Filterless, High Efficiency, Mono 2.8 W, Class-D Audio Amplifier SSM2305 Data Sheet The SSM2305 features a high efficiency, low noise modulation scheme that does not require external LC output filters. The modulation provides high efficiency even at low output power. The SSM2305 operates with 90% efficiency at 1.3 W into 8 or 83% efficiency at 2.2 W into 4 from a 5.0 V supply and has an SNR of >98 dB. Spread-spectrum pulse density modulation is used to provide lower EMI-radiated emissions compared with other Class-D architectures. FEATURES Filterless Class-D amplifier with - modulation No sync necessary when using multiple Class-D amplifiers from Analog Devices, Inc. 2.8 W into 4 load and 1.6 W into 8 load at 5.0 V supply with <10% total harmonic distortion (THD) 89% efficiency at 5.0 V, 1.3 W into 8 speaker >98 dB signal-to-noise ratio (SNR) Single-supply operation from 2.5 V to 5.5 V 20 nA ultralow shutdown current Short-circuit and thermal protection Available in 8-lead, 3 mm x 3 mm LFCSP and MSOP Pop-and-click suppression Built-in resistors reduce board component count Fixed and user-adjustable gain configurations The SSM2305 has a micropower shutdown mode with a maximum shutdown current of 30 nA. Shutdown is enabled by applying a Logic 0 to the SD pin. The device also includes pop-and-click suppression circuitry. This minimizes voltage glitches at the output during turn-on and turn-off, thus reducing audible noise on activation and deactivation. The fully differential input of the SSM2305 provides excellent rejection of common-mode noise on the input. Input coupling capacitors can be omitted if the dc input common-mode voltage is approximately VDD/2. APPLICATIONS Mobile phones MP3 players Portable gaming Portable electronics Educational toys The SSM2305 has excellent rejection of power supply noise, including noise caused by GSM transmission bursts and RF rectification. PSRR is typically 60 dB at 217 Hz. GENERAL DESCRIPTION The default gain of the SSM2305 is 18 dB, but users can reduce the gain by using a pair of external resistors. The SSM2305 is a fully integrated, high efficiency, Class-D audio amplifier designed to maximize performance for mobile phone applications. The application circuit requires a minimum of external components and operates from a single 2.5 V to 5.5 V supply. It is capable of delivering 2.2 W of continuous output power with less than 1% THD + N driving a 4 load from a 5.0 V supply. It has built-in thermal shutdown and output shortcircuit protection. The SSM2305 is specified over the commercial temperature range (-40C to +85C). It is available in both an 8-lead, 3 mm x 3 mm lead frame chip scale package (LFCSP) and an 8-lead mini small outline package (MSOP). FUNCTIONAL BLOCK DIAGRAM 0.1F 10F SSM2305 47nF* AUDIO IN+ AUDIO IN- IN+ 37k IN- 37k VBATT 2.5V TO 5.5V VDD 296k OUT+ MODULATOR (-) FET DRIVER OUT- 47nF* 296k SHUTDOWN SD BIAS INTERNAL OSCILLATOR POP/CLICK SUPPRESSION *INPUT CAPACITORS ARE OPTIONAL IF INPUT DC COMMON-MODE VOLTAGE IS APPROXIMATELY VDD/2. 