IS31LT3360 3CH DEMO Board Guide 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 3CH DEMO board is used in RGB lamp or general LED lamp applications. Quick Start Figure 1: Photo of IS31LT3360-SDLS3-EB3CH Recommended Equipment 40VDC Power supply 3 pcs of LED panel (3W LED, 10 LEDs in series on each panel) Multi-meter Recommended Input and Output Ratings Input: 6-40VDC Output: 1-10 LEDs in series/667mA Note: The input voltage must be 2V higher than the output voltage(total Vf). Absolute Maximum Ratings Input voltage ≤ 40VDC Caution: Do not exceed the conditions listed above, otherwise the board will be damaged. Procedure Features Simple low parts count Internal 40V power switch Wide input voltage range: 6V to 40V Up to 1.2A output current High efficiency (up to 98% ) Typical 1200:1 dimming rate Typical 3% output current accuracy 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 The IS31LT3360 DEMO 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) 2) 3) 4) 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) . 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. Connect the other two LED panels to LED2 and LED3 as above. Turn on the power supply and the LED panels (LED arrays) will be light. Ordering Information Part No. Temperature Range Package IS31LT3360-SDL3-EB3H -40°C ~ +85°C (Industrial) SOT 89-5 (3mmx3mm) Table1: Ordering Information For pricing, delivery, and ordering information, please contacts ISSI’s analog marketing team at [email protected] or (408) 969-6600. Integrated Silicon Solution, Inc. – www.issi.com V1.2, 5/15/2013 1 IS31LT3360 3CH DEMO Board Guide Bill of Materials No. 1 2 2 3 4 5 6 7 8 9 Name AL Capacitor AL Capacitor SMD Capacitor SMD Capacitor SMD Capacitor SMD Resistor SMD Resistor Schottky Diode SMD Inductor IC Description 220uF±10%,50V 22uF±10%,50V 100nF±20%,50V,0805 390pF±20%,50V,0603 1uF±20%,50V,0805 1KΩ±5%,0805 0.3Ω±1%,0805 SS26,2A,60V,SMA 47uH,Isat≥1A IS31LT3360,SOT89-5 Ref Des. C1 C2,C3,C4 C5,C6,C7 C8,C9,C10 C11,C12,C13 R1,R2,R3 R4,R6,R8 D1-D7 L1,L2,L3 U1,U2,U3 Qty. 1 3 3 3 3 3 6 7 3 3 Mfr Note: C8,C9,C10 is the optional components. They can filter the noise coupling to the ADJ pin. VCC R4 LED1+ RES R5 D5 RES PWM1 C5 CAP1 Vin 3 ADJ Isense GND LX C11 CAP1 U1 SN3360 L1 1 LED1INDOCTOR 2 C2 CAP2 4 5 DIODE R1 RES C8 CAP1 GND D1 DIODE R6 D3 DIODE LED2+ RES R7 PWM2 AC1 D6 RES C1 CAP2 AC2 C6 CAP1 Vin ADJ Isense GND LX C12 CAP1 U2 SN3360 L2 1 LED2INDOCTOR 2 3 D2 DIODE 4 C3 CAP2 5 DIODE R2 RES D4 DIODE C9 CAP1 VCC R8 LED3+ RES R9 PWM3 D7 RES C7 CAP1 4 DIODE C4 CAP2 5 R3 RES Vin ADJ Isense GND LX 1 L3 LED3INDOCTOR 2 3 C13 CAP1 U3 SN3360 C10 CAP1 GND Figure 2 IS31LT3360 3CH DEMO Board Schematic Integrated Silicon Solution, Inc. – www.issi.com V1.2, 5/15/2013 2 IS31LT3360 3CH DEMO 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: I OUT nom = 0.1/Rs [for Rs>0.082Ω] The table below gives values of nominal average output current for several preferred values of current setting resistor (Rs) in the typical application circuit shown on page 1: RS (Ω) Nominal average output current (mA) 0.082 0.1 0.15 0.3 1200 1000 667 333 Vsense is divided into two range to improve current accuracy, please refer to bin information on page 3. The above values assume that the ADJ pin is floating and at a nominal voltage of 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 inductor values are 47μH to 220μH. Higher values of inductance are recommended at higher 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 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 consideration 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. PCB Layout NOTE: Physical dimensions are (L x W x H): 58mm x 25mm x 22mm Figure 2 PCB Layout-Top Layer Figure 4 Component Placement Guide -Top Layer Integrated Silicon Solution, Inc. – www.issi.com V1.2, 5/15/2013 Figure 3 PCB Layout-Bottom Layer Figure 5 Component Placement Guide -Bottom Layer 3 IS31LT3360 3CH DEMO Board Guide Revision History Date Revision 2012.03.06 R1.0 2012.04.19 R1.1 2013.05.15 R1.2 Changes Initial release 1. Recommend equipment: 60V change to 40V. 2. BOM: Add Cap tolerance value. 3. BOM: C2,C3,C4 100uF change to 22uF. 4. BOM: C8,C9,C10 1nF change to 390pF. 5. BOM: Add R5, R7, R9 6. Add order information. 1. Revise the BOM of R1-R9. 2. Revise the schematic. Copyright © 2013 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. – www.issi.com V1.2, 5/15/2013 4