0
登录后你可以
  • 下载海量资料
  • 学习在线课程
  • 观看技术视频
  • 写文章/发帖/加入社区
会员中心
创作中心
发布
  • 发文章

  • 发资料

  • 发帖

  • 提问

  • 发视频

创作活动
LM4960SQX

LM4960SQX

  • 厂商:

    BURR-BROWN(德州仪器)

  • 封装:

    WFQFN28_EP

  • 描述:

    IC AMP AUDIO PWR MONO AB 28WQFN

  • 数据手册
  • 价格&库存
LM4960SQX 数据手册
LM4960 www.ti.com SNAS221C – OCTOBER 2004 – REVISED MAY 2013 LM4960 Piezoelectric Speaker Driver Check for Samples: LM4960 FEATURES DESCRIPTION • • • • • • • • The LM4960 utilizes a switching regulator to drive a dual audio power amplifier. It delivers 24VP-P monoBTL to a ceramic speaker with less than 1.0% THD+N while operating on a 3.0V power supply. 1 23 Low Current Shutdown Mode "Click and Pop" Suppression Circuitry Low Quiescent Current Unity-Gain Stable Audio Amplifiers External Gain Configuration Capability Thermal Shutdown Protection Circuitry Wide Input Voltage Range (3.0V - 7V) 1.6MHz Switching Frequency APPLICATIONS • • Mobile Phone PDA's KEY SPECIFICATIONS • • • VOUT @ VDD = 3.0 THD+N ≤ 1%: 24 VP-P (typ) Power Supply Range: 3.0 to 7 V Switching Frequency: 1.6 MHz (typ) The LM4960's switching regulator is a current-mode boost converter operating at a fixed frequency of 1.6MHz. Boomer™ audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4960 does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for mobile phone and other low voltage applications where minimal power consumption is a primary requirement. The LM4960 features a low-power consumption externally controlled micropower shutdown mode. Additionally, the LM4960 features and internal thermal shutdown protection mechanism along with a short circuit protection. The LM4960 is unity-gain stable and can be configured by external gain-setting resistors. Connection Diagram Figure 1. 28-Pin WQFN (Top View) See RSG0028A Package 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 LM4960 SNAS221C – OCTOBER 2004 – REVISED MAY 2013 www.ti.com Typical Application VDD L1 10 PH 230 pF 4.7 PF 4 11 4.7 PF 115k SW VDD FB 7,12,24,25 8 GND 13k 6 S/D Reg Shutdown 150k V1 21 1 Amp Shutdown GND 27 7,12,24,25 4.7 PF Bypass 0.22 PF VOUT B 28 10 Ceramic Speaker 20k Audio In 0.039 PF 20 2 VOUT A 23 VIN A 10 800 nF VIN B 200k 82p 20k 20k Figure 2. Typical Audio Amplifier Application Circuit 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: LM4960 LM4960 www.ti.com SNAS221C – OCTOBER 2004 – REVISED MAY 2013 ABSOLUTE MAXIMUM RATINGS (1) (2) (3) Supply Voltage (VDD) 8.5V Supply Voltage (V1) (Pin 27 referred to GND) 18V −65°C to +150°C Storage Temperature −0.3V to VDD + 0.3V Input Voltage Power Dissipation (4) Internally limited ESD Susceptibility (5) 2000V ESD Susceptibility (6) 200V Junction Temperature 150°C θJA (WQFN) Thermal Resistance °C/W See SNOA401 'Leadless Leadframe Packaging (LLP).' (1) (2) (3) (4) (5) (6) All voltages are measured with respect to the GND 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. 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 given in Absolute Maximum Ratings, whichever is lower. For the LM4960 typical application (shown in Figure 2) with VDD = 12V, RL = 4Ω stereo operation the total power dissipation is 3.65W. θJA = 35°C/W. Human body model, 100pF discharged through a 1.5kΩ resistor. Machine Model, 220pF–240pF discharged through all pins. OPERATING RATINGS TMIN ≤ TA ≤ TMAX Temperature Range −40°C ≤ TA ≤ +85°C Supply Voltage (VDD) 3.0V ≤ VDD ≤ 7V Supply Voltage (V1) 9.6V ≤ V1 ≤ 16V ELECTRICAL CHARACTERISTICS VDD = 3.0V (1) (2) The following specifications apply for VDD = 3V, AV = 10, RL = 800nF+20Ω, V1 = 12V unless otherwise specified. Limits apply for TA = 25°C. Symbol Parameter Conditions IDD Quiescent Power Supply Current VIN = GND, No Load ISD Shutdown Current VSHUTDOWN = GND VOS Output Offset Voltage VSDIH Shutdown Voltage Input High VSDIL Shutdown Voltage Input Low TWU Wake-up Time TSD Thermal Shutdown Temperature VO Output Voltage (1) (2) (3) (4) (5) (6) (6) CB = 0.22µF THD = 1% (max); f = 1kHz LM4960 Typical (3) Limit (4) (5) Units (Limits) 85 150 30 100 µA (max) 5 40 mV (max) 2 V (max) 0.4 V (min) 170 150 190 °C (min) °C (max) 24 20 VP-P (min) 50 mA (max) ms All voltages are measured with respect to the GND 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. Typicals are measured at 25°C and represent the parametric norm. Limits are ensured to 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. The Shutdown pin should be driven as close as possible to VDD for minimum shutdown current. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 3 LM4960 SNAS221C – OCTOBER 2004 – REVISED MAY 2013 www.ti.com ELECTRICAL CHARACTERISTICS VDD = 3.0V (1)(2) (continued) The following specifications apply for VDD = 3V, AV = 10, RL = 800nF+20Ω, V1 = 12V unless otherwise specified. Limits apply for TA = 25°C. Symbol Parameter Conditions THD+N Total Harmomic Distortion + Noise VO = 3Wrms; f = 1kHz εOS Output Noise A-Weighted Filter, VIN = 0V PSRR Power Supply Rejection Ratio VRIPPLE = 200mVp-p, f = 1kHz VFB Feedback Pin Reference Voltage LM4960 Typical (3) (4) (5) Limit 0.04 % 90 µV 55 50 1.23 ELECTRICAL CHARACTERISTICS VDD = 5.0V Units (Limits) dB (min) V (max) (1) (2) The following specifications apply for VDD = 5V, AV = 10, RL = 800nF+20Ω unless otherwise specified. Limits apply for TA = 25°C. Symbol Parameter Conditions LM4960 Typical IDD Quiescent Power Supply Current VIN = GND, No Load VSHUTDOWN = GND (6) (3) Limit (4) (5) 45 mA (max) ISD Shutdown Current 100 µA (max) VSDIH Shutdown Voltage Input High 2 V (max) VSDIL Shutdown Voltage Input Low 0.4 V (min) TWU Wake-up Time 170 150 190 °C (min) °C (max) 24 20 VP-P (min) CB = 0.22µF TSD Thermal Shutdown Temperature VO Output Voltage THD = 1% (max); f = 1kHz RL = Ceramic Speaker THD+N Total Harmomic Distortion + Noise VO = 3Wrms; f = 1kHz εOS Output Noise A-Weighted Filter, VIN = 0V PSRR Power Supply Rejection Ratio VRIPPLE = 200mVp-p, f = 1kHz VFB Feedback Pin Reference Voltage (1) (2) (3) (4) (5) (6) 4 55 Units (Limits) 50 ms 0.04 % 90 µV 60 dB (min) 1.23 V (max) All voltages are measured with respect to the GND 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. Typicals are measured at 25°C and represent the parametric norm. Limits are ensured to 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. The Shutdown pin should be driven as close as possible to VDD for minimum shutdown current. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 LM4960 www.ti.com SNAS221C – OCTOBER 2004 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS 10 THD+N vs Frequency VDD = 3V, V1 = 9.6V, V0 = 3Vrms THD+N vs Frequency snas2202906 VDD = 3V, V1 = 12V, V0 = 3Vrms 10 1 THD+N (%) THD+N (%) 1 0.1 0.01 0.001 20 0.1 0.01 200 2k 0.001 20 20k FREQUENCY (Hz) 10 Figure 4. THD+N vs Frequency VDD = 3V, V1 = 15V, V0 = 3Vrms THD+N vs Frequency VDD = 5V, V1 = 9.6V, V0 = 3Vrms 10 THD+N (%) THD+N (%) 0.01 0.1 0.01 200 2k 0.001 20 20k FREQUENCY (Hz) 2k 20k Figure 6. THD+N vs Frequency VDD = 5V, V1 =12V, V0 = 3Vrms 10 THD+N vs Frequency VDD = 5V, V1 =15V, V0 = 3Vrms 1 THD+N (%) 1 THD+N (%) 200 FREQUENCY (Hz) Figure 5. 0.1 0.01 0.001 20 20k 1 0.1 10 2k Figure 3. 1 0.001 20 200 FREQUENCY (Hz) 0.1 0.01 200 2k 20k FREQUENCY (Hz) 0.001 20 200 2k 20k FREQUENCY (Hz) Figure 7. Figure 8. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 5 LM4960 SNAS221C – OCTOBER 2004 – REVISED MAY 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) THD+N vs Output Power VDD = 3V, V1 = 12V, f = 100Hz, 1kHz, 10kHz 10 10 1 1 THD+N (%) THD+N (%) THD+N vs Output Power VDD = 3V, V1 = 9.6V, f = 100Hz, 1kHz, 10kHz 0.1 0.01 0.001 2.83 0.1 0.01 9.05 15.27 21.5 27.72 0.001 2.83 33.94 THD+N vs Output Power VDD = 3V, V1 = 15V, f = 100Hz, 1kHz, 10kHz THD+N vs Output Power VDD = 5V, V1 = 9.6V, f = 100Hz, 1kHz, 10kHz 1 1 0.1 0.01 0.01 9.05 15.27 21.5 27.72 0.001 2.83 33.94 9.05 15.27 21.5 27.72 33.94 OUTPUT VOLTAGE (Vrms) Figure 11. Figure 12. THD+N vs Output Power VDD = 5V, V1 = 12V, f = 100Hz, 1kHz, 10kHz THD+N vs Output Power VDD = 5V, V1 = 15V, f = 100Hz, 1kHz, 10kHz 10 10 1 1 THD+N (%) THD+N (%) 33.94 0.1 OUTPUT VOLTAGE (Vrms) 0.1 0.01 0.1 0.01 9.05 15.27 21.5 27.72 33.94 OUTPUT VOLTAGE (Vrms) 0.001 2.83 9.05 15.27 21.5 27.72 33.94 OUTPUT VOLTAGE (Vrms) Figure 13. 