07243-001 GND Figure 1. Rev. B Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 (c)2008-2016 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com SSM2305* PRODUCT PAGE QUICK LINKS Last Content Update: 02/23/2017 COMPARABLE PARTS DISCUSSIONS View a parametric search of comparable parts. View all SSM2305 EngineerZone Discussions. EVALUATION KITS SAMPLE AND BUY * SSM2305 Evaluation Board Visit the product page to see pricing options. DOCUMENTATION TECHNICAL SUPPORT Data Sheet Submit a technical question or find your regional support number. * SSM2305: Filterless, High Efficiency, Mono 2.8 W, Class-D Audio Amplifier Data Sheet DOCUMENT FEEDBACK DESIGN RESOURCES Submit feedback for this data sheet. * SSM2305 Material Declaration * PCN-PDN Information * Quality And Reliability * Symbols and Footprints This page is dynamically generated by Analog Devices, Inc., and inserted into this data sheet. A dynamic change to the content on this page will not trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified. SSM2305 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Applications Information .............................................................. 11 Applications ....................................................................................... 1 Overview ..................................................................................... 11 General Description ......................................................................... 1 Gain .............................................................................................. 12 Functional Block Diagram .............................................................. 1 Pop-and-Click Suppression ...................................................... 12 Revision History ............................................................................... 2 Output Modulation Description .............................................. 12 Specifications..................................................................................... 3 Layout .......................................................................................... 12 Absolute Maximum Ratings............................................................ 4 Input Capacitor Selection .......................................................... 12 Thermal Resistance ...................................................................... 4 Proper Power Supply Decoupling ............................................ 13 ESD Caution .................................................................................. 4 Outline Dimensions ....................................................................... 14 Pin Configurations and Function Descriptions ........................... 5 Ordering Guide .......................................................................... 14 Typical Performance Characteristics ............................................. 6 REVISION HISTORY 5/2016--Rev. A to Rev. B Changed CP-8-2 to CP-8-13 ........................................ Throughout Changes to Figure 2 and Table 4 ..................................................... 5 Updated Outline Dimensions ....................................................... 14 Changes to Ordering Guide .......................................................... 14 7/2008--Rev. 0 to Rev. A Changes to Figure 1 .......................................................................... 1 Change to Shutdown Current Parameter, Table 1 ........................ 3 Change to Differential Input Impedance Parameter, Table 1 ..... 