PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Key Features General Description n 3W Output at 10% THD with a 4 Ω Load and 5V Power Supply n Filterless, Low Quiescent Current and Low EMI n Low THD+N n 64-step Digital Volume Control n Superior Low Noise n Low pop noise n Efficiency up to 90% n Short Circuit Protection n Thermal Shutdown n Few External Components to Save Space and Cost n Pb-Free Package The PAM8803 is a 3W, class-D audio amplifier with 64-step digital volume control. It offers low THD+N, allowing it to produce high-quality sound reproduction. The new filterless architecture allows the device to drive the speaker directly, without needing low-pass output filters , which will save 30% system cost and 75% PCB area. With the same numbers of external components, the efficiency of the PAM8803 is much better than class-AB cousins. It can extend the battery life, ideal for portable applications. The PAM8803 is available in a SSOP-24 package. Applications n n n n n LCD Monitors/TV Projectors Notebook Computers Portable Speakers Portable DVD Players, Game Machines Cellular Phones/Speaker Phones Typical Application Efficiency vs Output Power 100 90 VDD PVDD C3 10μF 80 7 4 Efficiency(%) C1 C2 1μF 1μF 18 5 VDD GND PVDD +OUT_L 2 3 PGND PGND 21 +OUT_R 70 RL=8Ω RL=4Ω 60 50 40 30 20 10 1 SP_L C6 8 INL -OUT_L INR INL 0.47μF 10 -OUT_R VREF 24 17 ON MUTE 0 0 C7 INR 0.5 1 1.5 2 2.5 3 Output Pow er(W) 0.47μF PAM8803 UP 14 6 MUTE DN Radiated Emissions S1 C8 1μF MUTE SP_R 13 S2 ON SHDN SHDN 19 SHDN NCNCNCNCPVDD 9 11 12 16 20 PGND 22 RST PGND 23 15 FCC Class B Limit S3 C4 1μF PVDD C5 10μF Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 1 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Block Diagram VDD PVDD PGND VDD/2 + - INR +OUT_R DRIVER -OUT_R MODULATOR RST MUTE SHDN Attenuation Decoder Interface Control UP DN Thermal Protection INTERNAL OSCILLATOR BIAS AND REFERENCES OSC Current Protection +OUT_L MODULATOR INL VREF DRIVER + -OUT_L VDD/2 GND PVDD PGND Pin Configuration & Marking Information Top View SSOP-24 24 -OUT_R PAM8803 XXXYWWLL -OUT_L 1 PGND 2 PGND 3 +OUT_L 4 PVDD 5 MUTE 6 VDD 7 INL 8 NC 9 VREF 10 NC 11 NC 12 23 PGND 22 PGND 21 +OUT_R 20 PVDD 19 SHDN 18 GND 17 INR X: Internal Code Y: Year WW: Week LL: Internal Code 16 NC 15 RST 14 UP 13 DN Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 2 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Pin Descriptions Pin Number Pin Name Description 1 -OUT_L Left Channel Negative Output 2 PGND Power GND 3 PGND Power GND 4 +OUT_L 5 PVDD Power VDD 6 MUTE Mute Control Input（active low）, pull-up 7 VDD Analog VDD 8 INL Left Channel Input 9 NC No Connect 10 VREF 11 NC No Connect 12 NC No Connect 13 DN Volume down Control (active low) 14 UP Volume up Control (active low) 15 RST Volume Controller Reset (active low) 16 NC No Connect 17 INR Right Channel Input 18 GND Analog GND 19 SHDN Shutdown Control Input(active low), pull-down 20 PVDD Power VDD 21 +OUT_R 22 PGND Power GND 23 PGND Power GND 24 -OUT_R Left Channel Positive Output Internal analog reference, connect a bypass capacitor from VREF to GND Right Channel Positive Output Right Channel Negative Output Absolute Maximum Ratings These are stress ratings only and functional operation is not implied . Exposure to absolute maximum ratings for prolonged time periods may affect device reliability . All voltages are with respect to ground . Maximum Junction Temperature..................150°C Storage Temperature.....................-65 °C to 150 °C Soldering Temperature....................... 300°C, 5sec Supply Voltage at no Input Signal...................6.0V Input Voltage.............................-0.3V to V DD +0.3V Recommended Operating Conditions Supply voltage Range........................ 2.2V to 5.5V Ambient Temperature Range...........-40° C to 85 °C Junction Temperature Range.........