Linear公司的LTC7103是采采用恒頻平均電流模式控制架構的高效單片同步降壓DC/DC轉換器,輸入電壓從4.4V到105V,可調輸出電壓從1V到VIN,輸出電流高達2.3A.具有超低EMI/EMC,CISPR 25兼容,100%最大占空比工作,可編固定頻率200kHz-2MHz.主要用在電池充電器和CC/CV電源,汽車和軍用系統,工業,航空和重型設備以及醫療設備和通信系統.本文介紹了LTC7103主要特性,框圖和多種應用電路,以及演示板DC2317A,電路圖和材料清單.

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應用:

Battery Chargers and CC/CV Supplies
Automotive and Military Systems
Industrial, Avionics and Heavy Equipment
Medical Instruments and TelecommunicationSystems

圖1.LTC7103框圖

圖2.LTC7103應用電路:高效5V-100V輸入,5V/2.3A輸出

圖3.LTC7103應用電路:高效12V-100V輸入,12V/2.3A輸出

圖4.LTC7103應用電路:低EMI 5V-100V輸入,5V/2.3A輸出

圖5.LTC7103應用電路:2相,12V-100V輸入,12V/4.6A輸出

圖6.LTC7103應用電路:汽車12V/24V輸入,12V/24V 2.3A輸出,100V輸入浪涌,0.5秒故障計時器

圖7.LTC7103應用電路:50W LED驅動器

圖8.LTC7103應用電路:帶充電終止的2.5A 6顆SLA電池充電器

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.

圖9.演示板DC2317A外形圖

圖10.演示板DC2317A測量建立圖

圖11.演示板DC2317A電路圖
演示板DC2317A材料清單: