Si824xClassD-KIT C L ASS D A UDIO A MP LIF IE R R EF ERENCE D E S I G N U S E R ’ S G U ID E 1. Kit Contents The Si824x Class D Audio Amplifier Reference Design Kit contains the following items: Audio Class D Amplifier reference design board featuring: Si8241 Si8410 ISOdriver Digital Isolator 2. Introduction This User's Guide discusses the Silicon Labs Audio Class D amplifier reference design, a stereo, two-state, halfbridge Class D amplifier leveraging the performance advantages of the Si8241 ISOdriver. This two-channel Class D Audio Amplifier delivers 120 W per channel into 8 Ω, while enabling < 0.02% THD at 60 W and > 95 dB SNR. High-power audio systems are adopting digital audio technology and evolving toward lower-power, “green” products that meet Energy Star™ guidelines. Class-D audio systems have started penetrating the high-end markets where low noise, extremely good THD performance, and very high output power are required in consumer and industrial applications. The Si824x audio driver family consists of single-chip, isolated, Class-D gate drivers powering audio systems delivering from 30 W up to 1000 W of audio power. Occasionally, a new IC is introduced that challenges the current technological hegemony. With features that make these products the perfect drivers for Class D amplification, the Silicon Labs Si8241/44 Audio Gate Drivers represent a new standard for the Class D amplifier industry. Based on Silicon Labs' proprietary isolation technology, the Si824x audio drivers incorporate input-to-output isolation that enables level-translation of signals without additional external circuits. The Si824x audio drivers feature adjustable dead-time control for achieving optimal THD, overlap protection that safeguards against shoot-through current damage, robust immunity to latchup and high-voltage transients, and lower BOM costs and PCB footprints compared to non-isolated gate drive solutions. A typical audio driver application using the Si824x is shown in Figure 1. For more information on the Si824x audio driver, refer to the Si824x data sheet at www.silabs.com/audio. Figure 1. Si824x-Based Class D Audio Driver Block Diagram Rev. 0.2 12/10 Copyright © 2016 by Silicon Laboratories Si824xClassD-KIT Si824xClassD-KIT 3. Hardware Overview and Demo 3.1. Reference Design Board Architecture The Silicon Labs Class D reference design architecture uses a phase-shift, self-oscillating modulation approach that is capable of achieving far greater signal-to-noise ratio than clock driven amplifiers (see Figure 2). This selfoscillating implementation eliminates the circuitry necessary to generate the triangle waveform. To keep the circuit as simple as possible, a two-state, half-bridge is implemented and exemplifies the benefits of using the Si8241 Audio Gate Driver. Figure 2. Block Diagram of Si8241-Based Class D Amplifier 3.2. Setting up the Class D Amplifier Figure 3 illustrates connections necessary to power the Class D amplifier. The user will need the following items: MP3 player (or equivalent line out audio source) Audio Y-Cable (stereo male to Dual RCA Male) ±50 V supply capable of sourcing 3 Amps ±12 V supply capable of sourcing 500 mA Two speakers (up to 150 W) Silicon Labs Class D reference design board Warning: 1. To protect the amplifier and speakers, before turning on the main power (the ±50 V supplies) to the amplifier, ensure that the audio source from the MP3 player has its volume set to the lowest possible level. 