PT5301 2 Watts Audio Power Amplifier GENERAL DESCRIPTION FEATURES z Low Distortion 0.50W @ VDD=5.0V, RL=8Ω THD+N = 0.03% 0.25W @ VDD=3.0V, RL=8Ω THD+N = 0.04% 0.15W @ VDD=2.6V, RL=8Ω THD+N = 0.05% The PT5301 is an audio power amplifier mainly designed for applications in mobile phones and other portable communication device applications. It is capable of delivering 1.25 watts of continuous average power to an 8Ω load and 2 watts of continuous average power to a 4Ω load with less than 1% distortion (THD+N) from a 5V power supply. The PT5301 does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for mobile phone and other low voltage applications where minimal power consumption is a primary requirement. The PT5301 features a low-power shutdown mode and improved pop & click circuitry that attenuates noise which would otherwise occur during turn on and turn off transactions. The PT5301 is delivered with miniature MSOP-8, DFN-8 and SMD-9 packages (Pd free). z z Ultra low shutdown current z Improved pop & click noise eliminating function z No need for output coupling or bootstrap capacitors z 2.2 -5.5V operation supply voltage z Thermal protection z External gain configuration capability z Pd free MSOP-8, DFN-8, and SMD-9 packages z Unity-gain stable APPLICATION z z z Output Power @ 1% THD+N 1.25W @ VDD=5.0V, RL=8Ω 2.0W @ VDD=5.0V, RL=4Ω 0.425W @ VDD=3.0V, RL=8Ω 0.60W @ VDD=3.0V, RL=4Ω 0.30W @ VDD=2.6V, RL=8Ω 0.40W @ VDD=2.6V, RL=4Ω Mobil Phones PDAs Portable electronic devices ORDERING INFORMATION Pd-Free PACKAGE TEMPERATURE ORDER PART NUMBER TRANSPORT MEDIA MARKING MSOP-8 -40oC to 85 oC PT5301EMSO Tape and Reel PT5301 XXXXXC SMD-9 -40oC to 85 oC PT5301ESMD Tape and Reel P5301 XXXXX DFN-8 -40oC to 85 oC PT5301EQFN Tape and Reel PT5301 XXXXXC TYPICAL APPLICATION RF 20kΩ VDD=5.0V,RL=4.0ohm, f=1KHz Vo1 1 20kΩ 20kΩ CB 1μF 8 Vo Bypass BIA THD+N(%) + Ω Shutdown control 10 VD -I +I THD+N vs Output Power CS 1μ Ci 0.39μ Ri 20k KEY PERFORMANCE CHART 0.1 + Shutdown GND 0.01 10 Figure 1. Typical Audio Amplifier Application Circuit. China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM 100 1000 3000 Output Power (mW) Page1 PT5301 2 Watts Audio Power Amplifier PIN ASSIGNMENT 1 2 3 4 Vo2 Shutdown Bypass GND +IN VDD -IN Vo1 8 7 6 A -IN B GND GND VDD C Bypass Vo2 Shutdown Vo1 +IN 5 MSOP8/DFN8 Top View 1 3 2 SMD9 Top View PIN DESCRIPTIONS MSOP8/ DFN8 1 SMD9 NAMES DESCRIPTION C3 Shutdown Turn-on or turn-off the chip 2 C1 Bypass 3 A3 +IN The non-inverting input node 4 A1 -IN The inverting input node 5 A2 Vo1 The 1st node of outputs 6 B3 VDD Power supply 2.5~5.5V 7 B1, B2 GND ground 8 C2 Vo2 The 2nd node of outputs Set the common voltage ABSOLUTE MAXIMUM RATINGS (Note 1) ITEMS Supply Voltage Input Voltage UNIT 6 V -0.3～VDD+0.3 V 190/56 ℃/W 180 ℃/W Thermal Resistance, MSOP8: θJA/θJC Thermal Resistance, SMD9: θJA (Note 3) Power Dissipation (Notes 5, 6) VALUE Internal limited Operating Temperature -40 to 85 ℃ 2500 V Storage Temperature -65 to 150 ℃ Package Lead Soldering Temperature 260℃, 10s ℃ ESD Susceptibility (Note 4) RECOMMENDED OPERATING RANGE (Note 2) SYMBOL PARAMETER VALUE TA Temperature Range -40°C≤TA≤85°C VDD Supply Voltage 2.2V≤VDD≤5.5V Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Note 2: Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. Note 3: All bumps have the thermal resistance and contribute equally when used to lower thermal resistance. All bumps must connected to achieve specified thermal resistance Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor. China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page2 PT5301 2 Watts Audio Power Amplifier Note 5: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature TA. The maximum allowable power dissipation is PDMAX = (TJMAX–TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the