3 Added Exposed Pad Notation to Figure 2 ..................................... 5 Change to Figure 24 ......................................................................... 9 Changes to Figure 32 and Figure 33 ............................................. 11 Changes to Gain Section................................................................ 12 Updated Outline Dimensions ....................................................... 14 3/2008--Revision 0: Initial Version Rev. B | Page 2 of 16 Data Sheet SSM2305 SPECIFICATIONS VDD = 5.0 V, TA = 25oC, RL = 8 + 33 H, unless otherwise noted. Table 1. Parameter DEVICE CHARACTERISTICS Output Power Symbol Test Conditions/Comments PO RL = 8 , THD = 1%, f = 1 kHz, BW = 20 kHz RL = 8 , THD = 1%, f = 1 kHz, BW = 20 kHz, VDD = 3.6 V RL = 8 , THD = 10%, f = 1 kHz, BW = 20 kHz RL = 8 , THD = 10%, f = 1 kHz, BW = 20 kHz, VDD = 3.6 V RL = 4 , THD = 1%, f = 1 kHz, BW = 20 kHz RL = 4 , THD = 1%, f = 1 kHz, BW = 20 kHz, VDD = 3.6 V RL = 4 , THD = 10%, f = 1 kHz, BW = 20 kHz RL = 4 , THD = 10%, f = 1 kHz, BW = 20 kHz, VDD = 3.6 V PO = 1.3 W, 8 PO = 1 W into 8 , f = 1 kHz PO = 0.5 W into 8 , f = 1 kHz, VDD = 3.6 V Efficiency Total Harmonic Distortion + Noise THD + N Input Common-Mode Voltage Range Common-Mode Rejection Ratio Average Switching Frequency Differential Output Offset Voltage POWER SUPPLY Supply Voltage Range Power Supply Rejection Ratio VCM CMRRGSM fSW VOOS Min Typ Max 1.34 0.68 1.67 0.85 2.22 1.1 2.8 1.3 89 0.02 0.02 1.0 VCM = 2.5 V 100 mV at 217 Hz, output referred VDD - 1 55 280 2.0 G = 18 dB Supply Current Shutdown Current ISD Guaranteed from PSRR test VDD = 2.5 V to 5.0 V, dc input floating VRIPPLE = 100 mV at 217 Hz, inputs ac GND, CIN = 0.1 F VIN = 0 V, no load VIN = 0 V, VIN = 0 V, no load, VDD = 3.6 V VIN = 0 V, VDD = 3.6 V VIN = 0 V, no load, VDD = 2.5 V VIN = 0 V, VDD = 2.5 V SD = GND GAIN CONTROL Closed-Loop Gain Differential Input Impedance Av ZIN SD = VDD 18 37 dB k SHUTDOWN CONTROL Input Voltage High Input Voltage Low Wake-Up Time Shutdown Time Output Impedance VIH VIL tWU tSD ZOUT ISY 1 mA ISY 300 nA SD rising edge from GND to VDD SD falling edge from VDD to GND SD = GND 1.2 0.5 30 5 >100 V V ms s k NOISE PERFORMANCE Output Voltage Noise en VDD = 3.6 V, f = 20 Hz to 20 kHz, inputs are ac grounded, AV = 18 dB, A-weighted PO = 1.4 W, RL = 8 40 V 98 dB SNR Rev. B | Page 3 of 16 5.5 W W W W W W W W % % % V dB kHz mV VDD PSRR PSRRGSM ISY Signal-to-Noise Ratio 2.5 70 Unit 85 60 3.2 3.3 2.8 2.9 2.4 2.4 20 30 V dB dB mA mA mA mA mA mA nA SSM2305 Data Sheet ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Absolute maximum ratings apply at TA = 25C, unless otherwise noted. JA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Table 2. Parameter Supply Voltage Input Voltage Common-Mode Input Voltage Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec) Rating 6V VDD VDD -65C to +150C -40C to +85C -65C to +165C 300C Table 3. Package Type 8-Lead, 3 mm x 3 mm LFCSP 8-Lead MSOP ESD CAUTION Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability. Rev. B | Page 4 of 16 JA 62 210 JC 20.8 45 Unit C/W C/W Data Sheet SSM2305 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS SD 1 SSM2305 TOP VIEW (Not to Scale) 7 GND 6 VDD 5 OUT+ IN- 4 NOTES: 1. NC = NO CONNECT. 