SSM2317-EVALZ

Evaluation Board User Guide UG-192 One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com Evaluation Board for SSM2317 Filterless Class-D Audio Amplifier Automatic level control (ALC) can be activated to suppress clipping and improve dynamic range. This feature only requires one external resistor tied to GND via the VTH pin and an activation voltage on the ALC_EN pin. For setup configuration and sync operation, see the SSM2317 data sheet. PACKAGE CONTENTS SSM2317-EVALZ OTHER SUPPORTING DOCUMENTATION SSM2317 data sheet GENERAL DESCRIPTION The SSM2317 is a fully integrated, single-chip, mono Class-D audio amplifier that is 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 3 W of continuous output power with less than 1% THD + N driving a 3 Ω load from a single 5.0 V supply. The SSM2317 is equipped with a differential mode input port and a high efficiency, full H-bridge at the output that enables direct coupling of the audio power signal to the loudspeaker. The differential mode input stage allows for cancelling of common-mode noise. The part also features a high efficiency, low noise output modulation scheme that does not require external LC output filters when attached to an inductive load. The modulation provides high efficiency even at low output power. Filterless operation also helps to decrease distortion due to the nonlinearities of output LC filters. This user guide describes how to configure and use the SSM2317 evaluation board to evaluate the SSM2317. It is recommended that this data sheet be read in conjunction with the SSM2317 data sheet, which provides more detailed information about the specifications, internal block diagrams, and application guidance for the amplifier IC. EVALUATION BOARD OVERVIEW 09354-001 09354-002 The SSM2317 evaluation board carries a complete application circuit for driving a loudspeaker. Figure 1 shows the top view of the evaluation board, and Figure 2 shows the bottom view. Figure 2. SSM2317 Evaluation Board Bottom View Figure 1. SSM2317 Evaluation Board Top View PLEASE SEE THE LAST PAGE FOR AN IMPORTANT WARNING AND LEGAL TERMS AND CONDITIONS. Rev. 0 | Page 1 of 8 UG-192 Evaluation Board User Guide TABLE OF CONTENTS Package Contents.............................................................................. 1 Output Configuration...................................................................3 Other Supporting Documentation................................................. 1 Power Supply Configuration .......................................................3 General Description ......................................................................... 1 Component Selection ...................................................................3 Evaluation Board Overview ............................................................ 1 Getting Started...............................................................................4 Revision History ............................................................................... 2 What to Test ...................................................................................4 Setting Up the Evaluation Board .................................................... 3 Evaluation Board Schematic and Artwork.....................................5 Input Configuration ..................................................................... 3 Ordering Information.......................................................................8 Operation Mode Configuration ................................................. 