IS31BL3508B-STLS2-TR ISSI

IS31BL3508B 1.0MHZ BOOST CONVERTER WITH 38V INTERNAL MOSFET SWITCH December 2013 GENERAL DESCRIPTION FEATURES IS31BL3508B is a boost converter featuring an Supply voltage: 2.7V~5.5V integrated MOSFET switch designed for driving series Built-in soft start strings of LED or other device. Input operating voltage Drive series strings of 10 LEDs or 38 LEDs range is 2.7V~5.5V. The device regulates the LED load PWM or DC voltage dimming current is set using an external, low value sensing Frequency of PWM is 500Hz ~ 500kHz resistor. The device adjusts the PWM duty cycle of the 1.0MHz high speed switching frequency switch to maintain the voltage at the FB pin at a value of 0.2V. 0.2V feedback voltage Integrated high power MOSFET The IS31BL3508B operates at a constant switching Over voltage protection frequency of 1.0MHz to allow for small component size. IS31BL3508B features an over voltage shutdown pin -40C ~ +85C working temperature range which prevents the output voltage from exceeding 38V SOT-23-6 package (typ.) in the case of an open circuit condition. APPLICATIONS The device is offered in a SOT-23-6 package and a Small LCD Backlights temperature rating from -40C ~ +85C. Notebook PC GPS TYPICAL APPLICATION CIRCUIT Figure 1 Constant current white LED driver using PWM at the EN pin to control intensity Note 1: C must be rated for 50V. Smaller values of output capacitance will cause the LED current ripple to increase. OUT Note 2: The resistor R should be placed as close as possible to the FB pin to prevent the EMI. EST Note 3: D must choose 60V and peak current is determined by the load. Please refer to Page 9 for detail information. 1 Lumissil Microsystems www.lumissil.com 1 Rev. A, 12/17/2013 IS31BL3508B VBattery L1 D1 2.7~5.5V 10 H 2.2 F 0.1 F 6 1 COUT VCC LX 1 F 5 (50V) (4~8)2 PWM Signal OUT LEDs 4 Micro IS31BL3508B EN Controller 3 FB 100k 2 RSET GND 5 Figure 2 Constant current white LED driver using PWM at the EN pin to control intensity (4~8)2 LEDs Figure 3 Constant current white LED driver using PWM at the EN pin to control intensity 38 LEDs Figure 4 Constant output voltage for general purpose use Lumissil Microsystems www.lumissil.com 2 Rev. A, 12/17/2013