6 27.72 Figure 10. 10 0.001 2.83 21.5 OUTPUT VOLTAGE (Vrms) 10 0.001 2.83 15.27 Figure 9. THD+N (%) THD+N (%) OUTPUT VOLTAGE (Vrms) 9.05 Figure 14. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 LM4960 www.ti.com SNAS221C – OCTOBER 2004 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Power Dissipation vs Output Voltage VDD = 5V, from top to bottom: V1 = 15V, V1 = 12V, V1 = 9.6V 1400 800 1200 700 POWER DISSIPATION (mW) POWER DISSIPATION (mW) Power Dissipation vs Output Voltage VDD = 3V, from top to bottom: V1 = 15V, V1 = 12V, V1 = 9.6V 1000 800 600 400 200 600 500 400 300 200 100 0 0 0 10 20 30 40 0 10 OUTPUT VOLTAGE (Vp-p) 20 30 40 OUTPUT VOLTAGE (Vp-p) Figure 15. Figure 16. Supply Current vs Supply Voltage from top to bottom: VDD = 15V, VDD = 12V, VDD = 9.6V Power Supply Rejection Ratio VDD = 3V 400 0 -20 300 250 PSRR (dB) SUPPLY CURRENT (mA) 350 200 150 -40 -60 100 -80 50 0 2 3 4 5 6 7 8 9 -100 20 10 SUPPLY VOLTAGE (V) 200 2k 20k FREQUENCY (Hz) Figure 17. Figure 18. Power Supply Rejection Ratio VDD = 5V 0 PSRR (dB) -20 -40 -60 -80 -100 20 200 2k 20k FREQUENCY (Hz) Figure 19. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 7 LM4960 SNAS221C – OCTOBER 2004 – REVISED MAY 2013 www.ti.com APPLICATION INFORMATION BRIDGE CONFIGURATION EXPLANATION The Audio Amplifier portion of the LM4960 has two internal amplifiers allowing different amplifier configurations. The first amplifier’s gain is externally configurable, whereas the second amplifier is internally fixed in a unity-gain, inverting configuration. The closed-loop gain of the first amplifier is set by selecting the ratio of Rf to Ri while the second amplifier’s gain is fixed by the two internal 20kΩ resistors. Figure 2 shows that the output of amplifier one serves as the input to amplifier two. This results in both amplifiers producing signals identical in magnitude, but out of phase by 180°. Consequently, the differential gain for the Audio Amplifier is AVD = 2 *(Rf/Ri) (1) 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 classic 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. It provides differential drive to the load, thus doubling the 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. The bridge configuration 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. AMPLIFIER 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 amplifier portion of the LM4960 has two operational amplifiers, the maximum internal power dissipation is 4 times that of a single-ended amplifier. The maximum power dissipation for a given BTL application can be derived from Equation (2). PDMAX(AMP) = 4(VDD)2 / (2π2ZL) where • ZL = Ro1 + Ro2 +1/2πfc (2) BOOST CONVERTER POWER DISSIPATION At higher duty cycles, the increased ON-time of the switch FET means the maximum output current will be determined by power dissipation within the LM2731 FET switch. The switch power dissipation from ON-time conduction is calculated by Equation (3). PDMAX(SWITCH) = DC x IIND(AVE)2 x RDS(ON) where • DC is the duty cycle (3) There will be some switching losses as well, so some derating needs to be applied when calculating IC power dissipation. TOTAL POWER DISSIPATION The total power dissipation for the LM4960 can be calculated by adding Equation (2) and Equation (3) together to establish Equation (4): PDMAX(TOTAL) = [4*(VDD)2/2π2ZL] + [DC x IIND(AVE)2 xRDS(ON)] (4) The result from Equation (4) must not be greater than the power dissipation that results from Equation (5): PDMAX = (TJMAX - TA) / θJA 8 (5) Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 LM4960 www.ti.com SNAS221C – OCTOBER 2004 – REVISED MAY 2013 For the LQA28A, θJA = 59°C/W. TJMAX = 125°C for the LM4960. Depending on the ambient temperature, TA, of the system surroundings, Equation (5) can be used to find the maximum internal power dissipation supported by the IC packaging. If the result of Equation (4) is greater than that of Equation (5), then either the supply voltage must be increased, the load impedance increased or TA reduced. For the typical application of a 3V power supply, with V1 set