PT5301, see power derating curves for additional information. Note 6: Maximum power dissipation in the device (PDMAX) occurs at an output power level significantly below full output power. PDMAX can be calculated using Equation 1 shown in the Application Information section. It may also be obtained from the power dissipation graphs. ELECTRICAL CHARACTERISTICS VDD = 5V (Notes 7, 8) The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. TA = 25˚C. SYMBOL Idd Isd ITEMS TYP LIMIT UNITS Vin=0V,IO =0A,No Load 2.9 4.5 mA Current Vin=0V,IO =0A, 8Ω Load 2.9 5 mA Shutdown current Vshutdown =0 (Note 9) 0.1 2 uA Quiescent CONDITIONS Power Supply Vsdih Shutdown Voltage Input High 1.6 V Vsdil Shutdown Voltage Input Low 1.4 V Vos Output Offset Voltage 1.3 50 mV 0.9 W Po Twu THD Output Power (8Ω Load) f=1k; THD+N=1% (max) 1.25 Output Power (4Ω Load) f=1k; THD+N=1% (max) 2 W 146 ms 0.03 % Wake-up time Total Harmonic Distortion + Noise Po=0.5Wrms; f=1k, 8Ω Load Input float, Vripple=200mV sine wave p-p PSRR Power Supply Rejection Ratio Input terminated with 10Ω, Vripple=200mV sine wave p-p Ro Resistor Output to GND(Note 71 (f=217Hz), 69 (f=1k) 11.0 10) China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 90 (f=217Hz), 79 (f=1k) WWW.CRPOWTECH.COM 57 (min) dB 9.7 kΩ(min) 12.5 kΩ(max) Page3 PT5301 2 Watts Audio Power Amplifier ELECTRICAL CHARACTERISTICS VDD = 3V (Notes 7, 8) The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. TA = 25˚C. SYMBOL ITEMS Idd Quiescent Power Supply Current Isd Shutdown current CONDITIONS TYPICAL LIMIT UNITS Vin=0V, Io=0A, No Load 2.8 4.3 mA Vin=0V, Io=0A, 8Ω Load 2.8 5 mA Vshutdown =0 (Note 9) 0.1 2 uA Vsdih Shutdown Voltage Input High 1.1 V Vsdil Shutdown Voltage Input Low 1.0 V Vos Output Offset Voltage 1.3 50 mV Output Power (8Ω Load) f=1k;THD+N=1%(max) 425 mW Output Power (4Ω Load) f=1k;THD+N=1% (max) 600 mW 150 ms 0.04 % Po Twu THD PSRR Wake-up time Total Harmonic Distortion + N i Power Supply Rejection Ratio Po=0.25Wrms;f=1k,8Ω L d Input float, Vripple=200mV sine wave p-p Input terminated with 10Ω, Vripple=200mV sine wave p-p Ro Resistor Output to GND(Note 10) 88 (f=217), 79 (f=1k) 67 (f=217), 68 (f=1k) 11.0 55 (min) dB 9.7 kΩ(min) 12.5 kΩ(max) ELECTRICAL CHARACTERISTICS VDD = 2.6V (Notes 7, 8) The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. TA = 25˚C. SYMBOL ITEMS Idd Quiescent Power Supply Current Isd Shutdown current CONDITIONS TYPICAL LIMIT UNITS Vin=0V, Io=0A, No Load 2.8 4.3 mA Vin=0V, Io=0A, 8Ω Load 2.8 5 mA Vshutdown =0 (Note 9) 0.1 2 uA Vsdih Shutdown Voltage Input High 1 V Vsdil Shutdown Voltage Input Low 0.9 V Vos Output Offset Voltage 1.3 50 mV Output Power (8Ω Load) f=1k;THD+N=1%(max) 300 mW Output Power (4Ω Load) f=1k;THD+N=1% (max) 400 mW Po China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page4 PT5301 2 Watts Audio Power Amplifier ELECTRICAL CHARACTERISTICS VDD = 2.6V (Continued) (Notes 7, 8) The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. TA = 25˚C. SYMBOL Twu ITEMS CONDITIONS Wake-up time THD Total Harmonic Distortion + Noise PSRR Power Supply Rejection Ratio Ro TYPICAL Po=0.15Wrms; 8Ω Load UNITS 153 ms 0.05 % 66 (f=217), 68 (f=1k) dB f=1k, Input terminated with 10Ω, V 200 V i LIMIT Resistor Output to GND (Note 10) 9.7 kΩ(min) 12.5 kΩ(max) 11.0 Note 7: Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 8: “Typical” means that measured at 25˚C and represent the parametric norm. “Limit” indicates that are guaranteed by PowTech’s quality control standards. Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. Note 9: For micro SMD package, shutdown current is measured in a Normal Room Environment. Exposure to direct sunlight will increase ISD by a maximum of 2µA. Note 10: RO is measured from the output pin to ground. This value represents the parallel combination of the 15kΩ output resistors and the two 20kΩ resistors. EXTERNAL COMPONENTS DESCRIPTION RF 20k CS 1μF Ω Ci 0.39μF VDD -IN Ri 20k Ω +IN Vo1 + 20kΩ 20kΩ CB 1μF Vo2 Bypass Shutdown control 8Ω BIAS + Shutdown GND Figure 1. Typical Audio Amplifier Application Circuit. China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page5 PT5301 2 Watts Audio Power Amplifier COMPONENTS 1 Ri 2 Ci 3 RF 4 CS 5 CB FUNCTIONAL DESCRIPTION Inverting input resistor that sets the closed-loop gain together with RF. This resistor also performs as a high pass filter with Ci at fC = 1/(2πRiCi) Input coupling capacitor which blocks the DC voltage at the input terminals. It also creates a high pass filter with Ri at fC = 1/(2πRiCi). For more details of how to determine the value of Ci, look at the section of Proper Selection of External Components. Feedback resistor which sets the closed-loop gain together with RF. Supply bypass capacitor which provides supply voltage filtering. For more details of how to determine the value of CB, refer to the section of Power Supply Bypassing. Bypass pin capacitor which provides half-supply filtering. For more details of how to determine the value of CB, look at the section of Proper Selection of External Components. TYPICAL FERFORMANCE CHARACTERISTICS THD+N vs Frequency VDD=5.0V,RL=4.0ohm,f=1KHz 10 1 1 THD+N(%) THD+N(%) THD+N vs Output Power VDD=5.0V,RL=4.0ohm,Po=1W 10 0.1 0.1 0.01 10 0.01 100 1000 100 10000 THD+N vs Frequency THD+N vs Frequency VDD=5.0V,RL=8.0ohm,Po=500mW VDD=3.0V,RL=8.0ohm,Po=250mW 10 THD+N(%) THD+N(%) 1 0.1 0.01 20 3000 Output Power (mW) Frequency(Hz) 10 1000 1 0.1 100 1000 10000 20000 0.01 20 100 Frequency(Hz) China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM 1000 Frequency(Hz) 10000 20000 Page6 PT5301 2 Watts Audio Power Amplifier TYPICAL FERFORMANCE CHARACTERISTICS (Continued) THD+N vs Frequency THD+Nvs Frequency VDD=3V, RL=4Ω, and Po=500mW 1 10 VDD=2.6V,RL=8.0ohm,Po=150mW THD+N(%) THD(%) 1 0.1 0.1 0.01 10 100 1000 10000 100000 0.01 20 F(Hz) THD+N vs Frequency 100 1000 10000 20000 Frequency(Hz) THD+N vs Output Power VDD=2.6V,RL=4Ω,Po=150mW 10 1 VDD=5.0V,RL=8.0 ohm,f=1KHz THD+N(%) THD(%) 1 0.1 0.1 0.01 0.01 10 100 1000 10000 100000 0.0016 10 100 1000 3000 Output Power(mW) THD+N vsF(Hz) Output Powe r THD+N vs Output Power Vdd=3V,RL=4Ω,and f=1kHz VDD=3.0V,RL=8.0 ohm,f=1KHz 10 10 1 THD(%) THD+N(%) 1 0.1 0.1 0.01 0.0016 10 0.01 10 100 1000 100 1000 Output Power(mW) OUTPUT POWER(mW) China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page7 PT5301 2 Watts Audio Power Amplifier TYPICAL FERFORMANCE CHARACTERISTICS (Continued) THD+N vs Output Power THD+N vs Ouput Power Vdd=2.6V, RL=4Ω,f=1KHz 10 VDD=2.6V,RL=8.0ohm,f=1KHz 10 1 THD(%) THD+N(%) 1 0.1 0.1 0.01 0.01 10 100 10 1000 100 OUTPUT POWER(mW) PSRR vs Frequency PSRR vs Frequency VDD=5.0V,RL=8.0ohm,Input to GND 0 0 -20 -20 -30 PSRR(dB) -30 -40 PSRR(dB) VDD=3.0V,RL=8.0ohm,Input to GND -10 -10 -50 -60 -40 -50 -60 -70 -70 -80 -80 -90 -90 -100 20 100 1000 10000 -100 20 20000 100 1000 PSRR vs Frequency 0 Power Dissipation vs Output Power VDD=2.6V,RL=8.0ohm,Input to GND VDD=5.0V 1.4 4ohm 1.3 -10 1.2 -20 1.1 Power Dissipation(W) -30 -40 -50 -60 -70 -80 1.0 0.9 0.8 8ohm 0.7 0.6 0.5 0.4 0.3 -90 -100 10000 20000 Frequency(Hz) Frequency(Hz) PSRR(dB) 500 Output Power(mW) 0.2 100 1000 Frequency(Hz) 10000 0.1 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.42.5 Output Power(W) China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page8 PT5301 2 Watts Audio Power Amplifier TYPICAL FERFORMANCE CHARACTERISTICS (Continued) Power Dissipation vs Output Power Power Dissipation vs Output Power VDD=3.0V 0.50 0.45 0.35 4ohm Power Dissipation(W) Power Dissipation(W) 0.40 0.35 0.30 8ohm 0.25 VDD=2.6V 0.40 0.20 0.15 4ohm 0.30 0.25 8ohm 0.20 0.15 0.10 0.10 0.05 0.05 0.00 