybrid Class-D Mode
The CRD35L01-SD schematic is shown in Figure 2 on page 8. The CRD35L01-FSD schematic is shown in
Figure 3 on page 8. The C RD35L01-HD schematic is shown in Figure 5 on page 8. The CRD35L01-FHD
schematic is shown in Figure 5 on page 8.
1.4 Shutdown Control
The J2 header contains shutdown control for the CS35L01 device. Placing a jumper across the J2 header
pulls the SD line LOW and shuts down the amplifier. When no jumper is present, the SD line is pulled HIGH
by the R3 resistor, enabling normal operation.
1.5 Amplifier Gain
The amplifier gain of the CS35L01 device is +6 dB by default. Th e amplifier gain can be redu ced through
the use of the optional input gain adjustment resistors on the CRD35L01.
1.5.1 Optional Input Gain Adjustment Resistors
The CRD35L01 contains optional gain adjustment resistor plac eholders (R1 a nd R2). By default, these
placeholders are no t populated and ar e bypassed with a signal trace configuring the CS35L01 to operate
at its default gain. The gain adjustment resistors are necessary only when a gain of +6 dB is not desired.
DS914RD2 5
CRD35L01
By adding series resistance to the input, the signal amplitude to the CS35L01 will be reduced, and will
reduce the overall system gain. The typical input impedance values of the CS35L01 can be found in the
device datasheet.
In order to use the optional gain adjustment resistors, the traces between the R1 pads and the traces be-
tween the R2 pads must b e cut to break the bypass circu it, before popula ting R1 and R2 with the desired
resistance values. Th e loca tio n of th ese requ ire d cuts are sho wn in F i gur e 1. After th e tr ace betwe en th e
pads has been broken, the gain adjustment resistors can be added to the board.
1.6 Differential Analog Inputs
The differential audio inputs into the CS35L01 are provided by the 3-pin header (J1) through DC blocking
capacitors (C1 and C2). The C1 and C2 capacitors allow for an analog source to connect directly to the
CS35L01 regardless of any DC bias that may be present between the analog audio source’s outputs and
CS35L01 inputs.
1.7 Speaker Outputs
The CS35L01 power outputs are configured for a full-bridge, single audio channel. The outputs are routed
through an opt ion al EM I out pu t filte r an d then presented at the J3 header (OUT- and OUT+).
1.7.1 Optional Speaker Output EMI Filter Components
As mentioned above, the CS35L01 contains optional placeholders for a serie s ferrite bead an d shunt ca-
pacitor output filter. For most applications with very short speaker leads between the CS35L01 and the
speaker, use of these components will not be necessary. However, if there is a long signal path between
the CS35L01 and the speaker or if the system requires conne cting to cables off the PCB, it is suggested
that the ferrite bead and capacitor are populated with the recommended values shown in Figure 3 on
page 9.
In order to use the optional output filter ferrite beads, the traces between the L1 pads and the traces be-
tween the L2 pads must be cut to break the bypass circuit, before populating L1 and L2 with the desired
component values. The location of these required cuts are shown in Figure 1.
Figure 1. Optional Bypass Trac e Cut Locations
Cut the bypass
traces before insert-
ing the optional
input gain adjust-
ment resistors
Cut the bypass
traces before insert-
ing the optional out-
put filter ferrite
beads
6DS914RD2
CRD35L01
2. GROUNDING AND POWER SUPPLY DECOUPLING
The CS35L01 requires car eful attention to power supply an d grounding arran gements to optimize performa nce and
minimize radiated emissions. The decoupling capacitors should be located as close to the CS35L01 as possible.
This can be optimized by using both top and bottom side componen t population as demonstrated by the CRD35L01
boards.
2.1 Power Supply Decoupling
Proper power supply de coupling is one key to maximizing the performance of a Class-D amplifier. Figure 6
and Figure 7 on page 10 show the component placement for the CRD35L01- SD board . Figure 18 and Fig-
ure 19 on page 12 shows the component side placement for the CRD35L01-HD board. Note the addition of
the C8 capacitor connected to the LFILT+ pin . This pin is used as decoupling fo r the intern al LDO regulator
when operating in HD or FHD modes.
The small value decoupling capacitors are placed as close as possible to the power pins of the CS35L01
on the CRD35L01 boards. For the WLCSP package it is recommended that the power supply decoupling
capacitors re side on the opposite si de of the board from which the CS35L01 is populated on. This allows
for very close placement of the decoupling capacitors to the power supply pins of the CS35L01 without in-
terfering with the differential audio inputs or differential audio outputs. This placement keeps the high-fre-
quency current loop small to minimize power supp ly variatio ns an d EMI. These ca pacitor s are no t r equir ed
to be expensive low-ESR capacitors.