2. EXPOSED PAD IS NOT CONNECTED INTERNALLY. FOR INCREASED RELIABILITY OF THE SOLDER JOINTS AND MAXIMUM THERMAL CAPABILITY IT IS RECOMMENDED THAT THE PAD BE SOLDERED TO THE GROUND PLANE. SD 1 NC 2 IN+ 3 IN- 4 8 SSM2305 OUT- 7 TOP VIEW (Not to Scale) GND 6 VDD 5 OUT+ 07243-103 IN+ 3 8 OUT- 07243-002 NC 2 NC = NO CONNECT Figure 2. LFSCP Pin Configuration Figure 3. MSOP Pin Configuration Table 4. Pin Function Descriptions Pin No. LFCSP MSOP 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 0 N/A1 1 Mnemonic SD NC IN+ IN- OUT+ VDD GND OUT- EPAD Description Shutdown Input. Active low digital input. No Connect. This pin has no function; tie it to GND. Noninverting Input. Inverting Input. Noninverting Output. Power Supply. Ground. Inverting Output. Exposed Pad. The exposed pad is not connected internally. For increased reliability of the solder joints and maximum thermal capability it is recommended that the pad be soldered to the ground plane. N/A means not applicable. Rev. B | Page 5 of 16 SSM2305 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS 100 100 RL = 4 + 33H GAIN = 18dB THD + N (%) VDD = 3.6V 1 VDD = 2.5V 10 VDD = 2.5V 10 THD + N (%) RL = 8 + 33H GAIN = 6dB 1 VDD = 3.6V 0.1 0.1 0.01 VDD = 5V 0.01 0.1 OUTPUT POWER (W) 1 10 0.001 0.0001 Figure 4. THD + N vs. Output Power into 4 + 33 H, AV = 18 dB 0.001 1 0.01 0.1 OUTPUT POWER (W) 10 07243-007 0.001 07243-004 0.01 0.0001 VDD = 5V Figure 7. THD + N vs. Output Power into 8 + 33 H, AV = 6 dB 100 100 RL = 4 + 33H GAIN = 6dB 10 10 VDD = 5V GAIN = 18dB RL = 4 + 33H VDD = 2.5V 0.01 0.001 0.01 0.1 OUTPUT POWER (W) 1 1W 0.1 0.01 VDD = 5V 0.001 0.0001 1 10 0.001 10 Figure 5. THD + N vs. Output Power into 4 + 33 H, AV = 6 dB 100 1000 FREQUENCY (Hz) 10000 100000 Figure 8. THD + N vs. Frequency, VDD = 5 V, RL = 4 + 33 H, AV = 18 dB 100 100 RL = 8 + 33H GAIN = 18dB VDD = 2.5V 10 10 VDD = 3.6V THD + N (%) THD + N (%) 0.5W 07243-008 THD + N (%) 0.1 07243-005 THD + N (%) 2W VDD = 3.6V 1 1 0.1 VDD = 5V GAIN = 18dB RL = 8 + 33H 1 0.1 1W 0.5W 0.01 0.01 VDD = 5V 0.01 0.1 OUTPUT POWER (W) 1 10 Figure 6. THD + N vs. Output Power into 8 + 33 H, AV = 18 dB 07243-006 0.001 0.001 10 100 1000 FREQUENCY (Hz) 10000 100000 07243-009 0.25W 0.001 0.0001 Figure 9. THD + N vs. Frequency, VDD = 5 V, RL = 8 + 33 H, AV = 18 dB Rev. B | Page 6 of 16 Data Sheet SSM2305 100 10 VDD = 3.6V GAIN = 18dB RL = 4 + 33H 1 1W VDD = 2.5V GAIN = 18dB RL = 8 + 33H 10 0.1 THD + N (%) THD + N (%) 100 0.5W 1 0.1 0.01 0.01 0.25W 0.25W 0.075W 1000 FREQUENCY (Hz) 10000 100000 07243-010 100 0.001 10 Figure 10. THD + N vs. Frequency, VDD = 3.6 V, RL = 4 + 33 H, AV = 18 dB 3.4 SUPPLY CURRENT (mA) 0.5W 0.25W RL = 4 + 33H 3.2 3.0 RL = 8 + 33H 2.8 NO LOAD 2.6 2.4 0.01 2.2 0.25W 1000 FREQUENCY (Hz) 10000 100000 2.0 2.5 07243-011 100 3.5 4.0 4.5 5.0 5.5 6.0 Figure 14. Supply Current vs. Supply Voltage 100 12 VDD = 2.5V GAIN = 18dB RL = 4 + 33H SHUTDOWN CURRENT (A) 10 0.5W 1 0.25W 0.01 0.125W 100 1000 FREQUENCY (Hz) 8 VDD = 5V 6 VDD = 3.6V 4 VDD = 2.5V 2 10000 100000 07243-015 0.1 0 07243-012 THD + N (%) 3.0 SUPPLY VOLTAGE (V) Figure 11. THD + N vs. Frequency, VDD = 3.6 V, RL = 8 + 33 H, AV = 18 dB 0.001 10 07243-014 THD + N (%) 3.6 0.1 10 100000 3.8 VDD = 3.6V GAIN = 18dB RL = 8 + 33H 1 0.001 10 10000 1000 FREQUENCY (Hz) Figure 13. THD + N vs. Frequency, VDD = 2.5 V, RL = 8 + 33 H, AV = 18 dB 100 10 100 07243-013 0.125W 0.001 10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 SHUTDOWN VOLTAGE (V) Figure 12. THD + N vs. Frequency, VDD = 2.5 V, RL = 4 + 33 H, AV = 18 dB Rev. B | Page 7 of 16 Figure 15. Shutdown Current vs. Shutdown Voltage 0.8 SSM2305 Data Sheet 3.0 f = 1kHz GAIN = 18dB RL = 4 + 33H f = 1kHz GAIN = 6dB RL = 8 + 33H 1.6 1.4 OUTPUT POWER (W) OUTPUT POWER (W) 2.5 1.8 2.0 10% 1.5 1% 1.0 1.2 1.0 10% 0.8 1% 0.6 0.4 3.0 3.5 4.0 4.5 07243-019 0 2.5 07243-016 0.5 0.2 0 2.5 5.0 Figure 19. Maximum Output Power vs. Supply Voltage, RL = 8 + 33 H, AV = 6 dB 100 3.0 VDD = 5V 80 VDD = 3.6V 70 EFFICIENCY (%) 10% 1.5 1% 1.0 VDD = 2.5V 60 50 40 30 20 07243-017 0.5 3.0 3.5 4.0 4.5 07243-020 OUTPUT POWER (W) RL = 4 + 33H GAIN = 18dB 90 f = 1kHz GAIN = 6dB RL = 4 + 33H 2.0 0 2.5 10 0 5.0 0 0.2 0.4 0.6 Figure 17. Maximum Output Power vs. Supply Voltage, RL = 4 + 33 H, AV = 6 dB RL = 8 + 33H GAIN = 18dB 90 f = 1kHz GAIN = 18dB RL = 8 + 33H 80 1.4 1.6 1.8 2.0 EFFICIENCY (%) 1.0 10% 0.8 1% 0.6 VDD = 5V VDD = 3.6V VDD = 2.5V 70 60 50 40 30 0.4 0.2 3.0 3.5 4.0 4.5 07243-021 20 07243-018 OUTPUT POWER (W) 1.2 100 1.2 0 2.5 1.0 Figure 20. Efficiency vs. Output Power into 4 + 33 H 1.8 1.4 0.8 OUTPUT POWER (W) SUPPLY VOLTAGE (V) 1.6 5.0 SUPPLY VOLTAGE (V) Figure 16. Maximum Output Power vs. Supply Voltage, RL = 4 + 33 H, AV = 18 dB 2.5 4.5 4.0 3.5 3.0 SUPPLY VOLTAGE (V) 10 0 5.0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 OUTPUT POWER (W) SUPPLY VOLTAGE (V) Figure 21. Efficiency vs. Output Power into 8 + 33 H Figure 18. Maximum Output Power vs. Supply Voltage, RL = 8 + 33 H, AV = 18 dB Rev. B | Page 8 of 16 Data Sheet SSM2305 0.6 0.14 VDD = 5.0V RL = 4 + 33H 0.4 0.3 0.2 0.1 0 0.5 1.0 1.5 2.0 2.5 0.10 0.08 0.06 0.04 0 3.0 07243-025 0.02 07243-022 0 VDD = 3.6V RL = 8 + 33H 0.12 POWER DISSIPATION (W) POWER DISSIPATION (W) 0.5 0 0.1 0.2 0.3 0.5 0.6 0.7 0.8 0.9 1.0 Figure 25. Power Dissipation vs. Output Power into 8 + 33 H at VDD = 3.6 V Figure 22. Power Dissipation vs. Output Power into 4 + 33 H at VDD = 5.0 V 0.20 800 RL = 4 + 33H 0.18 VDD = 5.0V RL = 8 + 33H VDD = 5V 700 SUPPLY CURRENT (mA) 0.16 POWER DISSIPATION (W) 0.4 OUTPUT POWER (W) OUTPUT POWER (W) 0.14 0.12 0.10 0.08 0.06 600 VDD = 3.6V 500 400 VDD = 2.5V 300 200 0.04 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0 1.8 07243-026 0 100 07243-023 0.02 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 OUTPUT POWER (W) OUTPUT POWER (W) Figure 23. Power Dissipation vs. Output Power into 8 + 33 H at VDD = 5.0 V Figure 26. Supply Current vs. Output Power into 4 + 33 H 0.40 450 VDD = 3.6V RL = 4 + 33H VDD = 5V 350 SUPPLY CURRENT (mA) 0.30 0.25 0.20 0.15 0.10 VDD = 3.6V 300 250 VDD = 2.5V 200 150 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 07243-027 100 0.05 0 RL = 8 + 33H 400 07243-024 POWER DISSIPATION (W) 0.35 50 0 1.6 0 OUTPUT POWER (W) 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 OUTPUT POWER (W) Figure 24. Power Dissipation vs. Output Power into 4 + 33 H at VDD = 3.6 V Figure 27. Supply Current vs. Output Power into 8 + 33 H Rev. B | Page 9 of 16 1.8 Data Sheet 0 8 -10 7 -20 6 -30 5 VOLTAGE (V) -40 -50 -60 -70 SD INPUT 4 3 2 0 -90 -1 100 1000 FREQUENCY (Hz) 10000 100000 07243-028 -80 -2 -10 07243-030 1 -100 