MIC3223 Evaluation Board High-Power Boost LED Driver with Integrated FET Bringing the Power to Light™ General Description How It Works The MIC3223 is a constant-current boost switching controller specifically designed to power a string of highpower LEDs. The MIC3223 has an input voltage range from 4.5V to 20V and is ideal for a variety of applications. The MIC3223 evaluation board is designed to accommodate for a VIN of 6V to 20V. The MIC3223 utilizes an internal power device which offers a cost-conscious solution for driving high-power LED applications. Power consumption has been minimized through the implementation of a 200mV feedback-voltage reference providing an initial accuracy of ±5%. The MIC3223 controller is dimmable via a PWM input signal. An external FET (Q1) is in series with the LED string and is used to PWM Dim the LEDs. The MIC3223 also features an enable pin for low-power shutdown. The LED current is regulated by keeping the voltage drop across the current-sense resistor (R5) constant. The LED current can be set by selecting the value of R5. In this version of the evaluation board, the output current is limited to 700mA. Table 1 provides a summary of the evaluation board specifications. The evaluation board schematic is shown in Figure 1 and the parts list is shown in the Bill of Materials table. The MIC3223 evaluation board is set to operate as a boost converter, which requires the output voltage to be greater than the input voltage. It is important to have the series LED forward voltage drops be greater than the input voltage because when the converter is off the input is connected to the output through the inductor (L1) and diode (D1). VIN is effectively applied across the LEDs and will turn on if the series sum of their forward voltage drop is not greater than VIN. For 100% dimming duty-cycle, simply pull DIM IN to 5V. For a different LED current, change R5 using the following equation (when R5 is 0.56Ω and the LED current is equal to 0.35A): The switching frequency is fixed to 1MHz ±30%. Requirements 1. 2. 3. 4. 5. Voltage source capable of supplying 50 Watts Load: LED, resistive, or electronic load Scope Voltage meter (Optional) Function generator for PWM Dimming VFB = VREF = ILED ×R5 where VREF = 0.2V PWM Dimming The PWM DIM signal applied to the DIM IN pin switches the current to the LEDs on and off. When DIM IN is high, the MIC3223 is enabled and the boost converter regulates the LED current by keeping the voltage drop across R5 constant. DIM IN also controls the DIM OUT pin. DIM OUT drives the gate of the external dimming FET (Q1). When DIM IN is high, DIM OUT is also high. When DIM IN is low, the converter turns off and the DIM OUT pin is low while driving the gate of Q1 low. When the gate of Q1 is low, Q1 turns off and the LED current stops. Ordering Information Order Part Number Description MIC3223TE BOOST EV Boost Evaluation Board MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com March 2010 M9999-030210 Micrel, Inc. MIC3223 Evaluation Board Quick-Start Guide Output Over-Voltage Protection (OVP) The MIC3223 provides over-voltage protection (OVP) circuitry in order to protect the system from an overvoltage fault condition. This OVP threshold can be programmed through the use of external resistors (R3 and R4). A reference value of 1.245V is used for the OVP. The following equation can be used to calculate the resistor value for R3 to set the OVP point. Normally use 100k for R3: 1. Connect a load (LED series string or resistive) between VOUT and LED RTN (note that this is not the same as GND). 