LM4879IBL

LM4879 1.1 Watt Audio Power Amplifier October 2004 LM4879 1.1 Watt Audio Power Amplifier General Description The LM4879 is an audio power amplifier primarily designed for demanding applications in mobile phones and other portable communication device applications. It is capable of delivering 1.1 watt of continuous average power to an 8Ω BTL load with less than 1% distortion (THD+N) from a 5VDC power supply. Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4879 does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for lower-power portable applications where minimal space and power consumption are primary requirements. The LM4879 features a low-power consumption global shutdown mode, which is achieved by driving the shutdown pin with logic low. Additionally, the LM4879 features an internal thermal shutdown protection mechanism. The LM4879 contains advanced pop & click circuitry which eliminates noises which would otherwise occur during turn-on and turn-off transitions. The LM4879 is unity-gain stable and can be configured by external gain-setting resistors. Key Specifications j PSRR: 5V, 3V @ 217Hz j Power Output at 5V & 1% THD+N j Power Output at 3V & 1% THD+N j Shutdown Current 62dB (typ) 1.1W (typ) 350mW (typ) 0.1µA (typ) Features n No output coupling capacitors, snubber networks or bootstrap capacitors required n Unity gain stable n Ultra low current shutdown mode n Fast turn on: 80ms (typ), 110ms (max) with 1.0µF capacitor n BTL output can drive capacitive loads up to 100pF n Advanced pop & click circuitry eliminates noises during turn-on and turn-off transitions n 2.2V - 5.0V operation n Available in space-saving µSMD, LLP, and MSOP packages Applications n Mobile Phones n PDAs n Portable electronic devices Typical Application 20024301 FIGURE 1. Typical Audio Amplifier Application Circuit Boomer ® is a registered trademark of National Semiconductor Corporation. © 2004 National Semiconductor Corporation DS200243 www.national.com LM4879 Connection Diagrams 8 Bump micro SMD 8 Bump micro SMD Marking 20024383 20024382 Top View Order Number LM4879IBP, LM4879IBPX See NS Package Number BPA08DDB Mini Small Outline (MSOP) Package Top View X - Date Code T - Die Traceability G - Boomer Family N- LM4879IBP MSOP Marking 20024385 20024384 Top View G - Boomer Family 79-LM4879MM Top View NC = No Connect Order Number LM4879MM See NS Package Number MUB10A 9 Bump micro SMD 9 Bump micro SMD Marking 20024387 Top View X - Date Code T - Die Traceability G - Boomer Family 79 - LM4879IBL 20024386 Top View Order Number LM4879IBL, LM4879IBLX See NS package Number BLA09AAB www.national.com 2 LM4879 Connection Diagrams (Continued) 9 Bump micro SMD Marking 9 Bump micro SMD 200243B3 Top View X - Date Code T - Die Traceability G - Boomer Family B3 - LM4879ITL 20024386 Top View Order Number LM4879ITL, LM4879ITLX See NS package Number TLA09AAA Leadless Leadframe Package (LLP) LLP Marking 200243B6 20024302 Top View Order Number LM4879SD See NS Package Number SDC08A Top View N - NS Logo U - Fab Code Z - Assembly Plant Code XY - Date Code TT - Die Traceability L4879SD - LM4879SD 3 www.national.com LM4879 Absolute Maximum Ratings (Note 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (Note 9) Storage Temperature Input Voltage Power Dissipation (Note 3) ESD Susceptibility (Note 4) ESD Susceptibility (Note 5) Junction Temperature Thermal Resistance 6.0V −65˚C to +150˚C −0.3V to VDD +0.3V Internally Limited 2000V 200V 150˚C θJA (BPA08DDB) θJA (SDC08A) θJA (TLA09AAA) θJA (BLA09AAB) θJC (MUB10A) θJA (MUB10A) 220˚C/W (Note 10) 64˚C/W (Note 12) 180˚C/W (Note 10) 180˚C/W (Note 10) 56˚C/W 190˚C/W Operating Ratings Temperature Range TMIN ≤ TA ≤ TMAX Supply Voltage −40˚C ≤ TA ≤ 85˚C 2.2V ≤ VDD ≤ 5.5V Electrical Characteristics VDD = 5V (Notes 1, 2) The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for TA = 25˚C. LM4879 Symbol IDD ISD VOS Po THD+N Parameter Quiescent Power Supply Current Shutdown Current Output Offset Voltage Output Power Total Harmonic Distortion+Noise THD+N = 1% (max); f = 1kHz Po = 0.4Wrms; f = 1kHz Vripple = 200mVsine p-p, CB = 1.0µF Input terminated with 10Ω to ground Conditions VIN = 0V, 8Ω BTL Vshutdown = GND Typical (Note 6) 5 0.1 5 1.1 0.1 68 (f = 1kHz) 62 (f = 217Hz) Limit (Notes 7, 8) 10 2.0 40 0.9 Units (Limits) mA (max) µA (max) mV (max) W (min) % PSRR Power Supply Rejection Ratio 55 dB (min) VSDIH VSDIL TWU Shutdown High Input Voltage Shutdown Low Input Voltage Wake-up