2. The L-bracket can heat up to 80 °C and should be handled with care. 2 Rev. 0.2 Si824xClassD-KIT 3.3. Powering up the Class D Amplifier and Playing Music After the audio source, audio Y-cable, supplies, and speakers have been properly connected as shown in Figure 3. 1. Turn on the ±12 V supplies. 2. Then, turn on the ±50 V supplies. Notice that LED1 should turn on for about 1 sec and then turn off. This on and off sequence clears any overcurrent protection faults and indicates to the user that the amplifier is ready to amplify the audio input signal. If the LED does not turn off after about 1 sec, cycle on and off the ±12 V supplies. Repeat this step until the LED turns off. If the LED never turns off, the board has probably been damaged. 3. With the audio source's volume turned down to its lowest output level, start the audio source. 4. Adjust the volume to the desired listening level. 5. Enjoy your music! Note: If the power being delivered to the speakers is too great, the overcurrent protection circuitry will trip and shut off audio to the speakers, protecting the amplifier. LED1 will turn on in this condition. See "4.4. Overcurrent Protection" on page 4 for more details on clearing this fault condition. +50 V (3 A) PGND -50 V (3 A) +12 V (500 mA) GND -12 V (500 mA) _ Speaker B (up to 150 W) _ Speaker A (up to 150 W) Audio Source/ MP3 Player Figure 3. Si824xClassD-KIT (Top View) Figure 4. Si824xClassD-KIT (Bottom View) Rev. 0.2 3 Si824xClassD-KIT 4. Additional Features and Architectural Considerations 4.1. Gate Drive Structure Figure 5 illustrates the ease with which the Si8241 can drive a two-state, half-bridge class D amplifier. The boot supply tied to D1 must be 12 V higher than the –50 V reference (–38 V) so that the MOSFETs each have a 12 V drive signal. The closed loop gain of the Silicon Labs Class D reference design is implemented such that approximately 1 Vpp input will yield full output power into an 8 Ω load. +50V -38V Si8241 ISOdriver PWM PWM D1 C1 VDDA R1 NC +5V C2 SHDN_HI R3 VOA VDDI GNDA GNDI NC DISABLE NC DT VDDB NC VOB VDDI R2 C3 -38V GNDB C4 -50V Figure 5. Si8241 Audio Gate Driver Gate Drive Circuit 4.2. Self Oscillation The amplifier is self-oscillating, enabling its signal-to-noise ratio to far exceed that of a clock driven system. The main mechanism for this is the delta-sigma effect of shifting in-band noise to a much higher out-of-band frequency. The amplifier is a basic, phase-shift type, which has significant advantages over an amplifier running as a hysteretic oscillator. There is a pole in the forward path G(s) and a pole in the feedback path H(s). The 180 ° phase shift, coupled with the transport delay, yields an oscillation frequency of nearly 500 kHz. The frequency of oscillation is set by capacitors in each audio channel where reducing capacitance value increases oscillation frequency. Tight tolerance capacitors are used to keep the channel frequencies as close to each other as possible. 4.3. Heat Sink L-Bracket The amplifier design includes an L-bracket to sink excess heat from the power transistors. At full power, the Lbracket's temperature should increase to no higher than 80 degrees Celsius. 