MIC2196 LED Driver Evaluation Board Boost LED Driver w/PWM DIM Control General Description The MIC2196 current mode boost controller is used to implement a LED Driver with PWM DIM control (Figure 1). The LED series string is pulsed on and off by the PWM DIM input signal to provide true PWM dimming. When pulsed on the LED, current is regulated by the high frequency current mode boost converter. The converter is designed as a constant current not a constant voltage output boost converter. The under voltage lockout is used to prevent operation below about 9.5V. The input of the converter is 12V nominal and the output can be from 17V to 30Vdc. The LED current can be set by selecting the value of R3 (Table 2). The maximum input voltage to the MIC2196 is 16V. Table 1 provides a summary of the specifications. The evaluation board schematic is shown in Figure 1 and the parts list is shown in the Bill of Materials table. a current path through the inductor and through the fly back diode to the output. No current limit exists for this current path so care must be taken not to short circuit the output. How it works Switch Q3, turns off and on the current to the load. When the load current is turned on the boost converter regulates the load current by keeping the IR drop across R10+Q3_RDSON constant. Q3’s RDSON is a low (about 1/10 of R10) compared to R10. When the load is off the converter turns off (FB pin is pulled high by R14). When the load current is turned off the input is connected to the output through L1 and D1. For 100% duty cycle, simply keep PWM DIM high (5V). For a different LED current change R3 using the following equation. When R3 is 2.15K the LED current is at 1A. VFB = VREF = Specifications Max Typ Min VIN 16Vdc 12Vdc 10Vdc Output voltage 30Vdc 22Vdc 17Vdc Output current 1amp 700mA 0 Power out 30W 17W 0 efficiency (Approximate) Where: VREF = 1.245 VZ = 7.5V R3 = 2.43k. (used on evaluation board) R14 = 15k R10 = 330mΩ Q3RDSON = 34mΩ 92% Output ripple 1Vpp Switching Freq 400kHz PWM control 100% PWM Frequency 5kHz 0 300Hz R3 VZ + ILED × (R10 + Q3 RDSON ) R3 + R14 0Hz Table 1. Design Specifications Requirements 1. Voltage source at 3A 2. Pulse generator: TTL output, 100-300 HZ variable duty cycle 3. Load: LED string (series), a resistive or a electronic load (constant resistance mode) Precautions The evaluation board does not have input reverse polarity protection. Applying a negative voltage at the VIN terminal may damage the board. When the controller is off there is R3 I_LED Measured I_LED Calculated 2.15k 1.02amps 1A 2.21k 920mA 930mA 2.26k 860mA 870mA 2.32k 792mA 810mA 2.37k 744mA 760mA 2.43k 700mA 700mA 2.49k 616mA 640mA 2.55k 536mA 580mA 2.61k 490mA 520mA Table 2. R3 Values Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com January 2007 1 M9999-013107-A Micrel, Inc. MIC2196 LED Driver Evaluation Board Quick-Start Guide 1. Connect a load between VOUT and RTN. (LED series string or resistive load) 2. Connect a function generator to the PWM DIM input and