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| LXE1710 EVALUATION BOARD USER GUIDE A MICROSEMI COMPANY Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 1 LXE1710 EVALUATION BOARD INTRODUCING LX1710/1711 AUDIOMAX USER GUIDE Thank you for your interest in the latest generation of AudioMAX products. The enclosed LXE1710 evaluation board is a fully functional mono amplifier designed to demonstrate the "new and improved" Switching Class-D Power Amplifier IC from Linfinity Microsemi. The LX1710/1711 is a completely new controller design with superior performance over the LX1720 stereo controller IC. Key improvements include better SNR, lower noise floor, and reduced THD therefore resulting in a much "quieter" and "cleaner" sounding amplifier. The evaluation board has been configured with easy-to-use terminal block connections for power supply/battery hook up and speaker connections. An RCA jack or separate audio +/- pins allow a quick interface to your audio source. Jumpers are also provided to enable/disable the amplifier (Sleep control) and to turn off the audio input (Mute control). With minimal setup, the user can be listening to the amplifier in a matter of a few minutes. Both the LX1710 and LX1711 operate from a single supply voltage. The LXE1710 evaluation board can !e LX1711 can handle a higher supply voltage (7V to 25V) and provides greater than 50W continuous output power ! " " ! " change frequency response for other load optimization. Thank you again for your interest in the new "quieter", high efficiency Class-D Audio Amplifier from Linfinity Microsemi. Please let us know what you think and stay tuned for future product releases to our AudioMAX family of products. Regards, Linfinity Microsemi http://www.linfinity.com (714) 898-8121 Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 2 LXE1710 EVALUATION BOARD TABLE OF CONTENTS USER GUIDE LX1710 / 1710 AudioMAX Evaluation Board Features and Circuit Description .............................4 Input Compensation Output Stage Filter Stage Quick Start Guide............................................................................................................................................5 Application Schematic...................................................................................................................................6 Electrical Characteristics..............................................................................................................................7 Performance Graphs ......................................................................................................................................8 Application Information Filter Design Tradeoffs (1-Stage vs. 2-Stage).............................................................................................9 LC Filter Design...........................................................................................................................................9 MOSFET Selection....................................................................................................................................10 Inductor Selection......................................................................................................................................12 Capacitor Selection ...................................................................................................................................13 Gate Resistor ............................................................................................................................................14 Oscillator Configuration .............................................................................................................................14 Multi Channel Requirements and Frequency Synchronization..................................................................14 PCB Layout ...............................................................................................................................................15 