4.4. Overcurrent Protection The Silicon Labs Class D reference design has an overcurrent protection circuit consisting of a low-power comparator floating off the upper and lower bus voltages. The upper rail circuit is shown in Figure 6 and is duplicated on the lower rail. It monitors the current flowing through the 0.005 Ω resistor (RSENSE). Zener diode D1 and resistor R4 supply power to the comparator and the Silicon Labs Si8410 digital isolator. The Si8410 performs the necessary level shifting to interface to the shutdown circuitry. The circuit is set to trip at roughly a 20 A fault, usually caused by a short-circuit across the speaker terminals or a large overdrive signal at the audio inputs. Note the upper and lower overcurrent circuits are ORed together through a pair of diodes and sent to the reset control circuit. The normally low Si8410 A1 input is driven high upon detection of an overcurrent condition and asserts the SHUTDOWN signal, forcing the reset controller to assert a reset signal, momentarily halting amplifier operation. The reset control circuit attempts restart after one second, and, if the fault is still present, again cycles reset in “hiccup” mode with a frequency of one second. This process continues until the fault is removed. Overcurrent protection can be removed by uninstalling JP1 and JP2. 4 Rev. 0.2 Si824xClassD-KIT 50V R2 RSENSE C1 Si8410 Digital Isolator D1 VDD1 VDD1 A1 + - R1 R4 GND1 5V VDD2 B1 SHUTDOWN GND2 GND2 R3 To High Side MOSFET R5 Figure 6. Over Current Protection Circuit 4.5. Undervoltage Protection The undervoltage protection comparator monitors the positive bus voltage and releases the undervoltage lockout when the voltage is above 37 V. The amplifier starts up after a one-second delay. Note that the red LED remains lit when the amplifier is in shutdown mode and turns off when the amplifier is enabled. 4.6. Other Features A protection circuit jumper (JP 3) option is included that allows the amplifier to be manually shut down. This jumper can be replaced with a switch or other control circuit, allowing the amplifier to be muted. The one-second undervoltage lockout delay allows the op-amps and comparator to settle before the shut-down circuit is released, thereby preventing speaker pops. To aid in system performance evaluation, there are individual jumper options (JP1 and JP2) on each channel that allow the user to enable or disable each channel independently of the other. 4.7. Performance The Silicon Labs Class D reference design board was tested for THD + N, SNR, DFD, and IFD with an Audio Precision analyzer. During these tests, the main power (the ±50 V supplies) used a TR180 from Hypex electronics (a low-noise supply) to maximize the amplifier's measured performance. Refer to “AN542: Performance Improvements in Class D Audio Amplifiers using Si824x Audio Drivers” for additional information concerning the amplifier's noise and efficiency performance and a more in-depth discussion concerning the amplifier's architectural design. Please visit www.silabs.com/audio. Rev. 0.2 5 Si824xClassD-KIT 5. Si8241-Based Class D Amplifier Connection Description The Si8241-based Class D Amplifier has