to 12V and a 800nF + 20Ω load, the maximum ambient temperature possible without violating the maximum junction temperature is approximately 118°C provided that device operation is around the maximum power dissipation point. Thus, for typical applications, power dissipation is not an issue. Power dissipation is a function of output power and thus, if typical operation is not around the maximum power dissipation point, the ambient temperature may be increased accordingly. Refer to the TYPICAL PERFORMANCE CHARACTERISTICS curves for power dissipation information for lower output levels. EXPOSED-DAP PACKAGE PCB MOUNTING CONSIDERATIONS The LM4960’s exposed-DAP (die attach paddle) package (WQFN) provides a low thermal resistance between the die and the PCB to which the part is mounted and soldered. The low thermal resistance allows rapid heat transfer from the die to the surrounding PCB copper traces, ground plane, and surrounding air. The WQFN package should have its DAP soldered to a copper pad on the PCB. The DAP’s PCB copper pad may be connected to a large plane of continuous unbroken copper. This plane forms a thermal mass, heat sink, and radiation area. Further detailed and specific information concerning PCB layout, fabrication, and mounting a WQFN package is found in Texas Instruments' Package Engineering Group under application note SNOA401. SHUTDOWN FUNCTION 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, and a pull-up resistor. One terminal of the switch is connected to GND. The other side is connected to the two shutdown pins and the terminal of the pull-up resistor. The remaining resistance terminal is connected to VDD. If the switch is open, then the external pull-up resistor connected to VDD will enable the LM4960. This scheme ensures that the shutdown pins will not float thus preventing unwanted state changes. PROPER SELECTION OF EXTERNAL COMPONENTS Proper selection of external components in applications using integrated power amplifiers, and switching DC-DC converters, is critical for optimizing device and system performance. Consideration to component values must be used to maximize overall system quality. The best capacitors for use with the switching converter portion of the LM4960 are multi-layer ceramic capacitors. They have the lowest ESR (equivalent series resistance) and highest resonance frequency, which makes them optimum for high frequency switching converters. When selecting a ceramic capacitor, only X5R and X7R dielectric types should be used. Other types such as Z5U and Y5F have such severe loss of capacitance due to effects of temperature variation and applied voltage, they may provide as little as 20% of rated capacitance in many typical applications. Always consult capacitor manufacturer’s data curves before selecting a capacitor. High-quality ceramic capacitors can be obtained from Taiyo-Yuden, AVX, and Murata. 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 V1 and VDD pins should be as close to the device as possible. SELECTING INPUT CAPACITOR FOR AUDIO AMPLIFIER 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 2. 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. High value input capacitors are both expensive and space hungry in portable designs. Clearly, a certain value capacitor is needed to couple in low frequencies without severe attenuation. But ceramic speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to 150Hz. Thus, using a high value input capacitor may not increase actual system performance. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 9 LM4960 SNAS221C – OCTOBER 2004 – REVISED MAY 2013 www.ti.com In addition to system cost and size, click and pop performance is affected by the value of the input coupling capacitor, Ci. A high value 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 value based on desired low frequency response, turn-on pops can be minimized. SELECTING BYPASS CAPACITOR FOR AUDIO AMPLIFIER Besides minimizing the input capacitor value, 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 amplifer turns on. The slower the amplifier’s outputs ramp to their quiescent DC voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing CB equal to 1.0µF along with a small value of Ci (in the range of 0.039µF to 0.39µF), should produce a virtually clickless and popless shutdown function. Although the device will function properly, (no oscillations or motorboating), with CB equal to 0.1µF, the device will be much more susceptible to turn-on clicks and pops. Thus, a value of CB equal to 1.0µF is recommended in all but the most cost sensitive designs. SELECTING FEEDBACK CAPACITOR FOR AUDIO AMPLIFIER The LM4960 is unity-gain stable which gives the designer maximum system flexability. However, to drive ceramic speakers, a typical application requires a closed-loop differential gain of 10. In this case a feedback capacitor (Cf2) will be needed as shown in Figure 2 to bandwidth limit the amplifier. This feedback capacitor creates a low pass filter that eliminates possible high frequency oscillations. Care should be taken when calculating the -3dB frequency because an incorrect combination of Rf and Cf2 will cause rolloff before the desired frequency SELECTING OUTPUT CAPACITOR (CO) FOR BOOST CONVERTER A single 4.7µF to 10µF ceramic capacitor will provide sufficient output capacitance for most applications. If larger amounts of capacitance are desired for improved line support and transient response, tantalum capacitors can be used. Aluminum electrolytics with ultra low ESR such as Sanyo Oscon can be used, but are usually prohibitively expensive. Typical AI electrolytic capacitors are not suitable for switching frequencies above 500 kHz because of significant ringing and temperature rise due to self-heating from ripple current. An output capacitor with excessive ESR can also reduce phase margin and cause instability. In general, if electrolytics are used, we recommended that they be paralleled with ceramic capacitors to reduce ringing, switching losses, and output voltage ripple. SELECTING INPUT CAPACITOR (Cs1) FOR BOOST CONVERTER An input capacitor is required to serve as an energy reservoir for the current which must flow into the coil each time the switch turns ON. This capacitor must have extremely low ESR, so ceramic is the best choice. We recommend a nominal value of 4.7µF, but larger values can be used. Since this capacitor reduces the amount of voltage ripple seen at the input pin, it also reduces the amount of EMI passed back along that line to other circuitry. SETTING THE OUTPUT VOLTAGE (V1) OF BOOST CONVERTER The output voltage is set using the external resistors R1 and R2 (see Figure 2). A value of approximately 13.3kΩ is recommended for R2 to establish a divider current of approximately 92µA. R1 is calculated using the formula: R1 = R2 X (V2/1.23 − 1) (6) FEED-FORWARD COMPENSATION FOR BOOST CONVERTER Although the LM4960's internal Boost converter is internally compensated, the external feed-forward capacitor Cf is required for stability (see Figure 2). Adding this capacitor puts a zero in the loop response of the converter. The recommended frequency for the zero fz should be approximately 6kHz. Cf1 can be calculated using the formula: Cf1 = 1 / (2 X R1 X fz) 10 (7) Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 LM4960 www.ti.com SNAS221C – OCTOBER 2004 – REVISED MAY 2013 SELECTING DIODES The external diode used in Figure 2 should be a Schottky diode. A 20V diode such as the MBR0520 is recommended. The MBR05XX series of diodes are designed to handle a maximum average current of 0.5A. For applications exceeding 0.5A average but less than 1A, a Microsemi UPS5817 can be used. DUTY CYCLE The maximum duty cycle of the boost converter determines the maximum boost ratio of output-to-input voltage that the converter can attain in continuous mode of operation. The duty cycle for a given boost application is defined as: Duty Cycle = VOUT + VDIODE - VIN/ VOUT + VDIODE - VSW This applies for continuous mode operation. INDUCTANCE VALUE The first question we are usually asked is: “How small can I make the inductor.” (because they are the