Time CB = 1.0µF A-Weighted; Measured across 8Ω BTL Input terminated with 10Ω to ground 80 1.4 0.4 110 V (min) V (max) ms (max) NOUT Output Noise 26 µVRMS Electrical Characteristics VDD = 3.0V (Notes 1, 2) The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for TA = 25˚C. LM4879 Symbol IDD ISD VOS Po THD+N Parameter Quiescent Power Supply Current Shutdown Current Output Offset Voltage Output Power Total Harmonic Distortion+Noise THD+N = 1% (max); f = 1kHz Po = 0.15Wrms; f = 1kHz Vripple = 200mVsine p-p, CB = 1.0µF Input terminated with 10Ω to ground Conditions VIN = 0V, 8Ω BTL Vshutdown = GND Typical (Note 6) 4.5 0.1 5 350 0.1 68 (f = 1kHz) 62 (f = 217Hz) Limit (Notes 7, 8) 9 2.0 40 320 Units (Limits) mA (max) µA (max) mV (max) mW % PSRR Power Supply Rejection Ratio 55 dB (min) VSDIH VSDIL TWU Shutdown High Input Voltage Shutdown Low Input Voltage Wake-up Time CB = 1.0µF 80 1.4 0.4 110 V (min) V (max) ms (max) www.national.com 4 LM4879 Electrical Characteristics VDD = 3.0V (Notes 1, 2) The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for TA = 25˚C. (Continued) LM4879 Symbol Parameter Conditions A-Weighted; Measured across 8Ω BTL Input terminated with 10Ω to ground Typical (Note 6) Limit (Notes 7, 8) Units (Limits) NOUT Output Noise 26 µVRMS Electrical Characteristics VDD = 2.6V (Notes 1, 2) The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for TA = 25˚C. LM4879 Symbol IDD ISD VOS Po THD+N Parameter Quiescent Power Supply Current Shutdown Current Output Offset Voltage THD+N = 1% (max); f = 1kHz Output Power Total Harmonic Distortion+Noise RL = 8Ω RL = 4Ω Po = 0.1Wrms; f = 1kHz Vripple = 200mVsine p-p, CB = 1.0µF Input terminated with 10Ω to ground 250 350 0.1 55 (f = 1kHz) 55 (f = 217Hz) mW % Conditions VIN = 0V, 8Ω BTL Vshutdown = GND Typical (Note 6) 3.5 0.1 5 Limit (Notes 7, 8) Units (Limits) mA µA mV PSRR Power Supply Rejection Ratio dB Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified. Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. 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 3: 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 LM4879, see power derating curves for additional information. Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor. Note 5: Machine Model, 220pF–240pF discharged through all pins. Note 6: Typicals are measured at 25˚C and represent the parametric norm. Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 8: For micro SMD only, shutdown current is measured in a Normal Room Environment. Exposure to direct sunlight will increase ISD by a maximum of 2µA. Note 9: If the product is in shutdown mode, and VDD exceeds 6V (to a max of 8V VDD), then most of the excess current will flow through the ESD protection circuits. If the source impedance limits the current to a max of 10ma, then the part will be protected. If the part is enabled when VDD is above 6V, circuit performance will be curtailed or the part may be permanently damaged. Note 10: All bumps have the same thermal resistance and contribute equally when used to lower thermal resistance. Note 11: Maximum power dissipation (PDMAX) in the device occurs at an output power level significantly below full output power. PDMAX can be calculated using Equation 1 shown in the Application section. It may also be obtained from the power dissipation graphs. Note 12: The stated θJA is achieved when the LLP package’s DAP is soldered to a 4in2 copper heatsink plain. 5 www.national.com LM4879 External Components Description (Figure 1) Components 1. 2. Ri Ci Functional Description Inverting input resistance which sets the closed-loop gain in conjunction with Rf. This resistor also forms a high pass filter with Ci at fC= 1/(2π RiCi). Input coupling capacitor which blocks the DC voltage at the amplifiers input terminals. Also creates a highpass filter with Ri at fc = 1/(2π RiCi). Refer to the section, Proper Selection of External Components, for an explanation of how to determine the value of Ci. Feedback resistance which sets the closed-loop gain in conjunction with Ri. Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply Bypassing section for information concerning proper placement and selection of the supply bypass capacitor. Bypass pin capacitor which provides half-supply filtering. Refer to the section, Proper Selection of External Components, for information concerning proper placement and selection of CB. 3. 4. 