two Si8241 ISOdrivers and two Si8410 digital isolators installed. Refer to Figure 7 for the locations of the various I/O connectors and major components. Relevant user connection points are detailed below. J1 J2 J3 J4 J5 J6 J7 J8 J9 J10 JP1 JP2 JP3 LED1 +50 V PGND –50 V SPKA+ SPKA– SPKB+ SPKB– VBIAS AUDIO A AUDTIO B OCPDISA OCPDISB MUTE FAULT Positive Input Power: Input power connection +50 V, 3 A. Power Ground Return, 0 V. Negative Input Power: Input power connection –50 V, 3 A. Speaker A positive terminal Speaker A negative terminal Speaker B positive terminal Speaker B negative terminal ±12 V Bias supply connector (500 mA) RCA input female connector channel A RCA input female connector channel B Over current protection disable channel A channel Over current protection disable channel B channel Amplifier Mute or manual shut down Over current protection fault indicator LED Figure 7. Si8241 Si8241-Based Class D Amplifier Silkscreen 5.1. Voltage and Current Sense Test Points The Si824x Class D Audio Amplifier reference design has several test points. These test points correspond to the respective pins on the Si8241, Si8410 as well as other useful inspection points. See “6. Schematics” for more details. 6 Rev. 0.2 Figure 8. Si824x Class D Audio Amplifier Reference Design Schematic (1 of 2) Si824xClassD-KIT 6. Schematics Rev. 0.2 7 Figure 9. Si824x Class D Audio Amplifier Reference Design Schematic (2 of 2) Si824xClassD-KIT 8 Rev. 0.2 Si824xClassD-KIT 7. Bill of Materials Table 1. Si824x Class D Audio Amplifier Reference Design Bill of Materials Qty Ref Description Mfr. Part Number Mfr Digikey Part Number 2 C1, C2 1 µF, 25 V, X5R, 0805 Ceramic Capacitor 08053D105KAT2A AVX 478-1409-6-ND 2 C3, C4 1 µF, 16 V, 3216 Tantalum Capacitor T491A105M016AT Kemet 399-3681-6-ND 14 C24–C27, C29, C30, C37–C44 0.1 µF, 50 V, X7R, 0603 Ceramic Capacitor GRM188R71H104KA93D Murata 490-1519-6-ND 1 C6 10 µF, 10 V, 3216 Tantalum Capacitor T491A106M010AT Kemet 399-3686-6-ND 2 C7,C8 1 µF, 100 V, X7R, 1210 Ceramic Capacitor GRM32ER72A105KA01L Murata 490-1857-1-ND 4 C9, C10, C58, C60 1 µF, 25 V, X5R, 1206 Ceramic Capacitor GRM319R61E105K C36D Murata 490-1807-6-ND 2 C57, C59 1 µF, 10 V, X5R, 0603 Ceramic Capacitor GRM188R61A105KA61D Murata 490-1543-6-ND 7 C22, C23, C31, C49–C52 0.01 µF, 50 V, X7R, 0603 Ceramic Capacitor 06035C103KAT2A AVX 478-1227-6-ND 1 C32 10 pF, 50 V, COG, 0603 Ceramic Capacitor 06035A100JAT2A AVX 478-1163-6-ND 4 C5, C11, C33, C34 100 µF, 6.3 V, X5R, 1812 Ceramic Capacitor C4532X5R0J107M TDK 445-1413-2-ND 4 C19, C20, C45, C46 100 pF, 50 V, COG, 0603 Ceramic Capacitor GRM1885C1H101JA01D Murata 490-1427-6-ND 4 C53–C56 4.7 µF, 6.3 V, X5R, 0603 Ceramic Capacitor 06036D475MAT2A AVX 478-2582-6-ND 4 C61–C64 0.47 µF, 16 V, X5R, 0603 Ceramic Capacitor C0603X7R160474MNE AVX 478-1248-6-ND Rev. 0.2 9 Si824xClassD-KIT Table 1. Si824x Class D Audio Amplifier Reference Design Bill of Materials (Continued) Qty Ref Description Mfr. Part Number Mfr Digikey Part Number 4 C67–C70 82 µF, 63 V, KZE Series Electrolytic Cap EKZE630ESS820M JC5S Chemi-Con 565-1721-ND 4 C71–C74 0.1 µF, 100 V, X7R, 1206 Ceramic Capacitor 12061C104MAT2A AVX 478-3786-6-ND 4 C75–C78 0.01 µF, 100 V, COG, 1206 Ceramic Capacitor 12061C103JAT2A AVX 478-3783-6-ND 2 C79, C80 0.47 µF, 250 V