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SC104IMLTRT

SC104IMLTRT

  • 厂商:

    SEMTECH

  • 封装:

  • 描述:

    SC104IMLTRT - Micro Power Constant-Current DC-DC Converter - Semtech Corporation

  • 详情介绍
  • 数据手册
  • 价格&库存
SC104IMLTRT 数据手册
Micro Power Constant-Current DC-DC Converter POWER MANAGEMENT Description The SC104 is a micro power dc-dc step-up converter which converts an input voltage, in the range of 1.55V to 10V, to a constant current. The part features a range of user programmable voltages and currents including dynamic adjustment of the “constant” current. The converter is capable of generating output voltages as low as the input supply voltage and up to 38V. During shutdown, the part draws a typical 500nA standby current. The output current is set by the external resistor R1. Dynamic adjustment of the output current can be made by the application of an analog voltage to the ADJ input, or by PWMing this pin. The peak switch current is programmable through the external resistor RLIM enabling the use of a wide range of inductors and battery technologies. SC104 Features Adjustable output current using pulse width modulation or analog voltage input 38V output capability supports up to 10 white LEDs Wide range of input voltages 1.55V to 10V Low quiescent current 0.5µA standby current in shutdown Programmable cycle by cycle current limit Surface mount packaging (3x3mm 8pin MLP) Output voltage and over-temperature protection Applications White LED supplies Color LED supplies Cellular phones PDAs Electronic books Handheld computers Wireless web appliances Typical Application Circuit - 6 LEDs VIN = 3V to 5V IOUT ADJUST 1 2 U1 ADJ FB GND OUT SC104 EN LIM IN LX CIN 4.7uF 8 7 6 5 L1 12uH RLIM 7.50k ENABLE IOUT = 15mA LED4 LED5 LED6 3 4 LED3 LED2 LED1 RSET 23.2R COUT 0.47uF D1 March 22, 2005 1 www.semtech.com SC104 POWER MANAGEMENT Absolute Maximum Ratings Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Parameter Input Supply Voltage LX Pin Voltage (Power switch OFF) FB Pin Voltage EN Pin Voltage LIM Pin Voltage ADJ Pin Voltage OUT Pin Voltage Thermal Impedance Junction to Ambient Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Lead Temperature SC104IMLTR (Soldering) 10s - 30s SC104IMLTRT (Soldering) 20s - 40s ESD Rating (Human Body Model) Symbol VIN V LX V FB V EN VLIM V AD J VOUT θJ A TA TJ TSTG TLEAD V ESD Maximum -0.3 to 12 -0.3 to 55 -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 2 -0.3 to 55 84 -40 to +85 -40 to +125 -65 to +150 240 260 2 Units V V V V V V V °C/W °C °C °C °C kV Electrical Characteristics Unless specified: VIN = VEN = 2V, -40 ≤ TA ≤ 85°C, typical values are at room temperature. Parameter Input Supply Voltage Symbol VIN Test Conditions TA = 25oC Min 1.55 1.75 Typ Max 10 10 Units V Shutdown Current Feedback Voltage Feedback Input Current Power Switch Saturation Voltage Junction Temperature at Thermal Shutdown(1) Over-Voltage Protection Adjust Voltage Adjust Voltage Switching Inhibit Threshold  2005 Semtech Corp. IQ(OFF) V FB IFB VCE(SAT) TTSD VOVP V AD J VTH(ADJ) 2 V E N = 0V 340 VFB < 350mV ILX = 300mA 140 Test current = 10µA IADJ= 0A 36 0.97 200 0.5 350 700 150 150 38 1.00 3 360 1115 250 160 44 1.03 100 µA mV nA mV o C V V mV www.semtech.com SC104 POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: VIN = VEN = 2V, -40 ≤ TA ≤ 85°C, typical values are at room temperature. Parameter Adjust Input Current Symbol IADJ Test Conditions V A D J = 0V V A D J = 1V VADJ = 1.25V Min 6 -500 -1.3 -920 0.60 1.00 1.8 70 Typ 10 0 -2.3 Max 20 500 -3.8 Units µA nA µA mA Maximum Switch Current Switch Off Time ILX tOFF ILI M= 150µA VFB = 300mV V FB = 0V 0.76 1.25 2.25 1.00 1.60 2.7 µs Switch On Time Maximum Duty Cycle Switch Leakage Voltage Reference for Current Limit Setting Resistor ILX to ILIM Ratio Logic Inputs Enable Input Voltage tON %DC ILX VLIM ILX / ILIM excludes current limited conditions µs % switch off, VLX = 5V ILIM = 50µA ILIM = 50µA 385 7100 -0.01 400 8150 -1.0 410 8800 µA mV A/A VIH VIL IEN > 300nA 1.5 0.2 V Enable Input Bias Current IIL IIH VEN = 0.3V VEN = 1.3V 0.3 0.7 µA Note: (1) Guaranteed by design.  