CRD35L01 1 x 1.7 W CS35L01 Amplifier Reference Design Kit Features Description Four boards provided in the CS35L01 Amplifier The CRD35L01 demonstrates the CS35L01 high-efficiency Hybrid Class-D audio amplifier. This reference design implements a single-channel amplifier that delivers 1.7 W per full-bridge channel into 8- loads using a single +5-V supply. Reference Design Kit Separate boards for each mode configuration – SD, FSD, HD, and FHD CS35L01 produces a default +6-dB Gain Differential audio inputs can easily be connected through the J1 header. If desired, the gain can be adjusted through the optional input resistors. Delivers 1.4 W/Ch into 8 at 1% THD+N Delivers 1.7 W/Ch into 8 at 10% THD+N 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 corresponding modes of the CS35L01 device. Differential mono analog inputs Demonstrates recommended 4-layer layout and grounding arrangements – Optional output filter connections – Optional gain adjustment resistors Device shutdown control is available through the J2 header. Powered by a single 2.5- to 5.5-V power supply Device shutdown control Analog Input (J1) Optional Gain Adjustment ORDERING INFORMATION CRD35L01 CS35L01 Reference Design CS35L01 Optional Output Filter Speaker Output (J3) (SD Mode) Shutdown Control (J2) Analog Input (J1) VBATT Power (J4) Optional Gain Adjustment CS35L01 Optional Output Filter Speaker Output (J3) (FSD Mode) Shutdown Control (J2) Analog Input (J1) VBATT Power (J4) Optional Gain Adjustment CS35L01 Optional Output Filter Speaker Output (J3) (HD Mode) Shutdown Control (J2) Analog Input (J1) VBATT Power (J4) Optional Gain Adjustment CS35L01 Optional Output Filter Speaker Output (J3) (FHD Mode) Shutdown Control (J2) http://www.cirrus.com VBATT Power (J4) Copyright Cirrus Logic, Inc. 2010 (All Rights Reserved) APR '10 DS914RD2 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 JUMPERS ............................................................................................ 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 Placement .................................................................. 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 2 DS914RD2 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 DS914RD2 3 CRD35L01 1. SYSTEM OVERVIEW The CRD35L01 reference design is a practical means for evaluating the CS35L01 high-efficiency Class-D audio amplifier with idle current consumption. A differential mono analog input signal interface is provided. Optional input gain and output filtering component placeholders are provided for easy modification 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 available 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 power supply 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 terminal is labeled GND. 1.3 Operational Modes The CS35L01 device has four operational modes, each of which require slightly different hardware connections. Four boards are available to illustrate the hardware design differences between each of the four modes. More information on the specifics of each operational mode can be found in the CS35L01/03 product 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 CRD35L01-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. The amplifier gain can be reduced 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 placeholders (R1 and R2). By default, these placeholders are not populated and are 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. 4 DS914RD2 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 between the R2 pads must be cut to break the bypass circuit, before populating R1 and R2 with the desired resistance values. The location of these required cuts are shown in Figure 1. After the trace between the 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 optional EMI output filter and 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 series ferrite bead and shunt capacitor 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 connecting 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 between 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. Cut the bypass traces before inserting the optional output filter ferrite beads Cut the bypass traces before inserting the optional input gain adjustment resistors Figure 1. Optional Bypass Trace Cut Locations DS914RD2 5 CRD35L01 2. GROUNDING AND POWER SUPPLY DECOUPLING The CS35L01 requires careful attention to power supply and grounding arrangements to optimize performance 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 component population as demonstrated by the CRD35L01 boards. 