Board Layout ..................................................................................................................................................16 Printed Circuit Board ...................................................................................................................................17 Bill of Materials ..............................................................................................................................................18 Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 3 LXE1710 EVALUATION BOARD USER GUIDE Part Number LX1710CDB LX1711CDB LXE1710 Product AudioMAX High Fidelity Controller IC AudioMAX High Power Controller IC LX1710 AudioMAX Evaluation Board Description VDD = 7V to 15V, Switching Class-D Mono Power Amplifier IC, 28-Pin SSOP Package. VDD = 7V to 25V, Switching Class-D Mono Power Amplifier IC, 28-Pin SSOP Package. Fully Operational Mono Audio Amplifier. LX1710/1711 AUDIOMAX EVALUATION BOARD FEATURES AND CIRCUIT DESCRIPTION * * * * Fully Assembled Mono Evaluation Board with LX1710 Class-D Controller IC Improved SNR and Noise Floor Performance Output Power of 25W typical (LX1710, 15VDD, * * * * Supports Full Audio Bandwidth Terminal Block Connectors for Voltage and Speaker Connection RCA Plug for Audio Input Signal Supply Output Power of 54W typical (LX1711, 25VDD, The AudioMAX Evaluation Amplifier Board allows the user to quickly connect and evaluate the LX1710 Switching Class-D Mono Controller IC. Easy-toconnect terminal blocks and an RCA plug are provided for interfacing to Power, Speaker, and Audio Input connections. The single stage output filter has been configured to drive a 4 audio bandwidth amplification (See Application section LC filter design for component selection, calculations, and suggested inductor and capacitor values for other loads). The LXE1710 Evaluation Board operates from a single supply voltage. The Class-D Amplifier Controller IC requires a minimal number of external components to create a complete amplifier solution. See LXE1710 Evaluation Board Schematic and Bill of Materials for circuit specifics. A Class-D Amplifier is a "switching" amplifier that converts a low-level, analog audio input signal into a high power, pulse-width modulated (PWM) output. The switching frequency (500kHz typical but can be adjusted) is much higher than the audio bandwidth (20Hz to 20kHz), and is easily filtered out with a simple LC filter. The support circuitry can be generally grouped into three areas (input circuit, output power stage, and output filter). INPUT COMPENSATION The first group is the compensation network and control setting components. These resistors and capacitors set up the controller operating frequency, response characteristics, and comparator ramp fundamental to Class-D operation. OUTPUT STAGE The next section is the output stage. The controller IC generates a PWM output by controlling external FETs connected in a full bridge configuration. The full bridge configuration is connected between the single supply voltage (PVDD) and ground (PGND) with the output of the bridge driving the LC filter stage. Because the FETs are either fully "on" or fully "off", Class-D topology is extremely efficient (up to 85% typical), circuit power dissipation is minimal, and maximum power is delivered to the speaker. The bridge output also drives the RC low pass filter, which provides the feedback for the control loop through the FBK+ and FBK- inputs. FILTER STAGE The single stage, second order LC filter is used to remove the switching frequency. The frequency response and corner frequency can be easily adjusted for optimization of various loads. The LC evaluation board component values have been chosen for a 4 ! " # $ for component selection. Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 4 LXE1710 EVALUATION BOARD QUICK START GUIDE The LXE1710 Evaluation Board is a fully functional, Class-D Amplifier. Connection to a single supply voltage (VDD from either a battery or power supply), speakers, and your audio source is all that is required to begin evaluating the amplifier and listening to music. The following outlines the necessary connections and control jumpers. 1) Verify contents of Evaluation Kit: The easy-touse amplifier is all contained on a single board. Visually inspect to see if the board or any components were damaged during shipping. All components are located on the top side of the PCB except for the decoupling capacitor, C17. A copy of the LX1710/1711 Datasheet should also be enclosed or a PDF version can be downloaded from the Microsemi.com website (http://www.microsemi.com/datasheets/MSC1580.PDF). USER GUIDE can be used to drive other speaker loads but frequency response may not be optimal. See LC filter design section for recommended inductor and capacitor modifications. 4) Audio Input Connection: Connect your audio source to the RCA Jack CN1, Audio In. For other type interfaces, the audio input signal can also be connected to the amplifier board using the J3 (In- and In+) location. Strip Line Plugs can be inserted into J3 for connectivity. 5) Jumper Selection Controls: The "on/off" or enable to the module is controlled with the SLEEP/ signal. Jumper J1 connects the SLEEP/ to "on" or " off". SLEEP/ is an active Low control. Jumper J2 connects the MUTE control which enables/disables the audio input to the amplifier. MUTE is an active High signal. See table below. 6) Power Source: If a power supply is being used, make sure it is set to the correct voltage level and turn the power supply on. 7) Audio Source: Make sure the audio source signal is set to a minimum level. Start or "play" audio source and adjust source volume to desired level. 8) Listen to AudioMAX: If the amplifier is not operating properly, verify preceding steps or contact Linfinity for technical assistance (714) 898-8121. To Speaker + To Power Supply +V To Speaker - 2) Power and Ground Connections: The voltage supply and ground connections are made through terminal block TB1. Connect your "+" (+7V to +15V) power supply or battery to the +V input of TB1. Connect your supply or battery ground to the GND input of TB1. Please ensure the correct positive and ground connections are made before turning on the power supply. 3) Speaker Connection: The amplifier is designed $ ! #" "+" and "-" to the +OUT and -OUT input of terminal block TB2 respectively. The amplifier Jumper toward OFF J1 Jumper: SLEEP/ J2 Jumper: MUTE Amplifier enabled (SLEEP/ is OFF) Audio Input enabled (MUTE is OFF) Jumper toward ON Amplifier disabled (SLEEP/ is ON) Audio Input disabled (MUTE is ON) 7V-15V for LX1710 7V-25V for LX1711 Jumper floating Amplifier disabled (SLEEP/ is ON) Audio Input enabled (MUTE is OFF) To Power Supply Ground Optional Audio In Optional Audio In + To Audio Source Jumper Settings Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 5 LXE1710 EVALUATION BOARD SCHEMATIC USER GUIDE V IN 7V to 15V C9 0.1 F 35V + C 22 .1 F 25 VDD C LO C K 28 N C C 13 2.2 F + + C 11 4.7 F 24 P V D D IS 26 5 CP RPW M CPW M 27 C 17 220 F 25V R S1 .034 7 P + 23 R 12 10 o hm Q1 C 12 .1 F R 5 34.8 K C1 1 F L1 1 5 H 6 C 16 100 pF 1 4 VREF V 25 GND N+ 22 R 11 10 o hm Q2 C8 .1 F 50V R3 24.3 K C7 220 pF C 20 .68 F R 13 15 o hm 1W C 18 .47 F C2 1 F SLEEP 2 10 LX1710 P- 20 R6 10 o hm Q3 S LE E P C 21 .68 F C 19 .47 F MU TE 11 M U T E AU DIO IN PUT R 8 10K C3 470 nF NC 9 IN A M P O U T 7 IN P U T+ N21 R 10 10 o hm Q4 L2 1 5 H C 26 330 pF 8 R 9 10K C 14 470 nF C5 18p F R 1 56.2 K C4 150 pF PGND IN P U TNC CN 19 C 10 4.7 F R4 24.3 K C6 220 pF 3 + 18 16 17 12 NC 14 13 15 EAOUT E A IN FA O U T FB K + FB K S TA TU S R 2 10K - Evaluation Board Schematic Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 6 LXE1710 EVALUATION BOARD ELECTRICAL CHARACTERISTICS USER GUIDE Unless otherwise specified, the following specifications apply over the operating ambient temperature 0C SYMBOL VDD IDD IQ TEST CONDITIONS