PAM8403. Filterless 3W Class-D Stereo Audio Amplifier. Key Features. General Description. Applications. Typical Application

Size: px

Start display at page:

Download "PAM8403. Filterless 3W Class-D Stereo Audio Amplifier. Key Features. General Description. Applications. Typical Application"

Marcia Owens
6 years ago
Views:

1 Key Features 3W Output at THD with a 4Ω oad and Power Supply Filterless, ow Quiescent Current and ow EMI ow THD+N Superior ow Noise Efficiency up to 90 Short Circuit Protection Thermal Shutdown Few External Components to Save the Space and Cost Pb-Free Package Applications General Description The PAM8403 is a 3W, class-d audio amplifier. It offers low THD+N, allowing it to achieve highquality sound reproduction. The new filterless architecture allows the device to drive the speaker directly, requiring no low-pass output filters,thus to save the system cost and PCB area. With the same numbers of external components, the efficiency of the PAM8403 is much better than that of class-ab cousins. It can extend the battery life, ideal for portable applications. The PAM8403 is available in SOP-6 package. CD Monitors / T Projectors Notebook Computers Portable Speakers Portable DD Players, Game Machines Cellular Phones/Speaker Phones Typical Application IN 0.47μF Ri 7 8 IN DD REF DD PDD μf μf 470μF μf PDD PDD +OUT_ -OUT_ 3 Efficiency() Efficiency vs Output Power R=8Ω 60 R=4Ω Output Pow er(w) INR 0.47μF 0.μF Ri INR PAM8403 -OUT_R 4 Radiated Emissions SHDN MUTE 2 SHDN MUTE GND NC PGNDPGND +OUT_R 6 FCC Class B imit 9 2

2 ATTENUATION DECODER INTERFACE CONTRO PAM8403 XATYWW PAM8403 Block Diagram DD PDD PGND INR DD/2 + - MODUATOR DRIER +OUT_R -OUT_R THERMA PROTECTION MUTE INTERNA OSCIATOR BIAS AND REFERENCES REF SHDN OSC CURRENT PROTECTION IN DD/2 + - MODUATOR DRIER +OUT_ -OUT_ GND PDD PGND Pin Configuration & Marking Information Top iew SOP X: Internal Code A: Assembly Code T: Testing Code Y: Year WW: Week : Internal Code

3 Pin Descriptions Pin Number Pin Name Description +OUT_ eft Channel Positive Output 2 PGND Power GND 3 -OUT_ eft Channel Negative Output 4 PDD Power DD MUTE Mute Control Input(active low) 6 DD Analog DD 7 IN eft Channel Input 8 REF Internal analog reference, connect a bypass capacitor from REF to GND 9 NC No connect INR Right Channel Input GND Analog GND 2 SHDN Shutdown Control Input (active low) 3 PDD Power DD 4 -OUT_R Right Channel Negative Output PGND Power GND 6 +OUT_R Right Channel Positive 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. Supply oltage Input oltage to DD+0.3 Operation Temperature Range C to 8 C Maximum Junction Temperature...0 C Operation Junction Temperature C to 2 C Storage Temperature...-6 C to 0 C Soldering Temperature C, sec Recommended Operating Conditions Supply voltage Range to. Operation Temperature Range C to 8 C Max. Supply oltage (for Max. duration of Junction Temperature Range C to 2 C 30 minutes) Thermal Information Parameter Symbol Package Maximum Unit Thermal Resistance (Junction to Ambient) θ JA SOP-6 C/W Thermal Resistance (Junction to Case) θ JC SOP-6 23 C/W 3

