凌特公司(Linear Technology Corporation)创建于 1981 年，总部位于美国硅谷，是一家高性能线性集成电路制造商。

　　凌特于 1986 年成为一家上市公司，并于 2000 年成为由主要上市公司组成的 S&P 500 指数的成员之一。

　　凌特的产品包括高性能放大器、比较器、电压基准、单片滤波器、线性稳压器、DC/DC 变换器、电池充电器、数据转换器、通信接口电路、射频信号修整电路及其它众多模拟功能。凌特公司的高性能电路可用于电信、蜂窝电话、如光纤交换机的网络设备、笔记本电脑和台式电脑、计算机外围设备、视频/多媒体装置、工业仪表、安全监控设备、包括数码照相机、MP3 播放器在内的高端消费类产品、复杂医疗设备、汽车用电子设备、工厂自动化、过程控制、军事和航天系统等领域。

　　The LTCR7103 is a high efficiency, monolithic synchronousstep-down DC/DC converter utilizing a constant frequency,average current mode control architecture. It operates from an input voltage range of 4.4V to 105V and provides anadjustable regulated output voltage from 1V to VIN whiledelivering up to 2.3A of output current.

　　The LTC7103 features high frequency operation anda low minimum on-time that reduce inductor size andenable constant-frequency operation even at very highstep-down ratios. In addition, the LTC7103 achieves thelowest possible dropout voltage with 100% maximumduty cycle operation. During light load operation, converterefficiency and output ripple can be optimized by selectingBurst Mode or pulse-skipping operation.

　　The LTC7103 includes accurate, high speed average currentprogramming and monitoring without the need foran external sense resistor. Additional features include a bypass LDO to maximize efficiency, fixed or adjustableoutput voltage and loop compensation, and a wide arrayof protection features to enhance reliability.

　　LTC7103主要特性:

　　Wide VIN Range: 4.4V to 105V (110V Abs Max)

　　Ultralow EMI/EMC Emissions: CISPR 25 Compliant

　　2μA IQ When Regulating 48VIN to 3.3VOUT

　　Fast and Accurate Output Current Programming andMonitoring with No External RSENSE

　　Brick Wall Current Limit

　　Low Minimum On-Time: 40ns

　　Wide VOUT Range: 1V to VIN

　　100% Maximum Duty Cycle Operation

　　Programmable Fixed Frequency: 200kHz to 2MHz

　　Eight, Pin-Selectable Fixed (1.2V to 15V) orAdjustable Output Voltages

　　Selectable Pulse-Skipping or Low Ripple BurstModeR Operation at Light Loads

　　PLL Synchronization to External Clock

　　EXTVCC LDO Powers Chip from VOUT = 3.3V to 40V

　　OPTI-LOOPR or Fixed Internal Compensation

　　Input and Output Overvoltage Protection

　　Thermally Enhanced (5mm × 6mm) QFN Package

　　LTC7103应用:

　　Battery Chargers and CC/CV Supplies

　　Automotive and Military Systems

　　Industrial, Avionics and Heavy Equipment

　　Medical Instruments and TelecommunicationSystems

　　图1.LTC7103框图

　　图2.LTC7103应用电路:高效5V-100V输入,5V/2.3A输出

　　图3.LTC7103应用电路:高效12V-100V输入,12V/2.3A输出

　　图4.LTC7103应用电路:低EMI 5V-100V输入,5V/2.3A输出

　　图5.LTC7103应用电路:2相,12V-100V输入,12V/4.6A输出

　　图6.LTC7103应用电路:汽车12V/24V输入,12V/24V 2.3A输出,100V输入浪涌,0.5秒故障计时器

　　图7.LTC7103应用电路:50W LED驱动器

　　图8.LTC7103应用电路:带充电终止的2.5A 6颗SLA电池充电器

　　演示板DC2317A

　　Demonstration circuit 2317A is a 100V monolithic DC/DC step-down regulator featuring the LTC®7103. Thedemo board is designed for a 5V/2.3A output from a 5Vto 100V input at 400kHz switching frequency. The wideinput range makes it suitable for automotive, industrial,medical instrument, and telecom applications. This buckregulator has a peak efficiency of 93.5% at 12VIN, 88.3%at 48VIN and 81.5% at 100VIN.

　　The LTC7103 is a compact, high efficiency synchronousmonolithic step-down switching regulator with fast currentprogramming. The power switches, compensationnetwork and other necessary circuits are inside of theLTC7103 to minimize external components and simplifydesign. The LTC7103 has wide operating range from 4.4Vto 105V. A 40ns minimum on-time, together with 100%maximum duty cycle allow practical use at any output voltagebetween 1V and VIN. The switching frequency can beprogrammed either via an oscillator resistor or an externalclock over a 200kHz to 2MHz range. Additional featuresinclude a fast and accurate output current programmingand monitoring, and ultralow EMI/EMC emissions.

　　The demo board has an EMI filter installed. The EMIperformance of the board (with EMI filter) is shown inFigure 2. The figure shows that the circuit passes theCISPR 25 radiated emission test with a wide margin. Toachieve EMI/EMC performance as shown in Figure 2, theinput EMI filter is required and the input voltage shouldbe applied at +VIN_EMI turret pin.The demo board provides current monitor and outputclock signal to interface with an external application circuit.

　　User selectable mode selection (JP1) is provided andBurst Mode® operation position is selected by default.Burst Mode operation increases light load efficiency whilepulse-skipping mode allows constant-frequency operationto a lighter load. This demo board allows phase-lockedloop (PLL) synchronization to an external clock by selecting SYNC mode on JP1 and by providing a clock signalon CLKIN turret.

　　The LTC7103 data sheet gives a complete description ofthe part, operation and application information. The datasheet must be read in conjunction with this demo manualfor DC2317A. The LTC7103 is assembled in the 36 (26)lead QFN package. Proper board layout is essential formaximum thermal and electrical performance. See the data sheet sections for details.

　　图9.演示板DC2317A外形图

　　图10.演示板DC2317A测量建立图

　　图11.演示板DC2317A电路图

　　演示板DC2317A材料清单:

　　详情请见:

dc2317af.pdf

7103f.pdf

DC2317A.zip.zip