IS31BL3508A 1.0MHZ BOOST CONVERTER WITH 38V INTERNAL MOSFET SWITCH DESCRIPTION RECOMMENDED EQUIPMENT IS31BL3508A is a 2.7V~5.5V (input voltage) backlight LED boost converter with an integrated MOSFET switch. It is designed for driving a string of LEDs or other devices in a constant current mode. The device regulates the LED load current using an external, low value sensing resistor. The device adjusts the PWM duty cycle of the switch to maintain the voltage at the FB pin at a value of 0.3V. The IS31BL3508A operates at a constant switching frequency of 1.0MHz to utilize small component sizes. It features an over voltage shutdown pin which prevents the output voltage from exceeding 38V (typ.) for open circuit condition. FEATURES Supply voltage: 2.7V~5.5V Built-in soft start Drive series strings of 10 LEDs PWM or DC voltage dimming Frequency of PWM is 500Hz ~ 500kHz 1.0MHz high speed switching frequency 300mV feedback voltage Integrated high power MOSFET Over voltage protection -40°C ~ +85°C working temperature range TSOT-23-6 and SOT-23-6 package QUICK START 5.0V, 2A power supply ABSOLUTE MAXIMUM RATINGS ≤ 5.5V power supply Caution: Do not exceed the conditions listed above, otherwise the board will be damaged. PROCEDURE The IS31BL3508A 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 Power Supply ground terminal to the PCB GND input pin and the positive terminal to the PCB VCC input pin. Or connect a wall-mount DC power out plug (center power) to the PCB connector (CON1 / DC IN). 2) Turn on the power supply and pay attention to the supply current. If the current exceeds 2A, please check for circuit fault. EVALUATION BOARD OPERATION The WLED light intensity is adjusted by the onboard MCU (LPC936) which generates a PWM signal to the IS31BL3508A EN pin 4. There are 32 intensity levels with the lowest set as the power on default. Pressing the Level+ key will increase the intensity level while pressing the Level- key will decrease the level. The 7-segment LED (DIG1) will show the corresponding light intensity level. The SD/EN key is used to toggle between shutdown and enable modes. The LED+ and LED- are test points to monitor the output voltage. LED CURRENT SETTING Figure 1: Photo of IS31BL3508A Evaluation Board Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 07/24/2013 When the IS31BL3508A is used for driving LEDs, the LED current flows through the external feedback resistor R1 and R2 to regulate the LED current. The internal feedback regulation point is 0.3V. The maximum LED current may be calculated by the following Equation: I MAX VFB / RSET and RSET R1 / R2 , (R2=1Ω if zero ohm resistor used). For accurate LED current, resistors should be 1% or better tolerance. 