VIN=15V, PO=38W, RL THD+N=1% VIN=15V, No Input VIN=15V, RL 10Hz to 22kHz VIN=15V, RL 10Hz to 22kHz VIN=15V, RL 10Hz to 22kHz VIN=15V, fIN=1kHz, PO=10W VIN=15V, fIN=1kHz, PO=20W MIN. 7 TYP. MAX 15 UNITS V A mA W W W % % % 3 43 14 25 38 82 85 0.05 0.3 81 Output Power PO Efficiency Total Harmonic Distortion Plus Noise Signal-To-Noise Ratio Power Supply Rejection Ratio THD+N SNR PSRR fIN=1kHz, PO=1W fIN=20Hz to 20kHz, PO=1W VIN=15V, VRIPPLE=1VRMS, 10Hz to 10kHz % dBV dB -70 Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 7 LXE1710 EVALUATION BOARD PERFORMANCE GRAPHS 90% 85% 80% Efficency (%) USER GUIDE 60 50 Output Power (W) 75% 70% 65% 60% 55% 50% 45% 0 5 10 15 Output Power (W) 40 30 20 10 0 20 25 30 6 11 16 Supply Voltage (VIN) 21 26 VIN = 15V fIN=1kHz RL% THD+N=1% +20 +15 +10 Voltage Amplification (dBr) +5 100 50 20 10 5 2 THD + N (%) 1 0.5 0.26 0.1 0.04 0.02 0.01 0.005 0.002 -0.08 -0.59 -5 -10 -15 -20 10 18.2 50 100 200 500 1k 2k 5k 10k 17.88k 50k 80k 0.001 50m 100m 200m 500m 1.13 2 Output Power (W ) 5 10 20 24.56 30 Frequency (Hz) VIN=15V RL% RO=1W RMS VIN=15V fIN=1kHz RL% Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 8 LXE1710 EVALUATION BOARD USER GUIDE APPLICATION INFORMATION ! &' ( LX1710 Filter Implementation, 1-stage vs. 2- stage 100 50 20 10 5 2 1 Percent (%) 0.5 0.55626 0.2 0.05 0.02 0.01 0.005 0.002 0.001 50m 100m 200m 500m 11.15 Watts(W) 2 5 10 2025.04 30 2-Stage 1-Stage 0.12572 0.1 FILTER DESIGN TRADEOFFS (1-STAGE VS. 2-STAGE) A 1-stage or 2-stage filter may be used depending on your application and performance targets. The main tradeoff in this selection is price (number of components, component costs, PCB area) vs. performance. The primary advantage of the single stage filter is lower cost whereas the main benefit to a 2-stage filter is that it will provide steeper attenuation. This allows the corner frequency to be selected further outside of the audio band (to minimize the effects of impedance variations in the passband) and still provide adequate RF attenuation. * impedance changes could result in a +/- 6dB change. THD: There are minimal differences between the 1-stage and 2-stage implementations with other parameters such as THD+N as seen in the above graph. Single Stage Filter Disadvantages * EMI and Switching Frequency: For the 1stage, the switching frequency must be higher than 400kHz to ensure the corner frequency will provide adequate amplifier performance in the high end of the audio frequency range. If fS < 400kHz, then fC < fS /10 = 40kHz which is too close to the desired audio band. A higher oscillation frequency could translate into greater MOSFET switching losses, slightly lower efficiency, and increased EMI effects. With a 2-stage 4th order filter, the switching frequency fS can be reduced to 120kHz. If fS = 120kHz, then fC = fS /3 = 40kHz. The lower oscillation frequency could help minimize EMI issues. Single Stage Filter Advantages * Low Cost: The 1-stage LC filter uses one half the number of inductors/capacitors resulting in a substantial cost savings over a 2-stage design. Key parameters such as THD+N, frequency response, and nose performance do not change significantly. Power Loss: Since current will flow in two inductors and not four, the inductor power loss will be less in the single stage design. The overall amplifier will have a wider dynamic range and improved efficiency. Filter Design: This easy-to-design filter can limit audio signal changes within +/- 3dB across the audio band with impedance vari" ) *+ ,! a steeper rolloff with the 2-stage filter, * * LC FILTER DESIGN The output filter helps to reconstruct the amplified audio signal and filter out the switching frequency. The design of the filter depends on the type of attenuation and frequency response desired at the output. The output filter designed into the LXE1710 Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 9 LXE1710 EVALUATION BOARD evaluation board is a second order, LC type filter as shown below. Tradeoffs