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.00 0.0 1.0 0.2 Output Power(W) PSRR vs Frequency 0.8 1.0 PSRR vs Frequency -30 -40 -40 -50 -50 PSRR (dB) PSRR (dB) 0.6 VDD=3.0V,RL=8ohm,Input Float VDD=5.0V,RL=8ohm,Input Float -30 0.4 Output Power(W) -60 -70 -60 -70 -80 -80 -90 -90 -100 -100 100 1000 10000 100000 Frequency (Hz) 100 1000 10000 100000 Frequency (Hz) Noise Floor 60 VDD=5.0V,RL=8.0ohm Input to GND 55 Output Noise Voltage(uV) 50 45 40 35 30 25 20 20 100 1000 10000 20000 Frequency(Hz) China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page9 PT5301 2 Watts Audio Power Amplifier APPLICATION INFORMATION Bridge Configuration Explanation As shown in Figure1, the PT5301 has two internal operational amplifiers. The first amplifier’s gain is externally configurable, while the second amplifier is internally fixed in a unity-gain, inverting configuration. The closed-loop gain of the first amplifier is set by selecting the ratio of RF to Ri while the second amplifier’s gain is fixed by the two internal 20kΩ resistors. Figure1shows that the output of amplifier one serves as the input to amplifier two which results in both amplifiers producing signals identical in magnitude, but out of phase by 180˚. Consequently, the differential gain for the IC is AVD= 2 *(RF/Ri) By driving the load differentially through outputs Vo1 and Vo2, an amplifier configuration commonly referred to as “bridged mode” is established. Bridged mode operation is different from the classical single-ended amplifier configuration where one side of the load is connected to ground. A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling output swing for a specified supply voltage. Four times the output power is possible as compared to a single-ended amplifier under the same conditions. This increase in attainable output power assumes that the amplifier is not current limited or clipped. In order to choose an amplifier’s closed-loop gain without causing excessive clipping, please refer to the Audio Power Amplifier Design section. A bridge configuration, such as the one used in PT5301, also creates a second advantage over single-ended amplifiers. Since the differential outputs, Vo1 and Vo2, are biased at half-supply, no net DC voltage exists across the load. This eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. Without an output coupling capacitor, the half-supply bias across the load would result in both increased internal IC power dissipation and also possible loudspeaker damage. Power Dissipation Power dissipation is a major concern when designing a successful amplifier, whether the amplifier is bridged or single-ended. A direct consequence of the increased power delivered to the load by a bridge amplifier is an increase in internal power dissipation. Since the PT5301 has two operational amplifiers in one package, China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 the maximum internal power dissipation is 4 times that of a single-ended amplifier. The maximum power dissipation for a given application can be derived from the power dissipation graphs or from Equation 1. 2 2 PDMAX = 4*(VDD) /(2π RL) (1) It is critical that the maximum junction temperature TJMAX of 150˚C is not exceeded. TJMAX can be determined from the power derating curves by using PDMAX and the PC board foil area. By adding copper foil, the thermal resistance of the application can be reduced from the free air value of θJA, resulting in higher PDMAX values without thermal shutdown protection circuitry being activated. Additional copper foil can be added to any of the leads connected to the PT5301. It is especially effective when connected to VDD, GND, and the output pins. If TJMAX still exceeds 150˚C, then additional changes must be made. These changes can include reduced supply voltage, higher