IS31LT3360 MR16 DEMO BOARD GUIDE DESCRIPTION RECOMMENDED EQUIPMENT The IS31LT3360 is a continuous mode inductive 30VDC power supply step-down converter, designed for driving a single LED LED panel (3 WLEDs, 2 LEDs in series) or multiple series connected LEDs efficiently from a Multi-meter voltage source higher than the LED voltage. The chip operates from an input supply between 6V and 40V RECOMMENDED INPUT AND OUTPUT RATINGS and provides an externally adjustable output current of up to 1.2A. Input: 12~24VDC or 12VAC The IS31LT3360 includes an integrated output switch Output: 1~3 LEDs in series/667mA and a high-side output current sensing circuit, which Note: The input voltage must be 2V higher than the output uses an external resistor to set the nominal average voltage (total V ). F output current. Output current can be adjusted linearly by applying an ABSOLUTE MAXIMUM RATINGS external control signal to the ADJ pin. The ADJ pin will accept either a DC voltage or a PWM waveform. This Input voltage 25VDC will provide either a continuous or a gated output Caution: Do not exceed the conditions listed above, otherwise current. the board will be damaged. Applying a voltage of 0.2V or lower to the ADJ pin turns the output off and switches the chip into a low current standby state. PROCEDURE The chip is assembled in SOT89-5 package. The IS31LT3360 DEMO Board is fully assembled and IS31LT3360 MR16 DEMO board is used in MR16 tested. Follow the steps listed below to verify board lamp. operation. Caution: Do not turn on the power supply until all connections are completed. FEATURES 1) Connect the terminals of the power supply to the Simple low parts count AC1 and AC2 pin. Internal 40V power switch 2) Connect the negative of the LED panel (LED Wide input voltage range: 6V to 40V arrays) to the LED- terminal. Up to 1.2A output current 3) Connect the positive of the LED panel (LED High efficiency (up to 98% ) arrays) to the LED+ terminal. Typical 1200:1 dimming rate 4) Turn on the power supply and the LED panel Typical 3% output current accuracy (LED arrays) will light. Single pin on/off and brightness control using DC voltage or PWM Up to 1MHz switching frequency Inherent open-circuit LED protection Thermal shutdown protection circuitry QUICK START Figure 1: Photo of IS31LT3360 Evaluation Board Lumissil Microsystems www.lumissil.com 1 Rev. B, 08/26/2011 IS31LT3360 MR16 DEMO BOARD GUIDE ORDER INFORMATION Part No. Temperature Range Package IS31LT3360-SDLS3-EBMR16 -40C to +105C (Industrial) SOT89-5, Lead-free For pricing, delivery, and ordering information, please contacts Lumissils analog marketing team at analog Lumissil.com or (408) 969-6600. DETAILED DESCRIPTION result in increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in LED Current Control output current over the supply voltage range. The inductor should be mounted as close to LX pin as The nominal average output current in the LED(s) is possible with low resistance connections to LX and V IN determined by the value of the external current sense pins. resistor (R ) connected between V and I and in S IN SENSE is given by: PCB LAYOUT CONSIDERATION I = 0.1/Rs for Rs>0.082 OUT NOM Decoupling Capacitors And Coil The table below gives values of nominal average It is particularly important to mount the coil and the output current for several preferred values of current input decoupling capacitor close to the chip to setting resistor (Rs) in the typical application circuit minimize parasitic resistance and inductance, which shown on Page 1: will degrade efficiency. The input decoupling capacitor (0.1F fixed) must be placed as close to the V and IN Nominal Average Output R ( ) S GND pins as possible. It is also important to take Current (mA) account of any trace resistance in series with current 0.082 1200 sense resistor R . S 0.1 1000 LX Pin 0.15 667 The LX pin of the chip is a fast switching node, so PCB traces should be kept as short as possible. To 0.3 333 minimize ground bounce , the ground pin of the chip V is divided into two ranges to improve current SENSE should be soldered directly to the ground plane. accuracy, please refer to bin information on Page 3. ADJ Pin The above values assume that the ADJ pin is floating and at a nominal voltage of V =1.2V. The ADJ pin is a high impedance input, so when left REF floating, PCB traces to this pin should be as short as Note that R =0.082 is the minimum allowed value of S possible to reduce noise pickup. ADJ pin can also be sense resistor under these conditions to maintain connected to a voltage between 1.2V~5V. In this case, switch current below the specified maximum value. the internal circuit will clamp the output current at the It is possible to use different values of R if the ADJ pin value which is set by V =1.2V. S ADJ is driven from an external voltage. High Voltage Traces Inductor selection Avoid running any high voltage traces close to the ADJ Recommended inductor values are in the range 47 H pin, to reduce the risk of leakage due to board to 220 H. contamination. Any such leakage may raise the ADJ pin voltage and cause excessive output current. A Higher values of inductance are recommended at ground ring placed around the ADJ pin will minimize higher supply voltages and low output current in order changes in output current under these conditions. to minimize errors due to switching delays, which Lumissil Microsystems www.lumissil.com 2 Rev. B, 08/26/2011