largest sized component and usually the most costly). The answer is not simple and involves trade-offs in performance. Larger inductors mean less inductor ripple current, which typically means less output voltage ripple (for a given size of output capacitor). Larger inductors also mean more load power can be delivered because the energy stored during each switching cycle is: E = L/2 X (lp)2 where • “lp” is the peak inductor current. (8) An important point to observe is that the LM4960 will limit its switch current based on peak current. This means that since lp(max) is fixed, increasing L will increase the maximum amount of power available to the load. Conversely, using too little inductance may limit the amount of load current which can be drawn from the output. Best performance is usually obtained when the converter is operated in “continuous” mode at the load current range of interest, typically giving better load regulation and less output ripple. Continuous operation is defined as not allowing the inductor current to drop to zero during the cycle. It should be noted that all boost converters shift over to discontinuous operation as the output load is reduced far enough, but a larger inductor stays “continuous” over a wider load current range. To better understand these trade-offs, a typical application circuit (5V to 12V boost with a 10µH inductor) will be analyzed. We will assume: VIN = 5V, VOUT = 12V, VDIODE = 0.5V, VSW = 0.5V (9) Since the frequency is 1.6MHz (nominal), the period is approximately 0.625µs. The duty cycle will be 62.5%, which means the ON-time of the switch is 0.390µs. It should be noted that when the switch is ON, the voltage across the inductor is approximately 4.5V. Using the equation: V = L (di/dt) (10) We can then calculate the di/dt rate of the inductor which is found to be 0.45 A/µs during the ON-time. Using these facts, we can then show what the inductor current will look like during operation: Figure 20. 10μH Inductor Current 5V - 12V Boost (LM4960) Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 11 LM4960 SNAS221C – OCTOBER 2004 – REVISED MAY 2013 www.ti.com During the 0.390µs ON-time, the inductor current ramps up 0.176A and ramps down an equal amount during the OFF-time. This is defined as the inductor “ripple current”. It can also be seen that if the load current drops to about 33mA, the inductor current will begin touching the zero axis which means it will be in discontinuous mode. A similar analysis can be performed on any boost converter, to make sure the ripple current is reasonable and continuous operation will be maintained at the typical load current values. MAXIMUM SWITCH CURRENT The maximum FET switch current available before the current limiter cuts in is dependent on duty cycle of the application. This is illustrated in a graph in the TYPICAL PERFORMANCE CHARACTERISTICS section which shows typical values of switch current as a function of effective (actual) duty cycle. CALCULATING OUTPUT CURRENT OF BOOST CONVERTER (IAMP) As shown in Figure 20 which depicts inductor current, the load current is related to the average inductor current by the relation: ILOAD = IIND(AVG) x (1 - DC) where • "DC" is the duty cycle of the application. (11) The switch current can be found by: ISW = IIND(AVG) + 1/2 (IRIPPLE) (12) Inductor ripple current is dependent on inductance, duty cycle, input voltage and frequency: IRIPPLE = DC x (VIN-VSW) / (f x L) (13) Combining all terms, we can develop an expression which allows the maximum available load current to be calculated: ILOAD(max) = (1–DC)x(ISW(max)–DC(VIN-VSW))/fL (14) The equation shown to calculate maximum load current takes into account the losses in the inductor or turn-OFF switching losses of the FET and diode. DESIGN PARAMETERS VSW AND ISW The value of the FET "ON" voltage (referred to as VSW in Equation (11) through Equation (14)) is dependent on load current. A good approximation can be obtained by multiplying the "ON Resistance" of the FET times the average inductor current. FET on resistance increases at VIN values below 