-40 °C to 125 °C Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 3 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Thermal Information Parameter Symbol Package Maximum Unit Thermal Resistance (Junction to Ambient) θJA SSOP-24 96 °C/W Electrical Characteristic V DD=5V, Gain = 18dB, R L=8 Ω, T A=25 °C，unless otherwise noted. PARAMETER Supply Voltage Range Quiescent Current SYMBOL CONDITIONS MIN VDD IQ TYP 2.2 No Load 7 RL=8Ω 8 RL=4Ω 8.5 MAX UNITS 5.5 V 15 mA Mute Current IMUTE VMUTE=0V 2.5 4 mA Shutdown Current ISHDN VSHDN =0V 0.5 10 μA SHDN Input High VSH SHDN Input Low VSL MUTE Input High VMH MUTE Input Low VML Output Offset Voltage VOS No Load RDS (ON) IDS=0.5A Drain-Source On-State Resistance Output Power Total Harmonic Distortion Plus Noise Power Supply Ripple Rejection PO THD+N PSRR Channel Separation CS Oscillator Frequency fOSC Efficiency η 1.2 0.5 1.2 0.5 f=1kHz 120 300 P MOSFET 0.3 0.40 N MOSFET 0.22 0.35 RL= 8Ω,THD=1% 1.1 1.3 RL= 8Ω,THD=10% 1.5 1.7 RL= 4Ω,THD=1% 1.9 2.1 RL= 4Ω,THD=10% 2.8 3.0 RL=8Ω, P O=0.5W 0.19 RL=8Ω, P O=1.0W 0.22 RL=4Ω, P O=1.0W 0.17 RL=4Ω, P O=2.0W 0.25 V V mV Ω W % No input, f=1kHz, Vpp=200mV 45 55 dB PO=1W, RL=4Ω 60 80 dB 170 210 PO=1.7W, f=1kHz, RL =8Ω 85 89 % PO=3.0W, f=1kHz, RL =4Ω 80 83 % 250 kHz f =22 to 22kHz， RL=4Ω 85 dB THD=1% RL=8Ω 87 dB UVLO 1.95 V Over Temperature Protection OTP 150 °C Over Temperature Hysteresis OTH 60 °C Signal Noise Ratio SNR Under Voltage Lock-out Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 4 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Typical Operating Characteristics (T =25°C) A 1. THD+N vs Output Power R L=4 Ω , Gain = 18dB 30 20 30 V DD=3.6V V DD=2.5V 10 V DD=2.5V V DD=3.6V 10 5 5 2 2 1 1 % 2. THD+N vs Output Power R L=8 Ω , Gain = 18dB % 0.5 0.5 0.2 0.2 0.1 0.1 0.05 0.05 V DD=5V V DD=5V 0.02 0.02 0.01 10m 20m 50m 100m 200m 500m 1 2 0.01 10m 4 20m 50m 100m 200m W 3. THD+N vs Output Power V DD=5V, R L=4 Ω , Gain = 18dB % 100 50 50 20 20 10 10 5 5 2 f=1kHz 1 % 0.5 0.2 0.2 0.1 0.1 0.05 0.05 f=10kHz f=100Hz 0.02 50m 100m 200m 500m 1 2 f=100Hz 1 0.5 0.01 20m f=10kHz 0.01 20m 4 50m 100m 200m 500m 1 2 4 W 6. THD+N vs Frequency V DD=5V, R L=8 Ω , Gain = 18dB 100 100 50 50 20 20 10 10 5 5 2 Po=2W 1 % 0.5 0.2 0.2 0.1 0.1 Po=1.5W Po=2W 0.05 Po=1W 1 0.5 Po=0.5W Po=2W 0.05 0.02 0.02 0.01 20 4 0.02 5. THD+N vs Frequency V DD=5V, R L=4 Ω , Gain = 18dB % 2 f=1kHz W 2 1 4. THD+N vs Output Power V DD=5V, R L=8 Ω , Gain = 18dB 100 2 500m W 50 100 200 500 1k 2k 5k 10k 0.01 20 20k Hz 50 100 200 500 1k 2k 5k 10k 20k Hz Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 5 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Typical Operating Characteristics (continued) 7. THD+N vs. Frequency Po=0.8W,R L=4 Ω, Gain=18dB 8. THD+N vs. Frequency Po=0.1W,R L=8 Ω, Gain=18dB 100 100 50 50 20 20 10 10 5 5 2 2 % V DD=3.3V 1 % 1 0.5 0.5 0.2 0.2 0.1 0.1 0.05 0.05 V DD=5V V DD=3.3V V DD=5V 0.02 0.02 0.01 20 0.01 20 50 100 200 500 1k 2k 5k 10k 20k 50 100 200 500 Hz 1k 2k 5k 10k 20k Hz 10. Power Supply Ripple Rejection VS Frequency V DD=5V with 200mVpp Ripple 9. Frequency response V DD=5V, Gain =18dB +20 +35 +10 +30 +0 -10 +25 d B r d B +20 -20 -30 -40 -50 +15 -60 20 50 100 200 500 1k 2k 5k -70 10 10k 20k 20 50 100 200 500 1k 2k 5k 10k 20k Hz Hz Hz 11. FFT of Noise Output V DD=5V, Gain = 18dB +0 -40 12.Channel Separation V DD=5V, R L=4 Ω , P O=1.0W,Gain = 18dB -10 -20 -50 -30 -40 -60 -50 -60 d B V -70 -70 d B -80 -80 -90 -100 R to L -90 -110 -120 L to R -100 -130 -140 -150 20 50 100 200 500 1k 2k 5k 10k -110 20 20k Hz 50 100 200 500 1k 2k 5k 10k 20k Hz Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 6 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Typical Operating Characteristics (continued) 13. Output Power vs Power Supply R L=4 Ω 14. Output Power vs Power Supply R L=8 Ω 2.5 4 Output Power (W) Output Power(W) 3.5 3 2.5 10%ΤΗD 2 1.5 1%ΤΗD 1 2 1.5 10%ΤΗD 1 1%ΤΗD 0.5 0.5 0 0 2 3 4 5 2 6 3 DD 5 6 Supply Voltage (V) Supply Voltage (V) Gain Setting (V 4 =5V) Step Gain (dB) Step Gain (dB) Step Gain (dB) Step Gain (dB) 1 -75.0 17 4.8 33 11.2 49 17.6 2 -39.7 18 5.1 34 11.6 50 18.0 3 -34.0 19 5.5 35 12.0 51 18.4 4 -28.2 20 5.9 36 12.3 52 18.8 5 -22.4 21 6.3 37 12.7 53 19.2 6 -16.5 22 6.7 38 13.2 54 19.6 7 -10.5 23 7.1 39 13.6 55 20.0 8 -8.0 24 7.5 40 14.0 56 20.4 9 -5.5 25 7.9 41 14.4 57 20.9 10 -2.9 26 8.3 42 14.8 58 21.3 11 -0.4 27 8.7 43 15.2 59 21.7 12 1.1 28 9.1 44 15.6 60 22.1 13 2.6* 29 9.6 45 16.0 61 22.5 14 3.6 30 10.0 46 16.4 62 22.9 15 4.0 31 10.4 47 16.8 63 23.4 16 4.4 32 10.7 48 17.2 64 23.8 *Power on gain or gain after reset. Note: Gain could have 1dB deviation device to device. Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 7 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control we should notice that if the battery cell is 4 new dry batteries or alkaline batteries, even the voltage will be over 6V, it still can work safety. Since the output voltage of the 4 pack of new dry batteries will be reduced very quickly after turn on due to the internal resistance of the battery. There is no dangerous of damaging the chip when playing music or speech, even use 4 new dry batteries. To reduce the effect of the increasing of internal resistance of battery after long term discharging, it is recommended to connect a 1000uF electrolytic capacitor between the power supply and the ground. Application Notice 1． When PAM8803 works without filter, we must connect the speaker before turn on. Else, it will be easy to damage the chip. 2． When PAM8803 works without filter, it will be best that adding a ferrite chip bead at the outgoing line of speaker in order to suppress possible electromagnetic interference . 3． The absolute maximum rating of operation voltage is 6.0V. While using 6V power regulator, even the chip can deliver 4W sine wave with a 4 Ohm speaker, it is not recommended for long term using due to the heat dissipation. But if the input signal is a music signal, then it can work in long term since the average power output is much less than 4W. When using dry battery cell, 4． Because digital volume control has big gain, we can not make input signal too high to cause the clipping of the output signal when increase volume, also it may damage the chip. Test Setup for Performance Testing PAM8803 Demo Board Load +OUT AP System One Generator AP Low Pass Input Filter GND AP System One Analyzer AUX-0025 -OUT VDD Power Supply Notes 1. The AP AUX-0025 low pass filter is necessary for every class-D amplifier measurement done by AP analyzer. 2. Two 22 μ H inductors are used in series with load resistor to emulate the small speaker for efficiency and quiescent current measurement. Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 8 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Application Information Maximum Gain There are 64 discrete gain settings ranging from +24dB maximum to -75dB minimum. Upon device power on or applied a logic low to the RST pin, the amplifier's gain is set to a default value of 2.6dB. However, when coming out of mute mode, the PAM8803 will revert back to its previous gain setting. Volume levels for each step vary and are specified in Gain Setting table on page 7. As shown in block diagram(page 2),the PAM8803 has two internal amplifiers stage. The first stage's gain is externally con figurable, while the second stage's is internally fixed in a fixed-gain, inverting configuration. The closed-loop gain of the first stage is set by selecting the ratio of R f to R i while the second stage's gain is fixed at 2x. Consequently, the differential gain for the IC is If both the UP and DN pins are held high, no volume change will occur. Trigger points for the UP and DN pins are at 70% of V DD minimum for a logic high, and 20% of V DD maximum for a logic low. It is recommended, however, to toggle UP a n d D N b e t w e e n V DD a n d G N D f o r b e s t performance. A VD=20*log [2*(R f/R i)] The PAM8803 sets maximum R f=218k Ω and minimum R i=27k Ω , thus the maximum closedgain is 24dB. Digital Volume Control (DVC) UP/DN The PAM8803 features a digital volume control which consists of the UP, DN and RST pins. An internal clock is used where the clock frequency value is determined from the following formula: f CLK = f OSC / 2 VOLUME LEVEL 3.5 cycles 9.5 cycles 2 cycles 2 cycles Figure 1.Timming Diagram Mute Operation 13 The MUTE pin is an input for controlling the output state of the PAM8803. A logic low on this pin disables the outputs, and a logic high on this pin enables the outputs. This pin may be used as a quick disable or enable of the outputs without