between performance and component cost must be considered when determining the complexity or type of filter selected. OUT+ L 15H C 0.68F USER GUIDE the required audio response and is used in the calculation below. C= Q Q 0.707 = = = 0.56 F R R(2fC ) 4(2 )(50000) C = 0.68F is used in the Evaluation Board To Compute the Inductor Value: R L= L OUT- 15H C 0.68F 1 1 1 = = = 14.9 H 2 2 C (2fC ) C [(2 )(50000)]2 (.68 ) L = 15H is used in the Evaluation Board LXE1710 Evaluation Board Frequency Response Its Laplace Transform function is: +15 +12.5 Voltage Amplification (dBr) S S C C H(S) = = 1 1 2 2 S+ S+ S + S +2 RC LC Q +10 +7.5 +5 +2.5 +0 -2.5 -5 -7.5 -10 -12.5 Where = 1 LC -15 10 20 50 10 20 50 1k 2k 5k Frequency (Hz) 10 k 20 k 50 80 kk Q = RC The Class-D amplifier evaluation board design has a pass-band of 20Hz to 20kHz to support the audio frequency range and is configured to utilize a switching or oscillator frequency fs = 500kHz. Depending on the application, this oscillator frequency may be adjusted (see section on Oscillator Configuration) to optimize amplifier performance or modified for other considerations such as EMI effects. Further requirements of the filter are that the pass band attenuation of switching frequency fs should be lower than 40dB and the corner frequency of the LC filter should be set higher than 20kHz to avoid attenuating audio signals in the desired audio band by more than 1dB. A speaker DC impedance o '- C = 50kHz corner frequency are defined for the evaluation board. The Q (selectivity factor or ratio of the center frequency divided by the bandwidth) of the filter must also be considered when designing a filter. Too high a Q will result in a boost of the audio signal across the audio band whereas a low Q will cause too much attenuation of the signal. A Q value of 0.707 provides Copyright (c) 2000 Rev. 1.1, 2000-12-01 Frequency response of the audio amplifier was $ " ) ,! - $- + - - "" ' . ! - , ) " + )/ . -4dB attenuation respectively. Therefore, to improve frequency response performance for other loads, the value of Q must be increased/decreased by changing the capacitor. Since a different value C will affect the corner frequency, values for L and C must be recalculated. Below are recommended inductor and capacitor values for 2 , - single stage LC filter design. Filter Component Values Please note: These recommended values are guidelines for speaker loads. Actual speakers have varying impedances, which may require revised filter calculations and optimization. Furthermore, your application may have different design goals than those chosen for the LX1710 evaluation board. Capacitor C (F) 1.0 0.68 0.47 Inductor L (H) 10 15 22 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 10 LXE1710 EVALUATION BOARD MOSFET SELECTION As seen in previous sections, the user can design the output filter of the amplifier to meet performance or costs targets. In addition, the amplifier's power stage (selection of MOSFETs) can be selected depending on these tradeoffs. The efficiency of the amplifier circuit can be approximated by the following equation. USER GUIDE RNDS = 0.03, RPDS = 0.095 PDS = (2.5) 2 [2(0.03 + 0.095)] = 1.56W MOSFET power loss is proportional to on-resistance. MOSFET SwitchingLoss = PCROSS = CV 2 fSn Where C V fS n Assume C V fS = = = = Input Capacitance Supply Voltage Switching Frequency Number of MOSFETS POUT I 2 RL = =2 PIN I [2( RNDS + RPDS + RIND ) + RL ] + PCROSS Where RL = RNDS = RPDS RIND = = DC Resistance of Speaker n-channel MOSFET on-resistance p-channel MOSFET on-resistance DC Resistance of Inductor MOSFET Switching Loss PCROSS = = 1000pF = 15VDC = 500kHz PCROSS = (1x 10 -9 )(152 )(500 x103 )(4) = 0.45W The overall efficiency is a function of primarily the MOSFETs and output filter inductors. The "Inductor" section's contribution will be considered later. The MOSFET Power loss is a function of the on-resistance and gate charge. MOSFET switching loss is proportional to total gate