2. Connect 12V (or other input voltage) to VIN and GND. 3. Use a current probe to measure the load current and monitor the switch node with a scope to view the switch waveform. 4. PWM Dimming: a. For no PWM dimming, connect the DIM IN terminal to the EN terminal. This is a convenient way to turn on and off the converter. b. For PWM DIMMING, connect a function generator to the DIM IN input and GND (not LED RTN). Set the output at 0V − 5V square wave pulse at 100Hz − 20kHz. Make sure the pulse goes all the way to 0V. March 2010 R4 = R3 (VOVP /1.245) − 1 On the evaluation board, these values have been set as follows: R4 = 3.24kΩ and R3 = 100kΩ and VOVP = 40V. 2 M9999-030210 Micrel, Inc. MIC3223 Evaluation Board Evaluation Board Design Specifications Parameter Minimum Typical Maximum VIN 6V 12 20V Output Voltage VIN 18-25 37V 7 9 LED Current 0 0.2 − 0.5 .7A Power Out 0 20W 15W Number of LEDs Efficiency 90% Switching Frequency (FIXED) 1MHz PWM Dim Frequency 0 300Hz Line Regulation 500Hz <5% Load Regulation <5% Ambient Temperature –40°C +25°C +85°C Table 1. Evaluation Board Design Specifications LED Current Selection R5 (Ω) I_LED 5 40mA 2 100mA 1 200mA 0.62 320mA 0.5 400mA 0.56 350mA 0.4 500mA 0.28 700mA Table 2. LED Current Selection March 2010 3 M9999-030210 Micrel, Inc. MIC3223 Evaluation Board Evaluation Board Schematic March 2010 4 M9999-030210 Micrel, Inc. MIC3223 Evaluation Board Bill of Materials Item Part Number Manufacturer GRM319R61E475KA12D muRata(1) C3216X7R1E475M TDK(2) 12063D475KAT2A (3) C1 C2 C5 C8 Ceramic Capacitor, 4.7µF, 25V, X7R, Size 1206 1 Ceramic Capacitor, 0.027µF, 6.3V,X7R, Size 0603 1 Ceramic Capacitor, 10µF, 6.3V X7R, Size 0603 2 Ceramic Capacitor, 4.7µF, 50V, Size 1210, X7R 2 1 AVX muRata(1) GRM188R60J106ME47D muRata(1) C1608X5R0J106K TDK(2) 08056D106MAT2A AVX(3) 12105C475KAZ2A AVX(3) GRM32ER71H475KA88L. muRata(1) GRM188R71C473KA01D muRata(1) 0603YC473K4T2A AVX(3) Ceramic Capacitor, 0.047µF, 6.3V,X7R, Size 0603 GRM188R72A102KA37D muRata(1) Ceramic Capacitor, 1000pF, 100V, X7R 060 (4) D1 SK35B L1 MSD1260-223ML-LD Coilcraft(5) CRCW0603100KFKEA Vishay Dale(6) R2 CRCW0603549RFKEA (6) R4 CRCW06033K24FKEA R5 R6 R1, R3 Qty. GRM188R71C273KA01D C3, C7 C4, C6 Description Schottky Diode, 3A, 50V (SMB) 1 Inductor, 22µH, 5A 1 Resistor, 100k, 1%, Size 0603 2 Vishay Dale Resistor, 549Ω, 1%, Size 0603 1 Vishay Dale(6) Resistor, 3.24k, 1%, Size 0603 1 CRCW1206R560FKEA Vishay Dale(6) Resistor, 0.56Ω, 1%, 1/2W, Size 1206 (for .35A LED current change for different ILED) 1 RMC 1/4 2 1% R SEI Stackpole Electronics, Inc.(7) Resistor, 2Ω, 1%, 1/2W, Size 1210 1 N-Channel, 40V, MOSFET 1 High-Power Boost LED Driver with Integrated FET 1 Q1 U1 MCC (6) Si2318DS Vishay Siliconix AM2340N Analog Power MIC3223 Micrel, Inc.(9) (8) Notes: 1. Murata: www.murata.com. 2. TDK: www.tdk.com. 3. AVX: www.avx.com. 4. MCC: www.mccsemi.com. 5. Coilcraft: www.coilcraft.com. 6. Vishay: www.vishay.com. 7. SEI Stackpole Electronics, Inc.: www.seielect.com. 8. Analog Power: www.analogpowerinc.com. 9. Micrel, Inc.: www.micrel.com. March 2010 5 M9999-030210 Micrel, Inc. MIC3223 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer March 2010 6 M9999-030210 Micrel, Inc. MIC3223 Evaluation Board Package Information 16-Pin EPAD TSSOP (TSE) March 2010 7 M9999-030210 Micrel, Inc. MIC3223 Evaluation Board Recommended Land Pattern MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2010 Micrel, Incorporated. March 2010 8 M9999-030210