LM4671ITLBD

LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 LM4671 Filterless High Efficiency 2.5W Switching Audio Amplifier Check for Samples: LM4671 FEATURES DESCRIPTION • • • • • • • The LM4671 is a single supply, high efficiency 2.5W switching audio amplifier. A low noise, filterless PWM architecture eliminates the output filter, reducing external component count, board area consumption, system cost, and simplifying design. 1 2 No Output Filter Required for Inductive Loads Externally Configurable Gain Very Fast Turn On Time: 17μs (typ) Minimum External Components "Click and pop" Suppression Circuitry Micro-Power Shutdown Mode Available in Space-Saving DSBGA Package APPLICATIONS • • • Mobile Phones PDAs Portable Electronic Devices KEY SPECIFICATIONS • • • • • • Efficiency @ 3.6V, 100mW into 8Ω Speaker: 80 % (typ) Efficiency @ 3.6V, 400mW into 8Ω Speaker: 88 % (typ) Efficiency @ 5V, 1W into 8Ω Speaker: 86 % (typ) Quiescent Current, 3.6V Supply: 2.8 mA (typ) Total Shutdown Power Supply Current: 0.01 µA (typ) Single Supply Range: 2.4 to 5.5 V The LM4671 is designed to meet the demands of mobile phones and other portable communication devices. Operating on a single 5V supply, it is capable of driving a 4Ω speaker load at a continuous average output of 2.1W with less than 1% THD+N. Its flexible power supply requirements allow operation from 2.4V to 5.5V. The LM4671 has high efficiency with speaker loads compared to a typical Class AB amplifier. With a 3V supply driving an 8Ω speaker, the IC's efficiency for a 100mW power level is 80%, reaching 88% at 400mW output power. The LM4671 features a low-power consumption shutdown mode. Shutdown may be enabled by driving the Shutdown pin to a logic low (GND). The gain of the LM4671 is externally configurable which allows independent gain control from multiple sources by summing the signals. Typical Application Figure 1. Typical Audio Amplifier Application Circuit 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2005–2013, Texas Instruments Incorporated LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com Connection Diagram GND IN+ A Vo1 VDD B PGND IN- C Vo2 1 2 SHUTDOWN 3 PVDD Figure 2. 9 Bump DSBGA Package Top View See Package Number YZR0009AAA These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 2 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 Absolute Maximum Ratings (1) (2) (3) Supply Voltage (1) 6.0V −65°C to +150°C Storage Temperature VDD + 0.3V ≥ V ≥ GND - 0.3V Voltage at Any Input Pin Power Dissipation (4) Internally Limited ESD Susceptibility, all other pins (5) 2.0kV ESD Susceptibility (6) 200V Junction Temperature (TJMAX) 150°C θJA (DSBGA) Thermal Resistance 220°C/W Soldering Information See AN-1112 "MicroSMD Wafers Level Chip Scale Package" (Literature Number SNVA009) (1) (2) (3) (4) (5) (6) All voltages are measured with respect to the ground pin, unless otherwise specified. 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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not specified for parameters where no limit is given, however, the typical value is a good indication of device performance. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. 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 LM4671, TJMAX = 150°C. The typical θJA is 220°C/W for the DSBGA package. Human body model, 100pF discharged through a 1.5kΩ resistor. Machine Model, 220pF–240pF discharged through all pins. Operating Ratings (1) (2) TMIN ≤ TA ≤ TMAX Temperature Range −40°C ≤ TA ≤ 85°C 2.4V ≤ VDD ≤ 5.5V Supply Voltage (1) (2) All voltages are measured with respect to the ground pin, unless otherwise specified. 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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not specified for parameters where no limit is given, however, the typical value is a good indication of device performance. Electrical Characteristics (1) (2) The following specifications apply for AV = 2V/V (RI = 150kΩ), RL = 15µH + 8Ω + 15µH unless otherwise specified. Limits apply for TA = 25°C. Symbol Parameter Conditions LM4671 Typical (3) Limit (4) (5) Units (Limits) |VOS| Differential Output Offset Voltage VI = 0V, AV = 2V/V, VDD = 2.4V to 5.0V 5 mV (max) PSRRGSM GSM Power Supply Rejection Ratio VDD = 2.4V to 5.0V 61 dB (min) CMRRGSM VDD = 2.4V to 5.0V GSM Common Mode Rejection Ratio VIC = VDD/2 to 0.5V, VIC = VDD/2 to VDD – 0.8V 68 dB (min) |IIH| Logic High Input Current VDD = 5.0V, VI = 5.5V 17 100 μA (max) |IIL| Logic Low Input Current VDD = 5.0V, VI = –0.3V 0.9 5 μA (max) (1) (2) (3) (4) (5) All voltages are measured with respect to the ground pin, unless otherwise specified. 