PAM8301

PAM8301 Filterless Class-D Mono Audio Amplifier K ey Features n 1.5W Output at 10% THD with a 8 Ω Load and 5V Power Supply n Filterless, Low Quiescent Current and Low EMI n High Efficiency up to 88% n Superior Low Noise n Short Circuit Protection n Thermal Shutdown n Few External Components to Save Space and Cost n Tiny SOT23-6 Package n Pb-Free Package General Description The PAM8301 is a 1.5W class-D mono audio amplifier. Its low THD+N feature offers highquality sound reproduction. The new filterless architecture allows the device to drive speaker directly instead of using low-pass output filters, therefore save system cost and PCB area. With the same number of external components, the efficiency of the PAM8301 is much better than that of class-AB cousins. It can optimize battery life thus is ideal for portable applications. The PAM8301 is available in SOT23-6 package. Applications n n n n n n PMP/MP4 GPS Portable Speakers Walkie Talkie Handsfree phones/Speaker Phones Cellular Phones Typical Application VDD 10μF 5 VDD 3 Audio 0.1μF IN 1μF OUT+ 6 PAM8301 Shutdown 4 /SD GND 2 OUT- 1 Power Analog Microelectronics , Inc www.poweranalog.com 1 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier B lock Diagram VDD VDD/2 + IN RI RF DRIVER MODULATOR +OUT -OUT THERMAL PROTECTION SD SHUTDOWN INTERNAL OSCILLATOR CURRENT PROTECTION OSC GND Pin Configuration & Marking Information TOP VIEW SOT23-6 6 5 4 FPXYW FP: Product Code of PAM8301 X: Internal Code Y: Year W: Week 1 2 3 Pin Number 1 2 3 4 5 6 Pin Name OUTGND IN SD VDD OUT+ Negative Output Ground Input Shutdown, active low Power Supply Positive Output Description Power Analog Microelectronics , Inc www.poweranalog.com 2 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier 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 Voltage at no Input Signal...................6.6V Input Voltage.............................-0.3V to V DD +0.3V Maximum Junction Temperature..................150°C Storage Temperature.....................-65 °C to 150 °C Soldering Temperature...................... 300°C, 5sec Recommended Operating Conditions Supply voltage Range........................ 2.5V to 5.5V Max. Supply Voltage (for Max. duration of 30 minutes)................................................6.0V Operation Temperature Range........ -40 °C to 85 °C Junction Temperature Range.........-40 °C to 125 °C Thermal Information Parameter Thermal Resistance (Junction to Case) Thermal Resistance (Junction to Ambient) Symbol θJC θJA Package SOT23-6 SOT23-6 Maximum 130 °C/W 250 Unit Power Analog Microelectronics , Inc www.poweranalog.com 3 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier Electrical Characteristic PARAMETER Supply Voltage Range Quiescent Current Shutdown Current SHDN Input High SHDN Input Low Drain-Source On-State Resistance Output Power Total Harmonic Distortion Plus Noise Power Supply Ripple Rejection Gain Noise Oscillator Frequency Peak Efficiency Signal to Noise Ratio Over Temperature Protection Over Temperature Hysteresis V DD=5V, Gain = 24dB, R L=8 Ω, T A=25 °C，unless otherwise noted. SYMBOL VDD IQ ISHDN V SH VSL RDS(ON) PO THD+N PSRR Gv Vn fOSC η SNR OTP OTH f=1kHz f =20 to 20kHz No A-weighting A-weighting 200 85 IDS =100mA P MOSFET N MOSFET 0.45 0.20 1.2 1.5 0.2 0.3 45 50 24 180 120 250 88 78 135 30 300 W % dB dB μV kHz % dB °C °C No Load VSHDN=0V 1.2 0.4 CONDITIONS MIN 2.5 4 TYP MAX 5.5 8 1 UNITS V mA μA V Ω f=1kHz THD+N=1% THD+N=10% RL = 8Ω ，PO=200mW RL = 8Ω ，PO=0.5W No input, f=1kHz, Vpp=200mV Power Analog Microelectronics , Inc www.poweranalog.com 4 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier Typical Performance Characteristic T A=25°C,unless otherwise noted. 1. Frequency VS Supply Voltage 258 256 254 250 248 246 244 242 240 238 2 3 4 Supply Voltage (V) 5 6 F r e q u e n c y (k H z ) 2. Frequency VS Temperature 350 300 250 200 150 100 50 0 0 20 40 60 80 100 120 140 Frequency (kHz) 252 Tem perature 3.Efficiency VS Output Power 90% R L=8 Ω, V DD=3.6V/5V 85% 100% 95% 90% 4.Efficiency VS Output Power R L=16 Ω, V DD=3.6V/5V 80% Efficiency 75% Efficiency 85% 80% 75% 70% 70% 65% 60% VDD=5V 55% VDD=3.6V 65% 60% 2000 50% 0 200 400 600 800 1000 1200 1400 1600 1800 VDD=5V VDD=3.6V 0 200 400 600 800 1000 1200 Output Pow e r(m W) Output Pow er (mW) 5. THD+N VS Output Power 50 20 10 V V 6. THD+N VS Output Power 200 100 3.6 5 R L=8 Ω , Gain=23dB, f=1kHz, V DD=3.6V/5V R L=16 Ω , Gain=23dB, f=1kHz, V DD=3.6V/5V/5.5V 50 20 10 3.6V 5V 5 % 2 1 0.5 0.2 0.1 20m % 5 2 1 0.5 0.2 50m 100m 200 m W 500 m 1 2 3 0.1 20m 50m 100m 200m W 500m 1 2 3 Power Analog Microelectronics , Inc www.poweranalog.com 5 . 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier Typical Performance Characteristic T A=25°C,unless otherwise noted. 