2005 Semtech Corp. 3 www.semtech.com SC104 POWER MANAGEMENT Pin Configuration Top View Ordering Information Part Number SC104IMLTR(1) SC104IMLTRT(2) S C 104E V B Evaluation Board P ackag e MLP-8 Notes: (1) Only available in tape and reel packaging. A reel contains 3000 devices. (2) Lead free product. This product is fully WEEE and RoHS compliant. MLP-8 Block Diagram  2005 Semtech Corp. 4 www.semtech.com SC104 POWER MANAGEMENT Pin Descriptions Pin 1 2 3 4 5 6 7 8 Pin Name AD J FB GND OUT LX IN LIM EN Pin Function Apply a PWM or analog voltage to this pin for dynamic output current adjustment. Connects to the resistor in the ground leg of the series LEDs (feedback for the constant load current). Ground pin. Connect to the boost output at the cathode of the schottky diode. This pin is the input for the over-voltage protection circuit. Internal switch connection. Connect the inductor and the anode of the schottky diode to this pin. Input supply pin. Connect to a battery or power supply. Current limit set pin. A resistor (RLIM) connected from LIM to GND sets the peak inductor current limit threshold. Digital input for enable. Connect this pin to ground for shutdown or connect a voltage between 1.2V to 5.0V for enable. A 1MΩ pull-up resistor connecting to IN is also acceptable, provided 10µA > IEN > 300nA. Marking Information 104 yyww Marking for the MLP 8 Lead package: yyww = Date Code (Example: 0012)  2005 Semtech Corp. 5 www.semtech.com SC104 POWER MANAGEMENT Applications Information Component Selection - Introduction Referring to the 6 LED typical schematic below, there are three components that depend upon the application that need to be determined: RSET - this resistor sets the output current for the device RLIM - this resistor sets the peak inductor current L - the output inductor All the other components can be mostly generalized and are addressed below the following design steps. VIN = 3V to 5V Vf = 0.35V VCE(SAT) = 0.25V thus DC = 0.87 Since this value is greater than the guaranteed minimum value for maximum duty cycle, the device will be operating in discontinuous mode to provide the desired output. Note that the duty cycle does not depend upon the output current, and that unless the output to input ratio is low, the device will usually need to be in discontinuous mode, so we will cover that first (Step 1 through Step 5). Continuous mode calculations start at Step 6. Step 2: Calculating the Inductor for Discontinuous Mode Having determined that we need to be operating in discontinuous mode, we next need to calculate the maximum inductor value allowed that will permit the part to output the correct power. The maximum discontinuous inductor value, L(D) is given by: L(D ) = 2 • 1.4 • VOUT • IOUT • (t ON(MIN ) + t OFF(MIN ) ) t ON(MIN ) • VIN • (VIN − VCE ( SAT ) ) 2 IOUT ADJUST 1 2 U1 ADJ FB GND OUT SC104 EN LIM IN LX CIN 4.7uF 8 7 6 5 L1 12uH RLIM 7.50k ENABLE IOUT = 15mA LED4 LED5 LED6 3 4 LED3 LED2 LED1 RSET 23.2R COUT 0.47uF D1 Step 1: Continuous or Discontinuous? The first thing to do when designing with the SC104 is to determine whether the output inductor will be operating in continuous mode (where the inductor current does not drop to zero while the device is switching) or discontinuous mode (where the inductor current drops to zero while switching). This determination can be made simply by calculating the required duty cycle needed for the target output voltage, and comparing it to the guaranteed minimum value for the maximum duty cycle from the Electrical Characteristics on Page 3. %DC(MIN) = 70% (or 0.7 duty). If DC is greater than 0.7 then discontinuous mode is required. The required duty cycle is calculated as follows: DC = • (V OUT (VOUT − VIN + Vf ) − VCE ( SAT ) + Vf ) Where: tON(MIN) = minimum switch on-time = 1.8µs IOUT = required output current tOFF(MIN) = minimum switch off-time = 0.6µs Using our 6 LED example: IOUT = 15mA thus L(D) = 14.4µH Selecting the next lower standard value gives us L(D) = 12µH. Of course a lower value inductor may be used if desired, but may not necessarily be the most efficient choice. Step 3: Calculating the Current Limit Required with this Inductor for Discontinuous Mode Having determined the inductor value we are going to use, we next need to calculate the current limit required to meet the necessary output power. The discontinuous mode current limit, ILIM(D), is given by: ILIM(D ) = (V (VOUT − VIN + Vf ) OUT − VCE( SAT ) + Vf ) Where: VOUT = output voltage, the sum of the total LED (max.) forward voltage drop at the required output voltage plus the feedback voltage, 0.35V. VIN = minimum input voltage Vf = Schottky diode (D1) forward voltage drop