load impedance, or reduced ambient temperature. Internal power dissipation is a function of output power. Refer to the Typical Performance Characteristics curves for power dissipation information for different output powers and output loading. Power Supply Bypassing As with any amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. The capacitor location on both the bypass and power supply pins should be as close to the device as possible. Typical applications employ a 5V regulator with 10µF tantalum or electrolytic capacitor and a ceramic bypass capacitor which aid in supply stability. This does not eliminate the need for bypassing the supply nodes of the PT5301. The selection of a bypass capacitor, especially CB, is dependent upon PSRR requirements, click and pop performance (as explained in the section, Proper Selection of External Components), system cost, and size constraints. Shutdown Function In order to reduce power consumption while not in use, the PT5301 contains shutdown circuitry that is used to turn off the amplifier’s bias circuitry whenever the Shutdown pin is put at logical “low”. While the device may be disabled with shutdown voltages in between ground and supply, the idle current may be greater than the typical value of 0.1µA. Therefore, the shutdown pin should be tied to a definite voltage to avoid unwanted state changes. In many applications, WWW.CRPOWTECH.COM a microcontroller or Page10 PT5301 2 Watts Audio Power Amplifier microprocessor output is used to control the shutdown circuitry, which provides a quick, smooth transition to shutdown. Another solution is to use a single-throw switch in conjunction with an external pull-up resistor (or pull-down, depending on shutdown high or low application). This scheme guarantees that the shutdown pin will not float, thus preventing unwanted state changes. Proper Selection of External Components Proper selection of external components in applications using integrated power amplifiers is critical to optimize device and system performance. While the PT5301 is tolerant of external component combinations, consideration to component values must be used to maximize overall system quality. The PT5301 is unity-gain stable which gives the designer maximum system flexibility. The PT5301 should be used in low gain configurations to minimize THD+N+N values, and maximize the signal to noise ratio. Low gain configurations require large input signals to obtain a given output power. Input signals equal to or greater than 1Vrms are available from sources such as audio codecs. Please refer to the section, Audio Power Amplifier Design, for a more complete explanation of proper gain selection. Besides gain, one of the major considerations is the closed loop bandwidth of the amplifier. To a large extent, the bandwidth is dictated by the choice of external components shown in Figure1. The input coupling capacitor, Ci, forms a first order high pass filter which limits low frequency response. This value should be chosen based on needed frequency response for a few distinct reasons. 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 100Hz to 150Hz. Thus, using a large input capacitor may not increase actual system performance. In addition to system cost and size, click and pop performance is effected by the size of the input coupling capacitor, i. A larger input coupling capacitor requires more charge to reach its quiescent DC voltage (nominally 1/2 VDD). This charge comes from the output 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. Besides minimizing the input capacitor size, careful China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 consideration should be paid to the bypass capacitor value. Bypass capacitor, CB, is the most critical component to minimize turn-on pops since it determines