MIC3202/MIC3202-1 Evaluation Board High-Brightness LED Driver with Integrated MOSFET and High-Side Current Sense General Description Getting Started 1. Connect V supply to the input VIN and GND The MIC3202/MIC3202-1 is a hysteretic step-down, IN terminals. With the output of this supply disabled, constant-current, High-Brightness LED (HB LED) driver. set the supply voltage to the desired input test It provides an ideal solution for interior/exterior lighting, voltage (6V < V < 37V). This supply voltage should IN architectural and ambient lighting, LED bulbs, and other be monitored at the test boards input terminals to general illumination applications. allow voltage drops in the test cables (and ammeter This board enables the evaluation of the if used) to be accounted for. An ammeter can be MIC3202/MIC3202-1 for 1A LED current. The board is added inline with the +VIN input terminal to optimized for ease of testing, with all the components on accurately measure input current. a single side. The device operates from a 6V to 37V 2. Connect the LEDs to the output terminals input voltage range, and includes an integrated 1.0A between LED+ and LED. This LED voltage drop MOSFET. When the input voltage approaches and depends on manufacturer tolerance and number of crosses UVLO threshold, the internal 5V V is CC LEDs. The LED current can be measured using an regulated and the integrated MOSFET is turned on if EN ammeter or current probe. A 4.7F ceramic pin and DIM pin are high. The inductor current builds up capacitor helps to reduce the current ripple through linearly. When the CS pin voltage hits the V with CS(MAX) the LED. The LED current is set to 1A by a 200m respect to V , the internal MOSFET is turned off and the IN current-sense resistor (R ). Schottky diode takes over and returns the current to V . CS IN Then the current through inductor and LEDs starts 3. Enable the input supply. By default, the IC is decreasing. When CS pin hits V , the internal CS(MIN) enabled when the input voltage crosses the VIN MOSFET is turned on and the cycle repeats. threshold (4V) and the internal VCC regulator and internal MOSFET are turned on with the EN and Since the control scheme does not need loop DIM pins are high. To use the EN and DIM functions compensation, it makes for a very simple design and of the MIC3202/MIC3202-1, a test point is provided avoids problems of instability. for each of them. Datasheets and support documentation can be found on Micrels web site at: www.micrel.com. Ordering Information Requirements Part Number Description This board needs a single-bench power source adjustable over the input voltage of 6V < V < 37V that MIC3202YME EV MIC3202YME Evaluation Board IN can provide at least 1A of current. The loads can either be active (electronic load in CV mode) or passive (LEDs) with the ability to dissipate the maximum load power while keeping accessible surfaces ideally <70C. Precautions There is no reverse input protection on this board. When connecting the input sources, ensure that the correct polarity is observed. In the line transient condition, such as hot plug-in, an electrolytic capacitor may be required at the VIN and GND terminals in order to prevent IC damage from a surge voltage. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC3202/MIC3202-1 Evaluation Board Other Features EN Input Frequency of Operation The EN pin provides a logic level control of the output To calculate the frequency spread across input supply: and the voltage has to be 2.0V or higher to enable the current regulator. The output stage is gated by the DIM (V +I R +V )(V -I R - V ) D LED CS LED IN LED CS LED pin. When the EN pin is pulled low, the regulator goes to F = SW L I (V +V ) off-state and the supply current of the device is reduced L D IN to below 1A. Do not drive the EN pin above the supply voltage. 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 brightness of LED. DIM high enables the output and its where: voltage has to be 2.0V or higher. DIM low disables the V is Schottky diode forward drop D output, regardless of EN high-state. V is total LEDs voltage drop LED Current-Sense Input V is input voltage IN The CS pin provides the high-side current sense to set I is average LED current the LED current with an external sense resistor. LED A sense resistor R is placed between V and LED+ CS IN terminals. According to the above equation, choose the inductor to make the operating frequency no higher than 1MHz. The current through LED is sensed by the sense resistor (R ). The sensed voltage is fed back to the MIC3202 to Refer to the datasheet Application Information for more CS regulate the LED current information on components selection guidelines. R is given by: Frequency Dithering CS The MIC3202 is designed to modulate the V with CS(MAX) amplitude 6mV by a pseudo random generator to V + V 1 CS(MAX) CS(MIN) R = x( ) Error generate the 12% of the switching frequency dithering. CS 2 I LED This spreads the frequency spectrum over a wider range Bookmark not defined. and reduce the EMI noise peaks. The MIC3202-1 is non-dithering version of the MIC3202. I is LED current required to set. LED 2 R () I (A) I R (W) Size (SMD) CS LED 1.33 0.15 0.03 0603 0.56 0.35 0.07 0805 0.4 0.5 0.1 0805 0.28 0.7 0.137 0805 0.2 1.0 0.2 1206 For V and V refers to the Electrical CS(MAX) CS(MIN) Characteristics table. October 2010 2 M9999-102810