charge, supply voltage, and switching frequency. There are a few other important parameters to consider when selecting the output power components besides the on-resistance and gate charge of the MOSFETs. The drain-source voltage must provide ample margin for circuit noise and high speed switching transients. Since the amplifier configuration requires output bridge operation at the supply voltage, the MOSFETs should have a drain-source voltage of at least 50% greater than the supply voltage. The power dissipation of the MOSFETs should also be able to dissipate the heat generated by the internal losses and be greater than the sum of PDS and PCROSS. Linfinity recommends that in selecting MOSFETs, RDS 0 1!1 2g <10nC. The table below provides several MOSFET options. Si4532ADY IRF7105 MOSFET Power Loss = PDS = I 2 [2( RNDS + RPDS )] PO = 25W at 4 If Then I= P 25 = = 2.5 A R 4 The LX1710 Evaluation Board is designed using FDS4953 p-channel and FDS6612A n-channel MOSFETS. FDS6612A FDS4953 RDS(ON)@VGS = +/-10V n-channel p-channel n-channel p-channel n-channel p-channel Drain-Source On-Resistance Drain-Source Voltage Drain Current (continuous) Total Gate Charge Manufacturer 0.022 30 8.4 9 Fairchild 0.053 -30 -5 8 Fairchild 0.053 30 4.9 8 Vishay Siliconix 0.08 -30 -3.9 10 Vishay Siliconix 0.10 25 3.5 9.4 0.25 -25 -2.3 10 VDSS (V) ID(continuous) (A) Qg (typical) (nC) MOSFET Component Options Copyright (c) 2000 Rev. 1.1, 2000-12-01 International International Rectifier Rectifier Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 11 LXE1710 EVALUATION BOARD INDUCTOR SELECTION The output filter inductors are key elements in the performance of the Class-D audio power amplifier. Inductor selection criteria also involves tradeoffs between performance (efficiency) and component costs. The critical specifications for the inductor are the DC resistance, DC current, and peak current ratings. The inductors should be able to handle the amplifier's power as well as operate within its linear region. Saturating the inductors could decrease performance (increase THD) and even produce a short, which may damage either the circuit or the speaker. Other variables when selecting an inductor depend on the switching frequency of the designed amplifier. A higher switching frequency implies that the corner frequency of the LC filter is higher. With a higher fC, the inductor value is smaller. The amplifier's application and design constraints will help determine whether the inductors are selected for size, power, or performance. Various inductors such as those that are shielded may also have different EMI effects and distortion performance. The overall efficiency () of the amplifier circuit is given in the previous MOSFET section. The inductor's power loss contribution is a function of the inductor's DC resistance, RIND. USER GUIDE Inductor Power Loss = PIND = ( I 2 )(2)( RIND ) The LX1710 Evaluation board utilizes two 15H radial leaded R.F. inductors from Inductor Supply, Inc. (ISI). When evaluating component options, inductors such as from Coilcraft can be used for other performance / price tradeoffs. See inductor table below. PIND = (2.52 )(2)(.056) = 0.7W The efficiency approximation can now be completed. = POUT I 2 RL =2 PIN I [2( RNDS + RPDS + RIND) + RL] + PCROSS I 2 RL PDS + PIND + PCROSS + I 2 RL 25 1.56 + .7 + .45 + 25 = 90.2% = = The efficiency is a function of the power and switching loss in the MOSFETs and inductors. Manufacturer Part Number RL622-150K DO5022P-153HC Inductance 15.0 15.0 Q min 50 Test Frequency 2.520MHz 100kHz DC Resistance 56 32 DC Current max (ARMS) 2.50 4.4 Self Resonant Frequency min (MHz) 12.0 20 ISI Coilcraft Inductor Component Options Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 12 LXE1710 EVALUATION BOARD CAPACITOR SELECTION The LC filter design section discusses filter options and the calculation of component values. However, the specification of capacitor type depends on the application in the circuit. The table provides