3 Bill of Materials..............................................................................8 REVISION HISTORY 10/10—Revision 0: Initial Version Rev. 0 | Page 2 of 8 Evaluation Board User Guide UG-192 SETTING UP THE EVALUATION BOARD INPUT CONFIGURATION Polarity and Voltage A 4-pin header (J1) on the middle left side of the board feeds the audio signal into the board (see Figure 1). If the input audio signal is differential (IN+ and IN−), three pins of J1 are used for IN+, IN−, and signal ground. For a single-ended audio input, only two pins of J1 are used. One is for the signal ground and the other is for either IN+ or IN−. If IN+ is used, place a jumper between Pin 3 and Pin 4 of J1, shorting IN− to ground. If IN− is used, place the jumper between Pin 1 and Pin 2 of J1, connecting IN+ to ground. The wrong power supply polarity or an overvoltage may damage the board permanently. The maximum peak current is approximately 0.33 A when driving an 8 Ω load and when the input voltage is 5 V. OPERATION MODE CONFIGURATION When ALC mode is active, the maximum output amplitude threshold (VTH) during the limiting operation can be adjusted from 90% to 45% of VDD by inserting an external resistor, RTH, between the VTH pin and GND. Shorting the VTH pin to GND sets VTH to 90% of VDD. Leaving the VTH pin unconnected sets VTH to 45% of VDD. The relation of RTH to VTH is shown by the following equation: The 6-pin header, J2, is used to turn on/off the SSM2317 amplifier and configure the ALC operation modes. Placing a jumper across Pin 1 and Pin 2 of J2 shuts down the SSM2317 so that only a minimum current (about 20 nA) is drawn from the power supply (when R3 is shorted). Removing the jumper puts the SSM2317 in normal operation. Placing a jumper across Pin 3 and Pin 4 of J2 disables ALC mode, while removing the jumper activates ALC mode. When ALC is disabled, the SSM2317 behaves like a traditional amplifier with a fixed 18 dB. Placing a jumper across Pin 5 and Pin 6 of J2 shorts across the ALC threshold resistor (on board) and sets a maximum limiter level of 90% of VDD (when ALC is activated). COMPONENT SELECTION Selecting the proper components is the key to achieving the performance required at the cost budgeted. ALC Threshold Setting Resistor—R5 VTH = 0.9 × POUT Although the SSM2317 does not require any external LC output filters due to a low noise modulation scheme, if the speaker length is >10 cm, it is recommended to put a ferrite bead (L1 and L2) near each output pin of the SSM2317 to reduce electromagnetic interference (EMI), as shown in the schematic in Figure 3. Some users may want to replace the ferrite beads with these inductors to evaluate applications with specific EMI vs. audio performance constraints. As an aid, a properly tuned ferrite bead-based EMI filter is assembled at the output terminals of the device. For optimal performance, as specified in the SSM2317 data sheet (in particular, for THD and SNR), remove the entire EMI filter, short across the ferrite bead terminals, and open the capacitor terminals. POWER SUPPLY CONFIGURATION The evaluation board schematic is shown in Figure 3. The 2-pin header, J3, must be used to power the board. Care must be taken to connect the dc power with correct polarity and voltage. The positive voltage terminal of J3 (VDD) is indicated with an arrow in Figure 1. × VDD Maximum output power is derived from VTH by the following equation: OUTPUT CONFIGURATION The output connector, J4, is located on the right side of the board (see Figure 1). J4 drives a loudspeaker whose impedance should be no less than 3 Ω. 50 kΩ + RTH 50 kΩ + 2 × RTH ⎛ VTH ⎞ ⎜ ⎟ 2 ⎠ =⎝ RSP 2 where RSP is the speaker impedance. To tune a variety of VTH levels, a potentiometer, R5, is mounted on the evaluation board. To measure the potentiometer resistance setting, insert an ohmmeter across Pin 5 and Pin 6 of J2. Note that measuring the resistance across the potentiometer is not adequate to determine the actual RTH value. This is due to the internal input resistance of 50 kΩ at the VTH pin. The user must take into account the internal resistance while evaluating actual RTH. For example, after tuning R5 to a desirable level, the user measures the resistance from Pin 5 and Pin 6 of J2. Then, to infer the actual RTH, use this simple calculation: 1 1 1 = − RThreshold R Measured 50 kΩ where: RThreshold is the desired external resistor value from the VTH pin to