2.1 Power Supply Decoupling Proper power supply decoupling 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 Figure 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 for the internal 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 reside on the opposite side 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 interfering with the differential audio inputs or differential audio outputs. This placement keeps the high-frequency current loop small to minimize power supply variations and EMI. These capacitors are not required 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 suppressing 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 include the following: • As mentioned in Section 2.1, effective power supply decoupling of high-frequency currents and minimizing the loop area of the decoupling loop is one aspect of minimizing EMI. • Differential input and output signals should 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 return path. • Optional output EMI filter component 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. 6 DS914RD2 CRD35L01 3. SYSTEM CONNECTORS AND JUMPERS Connector Name Reference Designator Pin Signal Direction IN+ INGND SD GND OUT+ OUTVBATT GND J1 J1 J1 J2 J2 J3 J3 J4 J4 1 2 3 1 2 1 2 1 2 Input Input GND Input GND Output Output Input Input Connector Function Differential analog input (+) to CS35L01. Differential analog input (-) to CS35L01. GND reference connection. Device shutdown control. GND reference connection. Analog output (+) from CS35L01. Analog output (-) from CS35L01. 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 SD Function Shutdown Function Selected Low = CS35L01 shutdown enabled High = CS35L01 shutdown disabled Table 2. J2 Shutdown Control Settings DS914RD2 7 8 Figure 4. CRD35L01-HD Schematic Figure 2. CRD35L01-SD Schematic Figure 5. CRD35L01-FHD Schematic Figure 3. CRD35L01-FSD Schematic CRD35L01 4. CRD SCHEMATIC DS914RD2 CRD35L01 4.1 Bill of Materials The component listing below is shown for the four CRD35L01 board variations (-SD, -FSD, -HD, and -FHD). Unpopulated (DNP) components are listed with recommended components for reference purposes. 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 Capacitor, 1 F, X5R, 10 V Kemet / C0603C105K8PAC 1 R3 -SD, -FSD, -HD, -FHD Resistor 47k , 1/16 W Dale / CRCW040247K0JNED (Note 1) 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 Table 3. Bill of Materials Listing Note: 1. C8 is not present on SD or FSD boards. LFILT+ (B1) is connected directly to VBATT. DS914RD2 9 CRD35L01 5. CRD LAYOUT 10 Figure 6. CRD35L01-SD Top Side Component Placement Figure 7. CRD35L01-SD Bottom Side Component Placement Figure 8. CRD35L01-SD Layer 1 Copper Figure 9. CRD35L01-SD Layer 2 Copper Figure 10. CRD35L01-SD Layer 3 Copper Figure 11. CRD35L01-SD Layer 4 Copper DS914RD2 CRD35L01 Figure 12. CRD35L01-FSD Top Side Component Placement Figure 13. CRD35L01-FSD Bottom Side Component Placement Figure 14. CRD35L01-FSD Layer 1 Copper Figure 15. CRD35L01-FSD Layer 2 Copper Figure 16. CRD35L01-FSD Layer 3 Copper Figure 17. CRD35L01-FSD Layer 4 Copper DS914RD2 11 CRD35L01 12 Figure 18. CRD35L01-HD Top Side Component Placement Figure 19. CRD35L01-HD Bottom Side Component Placement Figure 20. CRD35L01-HD Layer 1 Copper Figure 21. CRD35L01-HD Layer 2 Copper Figure 22. CRD35L01-HD Layer 3 Copper Figure 23. CRD35L01-HD Layer 4 Copper DS914RD2 CRD35L01 Figure 24. CRD35L01-FHD Top Side Component Placement Figure 25. CRD35L01-FHD Bottom Side Component Placement Figure 26. CRD35L01-FHD Layer 1 Copper Figure 27. CRD35L01-FHD Layer 2 Copper Figure 28. CRD35L01-FHD Layer 3 Copper Figure 29. CRD35L01-FHD Layer 4 Copper DS914RD2 13 CRD35L01 6. REVISION HISTORY Release Changes RD1 – Initial Release RD2 – – – – – – Updated front page 1% and 10% output power numbers to match DS909A2 datasheet. 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 CRD35L01-SD, -FSD, -HD, and -FHD boards with an assembly date of 02/15/10 or earlier contain components from the Rev A0 BOM. 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