Filterless 3W Class-D Stereo Audio Amplifier

Transcription

1 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 new filterless architecture allows the device to drive the speaker directly, requiring no lowpass output filters,thus to save the system cost and PCB area. With the same numbers of external components, the efficiency of the is much better than that of class-ab cousins.it can extend the battery life, ideal for portable applications. The is available in SOP-6 package. Features 3W output at Power Supply, 0% THD with a 4Ω Load Filterless, Low EMI Low THD+N Superior Low Noise Efficiency up to 90% Short Circuit Protection Thermal Shutdown Few External Components to Save the Space and Cost Pb-Free Package Function Block Diagram Applications Portable Speakers LCD Monitors / T Projectors Notebook Computers Portable DD Players, Game Machines Cellular Phones/Speaker Phones DD PDD PGND INR DD/ Modulator Driver +OUT_R -OUT_R OCP MUTE Pop& Click Suppression Internal Oscillator OTP Bias and References REF SHDN OSC ULO DD/ INL Modulator Driver +OUT_L -OUT_L PDD PGND

2 Pin Configuration SOP Pin Descriptions Pin Number Pin Name +OUT_L PGND 3 -OUT_L 4 PDD MUTE 6 DD 7 INL 8 REF 9 NC 0 INR GND SHDN 3 PDD 4 -OUT_R PGND 6 +OUT_R Left Channel Positive Output Power GND Left Channel Negative Output Power DD Mute Control Input(active low) Analog DD Left Channel Input Description Internal analog reference, connect a bypass capacitor from REF to GND No connection Right Channel Input Analog GND Shutdown Control Input (active low) Power DD Right Channel Negative Output Power GND Right Channel Positive Output

3 Typical Application DD PDD uf C uf C C3 470 uf C4 uf INL INR SHDN MUTE 0.47uF Ci 0k 7 CBYP 8 uf 0.47uF 0 Ci 0k INL REF INR SHDN DD MUTE GND NC PDD PDD PGND +OUT_L -OUT_L -OUT_R +OUT_R PGND Figure. Typical Applycation 3 Radiated Emissions( FCC Part ClassB) 3

4 Absolute Maximum Ratings* ) Item alue Supply oltage 6 Input oltage to DD Operation Temperature Range - 40 to 8 Maximum Junction Temperature 0 Storage Temperature Range -6 to0 Operation Junction Temperature - 40 to Soldering Temperature 300( sec) Unit Recommended Operating Condition Item Min Max Unit Supply oltage.. Operation Temperature Range Junction Temperature Range -40 Thermal Information Symbol Description alue Unit JC(SOP6) Thermal Resistance-Junction to Case C/W JA(SOP6) Thermal Resistance-Junction to Ambient 08 C/W Ordering and Marking Information Device Package Type Device Marking Reel Size Tape Width Quantity SOP6 ṂD8403 XXXX Pipe 0 units ESD Susceptibility ESD Susceptibility-HBM k ESD Susceptibility-MM Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device.functional operation at conditions other than the operating conditions specified is not implied.only one Absolute Maximum Rating should be applied at one time.. The PCB is a -layer,-inch square area with oz copper thickness. com.cn. 4

5 Electrical Characteristics in = Gain=6dB, R L =8 Ω, T A =, unless otherwise noted. Symbol Parameter Test Conditions MIN TYP MAX UNIT IN PO THD+N=0%,f=kHz, RL=4Ω THD+N=%,f=kHz, R L =4Ω THD+N=0%,f=kHz, R L =8Ω THD+N=%,f=kHz, RL=8Ω DD= DD =4.... DD= DD=.0.4 DD=3.6. DD= DD =.0.8 DD = DD= DD=.0.4 DD = DD = DD=.0,Po=0.W,RL=8Ω 0.06 f=khz DD=3.6,Po=0.W,RL=8Ω 0.09 DD =.0,Po=W,R L =4Ω 0. f=khz DD =3.6,Po=W,R L =4Ω 0.3 Gv Gain 6 db PSRR Power Supply Ripple Rejection DD =.0, Inputs ac-grounded with f=00hz -6 C IN =0.47uF f=khz -6 db Cs Crosstalk DD =,Po=0.W,R L =8W,Gv=dB f =khz -9 db SNR Single-to-noise ratio DD =, orms=,gv=db f=khz 8 db n DD =, Inputs ac-grounded with A-weighting 80 C IN =0.47 uf No A-weighting 0 Dyn Dynamic range DD =.0, THD=% f=khz 90 db η IQ Supply Power Output Power THD+ N Total Harmonic Distortion Plus Noise Output noise Efficiency Quiescent Current R L =8Ω,THD=0% 88 f=khz R L =4Ω,THD=0% 84 DD= DD =3.6 No load 6 DD=3.0 DD=3.0. DD=4..7 =4..6 DD DD =4..0. W W W W % % m % ma

