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文档下载 免费文档下载 http://www.mianfeiwendang.com/ 本文档下载自文档下载网,内容可能不完整,您可以点击以下网址继续阅读或下载: http://www.mianfeiwendang.com/doc/b57e378979599972c8a666ce RT9277BGF MSOP-8 升压 IC 广泛应用于 TFT 面板、机顶盒、智能手机等产品 Preliminary RT9277A/B High Performance, Low Noise Boost Converter General Description The RT9277A/B is a high performance, low noise, fixedfrequency step up DC-DC Converter. The RT9277A/Bconverters input voltage ranging 2.5V to 5.5V into outputvoltage up to 16V. Current mode control with externalcompensation network makes it easy to stabilize thesystem and keep maximum flexibility. Soft start functionminimizes impact on the input power system. Internal powerMOSFET with very low RDS(ON) provides high efficiency.The RT9277A/B automatically transits from PWM to PSM(Pulse Skipping Mode) during light load condition furtherincreasing efficiency. 640kHz and 1.2MHz operationfrequency options provide flexibiltity of minimum outputinductor size, maximum efficiency and low BOM cost.The RT9277A/B also provides comprehensive protectionfunctions such as UVLO, OCP and OTP. Features zzzzzzzzz 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 90% Efficienchttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666cey VIN Operating Range : 2.5V to 5.5V 1.6A, 0.2Ω, 16V Internal Power MOSFET640kHz and 1.2MHz Operation FrequencyExternal Compensation Network Internal/External Programmable Soft Start FunctionSmall MSOP8 Package OCP and OTP Function are Included RoHS Compliant and 100% Lead (Pb)-Free Applications zzzz TFT LCD panelOLED DisplayPCMCIA CardsPortable Device Ordering Information A : Internal B : External Programmable Pin Configurations (TOP VIEW) 文档下载 免费文档下载 http://www.mianfeiwendang.com/ COMP FBENGND 2376NCFREQVINLX RT9277A Note : RichTek Pb-free and Green products are : `RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. COMP FBENGND 2376SSFREQVINLX `Suitable for use in SnPb or Pb-free soldering processes.`100%matte tin (Sn) plhttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceating. RT9277BMSOP-8 Marking Information For marking information, contact our sales representativedirectly or through a RichTek distributor located in yourarea, otherwise visit our website for detail. 文档下载 免费文档下载 http://www.mianfeiwendang.com/ DS9277A/B-02 March 2007 www.richtek.com 1 RT9277A/B Typical Application Circuit Preliminary VVOUTFigure 1 VVOUTFigure 2 Function Block Diagram RT9277A www.richtek.com2 DS9277A/B-02 Preliminary RT9277A/B RT9277B March 2007 文档下载 免费文档下载 http://www.mianfeiwendang.com/ Operation The RT9277A/B is a high efficiency step-up Boost converterwith a fixed-frequency, current-mode PWM architecture.It performs fast transient response and low noise operationwith appropriate component selection. The output voltageis regulated through a feedback control consisting of anerror amplifier, a summing comparator, ahttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666cend several controlsignal generators (as shown in function block diagram).The feedback reference voltage is 1.24V. The error amplifiervaries the COMP voltage by sensing the FB pin. The slopecompensation signal summed with the current -sensesignal will be compared with the COMP voltage throughthe summing comparator to determine the current trip pointand duty cycle. When driving light loads, the RT9277A/Bwill perform the pulse-skipping mode to preventovercharging the output voltage. In this mode, the switchingfrequency will be reduced to perform a higher efficiency.Soft-Start The RT9277B provides programmable soft-start function.When the EN pin is connected to high, a 4μA constantcurrent is sourced to charge an external capacitor. Thevoltage rate of rise on the COMP pin is limited during thecharging period, and so is the peak inductor current. When the EN pin is connected to GND, the externalcapacitor dischttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceharged will to be ground for the next timesoft-start. Current Limitation The switch current is monitored to limit the value not toexceed 1.6A typically. When the switch current reaches1.6A, the output voltage