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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not specified for parameters where no limit is given, however, the typical value is a good indication of device performance. Typical specifications are specified at 25°C and represent the parametric norm. Tested limits are specified to AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are specified by design, test, or statistical analysis. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 3 LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com Electrical Characteristics(1)(2) (continued) The following specifications apply for AV = 2V/V (RI = 150kΩ), RL = 15µH + 8Ω + 15µH unless otherwise specified. Limits apply for TA = 25°C. Symbol IDD Parameter Quiescent Power Supply Current Conditions LM4671 Typical (3) Limit (4) (5) Units (Limits) VIN = 0V, No Load, VDD = 5.0V 6.4 VIN = 0V, No Load, VDD = 3.6V 3.8 6.2 mA (max) mA VIN = 0V, No Load, VDD =2.4V 2.0 3.0 mA (max) VSHUTDOWN = 0V VDD = 2.4V to 5.0V 0.01 1 μA (max) ISD Shutdown Current VSDIH Shutdown voltage input high 1.2 1.4 V (min) VSDIL Shutdown voltage input low 1.1 0.4 V (max) ROSD Output Impedance 270kΩ/RI 330kΩ/RI V/V (min) V/V (max) AV Gain RSD Resistance from Shutdown Pin to GND PO Output Power VSHUTDOWN = 0.4V 100 300kΩ/RI kΩ 300 kΩ RL = 15μH + 4Ω + 15μH THD = 10% (max) f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V 2.5 1.3 520 W W mW RL = 15μH + 4Ω + 15μH THD = 1% (max) f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V 2.21 1.06 420 W W mW RL = 15μH + 8Ω + 15μH THD = 10% (max) f = 1kHz, 22kHz BW PO THD+N 4 Output Power Total Harmonic Distortion + Noise VDD = 5V 1.7 W VDD = 3.6V 870 mW VDD = 2.5V 425 mW RL = 15μH + 8Ω + 15μH THD = 1% (max) f = 1kHz, 22kHz BW VDD = 5V 1.19 VDD = 3.6V 700 VDD = 2.5V 350 mW VDD = 5V, PO = 0.1WRMS, f = 1kHz 0.09 % VDD = 3.6V, PO = 0.1WRMS, f = 1kHz 0.04 % VDD = 3.6V, PO = 0.1WRMS, f = 5kHz 0.12 % VDD = 3.6V, PO = 0.1WRMS, f = 10kHz 0.05 % Submit Documentation Feedback W 600 mW Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 Electrical Characteristics(1)(2) (continued) The following specifications apply for AV = 2V/V (RI = 150kΩ), RL = 15µH + 8Ω + 15µH unless otherwise specified. Limits apply for TA = 25°C. Symbol PSRR SNR εOUT Parameter Power Supply Rejection Ratio Conditions LM4671 Typical (3) Limit (4) (5) Units (Limits) VDD = 3.6V, 5V VRipple = 200mVPP Sine, fRipple = 217Hz Inputs to AC GND, CI = 2μF 61.8 dB VDD = 3.6V, 5V VRipple = 200mVPP Sine, fRipple = 1kHz Inputs to AC GND, CI = 2μF 59.8 dB VDD = 3.6V, 5V VRipple = 200mVPP Sine, fRipple = 10kHz Inputs to AC GND, CI = 2μF 48.7 dB VDD = 3.6V, 5V VRipple = 200mVPP Sine, fRipple = 217Hz fIN = 1kHz, PO = 10mWRMS 65.7 dB Signal to Noise Ratio VDD = 5V, PO = 1WRMS 93 dB 58 μVRMS Output Noise VDD = 3.6V, f = 20Hz – 20kHz Inputs to AC GND, CI = 2μF No Weighting VDD = 3.6V, Inputs to AC GND CI = 2μF, A Weighted 38 μVRMS 68.3 dB CMRR Common Mode Rejection Ratio VDD = 3.6V, VRipple = 1VPP Sine fRipple = 217Hz TWU Wake-up Time VDD = 3.6V TSD Shutdown Time 17 49 μs (max) 140 μs External Components Description (Figure 1) Components Functional Description 1. CS Supply bypass capacitor which provides power supply filtering. Refer to POWER SUPPLY BYPASSING for information concerning proper placement and selection of the supply bypass capacitor. 2. CI Input AC coupling capacitor which blocks the DC voltage at the amplifier's input terminals. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 5 LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics 6 THD+N vs Frequency VDD = 2.4V, RL = 15μH+4Ω+15μH, PO = 375mW, 22kHz BW THD+N vs Frequency VDD = 3.6V, RL = 15μH+4Ω+15μH, PO = 750mW, 22kHz BW Figure 3. Figure 4. THD+N vs Frequency VDD = 5V, RL = 15μH+4Ω+15μH, PO = 1.5mW, 22kHz BW THD+N vs Frequency VDD = 2.4V, RL = 15μH+8Ω+15μH, PO = 200mW, 22kHz BW Figure 5. Figure 6. THD+N vs Frequency VDD = 3.6V, RL = 15μH+8Ω+15μH, PO = 500mW, 22kHz BW THD+N vs Frequency VDD = 5V, RL = 15μH+8Ω+15μH, PO = 1W, 22kHz BW Figure 7. Figure 8. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 Typical Performance Characteristics (continued) THD+N vs Output Power VDD = 5V, RL = 15μH+4Ω+15μH, f = 1kHz, 22kHz BW THD+N vs Output Power VDD = 5V, RL = 15μH+8Ω+15μH, f = 1kHz, 22kHz BW Figure 9. Figure 10. CMRR vs Frequency VDD = 3.6V, RL = 15μH+8Ω+15μH, Vripple = 1Vp-p, 22kHz BW PSRR vs Frequency VDD = 3.6V, RL = 15μH+8Ω+15μH, Vripple = 200mVp-p, 22kHz BW Figure 11. Figure 12. Efficiency vs Output Power RL = 15μH+4Ω+15μH, f = 1kHz, 22kHz BW Efficiency vs Output Power RL = 15μH+8Ω+15μH, f = 1kHz, 22kHz BW Figure 13. Figure 14. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 7 LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) 8 Power Dissipation vs Output Power RL = 15μH+4Ω+15μH, f = 1kHz, 22kHz BW Power Dissipation vs Output Power RL = 15μH+8Ω+15μH, f = 1kHz, 22kHz BW Figure 15. Figure 16. Output Power vs Supply Voltage RL = 15μH+4Ω+15μH, VDD = 3.6V Output Power vs Supply Voltage RL = 15μH+8Ω+15μH, VDD = 3.6V Figure 17. Figure 18. Gain vs Supply Voltage Rin = 150kΩ Supply Current vs Supply Voltage RL = 15μH+8Ω+15μH Figure 19. Figure 20. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 Typical Performance Characteristics (continued) Shutdown Current vs Supply Voltage RL = 15μH+8Ω+15μH Figure 21. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 9 LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com APPLICATION INFORMATION GENERAL AMPLIFIER FUNCTION The LM4671 features a filterless modulation scheme. The differential outputs of the device switch at 300kHz from VDD to GND. When there is no input signal applied, the two outputs (VO1 and VO2) switch with a 50% duty cycle, with both outputs in phase. Because the outputs of the LM4671 are differential, the two signals cancel each other. This results in no net voltage across the speaker, thus there is no load current during an idle state, conserving power. With an input signal applied, the duty cycle (pulse width) of the LM4671 outputs changes. For increasing output voltages, the duty cycle of VO1 increases, while the duty cycle of VO2 decreases. For decreasing output voltages, the converse occurs, the duty cycle of VO2 increases while the duty cycle of VO1 decreases. The difference between the two pulse widths yields the differential output voltage. POWER DISSIPATION AND EFFICIENCY In general terms, efficiency is considered to be the ratio of useful work output divided by the total energy required to produce it with the difference being the power dissipated, typically, in the IC. The key here is “useful” work. For audio systems, the energy delivered in the audible bands is considered useful including the distortion products of the input signal. Sub-sonic (DC) and super-sonic components (>22kHz) are not useful. The difference between the power flowing from the power supply and the audio band power being transduced is dissipated in the LM4671 and in the transducer load. The amount of power dissipation in the LM4671 is very low. This is because the ON resistance of the switches used to form the output waveforms is typically less than 0.25Ω. This leaves only the transducer load as a potential "sink" for the small excess of input power over audio band output power. The LM4671 dissipates only a fraction of the excess power requiring no additional PCB area or copper plane to act as a heat sink. DIFFERENTIAL AMPLIFIER EXPLANATION As logic supply voltages continue to shrink, designers are increasingly turning to differential analog signal handling to preserve signal to noise ratios with restricted voltage swing. The LM4671 is a fully differential amplifier that features differential input and output stages. A differential amplifier amplifies the difference between the two input signals. Traditional audio power amplifiers have typically offered only single-ended inputs resulting in a 6dB reduction in signal to noise ratio relative to differential inputs. The