LXE1722SE AUDIOMAX USER’S GUIDE LXE1722SE AUDIOMAX EVALUATION KIT USER’S GUIDE ® TM Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 1 LXE1722SE AUDIOMAX USER’S GUIDE Table of Content Board Settings.............................................................................................................................................................................. 3 Single Supply & Single Ended...................................................................................................................................................... 4 “Pop” Noise Cancellation ............................................................................................................................................................. 5 Topology .............................................................................................................................................................................................................5 Time Sequence ...................................................................................................................................................................................................6 Slow VCC Start Up..............................................................................................................................................................................................7 Audio Measurements .................................................................................................................................................................. 8 Appendix .................................................................................................................................................................................... 10 Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Single Supply, Single-ended output schematic .......................................................................................................... 4 “POP” noise cancellation circuit.................................................................................................................................. 5 Timing sequence ........................................................................................................................................................ 6 Timing sequence test result........................................................................................................................................ 6 SLEEP ON/OFF switch circuit .................................................................................................................................... 7 Noise Floor Curve ...................................................................................................................................................... 8 THD+N vs. Power....................................................................................................................................................... 8 Frequency Response ................................................................................................................................................. 9 Efficiency Chart .......................................................................................................................................................... 9 LXE1722SE Schematic .......................................................................................................................................10-11 Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 2 LXE1722SE AUDIOMAX USER’S GUIDE LXE1722SE Evaluation Board Quick Start Guide The LXE1722SE Evaluation Board is a fully functional stereo class-D amplifier with single-supply and single-ended output. Its purpose is reducing half of inductors, MOSFET and some other Capacitors, lower the system cost. Also no dual power supply required, reduce the power supply cost comparing with normal single-ended systems. Only one thing needed to do is adding a series capacitor at the positive speaker output to block the DC output. But due to its single-ended output, it results in ¼ of BTL output power, so LXE1722SE is special for a low power, 5W~20W, application, like LCD TV, PDP, computer speaker, etc… Usually, the DC blocking capacitor will give a rolling down at low frequency range, so for a full 20Hz~20KHz audio band, a big value, like 1000uF~4700uF, capacitor needed, due to slow charge and discharge, this big capacitor will cause very loud “POP” noise during the system turned-ON/OFF. So how to cancel this loud “POP” noise is a big issue for this solution. LXE1722SE is using feedback circuit to force the PWM duty cycle slow up from 0% to 50%, cause a slow DC rising ramp after LC filter, to get rid of fast charge the output DC blocking capacitor, to cancel the “POP” noise. Board Setting 1. 2. 3. 4. Power and Ground Connections: The terminal TB3 is for the power supply connection. Vcc is connected to the positive polarity of the power supply or battery (+7V ~ +25V); the GND is connected to the negative polarity of the power supply or battery. +5V supply is not necessary on this evaluation board, it is for when the main Vcc is too slow start-up, which will cause “POP” noise even the circuit works, in that case, using +5V to control SLEEP fast start-up, it does not matter how slow the start-up of Vcc is. Speakers Connections: TB1 and TB2 are the speaker outputs. TB1 is for the left channel (CH1) and TB2 is for the right channel (CH2). Connect speaker “+” and “-“ to “LOUT+/ROUT+” and “LOUT-/ROUT-“ of TB1/TB2. This evaluation board is designed for standard 4 ohm speaker loads. For different impedance speakers, the output filter values should be modified to optimize the output frequency response. Please see AudioMAX Design Resource (AN-16) for LC filter values. Audio Input Connections: RCA1 and RCA2 are the audio input connections. It supports differential & single-ended audio inputs; JP1 and JP4 are GND connection headers, in case that the audio source GND is not connected to the evaluation board GND, it will be closed, otherwise leave them open. The default status is “OPEN”. SLEEP/MUTE Connections: JP2 is the jumper selection for SLEEP and JP3 for MUTE. Because this evaluation has “POP” noise cancellation circuit, it works with SLEEP and MUTE pins of IC. When the system starts up, it will automatically turn-OFF SLEEP and MUTE following the certain time sequences, so these two jumpers’ default setting is OPEN, unless you want to force the system MUTE and SLEEP, just close them to “ON” position. Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 3 LXE1722SE AUDIOMAX USER’S GUIDE Single Supply & Single-ended Vcc R22 1.21k,1% P_drv 4 4700pF 3 Q1 LFBK+ C26 8 7 N_drv L1 C100 1000uF/50V L2 5 2 LOUT+ 15uH 3.3uH 1 Si4532 + 6 R24 15, 5%,1W C27 0.22uF/35V C28 0.47uF/35V R16 1k C29 0.47uF/35V Half_Vcc LFBKR25 1.21k,1% C32 4700pF Figure 1 – Single Supply, Single-ended output schematic Using half of PFET & NFET drive of LX1722 to drive one pair of P/N MOSFET, and through one pair of LC filter to drive the speaker, the negative of speaker direct connected to the ground. Because single supply Vcc will give a half of Vcc DC offset, so a DC blocking capacitor must be added in series of speaker output. It will give you a rolling down at low frequency. The corner frequency is depended on the capacitor combined with the speaker impedance, it is: Fc = 1/2πRC; R-speaker impedance; C-DC blocking capacitance; Since LX1722 has differential feedback input, the positive feedback is still as usual way, but the negative feedback is input from a pair of resistors divider, half of Vcc. This half Vcc start-up timing is the key for “POP” noise cancellation. Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 4 LXE1722SE AUDIOMAX USER’S GUIDE “POP” Noise Cancellation Topology As described at 2., the negative feedback timing is the key to design the “POP” noise cancellation circuit. Fig 2. is the circuit for this “POP” noise cancellation, the whole this is just using Q101 to control FB- start-up timing, giving it a slow ramp to clamp up to half of Vcc. Then using the feedback and PWM modulation to force the positive PWM output start from 0% Duty Cycle (D.C.) slow up to 50% duty cycle. This will cause the DC offset after the LC filter slow up to half of Vcc, too, slow charging the DC blocking capacitor to get rid of “POP” noise. During the whole start-up time, the system must be muted. See the time sequence Fig 3. PMUTE R102 R103 1k,5% D102 1N4148 FB- Q100 BSS138 1 R104 100k,5% 2 1M,5% + C103 2.2uF/25V 1 + C104 2.2uF/25V Q101 BSS138 R106 10k,1% + C102 47uF/25V 2 R11 1M,5% 10k,1% TP1 3 3 D100 1N4148 R105 VDD D103 1N4148 MUTE_OFF R101 CN D104 1N4148 0 R100 OPTION +5V R107 10k,5% 3 D105 1N4148 1 R111 1M,5% R12 1M,5% 0 Q103 2N3904 VDD R110 100k,5% 2 VDD Q102 BSS138 R108 1k,5% + C106 22uF/25V R112 6.8k,5% "POP" Noise Cancellation Figure 2 – “POP” noise cancellation circuit Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 5 LXE1722SE AUDIOMAX USER’S GUIDE Time Sequence Fig 3. Shows some key test points timing sequence of the circuit. VCC SLEEP MUTE TP1 FB- PWM 0 DC 0-50% DC 50% 50-0% OUT 0 T1 T2 T3 T5 T6 Figure 3 – Timing sequence VCC 830ms 1000ms 180ms MUTE FB- Figure 4 – Timing sequence test result Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 6 LXE1722SE AUDIOMAX USER’S GUIDE Slow Vcc Start-up Sometimes Vcc starts up very slow because the big capacitor of power supply, if its slow up time is long enough, then when it gets 6.7V point, SLEEP will be OFF, the system starts POR, also the noise cancellation circuit starts working. But if POR ends up during the FB- rising, or over, the PWM duty cycle will not be from 0 to 50% slow up any more, it will start some duty cycle point. It will cause “POP” noise. So for this situation, a SLEEP-ON/OFF circuit must be added (Fig 5.), to make SLEEP sharp ON. (it is disable on this board) Q2 2N3906 Vcc VDD R8 1k,5% R9 1k,5% R10 Q3 2N3904 +5V 10k,5% + C46 1uF/25V SLEEP-ON/OFF Switch Figure 5 – SLEEP ON/OFF switch circuit Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 7 LXE1722SE AUDIOMAX USER’S GUIDE Audio Measurement MICROSEMI CORP. +0 dx=-7.0006kHz SONYLXE1721SE Noise Floor 12/19/02 16:02:38 dy=+1.621 dB -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60 -65 d B r -70 -75 -80 -85 -90 -95 -100 -100.334 -101.955 -105 -110 -115 -120 -125 -130 -135 -140 -145 -150 20 50 100 200 500 1k 4.65819k 5k 2k 11.6588k 10k 20k Hz noiseFFT.at1 Figure 6 – Noise Floor Curve 15VDC, 4 OHM load, 10Hz~22KHz BPF, None A-Weighted; Magenta-CH1, Blue-CH2 Noise Floor RMS: None A-Weighted, H1=490dBu;CH2=450dBu; A-weighted, CH1=320dBu; CH2=280dBu. MICROSEMI CORP. 100 dx=-4.649 W SONY LXE1721SE THD+Nvs. Power 12/19/02 16:09:13 dy=-9.5960 % 50 20 10 10.853 5 2 1.25698 1 % 0.5 0.2 0.1 0.05 0.02 0.01 100m 200m 500m 1 2 5 10 18.0920 22.74 50 W thdvspwr-4ohm.at1 Figure 7 – THD+N