7. THD+N VS Frequency 10 5 8. THD+N VS Frequency 10 5 R L=8 Ω , Gain=23dB, Cin=0.1 μ F, V DD=5V,Po=500mW R L=16 Ω , Gain=23dB, Cin=0.1 μ F, V DD=5V,Po=500mW 2 2 1 % 1 % 0.5 0.5 0.2 0.2 0.1 0.05 0.03 20 0.1 0.06 20 50 100 200 500 Hz 1k 2k 5k 10k 20k 50 100 200 500 Hz 1k 2k 5k 10k 20k 9. THD+N VS Frequency 10 10 10. THD+N VS Frequency 5 5 R L=8 Ω , Gain=23dB, Cin=0.1 μ F, V DD=3.6V,Po=200mW R L=16 Ω , Gain=23dB, Cin=0.1 μ F, V DD=3.6V,Po=200mW 2 2 % 1 % 1 0.5 0.5 0.2 0.2 0.08 20 50 100 200 500 Hz 1k 2k 5k 10k 20k 0.08 20 50 100 200 500 Hz 1k 2k 5k 10k 20k 11. Frequency Response + 50 + 45 + 40 + 35 d B r A + 30 + 25 + 20 + 15 + 10 +5 +0 20 12. Noise Floor +0 R L=16 Ω , Cin=0.1 μ F,V DD=5V Inputs floating, R L=8 Ω , Cin=0.1 μ F,V DD=5V -20 -40 -60 d B V -80 -100 -120 -140 50 100 200 500 Hz 1k 2k 5k 10k 20k 20 50 100 200 500 Hz 1k 2k 5k 10k 20k Power Analog Microelectronics , Inc www.poweranalog.com 6 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier Typical Performance Characteristic T A=25°C unless otherwise noted. 13. PSRR +0 - 10 - 20 - 30 - 40 dB - 50 - 60 - 70 - 80 - 90 - 100 20 14.EMI vs Frequency R L=8 Ω , Gain=23dB, V DD=5V, Po=500 mW TT T R L=8 Ω , Gain=23dB, V DD=5V,Input floating T 50 100 200 500 Hz 1k 2k 5k 10k . Test Setup for Performance Testing PAM8301 Demo Board Load +OUT AP System One Generator Input AP Low Pass Filter GND -OUT VDD AUX-0025 AP System One Analyzer Power Supply Notes 1. The AP AUX-0025 low pass filter is necessary for every 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. Power Analog Microelectronics , Inc www.poweranalog.com 7 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier Application Information Maximum Gain As shown in block diagram (page 2), the PAM8301 has two internal amplifier stages. The first stage's gain is externally con figurable, while the second stage's is internally fixed. 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.The output of amplifier 1 serves as the input to amplifier 2, thus the two amplifiers produce signals identical in magnitude, but different in phase by 180°. Consequently, the differential gain for the IC is A VD=20*log [2*(R f/R i)] The PAM8301 sets maximum R f=80k Ω , minimum R i=10k Ω , so the maximum closed-gain is 24dB. Input Capacitors (Ci) In typical application, an input capacitor, Ci, is required to allow the amplifier to bias input signals to a proper DC level for optimum operation. In this case, Ci and the minimum input impedance Ri (10k internal) form a high pass filter with a corner frequency determined by the following equation: fC = 1 capacitor is the best choice. When a polarized capacitor is used, the positive side of the capacitor should face the amplifier input in most applications as the DC level is held at VDD/2, which is likely higher than the source DC level. Please note that it is important to confirm the capacitor polarity in the application. Power Supply Decoupling (Cs) The PAM8301 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 a ff e c t s l o w f r e q u e n c y r e s p o n s e . O p t i m u m 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-series-resistance (ESR) ceramic capacitor, typically 1.0μF is good, placing it as close as possible to the device VDD terminal. For filtering lower-frequency noise signals, a capacitor of 10μF or larger, closely located to near the audio power amplifier is recommended. Shutdown Operation In order to reduce shutdown power consumption, the PAM8301 contains shutdown circuitry for turn off the amplifier. This shutdown feature turns the amplifier off when a logic low is applied on the SHDOWN pin. By switching the shutdown pin over to GND, the PAM8301 supply current draw will be minimized in idle mode. For the best power on/off pop performance, the amplifier should be set in the shutdown mode prior to power on/off operation. Under Voltage Lock-out (UVLO) The PAM8301 incorporates circuitry to detect low on or off voltage. When the supply voltage drops to 2.1V or below, the PAM8301 goes into a state of shutdown, and the device comes out of its shutdown state and starts to normal operation by reset the power supply or SD pin. (2p RiCi) It is important to choose the value of Ci as it directly affects low frequency performance of the circuit, for example, when an application requires a flat bass response as low as 100Hz. Equation is reconfigured as follows: Ci = 1 (2p Rifc ) As the input resistance is variable, for the Ci value of 0.16 μ F, one should actually choose the Ci within the range of 0.1 μ F to 0.22 μ F. A further consideration for this capacitor is the leakage path from the input source through the input network (Ri, RF, Ci) to the load. This leakage current creates a DC offset voltage at the input to the amplifier that reduces useful headroom, especially in high gain application. For this reason, a low leakage tantalum or ceramic Power Analog Microelectronics , Inc www.poweranalog.com 8 09/2008 Rev 1.2 PAM8301 Filterless Class-D Mono Audio Amplifier How to Reduce EMI (Electro Magnetic Interference) A simple solution is to put an additional capacitor 1000 μ F at power supply terminal for power line coupling if the traces from amplifier to speakers are short (