LM4671 also offers the possibility of DC input coupling which eliminates the two external AC coupling, DC blocking capacitors. The LM4671 can be used, however, as a single ended input amplifier while still retaining its fully differential benefits. In fact, completely unrelated signals may be placed on the input pins. The LM4671 simply amplifies the difference between the signals. A major benefit of a differential amplifier is the improved common mode rejection ratio (CMRR) over single input amplifiers. The common-mode rejection characteristic of the differential amplifier reduces sensitivity to ground offset related noise injection, especially important in high noise applications. PCB LAYOUT CONSIDERATIONS As output power increases, interconnect resistance (PCB traces and wires) between the amplifier, load and power supply create a voltage drop. The voltage loss on the traces between the LM4671 and the load results is lower output power and decreased efficiency. Higher trace resistance between the supply and the LM4671 has the same effect as a poorly regulated supply, increase ripple on the supply line also reducing the peak output power. The effects of residual trace resistance increases as output current increases due to higher output power, decreased load impedance or both. To maintain the highest output voltage swing and corresponding peak output power, the PCB traces that connect the output pins to the load and the supply pins to the power supply should be as wide as possible to minimize trace resistance. The use of power and ground planes will give the best THD+N performance. While reducing trace resistance, the use of power planes also creates parasite capacitors that help to filter the power supply line. 10 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 The inductive nature of the transducer load can also result in overshoot on one or both edges, clamped by the parasitic diodes to GND and VDD in each case. From an EMI standpoint, this is an aggressive waveform that can radiate or conduct to other components in the system and cause interference. It is essential to keep the power and output traces short and well shielded if possible. Use of ground planes, beads, and micro-strip layout techniques are all useful in preventing unwanted interference. As the distance from the LM4671 and the speaker increase, the amount of EMI radiation will increase since the output wires or traces acting as antenna become more efficient with length. What is acceptable EMI is highly application specific. Ferrite chip inductors placed close to the LM4671 may be needed to reduce EMI radiation. The value of the ferrite chip is very application specific. POWER SUPPLY BYPASSING As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection ratio (PSRR). The capacitor (CS) location should be as close as possible to the LM4671. Typical applications employ a voltage regulator with a 10µF and a 0.1µF bypass capacitors that increase supply stability. These capacitors do not eliminate the need for bypassing on the supply pin of the LM4671. A 1µF tantalum capacitor is recommended. SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the LM4671 contains shutdown circuitry that reduces current draw to less than 0.01µA. The trigger point for shutdown is shown as a typical value in the Electrical Characteristics Tables and in the Shutdown Hysteresis Voltage graphs found in the Typical Performance Characteristics section. It is best to switch between ground and supply for minimum current usage while in the shutdown state. While the LM4671 may be disabled with shutdown voltages in between ground and supply, the idle current will be greater than the typical 0.01µA value. The LM4671 has an internal resistor connected between GND and Shutdown pins. The purpose of this resistor is to eliminate any unwanted state changes when the Shutdown pin is floating. The LM4671 will enter the shutdown state when the Shutdown pin is left floating or if not floating, when the shutdown voltage has crossed the threshold. To minimize the supply current while in the shutdown state, the Shutdown pin should be driven to GND or left floating. If the Shutdown pin is not driven to GND, the