IS31LT3360 AIC LED Driver Evaluation Board Guide Quick Start Description The IS31LT3360 is a continuous mode inductive step-down converter, designed for driving a single LED or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The chip operates from an input supply between 6V and 40V and provides an externally adjustable output current of up to 1.2A. The IS31LT3360 includes an integrated output switch and a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current. Output current can be adjusted linearly by applying an external control signal to the ADJ pin. The ADJ pin will accept either a DC voltage or a PWM waveform. This will provide either a continuous or a gated output current. 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. The chip is assembled in SOT89-5 package. IS31LT3360 AIC DEMO board is used in RGB lamp or the general LED lamp. Features Internal 40V power switch 6V to 40V VIN Open-circuit protection Thermal shutdown protection IOUTPUT =1.2A (max output current) 98% efficiency (max) 1200:1 dimming rate (typical) 3% IOUTPUT accuracy (typical) PWM and DC line control mechanism • Single pin On/Off • Brightness control 1MHz switching frequency (max) SOT89-5 package Low part count and system resource overhead Figure 1: IS31LT3360 AIC Evaluation Board Photo Recommended Equipment 60VDC power supply 3 x LED panel (1W LED, 10 LEDs in series on each panel) Multi-meter Recommended I/O Ratings Input: 6-40VDC Output: 1-10 LEDs in series (333mA) Note: The input voltage must be 5V higher than the output voltage (∑VF). Absolute Maximum Ratings Input voltage ≤ 40VDC Caution: Do not exceed the conditions listed above, otherwise the board will be damaged. Ordering Information Part No IS31LT3360-SDLS3-EBAIC Temperature Range -40 to +85C (Industrial) IC Package SOT89-5 Table 1: IS31LT3360 AIC Ordering Information For information about ordering, delivery, and pricing, please contact ISSI at [email protected] or (408)969-6600. Integrated Silicon Solution, Inc. – www.issi.com R1.1, 3/22/2011 1 IS31LT3360 AIC LED Driver Evaluation Board Guide Procedure The IS31LT3360 AIC evaluation board is fully assembled and tested. Follow the steps listed below to verify board operation. Caution: Do not turn on the power supply until all connections are completed. 1. Connect the terminals of the power supply to the AC1 and AC2 pin(If the board don’t have the rectifier(D1-D4), Connect the positive terminal of the power supply to the DC+ of the board and the negative terminal of power supply to the DC- of the board) . 2. Connect the negative of the one of LED panel (LED arrays) to the LED1- terminal. And connect the positive of the same LED panel (LED arrays) to the LED1+ terminal. 3. Connect the other two LED panels to LED2 and LED3 as above. 4. Turn on the power supply to drive LED current and watch for lighting. D7 D4 D8 R4 D5 LEDS R5 D6 LEDS D1 AC/DC C0 R1 R2 L1 L2 C1 D9 D10 VIN ISENSE ADJ U1 LX GND LEDS R8 PWM2 VIN ADJ ISENSE U2 D3 R3 L3 C2 R7 PWM1 C4 R6 D2 C3 LX R9 GND PWM3 C5 VIN ISENSE ADJ U3 LX GND C6 Figure 2: IS31LT3360 AIC Application Schematic Application Notes C8-10 are optional components that enhance filtering of noise coupling from ADJ pin. D4-6 are optional component that serve to protect the IC during heavy load surge during the power on phase. Bill of Materials Name Description Symbol Qty Capacitor Aluminum, 220uF,50V C0 1 Capacitor 100nF,50V, Surface-mount C1,C2,C3 3 Capacitor 10nF,50V, Surface-mount C4,C5,C6 3 Resistor 6.8KΩ±5%,0805, Surface-mount R4,R5,R6 3 Resistor 1KΩ±5%,0805, Surface-mount R7,R8,R9 3 Resistor 0.3Ω±1%,0805, Surface-mount R1,R2,R3 3 Diode Schottky, SS26,2A,60V D1-D3,D7-D10 7 Zener Diode Zener, 39V,0.25W D4,D5,D6 3 Inductor 47uH,Isat≥600A, Surface-mount L1,L2,L3 3 Driver Inductive Step-down LED Driver U1,U2,U3 3 Supplier Part No. ISSI IS31LT3360 AIC Table 2: Bill of Materials; Refer to Figure 2. Integrated Silicon Solution, Inc. – www.issi.com R1.1, 3/22/2011 2 IS31LT3360 AIC LED Driver Evaluation Board Guide Detailed Description LED Current Control The nominal average output current in the LED(s) is determined by the value of the external current sense resistor (RS) connected between VIN and ISENSE and in is given by: . ; 0.082 The table below gives values of nominal average output current for several preferred values of current setting resistor (Rs) in Figure 2: Application Schematic. RS (Ω) IOUT (mA) 0.082 1200 0.1 1000 0.15 0.3 667 333 Table 3: Current Sense Resistance vs. Nominal Output Current Vsense is divided into two ranges for enhanced output current accuracy, and is explained in bin 3 more in depth. The above values assume a floating ADJ pin and a nominal voltage VREF =1.2V. Note that RS=0.082Ω is the minimum allowed value of sense resistor under these conditions to maintain switch current below the specified maximum value. It is possible to use different values of RS if the ADJ pin is driven from an external voltage. Inductor Selection Recommended inductances range from 47μH to 220μH. Higher inductances are igher supply voltages and low output current in order to minimize errors due to switching delays, which result in increased ripple and lower efficiency. Higher values of inductance also result Integrated Silicon Solution, Inc. – www.issi.com R1.1, 3/22/2011 in a smaller change in output current over the supply voltage range. The inductor should be mounted as close to LX pin as possible with low resistance connections to LX and VIN pins. PCB Layout Guide Decoupling capacitors and coil It is particularly important to mount the coil and the input decoupling capacitor close to the chip to minimize parasitic resistance and inductance, which will degrade efficiency. The input decoupling capacitor (0.1uF fixed) must be placed as close to the Vin and GND pins as possible. It is also important to take account of any trace resistance in series with current sense resistor RS. LX pin The LX pin of the chip is a fast switching node, so PCB traces should be kept as short as possible. To minimize ground 'bounce', the ground pin of the chip should be soldered directly to the ground plane. ADJ pin The ADJ pin is a high impedance input, so when left floating, PCB traces to this pin should be as short as possible to reduce noise pickup. ADJ pin can also be connected to a voltage between 1.2V~5V. In this case, the internal circuit will clamp the output current at the value which is set by ADJ=1.2V. High voltage traces Avoid running any high voltage traces close to the ADJ pin, to reduce the risk of leakage due to board contamination. Any such leakage may raise the ADJ pin voltage and cause excessive output current. A ground ring placed around the ADJ pin will minimize changes in output current under these conditions. 3 IS31LT3360 AIC LED Driver Evaluation Board Guide PCB Layout Physical dimensions (L x W x H): 55mm x 21mm x 22mm Figure 3: PCB Layout-Top Layer Figure 4: PCB Layout-Bottom Layer Figure 5: Component Placement Guide -Top Layer Figure 6: Component Placement Guide -Bottom Layer Copyright © 2011 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are advised to obtain the latest version of this device specification before relying on any published information and before placing orders for products. Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that: a.) the risk of injury or damage has been minimized; b.) the user assume all such risks; and c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances. Integrated Silicon Solution, Inc. – www.issi.com R1.1, 3/22/2011 4