MIC3203/MIC3203-1 Evaluation Board High Brightness LED Driver Controller with High-Side Current Sense General Description The MIC3203/MIC3203-1 is a hysteretic step-down, constant-current, High-Brightness LED (HB LED) driver. It provides an ideal solution for interior/exterior lighting, architectural and ambient lighting, LED bulbs, and other general illumination applications. This board enables the evaluation of the MIC3203/MIC3203-1 for 1A LED current. The board is optimized for ease of testing, with all the components on a single side. The device operates from a 4.5V to 42V input voltage range, and controls an external power MOSFET to drive high current LEDs. When the input voltage approaches and crosses UVLO threshold, the internal 5V VCC is regulated and the external MOSFET is turned on if EN pin and DIM pin are high. The inductor current builds up linearly. When the CS pin voltage hits the VCS(MAX) with respect to VIN, the external MOSFET is turned off and the Schottky diode takes over and returns the current to VIN. Then the current through inductor and LEDs starts decreasing. When CS pin hits VCS(MIN), the external MOSFET is turned on and the cycle repeats. Since the control scheme does not need loop compensation, it makes for a very simple design and avoids problems of instability. Requirements This board needs a single bench power source adjustable over the input voltage of 4.5V < VIN < 42V that can provide at least 1A of current. The loads can either be active (electronic load) or passive (LEDs) with the ability to dissipate the maximum load power while keeping accessible surfaces ideally < 70°C. Precautions There is no reverse input protection on this board. When connecting the input sources, ensure that the correct polarity is observed. Under extreme load conditions input transients can be quite large if long test leads are used. In such cases a 100µF, 63V electrolytic capacitor is needed at the VIN terminals to prevent over voltage damage to the IC. Getting Started 1. Connect VIN supply to the input terminals VIN and GND. With the output of this supply disabled, set its voltage to the desired input test voltage (4.5V < VIN < 42V). This supply voltage should be monitored at the test boards input terminals to allow voltage drops in the test cables (and ammeter if used) to be accounted for. An ammeter can be added inline with the +VIN input terminal to accurately measure input current. Connect the LEDs to the output terminals between LED+ and LED−. This LED voltage drop depends on manufacturer tolerance and number of LEDs. The LED current can be measured using an ammeter or current probe. A 4.7µF ceramic capacitor helps to reduce the current ripple through the LED. The LED current is set to 1A by current sense resistor RCS i.e., 200mΩ. Selecting the sense resistor refers to the table given in data sheet application sub-section. 2. Enable the input supply. By default, the controller is enabled when the input voltage approaches UVLO threshold and crosses 5V, the internal 5V VCC is regulated and the external MOSFET is turned on if EN pin and DIM pin are high. To use the EN and DIM functions of the MIC3203/MIC3203-1, a test point is provided for each of them. Ordering Information Part Number Description MIC3203YM EV Evaluation board with MIC3203YM device MIC3203-1YM EV Evaluation board with MIC3203-1YM device 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 2011 M9999-011311-B Micrel, Inc. MIC3203/3203-1 Evaluation Board RCS is given by Other Features 1 VCS(MAX ) + VCS(MIN) x( ) Error! Bookmark not 2 ILED defined. ILED is LED current required to set. For VCS(MAX) and VCS(MIN) , refers to electrical characteristics table in the data sheet. To calculate the frequency spread across input supply: R CS = EN Input The EN pin provides a logic level control of the output and the voltage has to be 2.0V or higher to enable the current regulator. The output stage is gated by the DIM pin. When the EN pin is pulled low, the regulator goes to off state and the supply current of the device is reduced to below 1µA. In the off state, the output drive is placed in a "tri-state" condition, where MOSFET is in an “off” or non-conducting state. Do not drive the EN pin above the supply voltage. FSW = DIM Input The DIM pin provides a logic level control for brightness of the LED. A PWM input can be used to control the