GND. RMeasured is the measured resistance from the VTH pin to GND. Rev. 0 | Page 3 of 8 UG-192 Evaluation Board User Guide Input Coupling Capacitor Selection—C1 and C2 Output Inductors The input coupling capacitors, C1 and C2, should be large enough to couple the low frequency signal components in the incoming signal but small enough to filter out unnecessary low frequency signals. For music signals, the cutoff frequency chosen is, typically, between 20 Hz and 30 Hz. The value of the input capacitor is calculated by If using inductors for the purpose of EMI filtering at the output nodes, choose inductance that is 600 mA (saturation current) for an 8 Ω load. Table 2 shows the recommended inductors. Note that these inductors are not populated on the evaluation board. C = 1/(2πRfc) where: R = 40 kΩ + Rext (the external resistor used to fine-tune the desired gain; on the schematics (see Figure 3), this is the 0 Ω resistor at the input pins). fc is the cutoff frequency. GETTING STARTED To ensure proper operation, carefully follow Step 1 through Step 7. 1. Output Ferrite Beads—L1 and L2 2. The output beads, L1 and L2, are necessary components for filtering out the EMI caused at the switching output nodes when the length of the speaker wire is greater than 10 cm. The penalty for using ferrite beads for EMI filtering is slightly worse noise and distortion performance at the system level due to the nonlinearity of the beads. 3. Ensure that these beads have enough current-conducting capability while providing sufficient EMI attenuation. The current rating needed for an 8 Ω load is approximately 420 mA, and impedance at 100 MHz should be ≥120 Ω. In addition, the lower the dc resistance (DCR) of these beads is, the better for minimizing their power consumption. Table 1 describes the recommended beads. 4. 5. 6. 7. Output Shunting Capacitors If a jumper is across Pin 1 and Pin 2 of J2, remove the jumper to enable the amplifier. Remove the jumper across Pin 3 and Pin 4 of J2 to ensure that the device is in ALC mode. To put in standard 12 dB configuration and disable ALC, insert a jumper across Pin 3 and Pin 4. For most audio quality testing, the EMI filtering (L1/L2 and C6/C7) must be removed. Short across the L1 and L2 terminals to make a direct connection from the device output to the J4 speaker header. Connect the load to the audio output connector, J4. Connect the audio input to the board in either differential mode or single-ended mode, depending on the application. Connect the power supply with the proper polarity and voltage. Turn R5 potentiometer to the desired VTH setting. WHAT TO TEST There are two output shunting capacitors, C6 and C7, that work with the ferrite beads, L1 and L2. Use small size (0603 or 0402), multilayer ceramic capacitors that are made of X7R or COG (NPO) materials. Note that the capacitors can be used in pairs: a capacitor with small capacitance (up to 100 pF) plus a capacitor with a bigger capacitance (less than 1 nF). This configuration provides thorough EMI reduction for the entire frequency spectrum. For BOM cost reduction and capable performance, a single capacitor of approximately 470 pF can be used. • • • • • • Electromagnetic interference (EMI)—connect wires for the speakers, making sure that they are the same length as the wires required for the actual application environment; then complete the EMI test. Signal-to-noise ratio. Output noise—make sure to use an A-weighted filter to filter the output before reading the measurement meter. Maximum output power. Distortion. Efficiency. Table 1. Recommended Output Beads Part No. BLM18PG121SN1D MPZ1608S101A MPZ1608S221A BLM18EG221SN1D Manufacturer Murata TDK TDK Murata Z (Ω) 120 100 220 220 IMAX (mA) 2000 3000 2000 2000 DCR (Ω) 0.05 0.03 0.05 0.05 Size (mm) 1.6 × 0.8 × 0.8 1.6 × 0.8 × 0.8 1.6 × 0.8 × 0.8 1.6 × 0.8 × 0.8 L (μH) 0.47 1.0 0.47 1.0 2.2 IMAX (mA) 1400 1200 1100 800 790 DCR (Ω) 0.07 0.12 0.12 0.19 0.1 Size (mm) 3.2 × 1.6 × 0.85 3.2 × 1.6 × 0.85 2.0 × 1.25 × 0.5 2.0 × 1.25 × 0.5 3.2 × 2.5 × 1.55 Table 2. Recommended Output Inductors Part No. LQM31PNR47M00 LQM31PN1R0M00 LQM21PNR47MC0 LQM21PN1R0MC0 LQH32CN2R2M53 Manufacturer Murata Murata Murata Murata Murata Rev. 0 | Page 4 of 8 Evaluation Board User Guide UG-192 EVALUATION BOARD SCHEMATIC AND ARTWORK VDD J3 HDR1X2 C3 10µF IN– 2A CON4 VDD VDD OUT+ SD R2 0Ω C2 0.1µF IN+ OUT– 3C TP1 3B TP2 VTH 1A IN- ALC_EN U1 SSM2317/BGA 1B OUT+ C6 1nF J4 HDR1X2 C7 1nF L2 B0603 OUT– 3A R1 0Ω IN+ 2B C1 0.1µF 1 2 3 4 GND J1 L1 B0603 2C 1C C4 0.1µF R3 100kΩ R4 100kΩ R5 C5 0.1µF 1 3 5 100kΩ CON6A 09354-003 2 4 6 J2 Figure 3. Schematic of the SSM2317 Evaluation Board Rev. 0 | Page 5 of 8 Evaluation Board User Guide Figure 4. Top Layer with Top Silkscreen 09354-006 09354-004 UG-192 Figure 5. Top Silkscreen 09354-006 09354-005 Figure 6. Top Layer Figure 7. Layer 2 (Ground Plane) Rev. 0 | Page 6 of 8 Figure 8. Layer 3 (Power Plane) 09354-009 UG-192 09354-008 Evaluation Board User Guide Figure 9. Bottom Layer Rev. 0 | Page 7 of 8 UG-192 Evaluation Board User Guide ORDERING INFORMATION BILL OF MATERIALS Table 3. Qty 3 1 2 1 1 2 2 2 2 2 1 1 1 Reference Designator C1, C2, C4 C3 C6, C7 J1 J2 J3, J4 L1, L2 R1, R2 R3, R4 TP1, TP2 U1 C5 R5 Description Ceramic capacitor, 0.1 μF Ceramic capacitor, 10 μF, 10 V Ceramic capacitor, 1 nF, 10%, 50 V CON4, header connector CON6A, six-position header connector HDR1X2 header connector Ferrite chip, B0603, 220 Ω Resistor, 0 Ω Resistor, 100 kΩ Test pad SSM2317/BGA Ceramic capacitor, 0.1 μF Potentiometer, 100 kΩ to 0 Ω Supplier/Part No. Panasonic, ECJ-ZEB1A104M Murata, GRM31MF51A106ZA01L Kemet, C0603C102J5GACTU Tyco, 640452-4 Tyco, 3-87589-6 Tyco, 640452-2 TDK, MPZ1608S221A Panasonic, ERJ-3GEY0R00V Yageo, RT0603FRE07100KL N/A Analog Devices, SSM2317 Panasonic, ECJ-ZEB1A104M Panasonic, EVN-D8AA03B15 ESD Caution ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality. Legal Terms and Conditions By using the evaluation board discussed herein (together with any tools, components documentation or support materials, the “Evaluation Board”), you are agreeing to be bound by the terms and conditions set forth below (“Agreement”) unless you have purchased the Evaluation Board, in which case the Analog Devices Standard Terms and Conditions of Sale shall govern. Do not use the Evaluation Board until you have read and agreed to the Agreement. Your use of the Evaluation Board shall signify your acceptance of the Agreement. This Agreement is made by and between you (“Customer”) and Analog Devices, Inc. (“ADI”), with its principal place of business at One Technology Way, Norwood, MA 02062, USA. Subject to the terms and conditions of the Agreement, ADI hereby grants to Customer a free, limited, personal, temporary, non-exclusive, non-sublicensable, non-transferable license to use the Evaluation Board FOR EVALUATION PURPOSES ONLY. Customer understands and agrees that the Evaluation Board is provided for the sole and exclusive purpose referenced above, and agrees not to use the Evaluation Board for any other purpose. Furthermore, the license granted is expressly made subject to the following additional limitations: Customer shall not (i) rent, lease, display, sell, transfer, assign, sublicense, or distribute the Evaluation Board; and (ii) permit any Third Party to access the Evaluation Board. As used herein, the term “Third Party” includes any entity other than ADI, Customer, their employees, affiliates and in-house consultants. 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Any legal action regarding this Agreement will be heard in the state or federal courts having jurisdiction in Suffolk County, Massachusetts, and Customer hereby submits to the personal jurisdiction and venue of such courts. The United Nations Convention on Contracts for the International Sale of Goods shall not apply to this Agreement and is expressly disclaimed. ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. UG09354-0-10/10(0) Rev. 0 | Page 8 of 8