IS31BL3506A 1.0MHZ BOOST CONVERTER WITH 35V INTERNAL MOSFET SWITCH January 2014 GENERAL DESCRIPTION FEATURES IS31BL3506A is a boost converter featuring an integrated MOSFET switch designed for driving series strings of LED or other device. Input operating voltage range is 2.7V~5.5V. The device regulates the LED load current is set 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 IS31BL3506A operates at a constant switching frequency of 1.0MHz to allow for small component size. IS31BL3506A features an over voltage shutdown pin which prevents the output voltage from exceeding 35V (typ.) in the case of an open circuit condition. The device is offered in a tiny TSOT-23-6, SOT-23-6 and DFN-8 (2mm×2mm) package and a temperature rating from -40°C ~ +85°C. Supply voltage: 2.7V~5.5V Built-in soft start Drive series strings of -9 LEDs (DFN-8) -8 LEDs (TSOT-23-6, SOT-23-6) 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, SOT-23-6 and DFN-8 (2mm×2mm) package APPLICATIONS Small LCD Backlights Notebook PC GPS TYPICAL APPLICATION CIRCUIT Figure 1 Constant current white LED driver using PWM at the EN pin to control intensity Note 1: COUT must be rated for 50V. Smaller values of output capacitance will cause the LED current ripple to increase. Note 2: The resistor REST should be placed as close as possible to the FB pin to prevent the EMI. Note 3: Because of the different packages, VOVP is not the same (Page 6). 9 LEDs can be driven by DFN-8 package and 8 LEDs can be driven by TSOT-23-6 and SOT-23-6 package most. Note 4: The high level of PWM signal for EN pin should last at least 200ns when power on, or the IC won’t start up. Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 1 IS31BL3506A VBattery 2.7~5.5V L1 10 H D1 0.1 F 2.2 F VCC COUT 1 F (50V) LX PWM Signal OUT Micro Controller (4~8)×2 LEDs EN IS31BL3506A FB 100k RSET 7.5 GND Figure 2 Constant current white LED driver using PWM at the EN pin to control intensity (4~8)×2 LEDs VBattery 2.7~5.5V 2.2 F L1 10 H D1 VOUT =VFB× (R1 +RSET)/RSET 0.1 F VCC LX OUT Micro Controller EN COUT 1 F (50V) R1 Load IS31BL3506A FB 100k RSET GND Figure 3 Figure 4 Constant output voltage for general purpose use Constant output current with DC dimming input Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 2 IS31BL3506A Figure 5 Constant output current with PWM dimming control Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 3 IS31BL3506A PIN CONFIGURATION Package Pin Configurations (Top View) TSOT-23-6 SOT-23-6 LX 1 6 VCC GND 2 5 OUT FB 3 4 EN DFN-8 PIN DESCRIPTION No. Pin Description 8 LX Switch input, connect to the inductor. 2 6 GND Ground. 3 5 FB Feedback input pin. 4 4 EN Device enable pin, active high. 5 3 OUT Output voltage sense pin for over voltage protection. 6 2 VCC Supply voltage input pin. - 7 NC No connection. - 1 PGND Power ground. Connect independently. Thermal Pad Connect to GND. TSOT-23-6 SOT-23-6 DFN-8 1 - Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 4 IS31BL3506A ORDERING INFORMATION Industrial Range: -40°C to +85°C Order Part No. Package IS31BL3506A-TTLS2-TR TSOT-23-6, Lead-free IS31BL3506A-STLS2-TR SOT-23-6, Lead-free IS31BL3506A-DLS2-TR DFN-8, Lead-free QTY/Reel 3000 Copyright © 2014 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. C, 01/09/2014 5 IS31BL3506A ABSOLUTE MAXIMUM RATINGS Supply voltage, VCC LX pin voltage Voltage at any input pin Maximum junction temperature, TJMAX Storage temperature range, TSTG Operating temperature range, TA ESD (HBM) ESD (CDM) -0.3V ~ +6.0V -0.3V ~ +40V -0.3V ~ +6.0V 150°C -65°C ~ +150°C -40°C ~ +85°C 2kV 1kV Note: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other condition beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS Test conditions：TA = -40°C ~ +85°C, VCC = 3.6V, unless otherwise noted. Typical values at TA = 25°C. Symbol Parameter Condition Min Typ 2.7 Max Unit 5.5 V VCC Supply Voltage ICC Quiescent current Switching 1.2 mA ISD Shutdown Current VEN = 0V 1.5 μA VEN_ON EN Input logic High VEN rising VEN_OFF EN Input logic Low VEN falling 1.4 V 0.4 V fOSC Operating Frequency 1 MHz DMAX Maximum Duty Cycle 90 % RDS_ON LX Switch On resistance 0.8 Ω ISW_LK LS Switch Leakage current VSW = 35V Switch over current limit Duty = 90% ISW_LIMIT 1.8 2.2 TSOT-23-6, SOT-23-6 35 DFN-8 38 1 μA 2.6 A VOVP OUT over voltage protection VFB Feedback Voltage 0.3 V TST Over temperature protection (Note 1) 160 °C tPWM_H EN pin PWM high level time (Note 1) (when power on) 200 V ns Note 1: Guaranteed by design. Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 6 IS31BL3506A TYPICAL PERFORMANCE CHARACTERISTIC 0.35 100 90 0.3 Reference Voltage(V) 80 Efficiency(%) 70 60 50 40 30 0.25 0.2 0.15 0.1 20 8 WLEDs ILED = 20mA 10 0 2. 8 3 3. 5 4 4. 5 8 WLEDs ILED = 20mA 0.05 0 2.8 5 3 3.5 Figure 8 Efficiency vs. VCC Power On from EN Figure 9 14 PWM Dimming from EN 25 EN Pin Dimming VEN = 2.8V VCC = 4.2V f = 5kHz 8WLEDs Output Current(mA) Output Current(mA) 16 5 VFB vs. VCC Figure 7 20 18 4.5 Power Supply(V) Power Supply(V) Figure 6 4 12 10 8 6 FB Pin PWM Dimming VPWM = 2.8V VCC = 3.6V f = 2kHz 8WLEDs 20 15 10 5 4 2 0 0 20 40 60 80 100 0 0 20 Enable Pin Dimming Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 60 80 100 Duty Cycle(%) Duty Cycle(%) Figure 10 40 Figure 11 FB pin PWM Dimming 7 IS31BL3506A Figure 12 Ripple Voltage Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 8 IS31BL3506A FUNCTIONAL BLOCK DIAGRAM LX VCC Band Gap Bias&Ref FB Vref R Slope Compensation OSC S Q Σ Ramp Generater GND Current Limite Thermal Shutdown Block OVP OUT EN Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 9 IS31BL3506A APPLICATION INFORMATION INPUT AND OUTPUT CAPACITOR FB PIN DC VOLTAGE DIMMING A 2.2μF input capacitor is used to reduce input ripple and noise, where the input ripple amplitude is inversely proportional to the value of the input capacitance. The input and output capacitors should be placed as close to the device as possible, so as to reduce the effect of voltage ripple. The value of the output capacitor is dependent upon the output ripple. A 1μF or 0.22μF ceramic capacitor with a 50V rating is sufficient for the majority of applications. The schematic of Figure 4 show an example of using a DC input voltage at the FB pin to implement LED dimming. When the DC input voltage increases, the current through R2 and R3 increases producing an offset voltage across R2, thereby causing the LED current to be reduced. The LED current may be computed using the following equation, (3). VFB is 0.3V (typ). VFB INDUCTOR VALUE The choice of the inductor value will affect the performance of the device. Large value inductors will reduce the current ripple in the inductor, thus reducing output voltage ripple. However large value inductors of the same current rating, typically also have larger DC resistance, thus reducing the system efficiency. For the majority of applications 4.7μH or 10μH is sufficient. LED CURRENT SETPOINT When the IS31BL3506A is used for LED driving applications (Figure 1), the LED current flows through the external feedback