VCE(SAT) = power switch saturation voltage Using the 6 LED example above: VOUT = (6 * 3.475) + 0.35 = 21.2V VIN = 3V  2005 Semtech Corp. 6 (V IN − VCE( SAT ) ) • t ON(MIN) L (D ) www.semtech.com SC104 POWER MANAGEMENT Applications Information (Cont.) Step 3: (Cont.) Using our 6 LED example: L(D) = 12µH thus ILIM(D) = 412mA Step 4: Calculating the Current Limit Resistor for Discontinuous Mode The current limit resistor value is calculated based upon the minimum ratio of the switch current to the current out of the LIM pin. It also takes into account the fact that there is a propagation delay during which time the inductor current ramps beyond the current limit trip point. Since ILIM increases as RLIM decreases, this value is a maximum. The maximum current limit resistor, RLIM(D), for discontinuous mode is therefore: RLIM(D ) =  t • (VIN − VCE(SAT ) )   ILIM(D ) − plh    L (D )   VLIM(MIN) • Ratio (MIN) equation: R SET = VFB IOUT Using our 6 LED example: IOUT = 15mA thus RSET = 23.3Ω We will select the 1% resistor value 23.2Ω. Note: this calculation is applicable to both continuous and discontinuous modes. Step 6: Calculating the Inductor for Continuous Mode Having determined that we need to be operating in continuous mode, we next need to calculate the maximum inductor value allowed that will permit the part to output the correct power. The maximum continuous inductor value, L(C) is given by: L(C) = 2 • VIN • t OFF(MIN) • (VOUT + Vf − VIN ) 1.4 • VOUT • IOUT Where: VLIM(MIN) = the minimum value of the current limit voltage reference = 385mV Ratio (MIN) = t he minimum value of the I LX t o I LIM r atio = 7100 A/A tplh = propagation delay from reaching the current limit trip point to the power switch turning off = 200ns Using our 6 LED example: ILIM(D) = 412mA thus RLIM(D) = 7.5kΩ Selecting this value or the next lower standard value in this case gives us 7.5kΩ. Of course a lower value resistor may be used if desired, but may not necessarily be the most efficient choice. Step 5: Calculating the Current Set Resistor The current set resistor is in series with the series LED string. Thus the voltage developed across it is proportional to the current flowing through the LEDs. The device will regulate this voltage so that its average value equals the feedback voltage, VFB, which is typically 350mV. Thus the current set resistor value is given by the following  2005 Semtech Corp. 7 Where: IOUT = required output current tOFF(MIN) = minimum switch off-time = 0.6µs Selecting the next lower standard value gives us a safe value for this inductor. Step 7: Calculating the Current Limit Required with this Inductor for Continuous Mode Having determined the inductor value we are going to use, we next need to calculate the current limit required to meet the necessary output power. The continuous mode current limit, ILIM(C), is given by: ILIM( C ) = (VOUT + Vf − VIN ) • t OFF(MIN) 0.4 • L( C ) Step 8: Calculating the Current Limit Resistor for Continuous Mode The current limit resistor value is calculated based upon the minimum ratio of the switch current to the current out of the LIM pin. It also takes into account the fact that there is a propagation delay during which time the www.semtech.com SC104 POWER MANAGEMENT Applications Information (Cont.) Step 8: (Cont.) inductor current ramps beyond the current limit trip point. Since ILIM increases as RLIM decreases, this value is a maximum. The maximum current limit resistor, RLIM(C), for continuous mode is therefore: RLIM( C ) =  t • (VIN − VCE(SAT ) )   ILIM( C ) − plh    L(C)   VLIM(MIN ) • Ratio (MIN) Schottky diode: any schottky diode rated for the average and peak currents being seen in the circuit will suffice. However a higher current rated schottky diode will result in lower forward voltage drops and hence higher efficiency. The selection of the schottky will depend upon the optimum choice between efficiency, board space, and cost. Inductor: similarly, any inductor rated for the average and peak currents required by the design and capable of operating at the fixed off-time of 760ns will suffice, but inductors with lower series resistance will result in lower losses. The selection of the inductor will depend upon the optimum choice between efficiency, board space, component height, and cost. Toko D62LCB and D63LCB series work very well. LED Dimming Dimming the LEDs (i.e. reducing the output current from the set level to reduce brightness) can be achieved a couple of ways: 1) PWMing the ADJ pin using an open drain or open collector (with no pull-up). Using a PWM signal at this pin will reduce the output current by alternating between OFF (ADJ < 100mV) and switching normally. The lower the duty cycle, the lower the output current. A PWM frequency of 1kHz maximum is recommended. 