5V, since the internal N-FET has less gate voltage in this input voltage range (see TYPICAL PERFORMANCE CHARACTERISTICS curves). Above VIN = 5V, the FET gate voltage is internally clamped to 5V. The maximum peak switch current the device can deliver is dependent on duty cycle. For higher duty cycles, see TYPICAL PERFORMANCE CHARACTERISTICS curves. INDUCTOR SUPPLIERS Recommended suppliers of inductors for the LM4960 include, but are not limited to Taiyo-Yuden, Sumida, Coilcraft, Panasonic, TDK and Murata. When selecting an inductor, make certain that the continuous current rating is high enough to avoid saturation at peak currents. A suitable core type must be used to minimize core (switching) losses, and wire power losses must be considered when selecting the current rating. 12 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 LM4960 www.ti.com SNAS221C – OCTOBER 2004 – REVISED MAY 2013 PCB LAYOUT GUIDELINES High frequency boost converters require very careful layout of components in order to get stable operation and low noise. All components must be as close as possible to the LM4802 device. It is recommended that a 4-layer PCB be used so that internal ground planes are available. Some additional guidelines to be observed: 1. Keep the path between L1, D1, and Co extremely short. Parasitic trace inductance in series with D1 and Co will increase noise and ringing. 2. The feedback components R1, R2 and Cf 1 must be kept close to the FB pin of U1 to prevent noise injection on the FB pin trace. 3. If internal ground planes are available (recommended) use vias to connect directly to ground at pin 2 of U1, as well as the negative sides of capacitors Cs1 and Co. GENERAL MIXED-SIGNAL LAYOUT RECOMMENDATION 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. 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. Single-Point Power / Ground Connection 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 place 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 crosstalk. Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 13 LM4960 SNAS221C – OCTOBER 2004 – REVISED MAY 2013 www.ti.com REVISION HISTORY Changes from Revision B (May 2013) to Revision C • 14 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 13 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Product Folder Links: LM4960 PACKAGE OPTION ADDENDUM www.ti.com 3-May-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Top-Side Markings (3) (4) LM4960SQ/NOPB ACTIVE WQFN RSG 28 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM L4960SQ LM4960SQX/NOPB ACTIVE WQFN RSG 28 4500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM L4960SQ (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) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Top-Side Marking for that device. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 Samples PACKAGE MATERIALS INFORMATION www.ti.com 8-May-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM4960SQ/NOPB WQFN RSG 28 1000 178.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1 LM4960SQX/NOPB WQFN RSG 28 4500 330.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 8-May-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM4960SQ/NOPB WQFN RSG 28 1000 203.0 190.0 41.0 LM4960SQX/NOPB WQFN RSG 28 4500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA RSG0028A SQA28A (Rev B) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily performed. TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications. In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. Nonetheless, such components are subject to these terms. No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use. Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of non-designated products, TI will not be responsible for any failure to meet ISO/TS16949. Products Applications Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com Wireless Connectivity www.ti.com/wirelessconnectivity Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2013, Texas Instruments Incorporated
LM4960SQX 价格&库存

很抱歉,暂时无法提供与“LM4960SQX”相匹配的价格&库存,您可以联系我们找货

免费人工找货