5. Rf CS CB www.national.com 6 LM4879 Typical Performance Characteristics THD+N vs Frequency VDD = 5V, RL = 8Ω, PWR = 250mW THD+N vs Frequency VDD = 3V, RL = 8Ω, PWR = 150mW 20024337 20024338 THD+N vs Frequency VDD = 2.6V, RL = 8Ω, PWR = 100mW THD+N vs Frequency VDD = 2.6V, RL = 4Ω, PWR = 100mW 20024339 20024340 THD+N vs Power Out VDD = 5V, RL = 8Ω, f = 1kHz THD+N vs Power Out VDD = 3V, RL = 8Ω, f = 1kHz 20024341 20024342 7 www.national.com LM4879 Typical Performance Characteristics THD+N vs Power Out VDD = 2.6V, RL = 8Ω, f = 1kHz (Continued) THD+N vs Power Out VDD = 2.6V, RL = 4Ω, f = 1kHz 20024343 20024344 Power Supply Rejection Ratio VDD = 5V Power Supply Rejection Ratio VDD = 3V 20024345 20024373 Power Supply Rejection Ratio VDD = 2.6V Power Dissipation vs Output Power VDD = 5V 20024346 20024347 www.national.com 8 LM4879 Typical Performance Characteristics Power Dissipation vs Output Power VDD = 3V (Continued) Power Dissipation vs Output Power VDD = 2.6V 20024349 20024348 Power Dissipation vs Output Power (LLP Package) VDD = 5V Power Derating - MSOP PDMAX = 670mW VDD = 5V, RL = 8Ω 20024313 20024379 Power Derating - 8 Bump µSMD PDMAX = 670mW VDD = 5V, RL = 8Ω Power Derating - 9 Bump µSMD PDMAX = 670mW VDD = 5V, RL = 8Ω 20024380 20024381 9 www.national.com LM4879 Typical Performance Characteristics Power Derating - LLP PDMAX = 670mV VDD = 5V, RL = 8 (Continued) Output Power vs Supply Voltage 20024351 200243B4 Output Power vs Supply Voltage Output Power vs Load Resistance 20024350 20024374 Clipping (Dropout) Voltage vs Supply Voltage Supply Current Shutdown Voltage 20024352 20024375 www.national.com 10 LM4879 Typical Performance Characteristics Shutdown Hysterisis Voltage VDD = 5V (Continued) Shutdown Hysterisis Voltage VDD = 3V 20024376 20024377 Shutdown Hysterisis Voltage VDD = 2.6V Open Loop Frequency Response 20024378 20024354 Frequency Response vs Input Capacitor Size 20024356 11 www.national.com LM4879 Application Information BRIDGE CONFIGURATION EXPLANATION As shown in Figure 1, the LM4879 has two operational amplifiers internally, allowing for a few different amplifier configurations. 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 20 kΩ resistors. Figure 1 shows 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 LM4879, 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 LM4879 has two operational amplifiers in one package, 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. (1) PDMAX = 4*(VDD)2/(2π2RL) 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 additional copper foil, the thermal resistance of the application can be reduced from a free air value of 150˚C/W, resulting in higher PDMAX. Additional copper foil can be added to any of the leads connected to the LM4879. It is especially effective when connected to VDD, GND, and the output pins. Refer to the application information on the LM4879 reference design board for an example of good heat sinking. If TJMAX still exceeds 150˚C, then additional changes must be made. These changes can include rewww.national.com 12 duced 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 10 µF 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 LM4879. 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 LM4879 contains a shutdown pin to externally turn off the amplifier’s bias circuitry. This shutdown feature turns the amplifier off when a logic low is placed on the shutdown pin. By switching the shutdown pin to ground, the LM4879 supply current draw will be minimized in idle mode. While the device will be disabled with shutdown pin voltages less than 0.4VDC, the idle current may be greater than the typical value of 0.1µA. (Idle current is measured with the shutdown pin tied to ground). In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry to provide a quick, smooth transition into shutdown. Another solution is to use a single-pole, single-throw switch in conjunction with an external pull-up resistor. When the switch is closed, the shutdown pin is connected to ground which disables the amplifier. If the switch is open, then the external pull-up resistor to VDD will enable the LM4879. 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 LM4879 is tolerant of external component combinations, consideration to component values must be used to maximize overall system quality. The LM4879 is unity-gain stable which gives the designer maximum system flexibility. The LM4879 should be used in low gain configurations to minimize THD+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 1 Vrms 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 closedloop bandwidth of the amplifier. To a large extent, the bandwidth is dictated by the choice of external components shown in Figure 1. 