GND (not RTN). Set the output at 0-5V square wave pulse at 300Hz. Make sure the pulse goes all the way to 0V. 3. Connect 12V to VIN and GND. 4. Use a current probe to measure the load current. I_LED vs. R3 1050 1000 950 900 850 800 mA 750 700 650 600 550 500 2.15 2.21 2.26 2.32 2.37 2.43 2.49 2.55 2.61 R3(kohm) Plot 1. I_LED vs R3 January 2007 2 M9999-013107-A Micrel, Inc. MIC2196 LED Driver Evaluation Board Figure 1. Schematic Diagram Bill of Materials Item Part Number Z1 33V, 500mW, SOD-80, Zener diodes 1 Diodes, Inc.(3) 65v/100mA, NPN Silicon transistor 1 Vishay Siliconix(1) MOSFET 1 Vishay Siliconix(1) N-MOSFET, 30V, 330 mil-Ohms 1 Schottky Diodes, 40V, 5A 1 Vishay Vishay(1) BC846AMTF SI4484EY SI4850EY SI3434DV Q3 Qty. TZMC33 BC846A Q2 Description (1) TZS4714 FLZ33VCC Q1 Manufacturer SI3424DV Faichild Semiconductor (2) PDS540 Diodes, Inc. (1) SSC54 Vishay(1) L1 CDR7D43MN-4R7NC. Sumida(4) 4.7µH, 6A inductor 1 C1 594D476X9035D2T Vishay Sprague(1) 47µF/35V, D case 1 10µF/50V, 1210 1 D1 C2 GRM32DF51H106ZA01 C4 C5 C6 (5) MuRata C3216X7R1H106M. TDK(6) 594D106X9035D2T Vishay Sprague(1) 10µF/35V, D case 594D156X9035D2T (1) Vishay Sprague 15µF/35V, D case VJ0805Y102KXAMT Vishay Vitramon(1) 1000pF, 50V, X7R ceramic cap 1 VJ0603Y102KXAMT (1) 1000pF, 50V, X7R ceramic cap 1 1µF/25V, ceramic cap 3 100pF, 50V, X7R ceramic cap 1 Vishay Vitramon (5) C3, C7, C9 GRM21BR71C105KA01B VJ0805S105KXJAT Vishay Victramon(1) C8 VJ0603Y101KXAMT Vishay Vitramon(1) LED R1, R17 R2 January 2007 LEW E3A CRCW06031002FRT1 CRCW08051501FRT1 1 MuRata OSRAM (7) OPEN 0 (1) 10K, 0603, 1% 2 (1) 1.5K, 0805, 1% 1 Vishay Dale Vishay Dale 3 M9999-013107-A Micrel, Inc. MIC2196 LED Driver Evaluation Board Item Part Number Manufacturer Description Qty. R3 CRCW06032431FRT1 Vishay Dale(1) 2.43K, 0603, 1%. 1 CRCW06031000FRT1 Vishay Dale (1) 100 Ohm , 0603, 1% 1 Vishay Dale (1) 1.82K, 0603, 1% 1 Vishay Dale (1) 220Ω, 0603, 1%. 1 Vishay Dale(1) 10mΩ, 1210 1 Vishay Dale(1) 5.11Ω, 0805, 1%. 1 Vishay Dale(1) 330mΩ, 1210, 1%. 1 CRCW08052742FRT1 Vishay Dale(1) 27.4K, 0805, 1% 1 CRCW06031502FRT1 Vishay Dale (1) 15K, 0603, 1% 1 Vishay Dale (1) 100K, 0603, 1% 1 Vishay Dale (1) 1.96K, 0603, 1% 1 Micrel, Inc. (8) Precision shunt Voltage references 1 Micrel, Inc. (8) Boost controller 1 R4 R6 R7 R8 R9 R10 R11 R14 R15 R16 Z2 CRCW06031821FRT1 CRCW06032200FRT1 WSL1210-R010-F WSL2010-R010-F CRCW08055R11FRT1 WSL1210-R330-F WSL2010-R330-F CRCW06031003FRT1 CRCW06031961FRT1 LM4041CYM3-ADJ IC1 MIC2196YM Notes: 1. Vishay: www.vishay.com 2. Fairchild Semiconductor: www.fairchildsemi.com 3. Diodes, Inc.: www.diodes.com 4. Sumida: www.sumida.com 5. Murata:: www.murata.com 6. TDK: www.tdk.com 7. Osram: osram.com 8. Micrel, Inc.: www.micrel.com January 2007 4 M9999-013107-A Micrel, Inc. MIC2196 LED Driver Evaluation Board PCB Layout Top Layer Bottom Layer January 2007 5 M9999-013107-A Micrel, Inc. MIC2196 LED Driver Evaluation Board 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. © 2007 Micrel, Incorporated. January 2007 6 M9999-013107-A