10 0 10 20 30 40 50 60 70 80 90 TIME (ms) Figure 28. Power Supply Rejection Ratio vs. Frequency Figure 30. Turn-On Response 8 -10 7 -20 6 -30 5 VOLTAGE (V) 0 -40 -50 -60 -70 OUTPUT 4 3 2 1 -80 0 -90 -1 SD INPUT -100 10 100 1000 FREQUENCY (Hz) 10000 100000 07243-029 CMRR (dB) OUTPUT Figure 29. Common-Mode Rejection Ratio vs. Frequency -2 -500 -400 -300 -200 -100 0 100 200 TIME (s) Figure 31. Turn-Off Response Rev. B | Page 10 of 16 300 400 07243-031 PSSR (dB) SSM2305 500 Data Sheet SSM2305 APPLICATIONS INFORMATION important benefits. - modulators do not produce a sharp peak with many harmonics in the AM frequency band, as pulse-width modulators often do. - modulation provides the benefits of reducing the amplitude of spectral components at high frequencies, that is, reducing EMI emission that might otherwise be radiated by speakers and long cable traces. Due to the inherent spreadspectrum nature of - modulation, the need for oscillator synchronization is eliminated for designs incorporating multiple SSM2305 amplifiers. OVERVIEW The SSM2305 mono Class-D audio amplifier features a filterless modulation scheme that greatly reduces the external components count that, in turn, conserves board space, thereby reducing systems cost. The SSM2305 does not require an output filter, relying instead on the inherent inductance of the speaker coil and the natural filtering of the speaker and human ear to fully recover the audio component of the square wave output. Most Class-D amplifiers use some variation of pulse-width modulation (PWM), but the SSM2305 uses - modulation to determine the switching pattern of the output devices, resulting in a number of The SSM2305 also offers protection circuits for overcurrent and temperature protection. EXTERNAL GAIN SETTINGS = 296k/(37k + REXT) 0.1F 10F SSM2305 AUDIO IN+ 47nF* R EXT REXT AUDIO IN- IN+ 37k IN- 37k VBATT 2.5V TO 5.5V VDD 296k OUT+ MODULATOR (-) FET DRIVER OUT- 47nF* 296k SD SHUTDOWN INTERNAL OSCILLATOR BIAS POP/CLICK SUPPRESSION 07243-032 GND *INPUT CAPACITORS ARE OPTIONAL IF INPUT DC COMMON-MODE VOLTAGE IS APPROXIMATELY VDD/2. Figure 32. Differential Input Configuration, User-Adjustable Gain EXTERNAL GAIN SETTINGS = 296k/(37k + REXT) 0.1F 10F SSM2305 AUDIO IN+ 47nF R EXT REXT IN+ 37k IN- 37k VBATT 2.5V TO 5.5V VDD 296k OUT+ MODULATOR (-) FET DRIVER OUT- 47nF 296k SHUTDOWN SD BIAS INTERNAL OSCILLATOR POP/CLICK SUPPRESSION 07243-033 GND Figure 33. Single-Ended Input Configuration, User-Adjustable Gain Rev. B | Page 11 of 16 SSM2305 Data Sheet GAIN LAYOUT The SSM2305 has a default gain of 18 dB that can be reduced by using a pair of external resistors with a value calculated as follows: As output power continues to increase, care needs to be taken to lay out PCB traces and wires properly between the amplifier, load, and power supply. A good practice is to use short, wide PCB tracks to decrease voltage drops and minimize inductance. Ensure that track widths are at least 200 mil for every inch of track length for lowest dc resistance (DCR), and use 1 oz or 2 oz of copper PCB traces to further reduce IR drops and inductance. A poor layout increases voltage drops, consequently affecting efficiency. Use large traces for the power supply inputs and amplifier outputs to minimize losses due to parasitic trace