Film Capacitor ECQ-E2474KB Panasonic ECG P10975-ND 3 D1–D3 100 V 150 mA SOD123 Diode 1N4148W-13-F Diodes Inc. 1N4148W-13-FDIDKR-ND 6 D4–D9 Fast Recovery 200 V 2 A Diode SMA MURA120T3G On Semi MURA120T3GOSCT-ND 2 ZD1, ZD2 Diode Zener 500 mW 5.1 V SOD-123 MMSZ4689-TP Micro Commercial Co. MMSZ4689-TPMSCT-ND 1 IC1 IC Voltage Reg 5.0 V 200 mA SOT223 ZSR500GTA ZETEX ZSR500GCT-ND 1 IC3 Adjustable Negative Regulators SOT223 LM337IMP National Semi LM337IMPDKR-ND 2 IC4, IC5 High-Voltage Adjustable Regulator TO220 TL783CKCSE3 TI 296-20687-5-ND 3 IC11, IC12, IC16 CMOS Comparator SOT23-5 LMC7211BIM5/ NOPB National Semi LMC7211BIM5CT-ND 2 IC13, IC14 Single Channel Digital Isolator SOIC8 Si8410BB-D-IS Silabs 1 IC15 Voltage Supervisor with Adjustable Power-on Reset SOT23-5 ISL88011IH531ZTK Intersil ISL88011IH531Z-TKDKR-ND 2 IC17, IC18 IC Opamp Audio Ster AB 8SOIC LM4562MA/NOPB National Semi LM4562MA-ND 10 Rev. 0.2 Si824xClassD-KIT Table 1. Si824x Class D Audio Amplifier Reference Design Bill of Materials (Continued) Qty Ref Description Mfr. Part Number Mfr Digikey Part Number 2 IC19, IC20 IC Comp Grnd-sensing LowPwr 8SOIC LT1671CS8#PBF Linear Tech LT1671CS8#PBF-ND 2 IC21, IC22 Isodriver Narrow Body Si8241BB-B-IS1 Silabs 7 J1–J7 1/4 inch-Faston 62409-1 Tyco Electronics A24742-ND 1 J8 3 Pin Conn Header 22-23-2031 Molex Inc. WM4201-ND 2 J9, J10 Conn RCA Jack Metal R/A YEL PCB RCJ-014 CUI Inc. CP-1403-ND 3 JP1–JP3 Jumper TSW-102-07-T-S Samtec SAM1035-02-ND 3 L1, L2, L35 Ferrite Bead 2773021447 Fair-Rite 2 L4, L5 22 µH, 7 A, 8.3 mΩ Inductor 7G14A-220M-R Sagami 1 LED1 LED Chip LED 645NM Red Diff 0805 LH R974-LP-1-020-R18 Osram 475-1415-6-ND 2 Q1, Q2 MOSFET N-CH 60 V 280 mA SOT-23 NDS7002A Fairchild Semi NDS7002ACT-ND 4 Q4–Q7 200V, 18A N-Channel MOSFET FDP18N20F Fairchild Semi FDP18N20F-ND 1 R1 249 Ω, 0603 1% SMT Resistor ERJ-3EKF2490V Panasonic ECG P249HDKR-ND 2 R2, R20 750 Ω, 0603 1% SMT Resistor ERJ-3EKF7500V Panasonic ECG P750HCT-ND 2 R3, R4 82.5 Ω, 0603 1% SMT Resistor ERJ-3EKF82R5V Panasonic ECG P82.5HDKR-ND 2 R5, R6 698 Ω, 0603 1% SMT Resistor ERJ-3EKF6980V Panasonic ECG P698HDKR-ND 4 R7, R8, R12, R13 49.9 kΩ, 0603 1% SMT Resistor ERJ-3EKF4992V Panasonic ECG P49.9KHCT-ND 1 R26 12 kΩ, 0603 1% SMT Resistor ERJ-3EKF1202V Panasonic ECG P12.0KHCT-ND 6 R10, R11, R14, R15, R35, R37 1 kΩ, 0603 1% SMT Resistor ERJ-3EKF1001V Panasonic ECG P1.00KHCT-ND Rev. 0.2 11 Si824xClassD-KIT Table 1. Si824x Class D Audio Amplifier Reference Design Bill of Materials (Continued) Qty Ref Description Mfr. Part Number Mfr Digikey Part Number 2 R16, R17 12.1 kΩ, 2010 1% SMT Resistor ERJ-12SF1212U Panasonic ECG P12.1KACCT-ND 3 R18, R21, R60 20 kΩ, 0603 1% SMT Resistor ERJ-3EKF2002V Panasonic ECG P20.0KHCT-ND 2 R29, R30 4.99 kΩ, 0603 1% SMT Resistor ERJ-3EKF4991V Panasonic ECG P4.99KHCT-ND 4 R23, R24, R39, R40 100 kΩ, 0603 1% SMT Resistor ERJ-3EKF1003V Panasonic ECG P100KHCT-ND 1 R25 121 kΩ, 0603 1% SMT Resistor ERJ-3EKF1213V Panasonic ECG P121KHCT-ND 2 R27, R28 1.3 kΩ, 0603 1% SMT Resistor ERJ-3EKF1301V Panasonic ECG P1.30KHCT-ND 2 R31, R32 7.5 kΩ, 0603 1% SMT Resistor ERJ-3EKF7501V Panasonic ECG P7.50KHCT-ND 2 R33, R34 300 kΩ, 0603 1% SMT Resistor ERJ-3EKF3003V Panasonic ECG P300KHCT-ND 3 R19, R41, R42 2 kΩ, 0603 1% SMT Resistor ERJ-3EKF2001V Panasonic ECG P2.00KHCT-ND 