a volume fade. Quiescent current is listed in the electrical characteristic table. The MUTE pin can be left floating due to the pull-up internal. The oscillator frequency f OSC value is 200kHz typical,with ±20% tolerance.The DVC’s clock frequency is 33Hz (cycle time 30ms ) typical. Volume changes are then effected by toggling either the UP or DN pins with a logic low. After a period of 3.5 clocks pulses with either the UP or DN pins held low, the volume will change to the next specified step, either UP or DN, and followed by a short delay. This delay decreases the longer the line is held low, eventually reaching a delay of zero. The delay allows the user to pull the UP or DN terminal low once for one volume change, or hold down to ramp several volume changes. The delay is optimally configured for push button volume control. Shutdown operation In order to reduce power consumption while not in use, the PAM8803 contains shutdown circuitry that is used to turn off the amplifier's bias circuitry. This shutdown feature turns the amplifier off when logic low is placed on the SHDN pin. By switching the SHDN pin connected to GND, the PAM8803 supply current draw will be minimized in idle mode. The SHDN pin cannot be left floating due to the pull-down internal. If either the UP or DN pin remains low after the first volume transition the volume will change again, but this time after 9.5 clock pulses. The followed transition occurs at 2 clock pulses for each volume transition. This is intended to provide the user with a volume control that pauses briefly after initial application, and then slowly increases the rate of volume change as it is continuously applied. This cycle is shown in the timing diagram shown in figure 1. Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 9 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This noise is from the internal analog reference to the amplifier, which appears as degraded PSRR and THD+N. Power supply decoupling The PAM8803 is a high performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output THD and PSRR are as low as possible. Power supply decoupling is affecting low frequency response. Optimum decoupling is achieved by using two capacitors of different types that target different types of noise on the power supply leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-seriesresistance (ESR) ceramic capacitor, typically 1.0μF, placed as close as possible to the device V DD terminal works best. For filtering lowerfrequency noise signals, a larger capacitor of 10μF (ceramic) or greater placed near the audio power amplifier is recommended. Bypass capacitor (C BYP) values of 0.47μF to 1.0μF ceramic is recommended for the best THD and noise performance. Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown. Under Voltage Lock-out (UVLO) The PAM8803 incorporates circuitry designed to detect when the supply voltage is low. When the supply voltage drops to 1.85V or below, the PAM8803 outputs are disable, and the device comes out of this state and starts to normal functional when the supply voltage increases. Input Capacitor (C i) Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low frequencies without severe attenu ation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to 150Hz. Thus, using a large input capacitor may not increase actual system perfor mance. In this case, input capacitor (C i) and input resistance (R i) of the amplifier form a high-pass filter with the corner frequency determined equation below, Short Circuit Protection (SCP) The PAM8803 has short circuit protection circuitry on the outputs that prevents damage to the device during output-to-output and outputto-GND short. When a short circuit is detected on the outputs, the outputs are disable immediately. If the short was removed, the device activates again. Over Temperature Protection 1 2πRiCi In addition to system cost and size, click and pop perfor mance is affected by the size of the input coupling capacitor, C i. A larger input coupling capacitor requires more charge to reach its quiescent DC voltage (nominally 1/2 V DD). This charge comes from the internal