LM4670SD/NOPB

LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 LM4670 Boomer™ Audio Power Amplifier Series Filterless High Efficiency 3W Switching Audio Amplifier Check for Samples: LM4670 FEATURES DESCRIPTION • • • • • • • • The LM4670 is a fully integrated single-supply high efficiency switching audio amplifier. It features an innovative modulator that eliminates the LC output filter used with typical switching amplifiers. Eliminating the output filter reduces external component count, simplifies circuit design, and reduces board area. The LM4670 processes analog inputs with a delta-sigma modulation technique that lowers output noise and THD when compared to conventional pulse width modulators. 1 23 No Output Filter Required for Inductive Loads Externally Configurable Gain Very Fast Turn on Time: 1.35ms (Typ) Minimum External Components "Click and Pop" Suppression Circuitry Micro-Power Shutdown Mode Short Circuit Protection Available in Space-Saving DSBGA and WSON Packages APPLICATIONS • • • Mobile Phones PDAs Portable Electronic Devices KEY SPECIFICATIONS • • • • • • Efficiency at 3.6V, 100mW into 8Ω Speaker, 77% (Typ) Efficiency at 3.6V, 600mW into 8Ω Speaker, 88% (Typ) Efficiency at 5V, 1W into 8Ω Speaker, 87% (Typ) Quiescent Current, 3.6V Supply, 4.8mA (Typ) Total Shutdown Power Supply Current, 0.01µA (Typ) Single Supply Range, 2.4 to 5.5V The LM4670 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 2.3W with less than 1% THD+N. Its flexible power supply requirements allow operation from 2.4V to 5.5V. The LM4670 has high efficiency with speaker loads compared to a typical Class AB amplifier. With a 3.6V supply driving an 8Ω speaker, the IC's efficiency for a 100mW power level is 77%, reaching 88% at 600mW output power. The LM4670 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 LM4670 is externally configurable which allows independent gain control from multiple sources by summing the signals. 1 2 3 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. Boomer is a trademark of Texas Instruments. All other 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 © 2004–2013, Texas Instruments Incorporated LM4670 SNAS240C – DECEMBER 2004 – REVISED MAY 2013 www.ti.com Typical Application Figure 1. Typical Audio Amplifier Application Circuit Connection Diagram GND IN+ A Vo1 VDD B GND IN- C Vo2 1 2 SHUTDOWN 3 PVDD Figure 2. 9 Bump DSBGA Package Top View See Package Number YZR0009 Figure 3. WSON Package Top View See Package Number NGQ0008A 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 © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 Absolute Maximum Ratings (1) (2) 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 (3) Internally Limited (4) 2.0kV ESD Susceptibility ESD Susceptibility (5) 200V Junction Temperature (TJMAX) Thermal Resistance 150°C θJA (DSBGA) 220°C/W θJA (WSON) 73°C/W Soldering Information See AN-1112 (SNVA009) "DSBGA Wafers Level Chip Scale Package." (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 ensured for parameters where no limit is given, however, the typical value is a good indication of device performance. 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 LM4670, TJMAX = 150°C. The typical θJA is 220°C/W for the DSBGA package and 64°C/W for the WSON package. Human body model, 100pF discharged through a 1.5kΩ resistor. Machine Model, 220pF – 240pF discharged through all pins. Operating Ratings (1) (2) Temperature Range (1) (2) (3) TMIN ≤ TA ≤ TMAX −40°C ≤ TA ≤ 85°C (3) 2.4V ≤ VDD ≤ 5.5V Supply Voltage 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 ensured for parameters where no limit is given, however, the typical value is a good indication of device performance. The maximum operating voltage for the LM4670 in the SDA (WSON) package when driving 4Ω loads to greater than 10% THD+N is 5.0V. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 3 LM4670 SNAS240C – DECEMBER 2004 – REVISED MAY 2013 www.ti.com 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 LM4670 Typical (3) Limit (4) (5) Units (Limits) 25 mV (max) |VOS| Differential Output Offset Voltage VI = 0V, AV = 2V/V, VDD = 2.4V to 5.0V PSRRGSM GSM Power Supply Rejection Ratio VDD = 2.4V to 5.0V, Input Referred 64 dB CMRRGSM GSM Common Mode Rejection Ratio VDD = 2.4V to 5.0V VIC = VDD/2 to 0.5V, VIC = VDD/2 to VDD – 0.8V, Input Referred 80 dB |IIH| Logic High Input Current VDD = 5.0V, VI = 5.8V 20 100 |IIL| Logic Low Input Current VDD = 5.0V, VI = –0.3V 1 5 μA (max) VIN = 0V, No Load, VDD = 5.0V 7.0 10 mA (max) VIN = 0V, No Load, VDD = 3.6V 4.8 VIN = 0V, No Load, VDD = 2.4V 3.8 5 mA (max) VSHUTDOWN = 0V VDD = 2.4V to 5.0V 0.01 1 μA (max) IDD Quiescent Power Supply Current μA (max) mA ISD Shutdown Current (6) VSDIH Shutdown voltage input high 1.0 1.4 V (min) VSDIL Shutdown voltage input low 0.8 0.4 V (max) ROSD Output Impedance AV Gain RSD Resistance from Shutdown Pin to GND PO (1) (2) (3) (4) (5) (6) (7) (8) 4 Output Power (7) (8) VSHUTDOWN = 0.4V >100 300kΩ/RI kΩ 270kΩ/RI 330kΩ/RI V/V (min) V/V (max) 300 kΩ RL = 15μH + 4Ω + 15μH, THD = 10% (max) f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V 3.0 1.5 675 W W mW RL = 15μH + 4Ω + 15μH, THD+N = 1% (max) f = 1kHz, 22kHz BW VDD = 5V, VDD = 3.6V, VDD = 2.5V, 2.3 1.2 550 W W mW 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 ensured 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 Texas Instruments' AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are ensured by design, test, or statistical analysis. Shutdown current is measured in a normal room environment. Exposure to direct sunlight will increase ISD by a maximum of 2µA. The Shutdown pin should be driven as close as possible to GND for minimal shutdown current. See Application Information under SHUTDOWN FUNCTION for more information. Typical output power numbers are for the LM4670 in the ITL (DSBGA) package. In the WSON (SDA) package, the output power will be lower due to higher resistance seen from the IC output pad to PCB trace. The difference increases with lower impedance loads. The maximum operating voltage for the LM4670 in the SDA (WSON) package when driving 4Ω loads to greater than 10% THD+N is 5.0V. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – 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 Parameter Conditions Output Power (7) PO THD+N PSRR SNR εOUT Total Harmonic Distortion + Noise Power Supply Rejection Ratio Signal to Noise Ratio Output Noise LM4670 Typical (3) Limit (4) (5) Units (Limits) RL = 15μH + 8Ω + 15μH, THD = 10% (max) f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V 1.65 850 400 W mW mW RL = 15μH + 8Ω + 15μH, THD+N = 1% (max) f = 1kHz, 22kHz BW VDD = 5V, VDD = 3.6V, VDD = 2.5V, 1.35 680 325 W mW (min) mW 600 VDD = 5V, PO = 1WRMS, f = 1kHz 0.35 % VDD = 3.6V, PO = 0.5WRMS, f = 1kHz 0.30 % VDD = 3.6V, PO = 0.5WRMS, f = 5kHz 0.30 % VDD = 3.6V, PO = 0.5WRMS, f = 10kHz 0.30 % VDD = 3.6V, VRipple = 200mVPP Sine, fRipple = 217Hz Inputs to AC GND, CI = 0.1μ, Input Referred 68 dB VDD = 3.6V, VRipple = 200mVPP Sine, fRipple = 1kHz Inputs to AC GND, CI = 0.1μF Input Referred 65 dB VDD = 3.6V, VRipple = 200mVPP Sine, fRipple = 217Hz fIN = 1kHz, PO = 10mWRMS Input Referred 62 dB VDD = 5V, PO = 1WRMS 93 dB VDD = 3.6V, f = 20Hz – 20kHz Inputs to AC GND, CI = 0.1μF No Weighting, Input Referred 85 μVRMS VDD = 3.6V, Inputs to AC GND CI = 0.1μF, A Weighted Input Referred 65 μVRMS 80 dB CMRR Common Mode Rejection Ratio VDD = 3.6V, VRipple = 1VPP Sine fRipple = 217Hz, Input Referred TWU Wake-up Time VDD = 3.6V 1.35 ms TSD Shutdown Time VDD = 3.6V 0.01 ms External Components Description See 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. RI Gain setting resistor. Differential gain is set by the equation AV = 2 * 150kΩ / Ri(V/V). Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 5 LM4670 SNAS240C – DECEMBER 2004 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (1) (1) 6 THD+N vs Frequency VDD = 2.5V, RL = 15µH + 4Ω + 15µH POUT = 375mW, 22kHz BW THD+N vs Frequency VDD = 3.6V, RL = 15µH + 4Ω + 15µH POUT = 750mW, 22kHz BW Figure 4. Figure 5. THD+N vs Frequency VDD = 5V, RL = 15µH + 4Ω + 15µH POUT = 1.5W, 22kHz BW THD+N vs Frequency VDD = 2.5V, RL = 15µH + 8Ω + 15µH POUT = 200mW, 22kHz BW Figure 6. Figure 7. THD+N vs Frequency VDD = 3.6V, RL = 15µH + 8Ω + 15µH POUT = 500mW, 22kHz BW THD+N vs Frequency VDD = 5V, RL = 15µH + 8Ω + 15µH POUT = 1W, 22kHz BW Figure 8. Figure 9. The performance graphs were taken using the Audio Precision AUX-0025 Switching Amplifier Measurement Filter in series with the LC filter on the board. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 Typical Performance Characteristics(1) (continued) THD+N vs Output Power RL = 15µH + 4Ω + 15µH f = 1kHz, 22kHz BW THD+N vs Output Power RL = 15µH + 8Ω + 15µH f = 1kHz, 22kHz BW Figure 10. Figure 11. CMRR vs Frequency VDD = 3.6V, RL = 15µH + 8Ω + 15µH VCM = 1VP-P Sine Wave, 22kHz BW PSRR vs Frequency VDD = 3.6V, RL = 15µH + 8Ω + 15µH VCM = 200mVP-P Sine Wave, 22kHz BW Figure 12. Figure 13. Efficiency and Power Dissipation vs Output Power RL = 15µH + 4Ω + 15µH, f = 1kHz, THD < 2% Efficiency and Power Dissipation vs Output Power RL = 15µH + 8Ω + 15µH, f = 1kHz, THD < 1% Figure 14. Figure 15. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 7 LM4670 SNAS240C – DECEMBER 2004 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics(1) (continued) 8 Output Power vs Supply Voltage RL = 15µH + 4Ω + 15µH, f = 1kHz, 22kHz BW Output Power vs Supply Voltage RL = 15µH + 8Ω + 15µH, f = 1kHz, 22kHz BW Figure 16. Figure 17. Supply Current (RMS) vs Output Power RL = 15µH + 4Ω + 15µH, f = 1kHz Supply Current (RMS) vs Output Power RL = 15µH + 8Ω + 15µH, f = 1kHz Figure 18. Figure 19. Shutdown Threshold RL = 15µH + 8Ω + 15µH Shutdwon Threshold vs Supply Voltage RL = 15µH + 8Ω + 15µH Figure 20. Figure 21. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 Typical Performance Characteristics(1) (continued) Supply Current vs Shutdown Voltage RL = 15µH + 8Ω + 15µH Supply Current vs Supply Voltage RL = 15µH + 8Ω + 15µH Figure 22. Figure 23. Supply Current vs Supply Voltage RL = Different µH loads Differential Gain vs Supply Voltage RL = 15µH + 8Ω + 15µH, Ri = 150kΩ, f = 1kHz Figure 24. Figure 25. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 9 LM4670 SNAS240C – DECEMBER 2004 – REVISED MAY 2013 www.ti.com APPLICATION INFORMATION GENERAL AMPLIFIER FUNCTION The output signals generated by the LM4670 consist of two, BTL connected, output signals that pulse momentarily from near ground potential to VDD. The two outputs can pulse independently with the exception that they both may never pulse simultaneously as this would result in zero volts across the BTL load. The minimum width of each pulse is approximately 350ns. However, pulses on the same output can occur sequentially, in which case they are concatenated and appear as a single wider pulse to achieve an effective 100% duty cycle. This results in maximum audio output power for a given supply voltage and load impedance. The LM4670 can achieve much higher efficiencies than class AB amplifiers while maintaining acceptable THD performance. The short (350ns) drive pulses emitted at the LM4670 outputs means that good efficiency can be obtained with minimal load inductance. The typical transducer load on an audio amplifier is quite reactive (inductive). For this reason, the load can act as it's own filter, so to speak. This "filter-less" switching amplifier/transducer load combination is much more attractive economically due to savings in board space and external component cost by eliminating the need for a filter. 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 LM4670 and in the transducer load. The amount of power dissipation in the LM4670 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 LM4670 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 LM4670 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 LM4670 also offers the possibility of DC input coupling which eliminates the two external AC coupling, DC blocking capacitors. The LM4670 can be used, however, as a single ended input amplifier while still retaining it's fully differential benefits. In fact, completely unrelated signals may be placed on the input pins. The LM4670 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 LM4670 and the load results is lower output power and decreased efficiency. Higher trace resistance between the supply and the LM4670 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 © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 The rising and falling edges are necessarily short in relation to the minimum pulse width (350ns), having approximately 16ns rise and fall times, typical, depending on parasitic output capacitance. 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 LM4670 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 LM4670 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 LM4670. 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 LM4670. A 1µF tantalum capacitor is recommended. SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the LM4670 contains shutdown circuitry that reduces current draw to less than 0.01µA. The trigger point for shutdown is shown as a typical value in Electrical Characteristics and in the Shutdown Hysteresis Voltage graphs found in Typical Performance Characteristics. It is best to switch between ground and supply for minimum current usage while in the shutdown state. While the LM4670 may be disabled with shutdown voltages in between ground and supply, the idle current will be greater than the typical 0.01µA value. Increased THD may also be observed with voltages less than VDD on the Shutdown pin when in PLAY mode. The LM4670 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 LM4670 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. (VSD - GND) / 300kΩ (1) With only a 0.5V difference, an additional 1.7µA of current will be drawn while in the shutdown state. PROPER SELECTION OF EXTERNAL COMPONENTS The gain of the LM4670 is set by the external resistors, Ri in Figure 1, The Gain is given by Equation 2. 