how fast the PT5301 turns on. The slower the PT5301’s outputs ramp to their quiescent DC voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing CB equal to 1.0µF along with a small value of Ci (in the range of 0.1µF to 0.39µF), should produce a virtually pop & click free shutdown function. While the device will function properly, (no oscillations or motorboating), with CB equal to 0.1µF, the device will be much more susceptible to turn-on clicks and pops. Thus, a value of CB equal to 1.0µF is recommended in all but the most cost sensitive designs. Audio Power Amplifier Design A 1W/8Ω Audio Amplifier Given: Power Output Load Impedance Input Level Input Impedance Bandwidth 1Wrms 8Ω 1Vrms 20kΩ 100Hz–20kHz ± 0.25dB 5V is a standard voltage in most applications, it is chosen for the supply rail. Extra supply voltage creates headroom that allows the PT5301 to reproduce peaks in excess of 1W without producing audible distortion. At this time, the designer must make sure that the power supply choice along with the output impedance does not violate the conditions explained in the Power Dissipation section. Once the power dissipation equations have been addressed, the required differential gain can be determined from Equation 2. AVD = (PO PL ) /(VIN ) = Vorms / Vinrms (2) RF / Ri = AVD / 2 From Equation 2, the minimum AVD is 2.83; use AVD =3. Since the desired input impedance was 20kΩ, and with an AVD impedance of 2, a ratio of 1.5:1 of RF to Ri results in an allocation of Ri = 20kΩ and RF = 30kΩ. The final design step is to address the bandwidth requirements which must be stated as a pair of −3dB frequency points. Five times away from a −3dB point is 0.17dB down from passband response which is better than the required ±0.25dB specified. fL = 100Hz/5 = 20Hz fH = 20kHz×5= 100kHz WWW.CRPOWTECH.COM Page11 PT5301 2 Watts Audio Power Amplifier The PT5301 is unity gain stable and requires no external components besides gain-setting resistors, an input coupling capacitor, and proper supply bypass in the typical application. However, if a closed-loop gain is much greater than the normal setting value (i.e. gain = 10), a feedback capacitor (C4) may be required as shown in Figure 2. to limit the bandwidth of the amplifier. The feedback capacitor creates a low pass filter that eliminates the possible high frequency oscillations. Be aware that an possible inadequate combination of R3 and C4 will cause roll-off before 20kHz. A typical combination is R3 = 20kΩ and C4 = 25pf. Users could refer this combination when design a high gain audio amplifier. As mentioned in the External Components section, Ri in conjunction with Ci create a high-pass filter. Ci ≥ 1/(2π×20kΩ×20Hz) = 0.397µF; use 0.39µF The high frequency pole is determined by the product of the desired frequency pole, fH, and the differential gain, AVD. With an AVD = 3 and fH = 100kHz, the resulting GBWP = 300kHz which is much smaller than the PT5301 GBWP of 2.0MHz. This figure displays that if a designer has a need to design an amplifier with a higher differential gain, the PT5301 can still be used without running into bandwidth limitations. C4 C1 1μF R3 C2 0.39μF VDD -IN R2 20kΩ R1 100k +IN Vo1 + 20kΩ 20kΩ C3 1μF 8Ω Vo2 Bypass + BIAS Shutdown GND Figure 2. High Gain Audio Amplifier C1 1μF R3 20kΩ C2 0.39μF R2 20kΩ VDD -IN +IN Vo1 + 20kΩ C4 0.39μF R1 100k 20kΩ R5 20kΩ R6 20kΩ 8Ω Vo2 Bypass BIAS + Shutdown GND C3 1μF Figure 3. Fully-differential Application for PT5301 China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page12 PT5301 2 Watts Audio Power Amplifier performance is achieved with the largest practical copper heat sink area. Thermal Considerations for Driving 4ΩLoad When driving 4Ω load, the internal power dissipation of the PT5301 must be carefully considerated. Failing to optimize thermal