6 Electrical Characteristics in = Gain=6dB, R L =8 Ω, T L =, unless otherwise noted. Symbol IMUTE Muting Current DD=.0 MUTE= ma ISD Shutdown Current DD=. to. sd =0.3 < ua Rdson Parameter Static Drain-to-to On-state Resisitor IDS=00mA,gs= Test Conditions MIN TYP MAX UNIT PMOS 3 NMOS 98 fsw Switching Frequency DD=3 to 00 khz os Output Offset oltage in=0, DD= 0 m IH Enable Input High oltage DD =.0..4 IL Enable Input Low oltage DD = IH MUTE Input High oltage DD =.0..4 IL MUTE Input Low oltage DD = OTP Over Temperature Protection 40 No Load, Junction Temperature DD= OTH Over Temperature Hysterisis 30 mω 6

7 Typical Operating Characteristics (T A = C) THD + N (% ) RL=4 THD+N vs Output Power THD+N vs Output Power Ω,Gain=6dB,f=kHz 0 RL=8 Ω,Gain=6dB,f=kHz DD =3.0 =3.6 DD THD + N (% ) DD =3.0 =3.6 DD = DD = DD 0.0 m 0m 00m 0m 00m m 0m 00m 0m 00m 4 Output Power( W) Output Power( W) THD+N vs Frequency THD+N vs Frequency DD =, R L =4Ω,Gain = 6dB Cin=uF 0 DD =, R L =8Ω,Gain = 6dB Cin=uF 0 0 THD + N (% ) L THD + N (% ) L R R k k k 0k k k k k 0k k Frenquency( Hz) Frenquency( Hz) Frequency response Crosstalk vs Frequency DD =, R L =8Ω,Gain = 6dB Cin=uF L TTTTTTTT DD =, R L =4Ω,G ain = 6dB PO= 0. W R L k k k 0k k R k k k 0k k 7

8 Typical Operating Characteristics (continued) Output Power vs Supply oltage Output Power vs Supply oltage. 3. Output Power ( W ) RL= 8Ω+ 33uH f= khz 0% THD % THD Output Power ( W ) RL= 4Ω+ 33uH f= khz 0% THD % THD Supply oltage( ) Supply oltage( ) Output Power vs Supply oltage Output Power vs Supply oltage Output Power ( W ) RL= 8Ω+ 33uH f= khz THD+ N= 0% Output Power ( W ) RL= 4Ω+ 33uH f= khz THD+ N= 0% Supply oltage( ) Supply oltage( ) Efficiency vs Output Power RL= 4Ω R L=8Ω Output Power(W) 8

9 Applications Information Maximum Gain As shown in block diagram, the 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 x.the output of amplifier serves as the input to amplifier, thus the two amplifiers produce signals identical in magnitude, but different in phase by 80. Conse- quently, the differential gain for the IC is A D =*log [*(R f /R i )] The sets maximum Rf = 300k Ω,minimum Ri = 30k Ω, so the maximum closed-gain is 6dB. Mute Operation The Mute pin is an input for controlling the output state of the. 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 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 Shutdown pin. By switching the Shutdown pin connected to GND, the supply current draw will be minimized in idle mode. The Shutdown pin can be left floating due to the internal pull-up. Power supply decoupling The is a high performance CMOS audio amplifier that requires adequate power supply de- coupling 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 lower frequency noise signals, a large capacitor of μf (ceramic) or greater is recommended, placing it near the audio power amplifier. Input Capacitor (Ci) 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 attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 00Hz to 0Hz. Thus, using a large input capacitor may not increase actual system performance. In this case, input capacitor (Ci) and input resistance (Ri) of the amplifier form a high-pass filter with the corner frequency determined by equation below: f C= πrc i i In addition to system cost and size, click and pop performance is affected by the size of the input coupling capacitor, Ci. A larger input coupling capacitor requires more charge to reach its quiescent DC voltage (nominally / 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 BYP) 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 9

10 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. Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown. Under oltage Lock-out (ULO) The incorporates circuitry designed to detect low supply voltage. When the supply voltage drops to.0 or below, the outputs are disabled, and the device comes out of this state and starts to normal function when DD.. Short Circuit Protection The 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. How to Reduce EMI (Electro Magnetic Interference) A simple solution is to put an additional capacitor 000uF at power supply terminal for power line coupling if the traces from amplifier to speakers are short (<CM). Most applications require a ferrite bead filter as shown in Figure. 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 pf pf Figure : Ferrite Bead Filter to reduce EMI Over Temperature Protection Thermal protection on the prevents the device from damage when the internal die tem- perature 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. 0

11 Package Information SOP6 A A B A D C L E E q e Symbol Dimensions Millimeters Min Max A A A.30.0 B C D E E e.70(typ) L q 0 8