descriptions and guidelines for capacitors in the AudioMAX amplifier board. USER GUIDE Reference Designator C10, C11 C3 C14 C18, C19, C20, C21 C8, C12 C22 C9, C13 C17 C16 C6, C7 C4, C5 C1, C2 C26 Capacitor FET gate drive Audio input path Output filter FET bypass LX1710 bypass VDD, PVDD bypass Output power stage Oscillator frequency Feedback filter Error amplifier Voltage references Audio input filter Comments These ! "#! $! $ "! % #! &'! These decoupling capacitors are used for the audio input +/- signals. The output filter metal film capacitors (low ESR, 5% tolerance) work well to set an accurate corner frequency at a low cost. These metal film capacitors are used for the power supply bypass for the FETs. Place adjacent to the FETs or consider lower value ESR solutions depending on the PCB component placement. The metal film capacitor is a high frequency bypass for the LX1710 IC. These tantalum capacitors provide the bypass for the IC supply voltage and output driver supply voltage utilizing a minimal footprint area. The electrolytic filter capacitor smoothes out ripple current and should be placed close to the output FETs. The timing capacitor (5% tolerance) sets the oscillator frequency. These (5%) capacitors are used in the RC filter to provide feedback for the control loop. These (5%) capacitors create the compensation network. "temperature grade" is used to ensure stability. Make sure the appropriate The filter capacitors provide the bypass for the 5V and 2.5V references. The RC filter minimizes high frequency noise to the amplifier. Capacitor Description Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 13 LXE1710 EVALUATION BOARD Gate Resistor Impact On THD+N 100 50 20 10 2 1 T HD+ N (% ) 0.26978 0.1 0.04675 0.01 0.005 0.001 50m 100m 200m 500m 1 1.131 O utput P ower (W ) 2 5 10 USER GUIDE No Gate Resistor W ith 10 Gate Resistor 20 24.56 30 VIN = 15V fIN = 1kHz RL GATE RESISTOR Series resistors (R6, R10, R11, R12) can be added to the gate of MOSFETs (Q1 to Q4) to control the switching transition times. This reduces signal distortion as seen in the THD+N vs. Output Power graph below. The slower switching speeds will however, increase power dissipation and therefore slightly decrease the overall efficiency of the amplifier. VIN and valley voltages, and the charge and discharge currents are proportional to the supply voltage. This keeps the frequency relatively constant while keeping the slope of the PWM ramp proportional to the voltage on the VDD pin. For operating frequencies other than 333kHz, the frequency can be approximated by the following equation: Frequency = 1 (0.577)( RPWM )(CPWM ) + 320ns R12 P+ 10 Q1 OUT+ R11 N+ 10 Q2 MULTI CHANNEL REQUIREMENTS AND FREQUENCY SYNCHRONIZATION For applications that require more than a single channel, the oscillators of multiple LX1710/1711 controllers can be configured for synchronous operation. One unit, the master, is programmed for the desired frequency with the RPWM and CPWM as usual. Additional units will be slave units, and their oscillators will be disabled by leaving the RPWM pin disconnected. The CLOCK pin and the CPWM pin of the slave units should be tied to the CLOCK pin and the CPWM pin of the master unit respectively. In this configuration, the CLOCK pins of the slave units begin receiving instead of transmitting clock pulses. Also, the CPWM pins quit driving the PWM capacitor in the slave units. Note that for optimum performance, all slave units should be located within a few inches of the master unit. - 3451 . 