brightness of LED. DIM high enables the output and its voltage has to be 2.0V or higher. DIM low disables the output, regardless of EN high state. ΔIL = VCS(MAX ) - VCS(MIN) RCS where : VD is Schottky diode forward drop VLED is total LEDs voltage drop VIN is input voltage ILED is average LED current According to the above equation, choose the inductor to make the operating frequency no higher than 1.5MHz. Refer to the datasheet “Application Information” for more information on components selection guidelines. Current Sense Input The CS pin provides the high-side current sense to set the LED current with an external sense resistor. A sense resistor RCS is placed between VIN and LED+ terminal. The current flowing through LED is sensed and current feedback is provided to the hysteretic step-down regulator. January 2011 (VD +ILED×RCS + VLED) ×(VIN - ILED×RCS - VLED) L × ΔIL ×(VD + VIN) Frequency Dithering The MIC3203 is designed to modulate the VCS(MAX) with amplitude ±6mV by a pseudo random generator to generate the ±12% of the switching frequency dithering to spread the frequency spectrum over a wider range and reduce the EMI noise peaks The MIC3203-1 is non-dithering version of the MIC3203. 2 M9999-011311-B Micrel, Inc. MIC3203/3203-1 Evaluation Board Evaluation Board Performance Efficiency vs Input Voltage 100 100 90 90 EFFICIENCY (%) EFFICIENCY (%) Efficiency vs. Input Voltage 80 4LED 6LED 8LED 10LED 70 10 15 20 25 30 35 40 6LED 8LED 10LED L=68µH ILED=1A 60 60 5 4LED 70 L=150µH ILED=1A 0 80 0 45 5 10 INPUT VOLTAGE (V) 35 40 45 Normalized LED Currents vs Input Voltage Normalized LED Currents vs. Input Voltage 1.03 1.03 L=150µH ILED=1A NORMALIZED LED CURRENTS (A) NORMALIZED LED CURRENTS (A) 15 20 25 30 INPUT VOLTAGE (V) 1.02 10LED 1.01 1LED 2LED 4LED 6LED 8LED 1 0.99 0.98 0.97 L=68µH ILED=1A 1.02 1.01 1 1LED 0.99 2LED 4LED 0.98 6LED 8LED 10LED 0.97 0 5 10 15 20 25 30 35 40 45 0 INPUT VOLTAGE (V) 5 10 15 20 25 30 35 40 45 INPUT VOLTAGE (V) * With regards to VIN January 2011 3 M9999-011311-B Micrel, Inc. MIC3203/3203-1 Evaluation Board Evaluation Board Schematic Notes: 1. If bulk capacitor on input rail is away (4 inches or more) from the MIC3203/MIC3203-1, install the 100µF bulk capacitor near VIN. 2. Source impedance should be as low as 10mΩ. January 2011 4 M9999-011311-B Micrel, Inc. MIC3203/3203-1 Evaluation Board Bill of Materials Item Part Number 12105C475KAZ2A C1, C2, C5 GRM32ER71H475KA88L C3 TDK 1 1µF/25V, Ceramic Capacitor, X7R, Size 0805 AVX(1) 270pF/50V, Ceramic Capacitor NPO, Size 0805 (2) Murata Fairchild(5) FDS5672 1µF/25V, Ceramic Capacitor, X7R, Size 0805 (3) SK36 SLF10145T-680M1R2 M1 Murata MCC(4) SK36-7-F 3 1µF/25V, Ceramic Capacitor, X5R, Size 0805 (2) SK36-TP D1 4.7µF/50V, Ceramic Capacitor, X7R, Size 1210 (3) AVX(1) (Open) GRM2165C2A271JA01D L1 Murata(2) TDK (Open) 08055A271JAT2A Qty. AVX 08053D105KAT2A GRM21BR71E105KA99L Description (1) C3225X7S1H475M C2012X7R1E105K C4 Manufacturer 270pF/100V, Ceramic Capacitor NPO, Size 0805 1 60V, 3A, SMC, Schottky Diode 1 68µH, 1.2A, SMT, Power Inductor 1 MOSFET, N-CH, 60V, SO-8 1 0.2Ω Resistor, 1/2W, 1%, Size 1206 1 (10) Diode SUMIDA(6) Fairchild (11) R1 CSR 1/2 0.2 1% I Stackpole (7) Electronics Inc R2, R3 CRCW08051003FKEA Vishay(8) 100kΩ Resistor, 1%, Size 0805 2 R4 CRCW08050000FKEA Vishay(8) 0 Ω Resistor, 1%, Size 0805 1 R5 (Open) CRCW08052R20FKEA Vishay(8) 2.2 Ω Resistor, 1%, Size 0805 1 (8) 10kΩ Resistor, 1%, Size 0805 1 R6 CRCW08051002FKEA Vishay High Brightness LED Driver Controller with High-Side Current Sense-Frequency Dithering MIC3203YM Micrel, Inc.(9) U1 MIC3203-1YM High Brightness LED Driver Controller with High-Side Current Sense-Frequency NonDithering 1 Notes: 1. AVX: www.avx.com 2. Murata: www.murata.com 3. TDK: www.tdk.com 4. MCC: www.mccsemi.com 5. Fairchild: www.fairchildsemi.com 6. Sumida Tel: www.sumida.com 7. Stackpole Electronics: www.seielect.com 8. Vishay: www.vishay.com 9. Micrel, Inc.: www.micrel.com January 2011 5 M9999-011311-B Micrel, Inc. MIC3203/3203-1 Evaluation Board PCB Layout Recommendations Top Assembly Top Layer Bottom Layer January 2011 6 M9999-011311-B Micrel, Inc. MIC3203/3203-1 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 Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. 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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. January 2011 7 M9999-011311-B