vs. Power 4 OHM Load, 1KHz, 10Hz~22KHz BPF 15V/18V/22V/25V Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 8 LXE1722SE AUDIOMAX USER’S GUIDE MICROSEMI CORP. +10 dx=-17.843kHz SONYLXE1721SE Frequency Response 12/19/02 16:46:22 dy=-3.835 dB +9 +8 +7 +6 +5 +4 +3 +2 +1 +1.093 d B r -0 -1 -2 -2.742-3 -4 -5 -6 -7 -8 -9 -10 10 20 44.725 50 100 200 500 1k 2k 5k 10k 17.8875k 20k 50k 80k Hz fr-30k.4ohm.at1 Figure 8 – Frequency Response 4 OHM Load, 30KHz LPF, 1W output LX1721SE Efficiency Curve 100% 90% 80% Efficiency 70% 60% 50% 40% 30% Efficiency 20% 10% 0% 0 1 2 3 4 5 6 7 8 9 10 Pout (W) Figure 9 – Efficiency Chart Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 9 LXE1722SE AUDIOMAX USER’S GUIDE Appendix APPLICATION SCHEMATIC R6 VCC R22 1.21k,1% 0.033 4 4700pF 3 R14 Q1 LFBK+ C26 8 5.1,5% 7 6 LFAOUT LFBK- CPWM LFBK+ 44 3.3uH LOUT+ Si4532 1 1 15uH C100 1000uF/50V 5 2 5.1,5% L2 LFBK- C1 2 100pF, 50V 34.8k, 1% 22pF, 50V LISN LMUTE VDD LEAOUT CN CN C12 100pF, 50V 1uF, 25V, 10%, TANT C6 6 7 + 8 9 0.1uF,50V C8 10 11 LIN+ LEAIN PVDD VREF PGND CLOCK LN+ GND LP+ V25 LP- LIN+ LN- 40 39 C9 LIN- 13 0.47uF/35V C10 14 RIN+ 0.47uF/35V 15 C11 RIN- 16 0.47uF/35V + C15 38 0.1uF,50V 37 LN+ 36 LP+ RP- RIN+ RP+ RIN- RN+ RAMPOUT PGND C31 10nF,50V C36 0.47uF/35V C37 10nF,50V LOUT- C14 47uF/25V LFBK35 R25 1.21k,1% C32 34 4700pF FB- 33 32 RFBK31 RP+ 30 RN+ R27 1.21k,1% C33 4700pF 29 20 100pF, 50V C5 21 22 STATUS RMUTE CP PVDD NC REAIN RISN REAOUT RFAOUT RFBK+ RFBK- 28 C17 4.7uF, 16V,TANT 27 0.1uF,50V + 19 MUTE _SLEEP + 18 C4 RN- LAMPOUT C29 0.47uF/35V C13 17 _SLEEP R5 56.2k, 1% LIN- LOUT+ 2 4.7uF, 16V,TANT 0.47uF/35V 12 TB1 1 AMPCON 41 C3 5 C7 RPWM C28 0.47uF/35V R16 1k C16 47uF/25V 26 25 24 23 C34 0.47uF/35V R29 15, 5%,1W RISN RFBK+ R20 4 Q4 RFBK- L4 L3 15uH 3.3uH 8 5.1,5% 7 22pF, 50V R17 1k LX1722CDB R21 ROUT+ ROUT+ AMPCON C101 1000uF/50V 5 2 RFBK+ Si4532 1 5.1,5% ROUT- 2 C38 10nF,50V 6 R4 10k,5% TB2 1 C35 0.22uF/35V + R3 56.2k, 1% 4 C27 0.22uF/35V LISN 42 C30 10nF,50V 3 C2 3 R24 15, 5%,1W LFBK+ + R1 43 + R15 U1 R2 10k,5% L1 R30 1.21k,1% C39 4700pF R7 VCC 0.033 Microsemi Corp. Title Main Circuit Size Document Number Custom Date: Thursday, December 19, 2002 Rev 1.0 Sheet 1 of 3 Figure 10 - LXE1722SE Schematic Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 10 LXE1722SE AUDIOMAX USER’S GUIDE APPLICATION SCHEMATIC(CONTINUED) +5V PMUTE C41 0.1uF,50V R102 R103 10k,1% 1k,5% TB3 3 R105 1 R11 1M,5% Vcc R104 100k,5% 2 1M,5% FB- Q100 BSS138 + C104 2.2uF/25V + C103 2.2uF/25V 1 Q101 BSS138 R106 10k,1% + C102 47uF/25V 2 Ferrite Beads + C42 1000uF/50V D102 1N4148 D100 1N4148 L5 1 2 3 VDD 3 + C40 47uF/25V C43 0.1uF,50V D103 1N4148 MUTE_OFF Power Supply Connector R101 CN D104 1N4148 R32 1 White R100 LIN+ 51K,5% 2 R33 22K,5% R107 10k,5% D105 1N4148 3 LIN- R34 1 RIN+ Red 51K,5% 2 R35 22K,5% 1 VDD R111 1M,5% C45 22pF, 50V Q102 BSS138 R108 1k,5% R12 1M,5% R110 100k,5% + C106 22uF/25V R112 6.8k,5% RIN1 2 1 2 JP4 HEADER 2 JP1 HEADER 2 "POP" Noise Cancellation Audio Input Connector JP2 OFF R36 10k,5% 1 2 3 Q2 2N3906 Vcc VDD _SLEEP CN LOUT+ VDD R? 1k,5% R8 1k,5% 1 Q? BSS138 2 ON 0 Q103 2N3904 VDD 2 RCA2 RCA JACK OPTION +5V C44 22pF, 50V 3 RCA1 RCA JACK 0 3 SLEEP PMUTE 1 Q? BSS138 ROUT+ 3 2 R9 1k,5% R10 Q3 2N3904 +5V 1 2 3 ON Q? BSS138 2 JP3 OFF 1 10k,5% MUTE_OFF MUTE CN + C46 1uF/25V Power-MUTE Circuit MUTE MUTE/SLEEP Connector SLEEP-ON/OFF Switch Microsemi Corp. Title LX1722SE - Input/SWT/POP Circuit Size Document Number Custom Date: Thursday, December 19, 2002 Rev 1.0 Sheet 2 of 3 Figure 11 - LXE1722SE Schematic (Continued) Copyright 2000 Rev. 0.2, 2002-01-25 Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 11