resistance. External Gain Settings = 296 k/(37 k + REXT) POP-AND-CLICK SUPPRESSION Voltage transients at the output of audio amplifiers can occur when shutdown activates or deactivates. Voltage transients as low as 10 mV can be heard as audio pops in the speaker. Clicks and pops can also be classified as undesirable audible transients generated by the amplifier system and, therefore, as not coming from the system input signal. Such transients can be generated when the amplifier system changes its operating mode. For example, the following can be sources of audible transients: system power-up/ power-down, mute/unmute, input source change, and sample rate change. The SSM2305 has a pop-and-click suppression architecture that reduces these output transients, resulting in noiseless activation and deactivation. OUTPUT MODULATION DESCRIPTION The SSM2305 uses three-level, - output modulation. Each output is able to swing from GND to VDD, and vice versa. Ideally, when no input signal is present, the output differential voltage is 0 V because there is no need to generate a pulse. In a real-world situation, there are always noise sources present. Due to this constant presence of noise, a differential pulse generates when it is required in response to this stimulus. A small amount of current flows into the inductive load when the differential pulse is generated. However, most of the time output differential voltage is 0 V due to the Analog Devices patented three-level, - output modulation. This feature ensures that the current flowing through the inductive load is small. In addition, good PCB layouts isolate critical analog paths from sources of high interference. Separate high frequency circuits (analog and digital) from low frequency circuits. Properly designed multilayer PCBs can reduce EMI emission and increase immunity to the RF field by a factor of 10 or more compared with double-sided boards. A multilayer board allows a complete layer to be used for the ground plane, whereas the ground plane side of a double-sided board is often disrupted with signal crossover. +5V If the system has separate analog and digital ground and power planes, place the analog ground plane underneath the analog power plane, and, similarly, place the digital ground plane underneath the digital power plane. There should be no overlap between analog and digital ground planes or analog and digital power planes. 0V +5V INPUT CAPACITOR SELECTION When the user wants to send an input signal, an output pulse is generated to follow the input voltage. The differential pulse density is increased by raising the input signal level. Figure 34 depicts three-level, - output modulation with and without input stimuli. OUTPUT = 0V OUT+ OUT- The SSM2305 does not require input coupling capacitors if the input signal is biased from 1.0 V to VDD - 1.0 V. Input capacitors are required if the input signal is not biased within this recommended input dc common-mode voltage range, if high-pass filtering is needed, or if using a single-ended source. If high-pass filtering is needed at the input, the input capacitor, together with the input resistor of the SSM2305, forms a high-pass filter whose corner frequency is determined by the following equation: 0V +5V VOUT Proper grounding guidelines help improve audio performance, minimize crosstalk between channels, and prevent switching noise from coupling into the audio signal. To maintain high output swing and high peak output power, the PCB traces that connect the output pins to the load and supply pins should be as wide as possible to maintain the minimum trace resistances. It is also recommended that a large ground plane be used for minimum impedances. 