circuit via the feedback and is apt to create pops upon device enable. Thus, by minimizing the capacitor size based on necessary low frequency response, turn-on pops can be minimized. Thermal protection on the PAM8803 prevents damage to the device when the internal die temperature exceeds 150°C. There is a 15 degree tolerance on this trip point from device to device. Once the die temperature exceeds the thermal set point, the device outputs are disabled. This is not a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 60°C. This large hysteresis will prevent motor boating sound well and the device begins normal operation at this point with no external system interaction. fC= How to Reduce EMI (Electro Magnetic Interference) Analog Reference Bypass Capacitor (C BYP) A simple solution is to put an additional capacitor 1000uF at power supply terminal for power line coupling if the traces from amplifier to speakers are short (<20cm). The Analog Reference Bypass Capacitor (C BYP) is the most critical capacitor and serves several important functions. During start-up or recovery from shutdown mode, C BYP determines the rate at which the amplifier starts up. The second Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 10 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Most applications require a ferrite bead filter which shows at Figure 3. The ferrite filter reduces EMI around 1 MHz and higher. When selecting a ferrite bead, choose one with high impedance at high frequencies, but low impedance at low frequencies. channel specific. A two channels amplifier has two mutually exclusive channels and consequently must have two mutually exclusive output noise ground traces. The layout of the PAM8803 offers separate PGND connections for each channel and in some cases each side of the bridge. Output noise grounds must tie to system ground at the power in exclusively. Signal currents for the inputs, reference, etc need to be returned to quite ground. This ground only ties to the signal components and the GND pin. GND then ties to system ground. Ferrite Bead OUT+ 220pF Ferrite Bead OUT- Power Supply Line 220pF As same to the ground, VDD and each channel PVDD need to be separated and tied together at the system power supply. Recommend that all the trace could be routed as short and thick as possible. For the power line layout, just imagine water stream, any barricade placed in the trace (shows in figure 4) could result in the bad performance of the amplifier. Figure 3: Ferrite Bead Filter to reduce EMI PCB Layout Guidelines Grounding At this stage it is paramount that we acknowledge the need for separate grounds. Noise currents in the output power stage need to be returned to output noise ground and nowhere else. Were these currents to circulate elsewhere, they may get into the power supply, the signal ground, etc, worse yet, they may form a loop and radiate noise. Any of these instances results in degraded amplifier performance. The logical returns for the output noise currents associated with Class D switching are the respective PGND pins for each channel. The switch state diagram illustrates that PGND is instrumental in nearly every switch state. This is the perfect point to which the output noise ground trace should return. Also note that output noise ground is Figure 4 Components Placement The power supply decoupling capacitors need to be placed as close to VDD and PVDD pins as possible. The inputs need to be routed away from the noisy trace. The VREF bypass capacitor also needs to be close to the pin of IC very much. PCB Top Layer PCB Bottom Layer Figure 5: Layout Example Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 11 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Ordering Information PAM8803 X X X Shipping Package Number of Pins Package Type Part Number PAM8803NHR Marking PAM8803 XXXYWWLL Package Type Shipping Package SSOP-24 2,500 Units/Tape & Reel Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 12 PAM8803 3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control Outline Dimension SSOP-24 Power Analog Microelectronics , Inc www.poweranalog.com 12/2009 Rev 1.4 13