amount of additional resistor current due to the internal shutdown resistor can be found by Equation (1) below. (VSD - GND) / 60kΩ (1) With only a 0.5V difference, an additional 8.3µA of current will be drawn while in the shutdown state. PROPER SELECTION OF EXTERNAL COMPONENTS The gain of the LM4671 is set by the external resistors, Ri in Figure 1, The Gain is given by Equation (2) below. Best THD+N performance is achieved with a gain of 2V/V (6dB). AV = 2 * 150 kΩ / Ri (V/V) (2) It is recommended that resistors with 1% tolerance or better be used to set the gain of the LM4671. The Ri resistors should be placed close to the input pins of the LM4671. Keeping the input traces close to each other and of the same length in a high noise environment will aid in noise rejection due to the good CMRR of the LM4671. Noise coupled onto input traces which are physically close to each other will be common mode and easily rejected by the LM4671. Input capacitors may be needed for some applications or when the source is single-ended (see Figures 3 and 5). Input capacitors are needed to block any DC voltage at the source so that the DC voltage seen between the input terminals of the LM4671 is 0V. Input capacitors create a high-pass filter with the input resistors, Ri. The –3dB point of the high-pass filter is found using Equation (3) below. fC = 1 / (2πRi Ci ) (Hz) (3) Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 11 LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com The input capacitors may also be used to remove low audio frequencies. Small speakers cannot reproduce low bass frequencies so filtering may be desired. When the LM4671 is using a single-ended source, power supply noise on the ground is seen as an input signal by the +IN input pin that is capacitor coupled to ground (see Figures 5 -7). Setting the high-pass filter point above the power supply noise frequencies, 217Hz in a GSM phone, for example, will filter out this noise so it is not amplified and heard on the output. Capacitors with a tolerance of 10% or better are recommended for impedance matching. DIFFERENTIAL CIRCUIT CONFIGURATIONS The LM4671 can be used in many different circuit configurations. The simplest and best performing is the DC coupled, differential input configuration shown in Figure 22. Equation (2) above is used to determine the value of the Ri resistors for a desired gain. Input capacitors can be used in a differential configuration as shown in Figure 23. Equation (3) above is used to determine the value of the Ci capacitors for a desired frequency response due to the high-pass filter created by Ci and Ri. Equation (2) above is used to determine the value of the Ri resistors for a desired gain The LM4671 can be used to amplify more than one audio source. Figure 24 shows a dual differential input configuration. The gain for each input can be independently set for maximum design flexibility using the Ri resistors for each input and Equation (2). Input capacitors can be used with one or more sources as well to have different frequency responses depending on the source or if a DC voltage needs to be blocked from a source. SINGLE-ENDED CIRCUIT CONFIGURATIONS The LM4671 can also be used with single-ended sources but input capacitors will be needed to block any DC at the input terminals. Figure 25 shows the typical single-ended application configuration. The equations for Gain, Equation (2), and frequency response, Equation (3), hold for the single-ended configuration as shown in Figure 25. When using more than one single-ended source as shown in Figure 26, the impedance seen from each input terminal should be equal. To find the correct values for Ci3 and Ri3 connected to the +IN input pin the equivalent impedance of all the single-ended sources are calculated. The single-ended sources are in parallel to each other. The equivalent capacitor and resistor, Ci3 and Ri3, are found by calculating the parallel combination of all Civalues and then all Ri values. Equations (4) and (5) below are for any number of single-ended sources. Ci3 = Ci1 + Ci2 + Cin ... (μF) (4) Ri3 = 1 / (1/Ri1 + 1/Ri2 + 1/Rin ...) (Ω) (5) The LM4671 may also use a combination of single-ended and differential sources. A typical application with one single-ended source and one differential source is shown in Figure 27. Using the principle of superposition, the external component values can be determined with the above equations corresponding to the configuration. 