2.2 Electromagnetic Interference (EMI)
This reference design is a board-level solution that is meant to control emissions by minimizing and sup-
pressing them at the source, in contrast to containing them in an enclosure.
2.2.1 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 inclu de the following:
• As mentione d in Section 2.1, effective power supply decoupling of high-frequency currents and mini-
mizing the loop are a of the de co up lin g loop is one aspect of minimizing EMI.
• Differential input and output signals sh ould be routed differentially whenever possible.
• A solid ground plane on the adjacent PCB layer underneath all high-frequency traces to minimize the
loop area of the retu rn path.
• Optional output EMI filter compone nt landings are available as described in Section 1.7.1, if emissions
need to be further reduced.
• Keeping the switching output filter components as close to the amplifier as possible.
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CRD35L01
3. SYSTEM CONNECTORS AND JUMPERS
Connector
Name Reference
Designator Pin Signal
Direction Connector Function
IN+
IN-
GND
J1
J1
J1
1
2
3
Input
Input
GND
Differential analog input (+) to CS35L01.
Differential analog input (-) to CS35L01.
GND reference connection.
SD
GND J2
J2 1
2Input
GND Device shutdown control.
GND reference connection.
OUT+
OUT- J3
J3 1
2Output
Output Analog output (+) from CS35L01.
Analog output (-) from CS35L01.
VBATT
GND J4
J4 1
2Input
Input Positive connection from power supply, +2.5 to +5.5 VDC.
GND connection from power supply.
Table 1. System Input and Output Connections
Control Name Function Function Selected
SD Shutdown Low = CS35L01 shutdown enabled
High = CS35L01 shutdown disabled
Table 2. J2 Shutdown Control Settings
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CRD35L01
4.1 Bill of Materials
The component listing below is shown for th e four CRD35L01 board variations (-SD, -FSD, - HD, and -FHD).
Unpopulated (DNP) components are listed with recommended components for reference purposes.
Table 3. Bill of Materials Listing
Note:
1. C8 is not present on SD or FSD boards. LFILT+ (B1) is connected directly to VBATT.
Qty Reference
Designator(s) CRD35L01 Boards Description MFG / Part Number
2 C1, C2 -SD, -FSD, -HD, -FHD Capacitor, 0.1 F, X7R, 16 V Kemet / C0402C104K4RAC
1 C3 -SD, -FSD, -HD, -FHD Capacitor, 1 F, X5R, 10 V Kemet / C0603C105K8PAC
1 C6 -SD, -FSD, -HD, -FHD Capacitor, 10 F, X5R, 6.3 V Kemet / C0603C106M9PAC
1 C7 -SD, -FSD, -HD, -FHD Capacitor, 0.1 F, X7R, 16 V Kemet / C0402C104K4RAC
1 C8 -HD, -FHD (Note 1) Capacitor, 1 F, X5R, 10 V Kemet / C0603C105K8PAC
1 R3 -SD, -FSD, -HD, -FHD Resistor 47k , 1/16 W Dale / CRCW040247K0JNED
1 U1 -SD, -FSD, -HD, -FHD Hybrid Class-D WLCSP Amp Cirrus Logic / CS35L01-CWZ
(DNP) C4, C5 -SD, -FSD, -HD, -FHD Capacitor, 1 nF, X7R, 50 V Murata / GRM155R71H102KA01D
(DNP) FB1, FB2 -SD, -FSD, -HD, -FHD Ferrite Bead, 220 @ 100 MHz TDK / MPZ1608S221A
(DNP) R1, R2 -SD, -FSD, -HD, -FHD Resistor, 0 , 1/16 W Yageo / RC0402JR-070RL
14 DS914RD2
CRD35L01
6. REVISION HISTORY
Release Changes
RD1 – Initial Release
RD2 – Updated front page 1% and 10% output power numbers to match DS909A2 datash eet.
– Updated Figure 2 on page 8 to match the updated CRD35L01-SD Rev A1 schematic.
– Updated Figure 3 on page 8 to match the updated CRD35L01-FSD Rev A1 schematic.
– Updated Figure 4 on page 8 to match the updated CRD35L01-HD Rev A1 schematic.
– Updated Figure 5 on page 8 to match the updated CRD35L01-FHD Rev A1 schematic.
– Updated BOM values for C6 & C7 in Table 3 on page 9 to match the updated Rev A1 schematics and
the typical connection diagram in the DS909A2 datasheet. All CRD3 5L01-SD, -FSD, -HD, and -FHD
boards with an assembly date of 02/15/1 0 or earlier contain components from the Rev A0 BOM.
Contacting Cirrus Logic Support
For all product questions and inq uiries, contact a Cirrus Logic Sales Representative.
To find the one nearest to you, go to www.cirrus.com.
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