PAM8302A

PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier K ey Features n 2.5W Output at 10% THD with a 4 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 MSOP-8, SOP-8 and DFN3x3 Packages Available n Pb-Free Package General Description The PAM8302A is a 2.5W 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 PAM8302A is much better than that of class-AB cousins. It can optimize battery life thus is ideal for portable applications. The PAM8302A is available in MSOP-8, SOP-8 and DFN3x3 packages. Applications n n n n n n PMP/MP4 GPS Portable Speakers Walkie Talkie Handsfree phones/Speaker Phones Cellular Phones Typical Application 1μF 6 VDD Ci INDifferential Input Ci IN+ ON OFF Ri Ri 4 INVO- 8 3 1 PAM8302A IN+ VO+ /SD GND 5 7 Power Analog Microelectronics , Inc www.poweranalog.com 1 09/2008 Rev 1.2 PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier B lock Diagram VDD IN+ MODULATOR DRIVER VO+ VO- IN- THERMAL PROTECTION SD SHUTDOWN INTERNAL OSCILLATOR SHORT PROTECTION OSC GND Pin Configuration & Marking Information Top View MSOP-8/SOP-8 Top View DFN3x3 SD 1 P8302A XXXXYW 8 7 6 5 VOGND VDD VO+ SD NC IN+ IN- 1 2 3 4 8 7 6 5 VOGND VDD VO+ X: Internal Code Y: Year W: Week NC 2 IN+ 3 IN- 4 P8302A XXXXYW Pin Number 1 2 3 4 5 6 7 8 Pin name SD Description Shutdown terminal ,active low No connection Positive differential input Negative differential input Positive BTL output Analog power supply Ground Negative BTL output NC IN+ INVO+ VDD GND VO- Power Analog Microelectronics , Inc www.poweranalog.com 2 09/2008 Rev 1.2 PAM8302A 2.5W 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 Ambient Operation Temperature Range......................................... -40 ° C to 85 ° C Junction Temperature Range.........-40 ° C to 125 ° C Thermal Information Parameter Thermal Resistance (Junction to ambient) Symbol Package SOP-8 Maximum 115 180 47.9 Unit °C/W °C/W °C/W θJA MSOP-8 DFN 3x3-8 Power Analog Microelectronics , Inc www.poweranalog.com 3 09/2008 Rev 1.2 PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier Electrical Characteristic V DD=5V, Gain = 24dB, R L=4 Ω, T A=25 ° C，unless otherwise noted. PARAMETER Supply Voltage Range Quiescent Current Shutdown Current SYMBOL VDD IQ ISHDN No Load VSHDN=0V f=1kHz, RL=4Ω THD+N=10% f=1kHz, RL=4Ω Output Power PO THD+N=1% f=1kHz, RL=8Ω THD+N=10% F=1kHz, RL=8Ω THD+N=1% Peak Efficiency Total Harmonic Distortion Plus Noise Gain Power Supply Ripple Rejection η VDD=5V VDD=3.6V VDD=5V VDD=3.6V VDD=5V VDD=3.6V VDD=5V VDD=3.6V f=1kHz 2.50 1.25 2.00 0.95 1.50 0.80 1.30 0.65 85 88 % W CONDITIONS MIN 2.5 4 TYP MAX 5.5 8 1 UNITS V mA μA RL = 8Ω，PO=0.1W, f=1kHz THD+N 0.30 0.45 0.35 0.40 24 dB dB 45 50 % RL = 8Ω，PO=0.5W, f=1kHz RL = 4Ω，PO=0.1W, f=1kHz RL = 4Ω，PO=0.5W, f=1kHz Gv PSRR No input, f=1kHz, Vpp=200mV Dynamic Range Signal to Noise Ratio Noise Oscillator Frequency Drain-Source On-State Resistance SHDN Input High SHDN Input Low Over Temperature Protection Over Temperature Hysteresis Dyn SNR Vn fOSC RDS(ON) VS H VSL OTP OTH f=20 to 20kHz f =20 to 20kHz No A-weighting A-weighting 200 IDS=100mA P MOSFET N MOSFET 1.2 90 80 180 120 250 0.45 0.20 0.4 135 30 300 dB dB μV kHz Ω V V °C °C Power Analog Microelectronics , Inc www.poweranalog.com 4 09/2008 Rev 1.2 PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier Typical Performance Characteristics T A=25 C, unless otherwise noted. THD+N VS Output Power R L=8 Ω , Gain=23dB, f=1kHz V DD= 3 . 6 V V DD= 4 . 2 V 5 % 2 1 0 .5 0 .2 0 .1 20 m O THD+N VS Output Power R L=4 Ω , Gain=23dB, f=1kHz 50 20 10 5 % 2 1 0. 5 50 20 10 V DD= 3 . 6 V V DD= 4 . 2 V V DD= 5 V 50 m 100 m 200 m W 500 m 1 2 3 0. 2 0. 1 20 m 50 m 100 m 200 m W 500 m 1 V DD= 5 V 2 3 THD+N VS Frequency R L=8 Ω , Cin=0.1 μ F, Gain=23dB, V DD=5V 10 5 THD+N VS Frequency R L=8 Ω , Cin=0.1 μ F, Gain=23dB, V DD=3.6V 10 5 2 1 Po=200mW 2 1 % 0.5 Po=500mW 0.5 % 0.2 Po=500mW 0.2 0.1 0.1 0.05 Po=200mW 0.05 0.02 0.02 20 50 100 200 500 Hz 1k 2k 5k 10k 20k 0.01 20 50 100 200 500 Hz 1k 2k 5k 10k 20k 10 5 2 1 0.5 % 0.2 0.1 0.05 0.02 THD+N VS Frequency R L=4 Ω , Cin=0.1 μ F, Gain=23dB, V DD=5V 10 5 2 THD+N VS Frequency R L=4 Ω , Cin=0.1 μ F, Gain=23dB, V DD=3.6V Po=200mW Po=500mW % 1 0.5 Po=500mW 0.2 Po=200mW 0.1 0.05 0.01 20 50 100 200 500 Hz 1k 2k 5k 10 k 20 k 0.02 20 50 100 200 500 Hz 1k 2k 5k 10 k 20 k Power Analog Microelectronics , Inc www.poweranalog.com 5 09/2008 Rev 1.2 PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier Typical Performance Characteristics T A=25 C, unless otherwise noted. Quiescent Current VS Temperature No input, No Load, V DD=5.0V Oscillator Frequency (kHz) O 8 Q uiescent Current(mA) 350 300 250 200 150 100 50 0 Frequency VS Temperature No input, No Load, V DD=5.0V 7 6 5 4 3 2 1 0 0 50 100 Temperature 150 0 50 Temperature 100 150 0.4 0.35 Supply Current VS Output Power R l=8 Ω +33 μ H 0.7 0.6 Supply Current(A) Supply Current VS Output Power V DD=5.0V Supply Current(A) 0.3 0.25 0.2 0.15 0.1 0.05 0 0 500 1000 Output Power(mW) 1500 VDD=3.6V VDD=5V 2000 0.5 0.4 0.3 0.2 0.1 0 0 500 1000 1500 2000 2500 3000 Output Power(mW) Load=8ohm+33uH L=4ohm+33uH 2.5 2 O u tp u t Po w er(W) Output Power VS. Supply Voltage R l=8 Ω 3.5 3 Output Power VS. Supply Voltage R l=4 Ω 1.5 1 0.5 0 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 Output Power(W) 2.5 2 1.5 1 0.5 0 2.5 THD+N=1% THD+N=10% 3 3.5 4 4.5 5 5.5 THD=1% THD=10% Supply Voltage(V) Supply Voltage(V) Power Analog Microelectronics , Inc www.poweranalog.com 6 09/2008 Rev 1.2 PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier Typical Performance Characteristics T A=25 C, unless otherwise noted. Efficiency VS Output Power V DD=5.0V Efficiency VS Output Power R l=8 Ω+33μΗ O 95% 90% 85% Efficiency 95% 90% 85% Efficiency Load=8ohm+33uH Load=4ohm+33uH 80% 75% 70% 65% 60% 0 500 1000 1500 2000 2500 3000 Output Pow er(m W) 80% 75% 70% 65% 60% 0 500 1000 Output Pow er(m W) 1500 2000 Vin=5V Vin=3.6V 4.5 4 Quiescent Current VS. Supply Voltage No load Oscillator Frequency (kHz) Frequency VS. Supply Voltage 350 300 250 200 150 100 50 0 2.5 3 3.5 4 4.5 5 5.5 Quiescent Current(mA) 3.5 3 2.5 2 1.5 1 0.5 0 2.5 3 3.5 4 4.5 5 5.5 Supply Voltage (V) Supply V oltage (V ) 0.16 0.14 Power Dissipation VS. Output Power R l=8 Ω Power Dissipation(W) 0.12 0.10 0.08 0.06 0.04 0.02 0.00 0 500 1000 Output Pow e r(W) VDD=5V VDD=3.6V 1500 2000 Power Analog Microelectronics , Inc www.poweranalog.com 7 09/2008 Rev 1.2 PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier Test Setup for Performance Testing PAM8302A 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 8 09/2008 Rev 1.2 PAM8302A 2.5W Filterless Class-D Mono Audio Amplifier Application Information Maximum Gain As shown in block diagram (page 2), the PAM8302A has two internal amplifier stages. The first stage's gain is externally con figurable, while the second stage's is internally fixed. The closedloop 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 PAM8302A 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: 1 fC = (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: 1 Ci = (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 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 PAM8302A 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 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 is good, placing it as close as possible to the device VDD terminal. For filtering lowerfrequency 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 PAM8302A contains shutdown circuitry for turn off the amplifier. This shutdown feature turns the amplifier off when a logic low is applied on the SD pin. By switching the shutdown pin over to GND, the PAM8302A 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 PAM8302A incorporates circuitry to detect low on or off voltage. When the supply voltage drops to 2.1V or below, the PAM8302A 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. Power Analog Microelectronics , Inc www.poweranalog.com 9 09/2008 Rev 1.2 PAM8302A 2.5W 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 (