4 Electrical Characteristic DD=, Gain=24dB, R =8 Ω, T A=2 C, unless otherwise noted. Symbol Parameter Test Conditions MIN TYP MAX UNIT IN Supply Power 2.. Po THD+N Output Power Total Harmonic Distortion Plus Noise THD+N=,f=kHz, R=4 Ω THD+N=,f=kHz, R =4 Ω THD+N=,f=kHz, R =8 Ω THD+N=,f=kHz, R =8 Ω DD= DD =3.6.6 DD =3.0.3 DD=.0 2. DD=3.6.3 DD= DD =.0.8 DD = DD= DD=.0.4 DD = DD = DD=.0,Po=0.W,R=8 Ω f=khz 0. DD=3.6,Po=0.W,R=8 Ω 0. DD =.0,Po=W,R =4 Ω 0. f=khz DD =3.6,Po=W,R =4 Ω 0. Gv Gain 24 db PSRR Power Supply Ripple Rejection DD =.0, Inputs ac-grounded with f=0hz -9 C IN =0.47μF f=khz -8 Cs Crosstalk DD =,Po=0.W,R =8Ω,Gv=20dB F=kHz -9 db SNR Signal-to-noise ratio DD =, orms=,gv=20db f=khz 80 db n Output noise DD =, Inputs ac-grounded with A-weighting 0 C IN =0.47μF No A-weighting 0 Dyn Dynamic range DD =.0, THD= f=khz 90 db η IQ Efficiency Quiescent Current R =8Ω, THD= 87 f=khz R =4Ω, THD= 83 DD=.0 6 DD =3.6 No load DD=3.0 8 W W W W db μ ma 4

5 Electrical Characteristic (Continued) DD= Gain=24dB, R =8 Ω, T A=2 C, unless otherwise noted. Symbol Parameter Test Conditions MIN TYP MAX UNIT I MUTE Muting Current DD=.0 MUTE= ma ISD Shutdown Current DD=2. to. sd=0.3 < μa Rdson Static Drain-to-source On-state Resistor IDS=00mA,gs= PMOS 80 NMOS 40 fsw Switching Frequency DD=3 to 260 khz os Output Offset oltage in=0, DD= m IH Enable Input High oltage DD =.0..4 I Enable Input ow oltage DD = IH MUTE Input High oltage DD =.0..4 I MUTE Input ow oltage DD = OTP Over Temperature Protection 40 No oad, Junction Temperature DD= OTH Over Temperature Hysterisis 30 mω C

6 Typical Operating Characteristics (T =2 C) A. THD+N vs Output Power THD+N vs Output Power DD = DD =2. DD =3.3 DD = DD= DD= m 0m 0m 200m 00m 2 4 W R =4 Ω, Gain = 24dB, f=khz m 0m 0m 200m 00m 2 4 W R =8 Ω, Gain = 24dB, f=khz 3. THD+N vs Frequency THD+N vs Frequency R k 2k k k 20k Hz DD=, R =4 Ω,Gain = 24dB, Cin=μF 0.02 R k 2k k k 20k Hz DD=, R =8 Ω,Gain = 24dB, Cin=μF 6

7 Typical Operating Characteristics (continued). Frequency response 6. Crosstalk S Frequency TTTTTTTT d B r A R d B k 2k k k 20k DD=, R =8 Ω,Gain = 24dB, Cin=μF Hz R k 2k k k 20k Hz DD=, R =4 Ω, Gv=24dB, Po=0.W 7. Noise Floor FFT d B d B R k 2k k k 20k Hz Inputs ac-ground, DD=, R =8 Ω,Cin=μF

8 Application Notes. When the PAM8403 works with C filters, it should be connected with the speaker before it's powered on, otherwise it will be damaged easily. 2. When the PAM8403 works without C filters, it's better to add a ferrite chip bead at the outgoing line of speaker for suppressing the possible electromagnetic interference. 3. The recommended operating voltage is.. When the PAM8403 is powered with 4 battery cells, it should be noted that the voltage of 4 new dry or alkaline batteries is over 6.0, higher than its operation voltage, which will probably damage the device. Therefore, it's recommended to use either 4 Ni-MH (Nickel Metal Hydride) rechargeable batteries or 3 dry or alkaline batteries. 4. One should not make the input signal too large. arge signal can cause the clipping of output signal when increasing the volume. This will damage the device because of big gain of the PAM When testing the PAM8403 without C filters by using resistor instead of speaker as the output load, the test results, e.g. THD or efficiency, will be worse than those of using speaker as load. Test Setup for Performance Testing PAM8403 Demo Board AP System One Generator Input +OUT oad AP ow Pass Filter AP System One Analyzer GND -OUT AUX-002 DD Power Supply Notes. The AP AUX-002 low pass filter is necessary for class-d amplifier measurement with AP analyzer. 2. Two 22µH inductors are used in series with load resistor to emulate the small speaker for efficiency measurement. 8