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. LM4879 Application Information Selection Of Input Capacitor Size (Continued) 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 100 Hz to 150 Hz. 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, Ci. 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 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 LM4879 turns on. The slower the LM4879’s outputs ramp to their quiescent DC voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing CB equal to 1.0 µF along with a small value of Ci (in the range of 0.1 µF to 0.39 µF), should produce a virtually clickless and popless shutdown function. While the device will function properly, (no oscillations or motorboating), with CB equal to 0.1 µF, the device will be much more susceptible to turn-on clicks and pops. Thus, a value of CB equal to 1.0 µF 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 1 Wrms 8Ω 1 Vrms 20 kΩ 100 Hz–20 kHz ± 0.25 dB formance Characteristics section, the supply rail can be easily found. A second way to determine the minimum supply rail is to calculate the required Vopeak using Equation 2 and add the output voltage. Using this method, the minimum supply voltage would be (Vopeak + (VODTOP + VODBOT)), where VODBOT and VODTOP are extrapolated from the Dropout Voltage vs Supply Voltage curve in the Typical Performance Characteristics section. (2) 5V is a standard voltage, in most applications, chosen for the supply rail. Extra supply voltage creates headroom that allows the LM4879 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 3. A designer must first determine the minimum supply rail to obtain the specified output power. By extrapolating from the Output Power vs Supply Voltage graphs in the Typical Per- (3) AVD = (Rf/Ri) 2 From Equation 3, the minimum AVD is 2.83; use AVD = 3. Since the desired input impedance was 20 kΩ, and with a AVD of 3, a ratio of 1.5:1 of Rf to Ri results in an allocation of Ri = 20 kΩ and Rf = 30 kΩ. The final design step is to address the bandwidth requirements which must be stated as a pair of −3 dB frequency points. Five times away from a −3 dB point is 0.17 dB down from passband response which is better than the required ± 0.25 dB specified. fL = 100 Hz/5 = 20 Hz fH = 20 kHz * 5 = 100 kHz As stated in the External Components section, Ri in conjunction with Ci create a highpass filter. Ci ≥ 1/(2π*20 kΩ*20 Hz) = 0.397 µF; use 0.39 µF The high frequency pole is determined by the product of the desired frequency pole, fH, and the differential gain, AVD. With a AVD = 3 and fH = 100 kHz, the resulting GBWP = 300 kHz which is much smaller than the LM4879 GBWP of 10 MHz. This figure displays that if a designer has a need to design an amplifier with a higher differential gain, the LM4879 can still be used without running into bandwidth limitations. 13 www.national.com LM4879 Application Information (Continued) 20024388 FIGURE 2. HIGHER GAIN AUDIO AMPLIFIER nates possible high frequency oscillations. Care should be taken when calculating the -3dB frequency in that an incorrect combination of R3 and C4 will cause rolloff before 20kHz. A typical combination of feedback resistor and capacitor that will not produce audio band high frequency rolloff is R3 = 20kΩ and C4 = 25pf. These components result in a -3dB point of approximately 320 kHz. The LM4879 is unity-gain stable and requires no external components besides gain-setting resistors, an input coupling capacitor, and proper supply bypassing in the typical application. However, if a closed-loop differential gain of greater than 10 is required, a feedback capacitor (C4) may be needed as shown in Figure 2 to bandwidth limit the amplifier. This feedback capacitor creates a low pass filter that elimi- www.national.com 14 LM4879 Application Information (Continued) 20024389 FIGURE 3. DIFFERENTIAL AMPLIFIER CONFIGURATION FOR LM4879 20024390 FIGURE 4. REFERENCE DESIGN BOARD and LAYOUT - micro SMD 15 www.national.com LM4879 Application Information (Continued) 20024368 FIGURE 5. REFERENCE DESIGN BOARD and PCB LAYOUT GUIDELINES - MSOP & SO Boards www.national.com 16 LM4879 Application Information LM4879 micro SMD BOARD ARTWORK Silk Screen (Continued) Top Layer 20024357 