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 LM4670. The Ri resistors should be placed close to the input pins of the LM4670. 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 LM4670. Noise coupled onto input traces which are physically close to each other will be common mode and easily rejected by the LM4670. Input capacitors may be needed for some applications or when the source is single-ended (see Figure 27 and Figure 29). Input capacitors are needed to block any DC voltage at the source so that the DC voltage seen between the input terminals of the LM4670 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. fC = 1 / (2πRi Ci ) (Hz) (3) Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 11 LM4670 SNAS240C – DECEMBER 2004 – 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 LM4670 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 Figure 29 to Figure 31). 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 LM4670 can be used in many different circuit configurations. The simplest and best performing is the DC coupled, differential input configuration shown in Figure 26. 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 27. 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 LM4670 can be used to amplify more than one audio source. Figure 28 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 LM4670 can also be used with single-ended sources but input capacitors will be needed to block any DC at the input terminals. Figure 29 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 29. When using more than one single-ended source as shown in Figure 30, 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. Equation 4 and Equation 5 below are for any number of single-ended sources. Ci3 = Ci1 + Ci2 + Cin ... (F) Ri3 = 1 / (1/Ri1 + 1/Ri2 + 1/Rin ...) (Ω) (4) (5) The LM4670 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 31. Using the principle of superposition, the external component values can be determined with the above equations corresponding to the configuration. Figure 26. Differential input configuration 12 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 Figure 27. Differential input configuration with input capacitors Figure 28. Dual differential input configuration Figure 29. Single-ended input configuration Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 13 LM4670 SNAS240C – DECEMBER 2004 – REVISED MAY 2013 www.ti.com Figure 30. Dual single-ended input configuration Figure 31. Dual input with a single-ended input and a differential input 14 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 REFERENCE DESIGN BOARD SCHEMATIC Figure 32. 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 32). 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. The commonly used Audio Precision analyzer is differential, but its ability to accurately reject fast pulses of 350ns width 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. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 15 LM4670 SNAS240C – DECEMBER 2004 – REVISED MAY 2013 www.ti.com LM4670 DSBGA BOARD ARTWORK 16 Figure 33. Composite View Figure 34. Silk Screen Figure 35. Top Layer Figure 36. Internal Layer 1, GND Figure 37. Internal Layer 2, VDD Figure 38. Bottom Layer Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 LM4670 www.ti.com SNAS240C – DECEMBER 2004 – REVISED MAY 2013 LM4670 WSON BOARD ARTWORK Figure 39. Composite View Figure 40. Silk Screen Figure 41. Top Layer Figure 42. Internal Layer 1, GND Figure 43. Internal Layer 2, VDD Figure 44. Bottom Layer Revision History Rev Date Description 1.0 12/15/04 Initial WEB of the D/S (TL pkg). 1.1 7/06/05 Re-released D/S to the WEB (added the SD package). 1.2 7/13/06 Edited Note 9, then re-released D/S to the WEB. C 5/02/13 Changed layout of National Data Sheet to TI format Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4670 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) LM4670ITL/NOPB ACTIVE DSBGA YZR 9 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -40 to 85 G E6 LM4670ITLX/NOPB ACTIVE DSBGA YZR 9 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -40 to 85 G E6 LM4670SD/NOPB ACTIVE WSON NGQ 8 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 85 L4670 (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