0V -5V OUTPUT > 0V +5V OUT+ 0V +5V OUT- 0V +5V VOUT 0V OUTPUT < 0V fC = 1/(2 x RIN x CIN) +5V OUT+ 0V +5V OUT- VOUT -5V 07243-003 0V 0V The input capacitor can significantly affect the performance of the circuit. Not using input capacitors degrades both the output offset of the amplifier and the dc PSRR performance. Figure 34. 3-Level, - Output Modulation with and Without Input Stimuli Rev. B | Page 12 of 16 Data Sheet SSM2305 PROPER POWER SUPPLY DECOUPLING To ensure high efficiency, low total harmonic distortion (THD), and high PSRR, proper power supply decoupling is necessary. Noise transients on the power supply lines are short duration voltage spikes. Although the actual switching frequency can range from 10 kHz to 100 kHz, these spikes can contain frequency components that extend into the hundreds of megahertz. The power supply input needs to be decoupled with a good quality low ESL, low ESR capacitor, usually of around 4.7 F. This capacitor bypasses low frequency noises to the ground plane. For high frequency transient noise, use a 0.1 F capacitor as close as possible to the VDD pin of the device. Placing the decoupling capacitor as close as possible to the SSM2305 helps maintain efficient performance. Rev. B | Page 13 of 16 SSM2305 Data Sheet OUTLINE DIMENSIONS 1.84 1.74 1.64 3.10 3.00 SQ 2.90 0.50 BSC 8 5 PIN 1 INDEX AREA 1.55 1.45 1.35 EXPOSED PAD 0.50 0.40 0.30 PIN 1 INDICATOR (R 0.15) BOTTOM VIEW 0.05 MAX 0.02 NOM COPLANARITY 0.08 0.203 REF 0.30 0.25 0.20 FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. 12-07-2010-A 0.80 0.75 0.70 SEATING PLANE 1 4 TOP VIEW COMPLIANT TO JEDEC STANDARDS MO-229-WEED Figure 35. 8-Lead Lead Frame Chip Scale Package [LFCSP] 3 mm x 3 mm Body and 0.75 mm Package Height (CP-8-13) Dimensions shown in millimeters 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5 5.15 4.90 4.65 4 PIN 1 0.65 BSC 0.95 0.85 0.75 1.10 MAX 0.15 0.00 0.38 0.22 COPLANARITY 0.10 0.23 0.08 8 0 0.80 0.60 0.40 SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 36. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters ORDERING GUIDE Model 1 SSM2305CPZ-R2 SSM2305CPZ-REEL SSM2305CPZ-REEL7 SSM2305RMZ-R2 SSM2305RMZ-REEL SSM2305RMZ-REEL7 SSM2305-EVALZ 1 Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description 8-Lead Lead Frame Chip Scale Package [LFCSP] 8-Lead Lead Frame Chip Scale Package [LFCSP] 8-Lead Lead Frame Chip Scale Package [LFCSP] 8-Lead Mini Small Outline Package [MSOP] 8-Lead Mini Small Outline Package [MSOP] 8-Lead Mini Small Outline Package [MSOP] Evaluation Board with LFCSP Model Z = RoHS Compliant Part. Rev. B | Page 14 of 16 Package Option CP-8-13 CP-8-13 CP-8-13 RM-8 RM-8 RM-8 Branding Y10 Y10 Y10 Y10 Y10 Y10 Data Sheet SSM2305 NOTES Rev. B | Page 15 of 16 SSM2305 Data Sheet NOTES (c)2008-2016 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07243-0-5/16(B) Rev. B | Page 16 of 16