will be pulled down to limit thetotal output power to protect the power switch and externalcomponents.Shutdown 文档下载 免费文档下载 http://www.mianfeiwendang.com/ Connect the EN to GND to turn the RT9277A/B off andreduce the supply current to 0.1μA. In this operation, theoutput voltage is the value of VIN to subtract the forwardvoltage of catch diode.Frequency Selection The switching frequency of RT9277A/B can be selected tooperate at either 640kHz or 1.2MHz. When the FREQ pinis connected to GND for 640kHz operation, and connectedto VIN for 1.2MHz operation. FREQ is preset to 640kHzoperation for allowing the FREQ pin unconnected. DS9277A/B-02 March 2007 www.richtek.com 3 RT9277A/B Preliminary ://www.mianfeiwendang.com/doc/b57e378979599972c8a666cerwww.richtek.com DS9277A/B-02 March 2007 4 Preliminary Absolute Maximum Ratings zzzz (Note 1) 文档下载 免费文档下载 http://www.mianfeiwendang.com/ RT9277A/B z zzzz Supply Voltage (VIN)-------------------------------------------------------------------------------------------------?0.3 to 6VLX to GND--------------------------------------------------------------------------------------------------------------?0.3V to 16VThe other pins---------------------------------------------------------------------------------------------------------?0.3V to 6VPower Dissipation, PD @ TA = 70°C MSOP-8----------------------------------------------------------------------------------------------------------------625mWPackage Thermal Resistance (Note 4) MSOP-8, θJA-----------------------------------------------------------------------------------------------------------160°C/WJunction Temhttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceperature-----------------------------------------------------------------------------------------------150°CLead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------260°C Storage Temperature Range---------------------------------------------------------------------------------------?65°C to 150°CESD Susceptibility (Note 2) 文档下载 免费文档下载 http://www.mianfeiwendang.com/ HBM (Human Body Mode)-----------------------------------------------------------------------------------------2kVMM (Machine Mode)-------------------------------------------------------------------------------------------------200V Recommended Operating Conditions (Note 3) zz Junction Temperature Range---------------------------------------------------------------------------------------?40°C to 125°CAmbient Temperature Range-----------------------------------------------------------------------------http://www.mianfeiwendang.com/doc/b57e378979599972c8a666ce----------?40°C to 85°C Electrical Characteristics To be continued DS9277A/B-02 www.richtek.com 5 RT9277A/B March 2007 文档下载 免费文档下载 http://www.mianfeiwendang.com/ Preliminary Note 1.Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in theoperational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extendedperiods may remain possibility to affect device reliability. Note 2. Devices are ESD sensitive. Handling precaution recommended. Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of ://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceJEDEC measurement standard. www.richtek.com 6 DS9277A/B-02 March 2007 Preliminary Typical Operating Characteristics Efficiency vs. Output Current 51-3 thermal 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 959085 RT9277A/B Efficiency vs. Output Current 100 90 Efficiency (%) Efficiency (%) 80757065605550 20 40 60 80 100120140160180200 80 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 70 60 50 50 100 150 200 250 300 350 400 Output Current (mA)Output Current (mA) Efficiency vs. Output Current 100 文档下载 免费文档下载 http://www.mianfeiwendang.com/ Output Voltage vs. Output Current 12.06 90 12.04 Efficiency (%) 80 Output Voltage (V) 12.0212.0011.9811.96 70 60://www.mianfeiwendang.com/doc/b57e378979599972c8a666cear 50 50 100 150 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 200 250 300 350 400 11.94 20 40 60 80 100120140160180200 Output Current (mA)Output Current (mA) Output Voltage vs. Output Current 12.0612.04 文档下载 免费文档下载 http://www.mianfeiwendang.com/ Output Voltage vs. Output Current 9.00 Output Voltage (V) 12.0011.9811.9611.9411.92 Output Voltage (V) 12.02 8.96 8.92 8.88 8.84 11.90 50 100 150 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 200 250 300 350 8.80 50 100 150 200 250 300 350 Output Current (mA)Output Current (mA) DS9277A/B-02 March 2007 文档下载 免费文档下载 http://www.mianfeiwendang.com/ www.richtek.com 7 RT9277A/B Prelimhttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceinary Output Voltage vs. Input Voltage 11.98611.984 Output Voltage vs. Input Voltage Output Voltage (V) 11.98211.98011.97811.97611.974 11.972 2.5 2.8 3.0 3.3 3.5 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 3.8 4.0 4.3 4.5 4.8 5.0 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 4.8 5.0 Input Voltage (V)Input Voltage (V) No Load Supply Current vs. Input Voltage 500 Current Limit vs. Input Voltage 1.81.7 No Load Supply Current (uA ) 450 Current Limit (mA ) 400350300250200150 2.5 3 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 3.5 4 4.5 5 5.5 1.61.51.41.3 1.22.5 3.0 3.5 4.0 http://www.mianfeiwendang.com/doc/b57e378979599972c8a666ce4.5 5.0 5.5 Input Voltage (V)Input Voltage (V) VFB vs. Temperature 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 1.2381.2381.2371.2371.2361.2361.2351.2351.2341.234 -40 -20 20 40 60 80 100 1200 Frequency vs. Temperature 1300 Frequency (kHz) VFB Voltage(V) 1100 文档下载 免费文档下载 http://www.mianfeiwendang.com/ 1000 900 800 -40 -20 20 40 60 80 100 Temperature(°C)Temperature(°C) www.richtek.com8 DS9277A/B-02 Preliminary March 2007 文档下载 免费文档下载 http://www.mianfeiwendang.com/ RT9277A/B Power Off Start Up VL1(10V/Div) VL1(10V/Div) VOUT(5V/Div)VEN(5V/Div)ILOAD(1A/Div) VIN = 3.3V, IOUT = 200mA, f = 640kHz VOUT(5V/Div)VEN(5V/Div)ILOAD(1A/Div) VIN = 3.3V, IOUT = 200mA, f = 640kHz http://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceTime (500μs/Div) SwitchingSwitching VL1(10V/Div)VOUT accoupled(100mV/Div) VL1(10V/Div)VOUT accoupled(100mV/Div) IL1 (500mA/Div) (2.5ms/Div)Time 文档下载 免费文档下载 http://www.mianfeiwendang.com/ VIN = 3.3V, IOUT = 200mA, f = 640kHz IL1 (500mA/Div) VIN = 3.3V, IOUT = 200mA, f = 1.2MHz Time (1μs/Div)Time (1μs/Div) Load Transient Response Load Transient Response VOUT accoupled(500mV/Div) VOUT accoupled(500mV/Div) ILOAD (200mA/Div) VIN = 3.3V, f = 640kHz ILOAD (100mA/Div) VIN = 3.3V, f = 1.2MHz 文档下载 免费文档下载 http://www.mianfeiwendang.com/ Time (250μs/Div) Time (250μs/Div) DS9277A/B-02 March 2007 www.richtek.com 9 RT9277A/B Application Information Preliminary The design procedure of Boost converter can start fromthe maximum input current, which is related about inductohttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666cer,catch-diode input/output capacitor selections and themaximum power which internal switch can stand. It canbe derived from maximum output power, minimum inputvoltage and the efficiency of Boost converter. Once themaximum input current is calculated, the inductor valuecan be determined and the other components as well.Inductor Selection For a better efficiency in high switching frequency converter,the inductor selection has to use a proper core materialsuch as ferrite core to reduce the core loss and chooselow ESR wire to reduce copper loss. The most importantpoint is to prevent the core saturated when handling themaximum peak current. Using a shielded inductor canminimize radiated noise in sensitive applications. Themaximum peak inductor 文档下载 免费文档下载 http://www.mianfeiwendang.com/ current is the maximum inputcurrent plus the half of inductor ripple current. Thecalculated peak current has to be smaller than the currentlimitation in the electrical characteristics.http://www.mianfeiwendang.com/doc/b57e378979599972c8a666ce A typical settingof the inductor ripple current is 20% to 40% of themaximum input current. If the selection is 40%, themaximum peak inductor current is : IPEAK = IIN(MAX) IRIPPLE=1.2×IIN(MAX) 2 ?IOUT(MAX)×VOUT? = 1.2×? ×VIN(MIN)?? Input Capacitor Selection For better input bypassing, low-ESR ceramic capacitors are recommended for performance. A 10μF input capacitoris sufficient for most applications. For a lower output powerrequirement