20024358 Bottom Layer Inner Layer Ground 20024359 20024360 Inner Layer VDD 20024361 17 www.national.com LM4879 Application Information Silk Screen (Continued) LM4879 MSOP DEMO BOARD ARTWORK Top Layer 20024365 20024366 Bottom Layer 20024367 TABLE 1. Mono LM4879 Reference Design Boards Bill of Material for all 3 Demo Boards Item 1 10 20 21 25 30 35 Part Number Part Description Qty 1 1 1 1 1 3 U1 C1 C2 C3 R1, R2, R3 J1, J2 Ref Designator 551011208-001 LM4879 Mono Reference Design Board 482911183-001 LM4879 Audio AMP 151911207-001 Tant Cap 1uF 16V 10 151911207-002 Cer Cap 0.39uF 50V Z5U 20% 1210 152911207-001 Tant Cap 1.0uF 16V 10 472911207-001 Res 20K Ohm 1/10W 5 210007039-002 Jumper Header Vertical Mount 2X1 0.100 2 www.national.com 18 LM4879 Application Information LM4879 LLP DEMO BOARD ARTWORK Silk Screen (Continued) Top Layer 200243C2 200243C0 Bottom Layer 200243C1 19 www.national.com LM4879 Application Information PCB LAYOUT GUIDELINES (Continued) Single-Point Power / Ground Connections The analog power traces should be connected to the digital traces through a single point (link). A "Pi-filter" can be helpful in minimizing high frequency noise coupling between the analog and digital sections. It is further recommended to put digital and analog power traces over the corresponding digital and analog ground traces to minimize noise coupling. Placement of Digital and Analog Components All digital components and high-speed digital signals traces should be located as far away as possible from analog components and circuit traces. Avoiding Typical Design / Layout Problems Avoid ground loops or running digital and analog traces parallel to each other (side-by-side) on the same PCB layer. When traces must cross over each other do it at 90 degrees. Running digital and analog traces at 90 degrees to each other from the top to the bottom side as much as possible will minimize capacitive noise coupling and cross talk. This section provides practical guidelines for mixed signal PCB layout that involves various digital/analog power and ground traces. Designers should note that these are only "rule-of-thumb" recommendations and the actual results will depend heavily on the final layout. General Mixed Signal Layout Recommendation Power and Ground Circuits For 2 layer mixed signal design, it is important to isolate the digital power and ground trace paths from the analog power and ground trace paths. Star trace routing techniques (bringing individual traces back to a central point rather than daisy chaining traces together in a serial manner) can have a major impact on low level signal performance. Star trace routing refers to using individual traces to feed power and ground to each circuit or even device. This technique will take require a greater amount of design time but will not increase the final price of the board. The only extra parts required may be some jumpers. www.national.com 20 LM4879 Physical Dimensions inches (millimeters) unless otherwise noted Note: Unless otherwise specified. 1. Epoxy coating. 2. 63Sn/37Pb eutectic bump. 3. Recommend non-solder mask defined landing pad. 4. Pin 1 is established by lower left corner with respect to text orientation pins are numbered counterclockwise. 5. Reference JEDEC registration MO-211, variation BC. 8-Bump micro SMD Order Number LM4879IBP, LM4879IBPX NS Package Number BPA08DDB X1 = 1.361 ± 0.03 X2 = 1.361 ± 0.03 X3 = 0.850 ± 0.10 21 www.national.com LM4879 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Note: Unless otherwise specified. 1. Epoxy coating. 2. 63Sn/37Pb eutectic bump. 3. Recommend non-solder mask defined landing pad. 4. Pin 1 is established by lower left corner with respect to text orientation pins are numbered counterclockwise. 5. Reference JEDEC registration MO-211, variation BC. 9-Bump micro SMD Order Number LM4879IBL, LM4879IBLX NS Package Number BLA09AAB X1 = 1.514 ± 0.03 X2 = 1.514 ± 0.03 X3 = 0.945 ± 0.10 www.national.com 22 LM4879 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) LLP Order Number LM4879SD NS Package Number SDC08A 23 www.national.com LM4879 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 9-Bump micro SMD Order Number LM4879ITL LM4879ITLX NS Package Number TLA09AAA X1 = 1.514 ± 0.03 X2 = 1.514 ± 0.03 X3 = 0.60 ± 0.075 MSOP Order Number LM4879MM NS Package Number MUB10A www.national.com 24 LM4879 1.1 Watt Audio Power Amplifier Notes National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.