design may compromise the PT5301’s high power performance and activate unwanted, though necessary, thermal protection. In all circumstances and conditions, the junction temperature must be held below 150°C to prevent activating the PT5301’s thermal protection. The maximum allowable power dissipation is limited by thermal resistance of the package. When the supply voltage is higher than 4V, the PT5301’s MSOP or SMD package isn’t recommended to drive 4Ω load. The PT5301’s exposed-PAD QFN package provides a low thermal resistance between the die and the PCB to which the part is mounted and soldered. This allows rapid heat transfer from the die to the surrounding PCB copper traces, ground plane and, finally, surrounding air. The result is a low voltage audio power amplifier that produces 2W at ≤1% THD with a 4Ω load. This high power is achieved through careful consideration of necessary thermal design. The QFN package must have its exposed-PAD soldered to a copper pad on the PCB. The exposed-PAD’s PCB copper pad is connected to a large plane of continuous unbroken copper. This plane forms a thermal mass and heat sink and radiation area. Place the heat sink area on either outside plane in the case of a two-sided PCB, or on an inner layer of a board with more than two layers. Connect the exposed-PAD’s copper pad to the inner layer or backside copper heat sink area with several vias. Ensure efficient thermal conductivity by plating through and solder-filling the vias. Best thermal China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 PCB Layout and Supply Regulation Considerations for Driving 4ΩLoad Power dissipated by a load is a function of the voltage swing across the load and the load’s impedance. As load impedance decreases, load dissipation becomes increasingly dependent on the interconnect (PCB trace and wire) resistance between the amplifier output pins and the load’s connections. Residual trace resistance causes a voltage drop, which results in power dissipated in the trace and not in the load as desired. For example, 0.1Ω trace resistance reduces the output power dissipated by a 4Ω load from 2.0W to 1.9W. This problem of decreased load dissipation is exacerbated as load impedance decreases. Therefore, to maintain the highest load dissipation and widest output voltage swing, PCB traces that connect the output pins to a load must be as wide as possible. Poor power supply regulation adversely affects maximum output power. A poorly regulated supply’s output voltage decreases with increasing load current. Reduced supply voltage causes decreased headroom, output signal clipping, and reduced output power. Even with tightly regulated supplies, trace resistance creates the same effects as poor supply regulation. Therefore, making the power supply traces as wide as possible helps maintain full output voltage swing WWW.CRPOWTECH.COM Page13 PT5301 2 Watts Audio Power Amplifier PACKAGE INFORMATION E SMD9 Package PIN A1 A2 D A1 e b A e SYMBOL MIN MAX A 0.635 0.735 A1 0.209 0.249 A2 0.426 0.486 b 0.25 0.35 D 1.47 1.53 E 1.47 1.53 e China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 MILLIMETERS 0.50 BSC WWW.CRPOWTECH.COM Page14 PT5301 2 Watts Audio Power Amplifier PACKAGE INFORMATION MSOP8 Package b e c θ A2 D A SYMBOL MILLIMETERS INCHES MIN MAX MIN MAX A 0.820 1.100 0.032 0.043 A1 0.020 0.150 0.001 0.006 A2 0.750 0.950 0.030 0.037 b 0.250 0.380 0.010 0.015 c 0.090 0.230 0.004 0.009 D 2.900 3.100 0.114 0.122 e 0.650(BSC) 0.026(BSC) E 2.900 3.100 0.114 0.122 E1 4.750 5.050 0.187 0.199 L 0.400 0.800 0.016 0.031 θ 0° 6° 0° 6° China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page15 PT5301 2 Watts Audio Power Amplifier PACKAGE INFORMATION DFN8 Package China Resources Powtech (Shanghai) Limited PT5301_DS Rev EN_1.3 WWW.CRPOWTECH.COM Page16