2 R45, R46 511 Ω, 0603 1% SMT Resistor ERJ-3EKF5110V Panasonic ECG P511HCT-ND 4 R47–R50 12.1 Ω, 0805 1% SMT Resistor ERJ-6ENF12R1V Panasonic ECG P12.1CCT-ND 2 R51, R52 1 Ω, 0805 1% SMT Resistor RC0805FR-071RL Yageo 311-1.00CRCT-ND 2 R53, R54 0.005 Ω, 3264 1% SMT Resistor MCS3264R005FE Panasonic ECG MCS3264R005FERCT-ND 1 R55 0 Ω, 1206 1% SMT Resistor ERJ-8GEY0R00V Panasonic ECG P0.0ECT-ND 1 R61 39.2 kΩ 0603 1% SMT Resistor ERJ-3EKF3922V Panasonic ECG P39.2KHCT-ND 2 HS1 Heatsink TO-220 5W BLK 576802B00000G AAVID Thermalloy HS121-ND 12 TP1-TP12 Test Pad 3103-2-00-21-0000-08-0 MILL-MAX MAN. ED5052-ND 4 Shoulder Washer Washer/bushing #4 X .031"L NYLON 3049 Keystone 3049-ND 12 Rev. 0.2 Si824xClassD-KIT Table 1. Si824x Class D Audio Amplifier Reference Design Bill of Materials (Continued) Qty Ref Description Mfr. Part Number Mfr Digikey Part Number 4 Insulator Insulator Mica .860X.520" .141" TO-220 4672 Keystone 4672K-ND 4 Screw Hdwr Mtg Screw TO220CASE 4/40 THR 1PC 4690 Keystone 4690K-ND 4 Screw Hdwr Mtg Screw 1/ 4" 4/40 , PCB LBracket Mount 9900 Keystone 9900K-ND 4 Lock Washer Hdwr Mtg Lockwasher Plastic 2PC 4693 Keystone 4693K-ND 4 Nut Hdwr Mtg Nut 4/40 Thread 2PC 4694 Keystone 4694K-ND Heat Compound Heat Trans Compound Silicone 860-150G MG Chemicals 473-1097-ND 4 Standoff Stdoff Hex M/F 4-40 .375"L Alum 8400 Keystone 8400K-ND 1 HTSNK L Bracket Heat Sink SIHS-1 Red River PRC MFG 4 Bumpons, Feet, Pads, Grips Bumpon Cylindrical .312X.215 BLK SJ61A6 3M SJ5744-0-ND 7 J1-J7 Conn Fast Recept 18-22 AWG .250 2-520264-2 Tyco Electronics A27821-ND 2 JP1, JP2 Shorting Jumper Conn Jumper Shorting Gold Flash SPC02SYAN Sullins Connector Solutions S9001-ND Rev. 0.2 13 Si824xClassD-KIT 8. Ordering Guide Ordering Part Number Si824xClassD-KIT 14 Type Audio Class D Amplifier reference design kit using Si8241BB-B-IS1. Rev. 0.2 Si824xClassD-KIT DOCUMENT CHANGE LIST Revision 0.1 to Revision 0.2 Updated Table 1, “Si824x Class D Audio Amplifier Reference Design Bill of Materials,” on page 9. Rev. 0.2 15 Smart. Connected. Energy-Friendly Products Quality Support and Community www.silabs.com/products www.silabs.com/quality community.silabs.com Disclaimer Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific written consent of Silicon Laboratories. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected to result in significant personal injury or death. Silicon Laboratories products are generally not intended for military applications. Silicon Laboratories products shall under no circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons. Trademark Information Silicon Laboratories Inc., Silicon Laboratories, Silicon Labs, SiLabs and the Silicon Labs logo, CMEMS®, EFM, EFM32, EFR, Energy Micro, Energy Micro logo and combinations thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZMac®, EZRadio®, EZRadioPRO®, DSPLL®, ISOmodem ®, Precision32®, ProSLIC®, SiPHY®, USBXpress® and others are trademarks or registered trademarks of Silicon Laboratories Inc. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of ARM Holdings. Keil is a registered trademark of ARM Limited. All other products or brand names mentioned herein are trademarks of their respective holders. Silicon Laboratories Inc. 400 West Cesar Chavez Austin, TX 78701 USA http://www.silabs.com