1 $ resistors, which improves (decreases) the THD+N from 0.1% to 0.05% with a slight impact on efficiency of approximately 2%. The recommended gate resistor 1 6! OSCILLATOR CONFIGURATION The oscillator is programmed by the external timing components RPWM and CPWM. For a nominal frequency of 333kHz, RPWM and CPWM should be set to 49.9kOhms and 100pF respectively. Note that in order to keep the slope of the PWM ramp voltage proportional to the supply voltage, both the ramp peak Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 14 LXE1710 EVALUATION BOARD PCB LAYOUT RECOMMENDATIONS Like most analog circuits, component placement, signal routing, and power/ground isolation can affect the overall performance of the design. The layout should utilize individual ground traces/planes for the audio amplifier whenever possible. The audio input and controller ground, FET ground, and output filter ground are routed using a "star" connection in the LXE1710 evaluation board. See PCB layer views. The power to the controller IC should be routed using separate traces that do not carry high current pulses USER GUIDE from the switching circuit. In general, minimizing the high frequency, high power currents from flowing through the same copper as the audio signal references are recommended. Signal traces that could be sensitive to noise should be node to node connections (no "shared" traces). Stray capacitance at the controller pins RPWM, EAOUT, EAIN, and FAOUT can affect the circuit performance and components associated with these pins should be placed as close to the controller IC as possible. Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 15 LXE1710 EVALUATION BOARD PRINTED CIRCUIT BOARD LAYOUT USER GUIDE CN1: RCA Jack Audio In J3: Optional Connections Audio In +, Audio In - TB1: Power Supply Terminal Block +V, GND Silkscreen Layer J1: Sleep Jumper J2: Mute Jumper TB2: Audio Output Terminal Block + OUT, - OUT Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 16 LXE1710 EVALUATION BOARD PRINTED CIRCUIT BOARD USER GUIDE Bottom Layer Top Layer Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 17 LXE1710 EVALUATION BOARD USER GUIDE BILL OF MATERIALS Line Item 1 2 3 4 5 6 7 8 9 Part Description Controller N-Channel MOSFET P-Channel MOSFET Printed Circuit Board Inductor, 15uH Phono Jacks, 90 Nickel Plated, Wht Strip Line Plugs, Straight, Single Row .100" Shorting Jumpers, Open Top, Black Terminal Block 2 pos 5mm Manufacturer & Part # LX1710 FDS6612A FDS4953 SGE2758 RL622-150K 161-4214 CA-S36-24B-44 151-8030 301-021-1000 Case SSOP 28 SO-8 SO-8 TH TH TH TH TH Reference Designators U1 Q2, Q4 Q1, Q3 REV.X L1, L2 CN1 J1, J2 J1 TB1, TB2 Qty 1 2 2 1 2 1 2 1 2 Line Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Part Description Capacitor, COG, 18pF, 50V, 5% Capacitor, COG, 150pF, 50V, 5% Capacitor, COG, 220pF, 50V, 5% Capacitor, X7R, 330pF, 50V, 10% Capacitor, X7R, .47uF, 16V, 20% Capacitor, X7R, 1uF, 50V, 10% Capacitor, COG, 100pF, 50V, 5% Capacitor Tant 0.1uF 35V 20% Capacitor Tant 2.2uF 25V 20% Capacitor, Tant, 4.7uF, 16V, 20% Capacitor Stacked MF 0.1uF 50V 5% Capacitor Stacked MF 0.47uF 50V 5% Capacitor Stacked MF 0.68uF 50V 5% Capacitor, Elect 220uF, 25V, 20% Part Description 1206N180J500NT 12065C180JAT2A 1206N151J500NT 12065C151JAT2A 12065C221JAT2A ECU-V1H331KBM 1206B474M160NT 1206YC474MAT2A 1206B105K500NT 12065C105KAT2A 0805N101J500NT 08055C101JAT2A TAJA104M035R ! T491A225M025AS ! T491A475M016AS TAJA475M016R ECQ-V1H104JL ECQ-V1H474JL ECQ-V1H684JL " RV-25V221MH10-R Case 1206 1206 1206 1206 1206 1206 0805 3216 3216 3216 TH TH TH NT Reference Designators C5 C4 C6, C7 C26 C3, C14 C1, C2 C16 C9 C13 C10, C11 C8, C12, C22 C18, C19 C20, C21 C17 Qty 1 1 2 1 2 2 1 1 1 2 3 2 2 1 Line Item 1 2 3 4 5 6 7 8 9 Part Description Resistor, 10K, 5%, 1/4W Resistor, 24.3K, 1%, 1/4W Resistor, 10 Ohm, 5%, 1/8W Resistor, 10K, 5%, 1/8W Resistor, 34.8K, 1%, 1/8W Resistor,20K, 5%, 1/8W Resistor, 56.2K, 1%, 1/8W Resistor, 15 Ohm 5% 1W Resistor, Low Value Flat .0374 Part Description # CR32J103T # CR32F2432T # CR J100T # CR21J103T # CR21F3482T # CR J203T # CR21F5622T $ RM73B3A150J %! MCR100JZHJ150 % LR2010-01-R0374-F Case 1206 1206 0805 0805 0805 0805 0805 2512 2512 Reference Designators R2 R3, R4 R6, R10, R11, R12 R8, R9 R5 R7 R1 R13 RS1 Qty 1 2 4 2 1 1 1 1 1 Copyright (c) 2000 Rev. 1.1, 2000-12-01 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 18 |
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