2) analog voltage applied to the ADJ pin: apply a DC voltage between 0V to 0.1V (OFF) and 1V (full current) to the ADJ pin. This pin should not be pulled above 1V under normal operation, and should never exceed the absolute maximum rating. Using a DC voltage will result in the modulation frequency of the inductor current ramp reducing and care must be taken to ensure that this does not become audible in sensitive applications. Where: VLIM(MIN) = the minimum value of the current limit voltage reference = 385mV Ratio (MIN) = t he minimum value of the I LX t o I LIM r atio = 7100 A/A tplh = propagation delay from reaching the current limit trip point to the power switch turning off = 200ns Selecting the calculated value or the next lower standard value is recommended. Component Selection - General Capacitor Selection: the SC104 has been designed to be used with ceramic input and output capacitors. The input to the device should be bypassed using a 4.7µF ceramic capacitor rated for the maximum input voltage. The output capacitor should be a ceramic capacitor in the range of 0.22µF to 1µF. Care should be taken that the voltage rating of this capacitor meets the output voltage requriements, and if the part is going to be run open circuit during assembly testing using the OVP feature, then the capacitor should be rated 50V.  2005 Semtech Corp. 8 www.semtech.com SC104 POWER MANAGEMENT Typical Characteristics Shutdown Current vs. Junction Temperature vs. Input Voltage 2.0 1.8 1.6 1.4 IQ(OFF) (µA) VFB (mV) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -50 -25 0 25 TA (°C) 50 75 100 V IN = 2V VIN = 5V VEN = 0V VIN = 10V 360 358 356 354 352 350 348 346 344 342 340 -50 -25 0 25 TJ (C) 50 75 100 125 V IN = 2V V IN = 5V V IN = 10V Average Feedback Voltage vs. Junction Temperature vs. Input Voltage Power Switch Saturation Voltage vs. Junction Temperature 250 225 200 175 VCE(SAT) (mV) 150 125 100 75 50 25 0 -50 -25 0 25 TJ (°C) 50 75 100 125 VLIM (mV) VIN = 2V ILX = 300mA 410.0 407.5 405.0 402.5 400.0 397.5 395.0 392.5 390.0 387.5 385.0 -50 Current Limit Reference Voltage vs. Junction Temperature VIN = 2V ILIM = 50µA -25 0 25 TJ (°C) 50 75 100 125 ILX to ILIM Ratio vs. Junction Temperature 9000 8800 8600 8400 ILX/ILIM (A/A) 8200 8000 7800 7600 7400 7200 7000 -50 -25 0 25 TJ (C) 50 75 100 125 VIN = 2V ILIM = 50µA  2005 Semtech Corp. 9 www.semtech.com SC104 POWER MANAGEMENT Typical Application Circuit - 3 LEDs VIN = 3V to 5V U1 IOUT ADJUST 1 2 IOUT = 15mA LED3 3 4 LED2 LED1 RSET 23.2R COUT 1uF D1 ADJ FB GND OUT SC104 EN LIM IN LX 8 7 6 5 L1 27uH CIN 4.7uF ENABLE RLIM 15k Typical Application Circuit - 10 LEDs VIN = 3V to 5V IOUT ADJUST 1 2 U1 ADJ FB GND OUT SC104 EN LIM IN LX CIN 4.7uF 8 7 6 5 L1 6.2uH RLIM 3.9k ENABLE IOUT = 15mA LED6 LED7 LED8 LED9 LED10 3 4 LED5 LED4 LED3 LED2 LED1 RSET 23.2R COUT 0.22uF D1  2005 Semtech Corp. 10 www.semtech.com SC104 POWER MANAGEMENT Outline Drawing - MLP-8 A N D B DIM A A1 A2 A3 b b2 D E e L L1 L2 N 01 aaa bbb DIMENSIONS MILLIMETERS INCHES MIN NOM MAX MIN NOM MAX .031 .039 .000 .002 .026 .030 (.008) .011 .012 .015 .007 .012 .114 .118 .122 .114 .118 .122 .026 BSC .008 .011 .018 .008 .011 .018 .005 8 0° 12° .003 .004 1.00 0.80 0.00 0.05 0.65 0.75 (0.20) 0.29 0.31 0.39 0.17 0.30 2.90 3.00 3.10 2.90 3.00 3.10 0.65 BSC 0.20 0.29 0.45 0.20 0.29 0.45 0.13 8 0° 12° 0.08 0.10 PIN 1 INDICATOR (LASER MARK) 12 01 aaa C C bxN bbb E A3 A2 A A1 CAB SEATING PLANE e e/2 L2 L b2 L1 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DIMENSIONS "D" AND "E" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. L2  2005 Semtech Corp. 11 www.semtech.com SC104 POWER MANAGEMENT Land Pattern - MLP-8 X DIM (C) G Y P Z C G P X Y Z DIMENSIONS INCHES MILLIMETERS (.114) .079 .026 .015 .035 .150 (2.90) 2.00 0.65 0.38 0.90 3.80 NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 FAX (805)498-3804 Visit us at: www.semtech.com  2005 Semtech Corp. 12 www.semtech.com
SC104IMLTRT
1. 物料型号: - 型号为SC104IMLTR和SC104IMLTRT,分别提供有铅和无铅版本,仅提供卷带和盘装。SC104EVB为评估板型号。

