MIC3203/MIC3203-1 Evaluation Board High Brightness LED Driver Controller with High-Side Current Sense Getting Started General Description 1. Connect V supply to the input terminals V IN IN The MIC3203/MIC3203-1 is a hysteretic step-down, and GND. With the output of this supply constant-current, High-Brightness LED (HB LED) driver. disabled, set its voltage to the desired input test It provides an ideal solution for interior/exterior lighting, voltage (4.5V < V < 42V). This supply voltage IN architectural and ambient lighting, LED bulbs, and other should be monitored at the test boards input general illumination applications. terminals to allow voltage drops in the test This board enables the evaluation of the cables (and ammeter if used) to be accounted MIC3203/MIC3203-1 for 1A LED current. The board is for. An ammeter can be added inline with the optimized for ease of testing, with all the components on +V input terminal to accurately measure input IN a single side. The device operates from a 4.5V to 42V current. input voltage range, and controls an external power Connect the LEDs to the output terminals MOSFET to drive high current LEDs. When the input between LED+ and LED. This LED voltage voltage approaches and crosses UVLO threshold, the drop depends on manufacturer tolerance and internal 5V VCC is regulated and the external MOSFET number of LEDs. The LED current can be is turned on if EN pin and DIM pin are high. The inductor measured using an ammeter or current probe. A current builds up linearly. When the CS pin voltage hits 4.7F ceramic capacitor helps to reduce the the V with respect to V , the external MOSFET is CS(MAX) IN current ripple through the LED. The LED current turned off and the Schottky diode takes over and returns is set to 1A by current sense resistor R i.e., CS the current to V . Then the current through inductor and IN 200m. LEDs starts decreasing. When CS pin hits V , the CS(MIN) Selecting the sense resistor refers to the table external MOSFET is turned on and the cycle repeats. given in data sheet application sub-section. Since the control scheme does not need loop compensation, it makes for a very simple design and 2. Enable the input supply. By default, the avoids problems of instability. controller is enabled when the input voltage approaches UVLO threshold and crosses 5V, Requirements the internal 5V VCC is regulated and the This board needs a single bench power source external MOSFET is turned on if EN pin and adjustable over the input voltage of 4.5V < V < 42V that IN DIM pin are high. To use the EN and DIM can provide at least 1A of current. The loads can either functions of the MIC3203/MIC3203-1, a test be active (electronic load) or passive (LEDs) with the point is provided for each of them. ability to dissipate the maximum load power while keeping accessible surfaces ideally < 70C. Ordering Information Precautions There is no reverse input protection on this board. When Part Number Description connecting the input sources, ensure that the correct Evaluation board with polarity is observed. MIC3203YM EV MIC3203YM device Under extreme load conditions input transients can be Evaluation board with MIC3203-1YM EV quite large if long test leads are used. In such cases a MIC3203-1YM device 100F, 63V electrolytic capacitor is needed at the V IN terminals to prevent over voltage damage to the IC. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC3203/3203-1 Evaluation Board R is given by CS Other Features V + V 1 CS(MAX) CS(MIN) R = x( ) Error Bookmark not EN Input CS 2 I LED The EN pin provides a logic level control of the output defined. and the voltage has to be 2.0V or higher to enable the is LED current required to set. I LED current regulator. The output stage is gated by the DIM For V and V refers to electrical pin. When the EN pin is pulled low, the regulator goes to CS(MAX) CS(MIN) , characteristics table in the data sheet. off state and the supply current of the device is reduced to below 1A. In the off state, the output drive is placed To calculate the frequency spread across input supply: in atri-stat condition, where MOSFET is in an off or (V +I R +V )(V -I R - V ) D LED CS LED IN LED CS LED non-conducting state. Do not drive the EN pin above the F = SW L I (V +V ) supply voltage. L D IN V - V CS(MAX) CS(MIN) DIM Input I = L R CS The DIM pin provides a logic level control for brightness of the LED. A PWM input can be used to control the where : V is Schottky diode forward drop D brightness of LED. DIM high enables the output and its V is total LEDs voltage drop LED voltage has to be 2.0V or higher. DIM low disables the V is input voltage IN output, regardless of EN high state. I is average LED current LED Current Sense Input According to the above equation, choose the inductor to The CS pin provides the high-side current sense to set make the operating frequency no higher than 1.5MHz. the LED current with an external sense resistor. Refer to the datasheet Application Information for more A sense resistor R is placed between V and LED+ CS IN information on components selection guidelines. terminal. Frequency Dithering The current flowing through LED is sensed and current The MIC3203 is designed to modulate the V with feedback is provided to the hysteretic step-down CS(MAX) amplitude 6mV by a pseudo random generator to regulator. 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. January 2011 2 M9999-011311-B