9 Application Information Maximum Gain As shown in block diagram (page 2), the PAM8403 has two internal amplifier stages. The first stage's gain is externally configurable, while the second stage's is internally fixed. The closed-loop gain of the first stage is set by selecting the ratio of Rf to Ri while the second stage's gain is fixed at 2x.The output of amplifier serves as the input to amplifier 2, thus the two amplifiers produce signals identical in magnitude, but different in phase by 80. Consequently, the differential gain for the IC is Mute Operation A =20*log [2*(R /R )] D f i The PAM8403 sets maximum R f=42k Ω, minimum R i=8k Ω, so the maximum closed-gain is 24dB. The MUTE pin is an input for controlling the output state of the PAM8403. 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 internal pull-up. Shutdown operation In order to reduce power consumption while not in use, the PAM8403 contains shutdown circuitry to turn off the amplifier's bias circuitry. This shutdown feature turns the amplifier off when logic low is applied to the SHDN pin. By switching the SHDN pin connected to GND, the PAM8403 supply current draw will be minimized in idle mode. The SHDN pin can be left floating due to the internal pull-up. Power supply decoupling The PAM8403 is a high performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output THD and PSRR as low as possible. Power supply decoupling affects low frequency response. Optimum decoupling is achieved by using two capacitors of different types targeting to 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.0μf, works best, placing it as close as possible to the device DD terminal. For filtering lowerfrequency noise signals, a large capacitor of 20μF (ceramic) or greater is recommended, placing it near the audio power amplifier. Input Capacitor (C ) i arge 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 attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 0Hz to 0Hz. Thus, using a large input capacitor may not increase actual system performance. 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 by equation below, f= C 2πRC i i In addition to system cost and size, click and pop performance 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 /2 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. Analog Reference Bypass Capacitor (C ) 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, CBYP determines the rate at which the amplifier starts up. The second function is to reduce noise caused by the power supply 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. A ceramic bypass capacitor (C BYP) with values of 0.47μF to.0μf is recommended for the best THD and noise performance. reasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown. BYP 9

10 Under oltage ock-out (UO) The PAM8403 incorporates circuitry designed to detect low supply voltage. When the supply voltage drops to 2.0 or below, the PAM8403 outputs are disabled, and the device comes out of this state and starts to normal function when 2.2. Short Circuit Protection (SCP) The PAM8403 has short circuit protection circuitry on the outputs to prevent damage to the device when output-to-output or output-to-gnd short occurs. When a short circuit is detected on the outputs, the outputs are disabled immediately. If the short was removed, the device activates again. Over Temperature Protection Thermal protection on the PAM8403 prevents the device from damage when the internal die temperature exceeds 40 C. There is a 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 30 C. This large hysteresis will prevent motor boating sound well and the device begins normal operation at this point without external system intervention. DD How to Reduce EMI (Electro Magnetic Interference) A simple solution is to put an additional capacitor 00μF at power supply terminal for power line coupling if the traces from amplifier to speakers are short (<20cm). Most applications require a ferrite bead filter as shown in Figure 2. The ferrite filter reduces EMI of around MHz and higher. When selecting a ferrite bead, choose one with high impedance at high frequencies, and low impedance at low frequencies. OUT+ OUT- Ferrite Bead Ferrite Bead 220pF 220pF Figure 2: Ferrite Bead Filter to reduce EMI

11 Ordering Information PAM8403 X X Shipping Package Package Type Part Number Marking Package Type MOQ/Shipping Package PAM8403DR PAM8403 XATYWW SOP-6 2,00 Units/Tape&Reel

12 Outline Dimension SOP-6 D E E A2 A B A C θ e Symbol Dimensions Millimeters Min Max A A A B C D E E e.270(typ) θ 0º 8º 2

Filterless 3W Class-D Stereo Audio Amplifier

Filterless 3W Class-D Stereo Audio Amplifier Attenuation Decoder Interface C ontrol General Description The is a class-d audio amplifier. It can provide 3W output power and low THD+N, allow- ing it to achieve high-quality sound reproduction. The