2. 器件简介: - SC104是一款微功率升压型DC-DC转换器,可以将1.55V至10V的输入电压转换为恒定电流输出,输出电压可低至输入电压,高达38V。具备用户可编程的电压和电流范围,包括动态调整“恒定”电流。在关闭状态下,器件的待机电流为500nA。

3. 引脚分配: - ADJ(1号引脚):用于动态输出电流调整,可通过PWM或模拟电压输入。 - FB(2号引脚):连接至LED串联的地腿电阻,用于恒定负载电流的反馈。 - GND(3号引脚):地线引脚。 - OUT(4号引脚):连接至肖特基二极管阴极的升压输出。 - LX(5号引脚):内部开关连接引脚,连接电感器和肖特基二极管阳极。 - IN(6号引脚):输入电源引脚,连接至电池或电源。 - LIM(7号引脚):电流限制设定引脚,通过连接至地的电阻设定峰值电感电流限制阈值。 - EN(8号引脚):数字使能输入引脚,接地以关闭或接1.2V至5.0V电压以启用。

4. 参数特性: - 可调输出电流、38V输出能力、宽输入电压范围、低静态电流、可编程电流限制、表面贴装封装、输出电压和过温保护。

5. 功能详解: - 详细介绍了SC104的主要功能和操作特性,包括输出电流的设定、电流限制的调整、引脚功能和应用电路设计步骤。

6. 应用信息: - 适用于白光LED供电、彩色LED供电、手机、掌上电脑、电子书籍、无线网络设备等。

7. 封装信息: - 提供3x3mm 8引脚的MLP封装,符合WEEE和RoHS标准。封装图纸和尺寸信息详细说明了引脚布局和尺寸要求。
SC104IMLTRT 价格&库存

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