resistor RSET to regulate the LED current. The internal feedback regulation point is 0.3V. The maximum LED current may be calculated by the following equation, (1). I MAX VFB / RSET (1) For accurate LED current, resistors should be 1% or better tolerance. LED INTENSITY CONTROL I LED FB PIN PWM DIMMING A PWM signal connected to the FB pin can also be used to directly control the LED current (Figure 5). A low pass filter converts the PWM duty cycle to a DC level, which is in turn summed together with the feedback voltage of RSET to effectively reduce the LED current proportionally. Due to the filtering of the PWM signal, the frequency of the PWM signal can have an affect on the output voltage ripple. For a PWM signal input signal of 2.8V, the recommended frequency is greater than 2kHz. Using a fixed frequency PWM signal and adjusting the PWM duty cycle effectively adjusts the LED intensity. LED current may be computed using the following equation, (4). VFB is 0.3V (typ). VFB I LED I MAX DPWM (2) IMAX is computed using equation (1). Recommended PWM frequency is in the range of 500Hz ~ 500kHz. So as to guarantee a reasonably good dimming effect, the minimum duty cycle should be about 1%. Driving the EN pin with a PWM signal can effectively adjust the LED intensity. The PWM signal voltage levels must meet the EN pin input voltage levels, VEN_ON and VEN_OFF. IS31BL3506A can also use a DC voltage or PWM signal to directly control the LED current, and thus provide fine adjustment for the LED intensity. Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 （3） When the DC voltage range is 0V~1.8V, a good value for R2 is 75kΩ，and for R3 is 360kΩ. EN PIN DIMMING The EN pin of the IS31BL3506A can accept a PWM signal to implement LED dimming (Figure 1). LED current may be computed using the following equation, (2). R2 (VDC VFB ) R3 RSET I LED R2 (VPWM Duty VFB ) R4 R3 RSET （4） For a PWM signal range of 0V~1.8V, a suitable value for R2 is 75kΩ, R3 is 150kΩ, R4 is 200kΩ. To ensure good dimming effect, the minimum duty cycle is about 10%. SETTING THE OUTPUT VOLTAGE The IS31BL3506A can be configured to provide a constant output voltage (Figure 3). The output voltage level can be computed using the following equation, (5). The device internal VFB is 0.3V (typ). VOUT VFB R1 RSET / RSET （5） OVERVOLTAGE THRESHOLD Device open circuit protection is realized using the overvoltage protection function (OVP). If the output voltage surpasses the overvoltage threshold, the overvoltage protection circuit is activated and the device will stop working. 10 IS31BL3506A CLASSIFICATION REFLOW PROFILES Profile Feature Pb-Free Assembly Preheat & Soak Temperature min (Tsmin) Temperature max (Tsmax) Time (Tsmin to Tsmax) (ts) 150°C 200°C 60-120 seconds Average ramp-up rate (Tsmax to Tp) 3°C/second max. Liquidous temperature (TL) Time at liquidous (tL) 217°C 60-150 seconds Peak package body temperature (Tp)* Max 260°C Time (tp)** within 5°C of the specified classification temperature (Tc) Max 30 seconds Average ramp-down rate (Tp to Tsmax) 6°C/second max. Time 25°C to peak temperature 8 minutes max. Figure 13 Classification Profile Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 11 IS31BL3506A PACKAGE OUTLINE DRAWING TSOT-23-6 Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 12 IS31BL3506A SOT-23-6 Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 13 IS31BL3506A DFN-8 Note: All dimensions in millimeters unless otherwise stated. Integrated Silicon Solution, Inc. – www.issi.com Rev. C, 01/09/2014 14