12 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 Figure 22. Differential input configuration Figure 23. Differential input configuration with input capacitors Figure 24. Dual differential input configuration Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 13 LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com Figure 25. Single-ended input configuration Figure 26. Dual single-ended input configuration 14 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 Figure 27. Dual input with a single-ended input and a differential input REFERENCE DESIGN BOARD SCHEMATIC Figure 28. Reference Design Board Schematic In addition to the minimal parts required for the application circuit, a measurement filter is provided on the evaluation circuit board so that conventional audio measurements can be conveniently made without additional equipment. This is a balanced input, grounded differential output low pass filter with a 3dB frequency of approximately 35kHz and an on board termination resistor of 300Ω (see Figure 28). Note that the capacitive load elements are returned to ground. This is not optimal for common mode rejection purposes, but due to the independent pulse format at each output there is a significant amount of high frequency common mode component on the outputs. The grounded capacitive filter elements attenuate this component at the board to reduce the high frequency CMRR requirement placed on the analysis instruments. Even with the grounded filter the audio signal is still differential, necessitating a differential input on any analysis instrument connected to it. Most lab instruments that feature BNC connectors on their inputs are NOT differential responding because the ring of the BNC is usually grounded. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 15 LM4671 SNAS258D – MARCH 2005 – REVISED MAY 2013 www.ti.com The commonly used Audio Precision analyzer is differential, but its ability to accurately reject high frequency signals is questionable necessitating the on board measurement filter. When in doubt or when the signal needs to be single-ended, use an audio signal transformer to convert the differential output to a single ended output. Depending on the audio transformer's characteristics, there may be some attenuation of the audio signal which needs to be taken into account for correct measurement of performance. Measurements made at the output of the measurement filter suffer attenuation relative to the primary, unfiltered outputs even at audio frequencies. This is due to the resistance of the inductors interacting with the termination resistor (300Ω) and is typically about -0.25dB (3%). In other words, the voltage levels (and corresponding power levels) indicated through the measurement filter are slightly lower than those that actually occur at the load placed on the unfiltered outputs. This small loss in the filter for measurement gives a lower output power reading than what is really occurring on the unfiltered outputs and its load. LM4671 DSBGA BOARD ARTWORK Figure 29. Composite View Figure 30. Silk Screen Figure 31. Top Layer 16 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 LM4671 www.ti.com SNAS258D – MARCH 2005 – REVISED MAY 2013 Figure 32. Internal Layer 1, GND Figure 33. Internal Layer 2, GND Figure 34. Bottom Layer Revision History Rev Date 1.0 03/16/05 Initial release. Description 1.01 12/17/07 Some text edits. 1.02 03/03/08 Edited the SHUTDOWN FUNCTION section (under Application Information). D 05/02/13 Changed layout of National Data Sheet to TI format Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM4671 17 PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LM4671ITL/NOPB ACTIVE DSBGA YZR 9 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -40 to 85 G E7 LM4671ITLX/NOPB ACTIVE DSBGA YZR 9 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -40 to 85 G E7 (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of