application, this value can be decreased.Output Capacitor Selection For lower output voltage ripple, low-ESR ceramic capacitorsare recommended. The tantalum capacitors can be usedas well, but the ESR is bigger than ceramic capacitor. Theoutput voltage ripple consists of two components: one isthe pulsating output ripple current flows through the ESR,and the other is the capacitive ripple caused by chargingand discharging. ://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceparVRIPPLE=VRIPPLE_ESR VRIPPLE_C 文档下载 免费文档下载 http://www.mianfeiwendang.com/ ?VIN?I?V ?IPEAK×RESR PEAK?OUT? COUT?VOUT×fOSC?Output Voltage The regulated output voltage is calculated by : VOUT=VREF×??1 ?? ?R2? Where VREF = 1.24V typical. For most applications, R2 is a suggested a value up to100kΩ Place the resistor-divider as close to the IC aspossible to reduce the noise sensitivity.Loop Compensation The RT9277A/B voltage feedback loop can be compensatedwith an external compensation network consisted of R3,C3 and C4 (As shown in Figure 1). Choose R3 to set thehigh-frequency integrator gain for fast transient responsewithout over or under compensation. Once R3 isdetermined, C3 is selected to set the integrator zero tomaintain loop stability. The purpose of C4 is to cancel thezero caused by output capacitor and the capacitor ESR. Ifthe ceramic capacitor is selected to be the output capacitor,Chttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666ce4 can be taken off because of the small ESR. C2 is theoutput capacitor as shown in Figure 1. The followingequations give approximate calculations of eachcomponent : The minimum inductance value is derived from the followingequation : 文档下载 免费文档下载 http://www.mianfeiwendang.com/ L = η×VIN(MIN)×[VOUT-VIN(MIN)] 2 0.4×IOUT(MAX)×VOUT×fOSC 2 Depending on the application, the recommended inductorvalue is between 2.2μH to 10μH.Diode Selection To achieve high efficiency, Schottky diode is good choicefor low forward drop voltage and fast switching time. Theoutput diode rating should be able to handle the maximumoutput voltage, average power dissipation and the pulsatingdiode peak current. www.richtek.com10 DS9277A/B-02 March Preliminary 200×VOUT2×C2R3 = L1 -3 2007 文档下载 免费文档下载 http://www.mianfeiwendang.com/ C3 =VIN 0.005×RESR×L1C4 =VOUT2 RT9277A/B The best criterihttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceon to optimize the loop compensation isby inspecting the transient response and adjusting thecompensation network.Soft-Start Capacitor The soft-start function begins from VSS = 0V to VSS = 1.24Vwith a 4μA constant current charging to the soft-startcapacitor, so the capacitor should be large enough to letthe output voltage reach regulation inside the soft-startcycle. Typical value of soft-start capacitor range is from10nF to 200nF. After the cycle finished, the load can startto draw maximum current as required.Layout Guideline For high frequency switching power supplies, the PCBlayout is important step in system application design. Inorder to let IC achieve good regulation, high efficiency andstability, it is strongly recommended the powercomponents should be placed as close as possible. Thesetraces should be wide and short. The feedback pin and thenetworks of feedback and compensation should keep phttp://www.mianfeiwendang.com/doc/b57e378979599972c8a666ceower shielded with a ground traceor plane to prevent noise coupling. DS9277A/B-02 www.richtek.com 11 March 2007 awayfrom loops, and the be 文档下载 免费文档下载 http://www.mianfeiwendang.com/ RT9277A/B Outline Dimension Preliminary L A2 8-Lead MSOP Plastic Package Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei CityHsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Richtek Technology Corporation Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien CityTaipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465Email: [email protected] 文档下载 免费文档下载 http://www.mianfeiwendang.com/ www.richtek.com 12 DS9277A/B-02 March 2007 文档下载网是专业的免费文档搜索与下载网站,提供行业资料,考试资料,教 学课件,学术论文,技术资料,研究报告,工作范文,资格考试,word 文档, 专业文献,应用文书,行业论文等文档搜索与文档下载,是您文档写作和查找 参考资料的必备网站。 文档下载 http://www.mianfeiwendang.com/ 亿万文档资料,等你来发现