1 IS31BL3508A 1.0MHZ BOOST CONVERTER WITH 38V INTERNAL MOSFET SWITCH IS31BL3508A LED driver. Please refer to the SW program for LPC936 code example. SOFTWARE SUPPORT JP1 is connected by default. Open it to disable the onboard MCU which will place the IS31BL3508A EN pin in High impedance. An external driving signal can then be connected to TP5 connector to control the Please refer to the datasheet to get more information about IS31BL3508A. ORDERING INFORMATION Part No. Temperature Range Package IS31BL3508A-STLS2-EB -40°C ~ +85°C (Industrial) SOT23-6, Lead-free Table1: Ordering Information For pricing, delivery, and ordering information, please contacts ISSI’s analog marketing team at [email protected] or (408) 969-6600. TP3 D1 DFLS240 L1 22uH VCC LED+ TP1 CON1 DC IN VCC C1 10uF 7 GND FB IS31BL3508A 6 Seg2 R2 0R 3 R4 NC 1 2 dp G C D E R14 1K R15 1K R16 1K R17 1K B C6 1uF 5 4 3 2 1 2 VOUT 5 C7 10nF SD GND BP C8 1uF C 3V P0.5 P0.4 RST GND D ICP 4 3V 26 25 24 P0.0 VDD P0.1 P1.6 P2.2 P2.3 P2.4 P2.5 P2.7 P1.7 P3.0 P3.1 P0.2 P0.3 P0.4 P0.5 P0.6 P1.1/RXD P0.7 RST/P1.5 U4 1 3 R12 100K 3V U3 3 R18 E 1K P0.4 23 R19 F 1K P0.5 22 R20 G 20 1K R21 dp 19 1K VCC LDO VCC TP4 EN PWM A 3V VDD R3 NC TP5 TP6 3 LED- R1 10R C5 NC 2281BS U2 1 D2 ~ D11 R6 0R 5 DIG1 VCC C4 NC C3 1uF/50V 1 R5 NC PWM dp a 4 g b c EN 5 8 9 Seg1 d 3 2 LX OUT Seg2 10 4 2 A f VCC R7 100K B Seg1 F e 6 EN TP2 1 U1 C2 0.1uF R13 100K G1 2 G2 4 D1 D2 Seg2 S1 S1 G1 S2 G2 S2 8 SD/EN 7 Seg1 Level- 6 Level+ 5 OPEN=EXT CTRL K1 R11 100K R10 100K R9 100K R8 100K K2 K3 JP1 TXD/P1.0 12 11 10 1 P1.2/T0/SCL P2.6 P1.3/INT0/SDA P2.1 21 5 13 14 15 16 28 4 9 8 17 G2 6 RST 18 G1 27 EN 2 PWM P1.4/INT1 P2.0 VSS 7 LPC936 APM4953 Figure 2: IS31BL3508A Application Schematic Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 07/24/2013 2 IS31BL3508A 1.0MHZ BOOST CONVERTER WITH 38V INTERNAL MOSFET SWITCH BILL OF MATERIALS Name Symbol Supplier Part No. LED Driver U1 LED boost converter driver LDO U2 Low-dropout regulator 1 ISSI IS31BL3508A 1 PAM PAM3101 MCU U3 Microcontroller 1 NXP LPC936 PMOS U4 Dual PMOS 1 ANPEC APM4953 Display DIG1 Dual digit display common anode 1 ZSO 2281BS Diode D1 Schottky Diode, SMD 1 Diode D2~D11 Diode, LED White, SMD 10 Everlight Inductor L1 IND,22µH±20%,SMD 1 murata Resistor R1 RES,10R,1/16W,±5%,SMD 1 Resistors R2,R6 RES,0R,1/16W,±5%,SMD 2 Not connect 5 R3,R4,R5,C4,C5 Description Qty Resistors R7~R13 RES,100k,1/16W,±5%,SMD 7 Resistors R14~R21 RES,1k,1/16W,±5%,SMD 8 Capacitor C1 CAP,10µF,16V,±20%,SMD 1 Capacitors C2 CAP, 0.1µF,16V,±20%,SMD 1 Capacitors C3,C6,C8 CAP,1µF,50V,±20%,SMD 3 Capacitor C7 CAP,10nF,16V,±20%,SMD 1 Buttons K1~K3 Buttons SMD 3 DFLS240 EHP-C04/UT01P01/TR Bill of materials, refer to Figure 2 above. Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 07/24/2013 3 IS31BL3508A 1.0MHZ BOOST CONVERTER WITH 38V INTERNAL MOSFET SWITCH 16 16 10 9 8 7 6 1 2 3 4 5 0 2 1 2 1 1 1 2 1 2 2 1 3 2 1 1 2 2 16 16 Figure 3: Board Component Placement Guide -Top Layer Figure 4: Board PCB Layout- Top Layer Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 07/24/2013 4 IS31BL3508A 1.0MHZ BOOST CONVERTER WITH 38V INTERNAL MOSFET SWITCH 16 16 10 9 8 7 6 1 2 3 4 5 0 2 1 2 1 1 1 2 1 2 2 1 3 2 1 1 2 2 16 16 Figure 5: Board Component Placement Guide -Bottom Layer Figure 6: Board PCB Layout-Bottom Layer 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. 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 Rev. A, 07/24/2013 5