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Technical content
Features
2.5V to 5.5V operating input voltage range Drives up to 8 series White LEDs 1.2MHz Fixed Switching Frequency Wide range for PWM dimming (200Hz to 200KHz) Internal 1.9A switching current limit Over Voltage Protection (OVP) Internal Soft-start Function Current limit and Thermal shutdown protection Under voltage Lockout Available in the 6-pin SOT-23 Package
Applications
Camera Flash White LED Mobile Phone, Smart Phone LED Backlight PDA LED Backlight Digital Still Cameras Camcorder
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 3 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver (2) LED Dimming application Pin Configuration SOT-23-6 Pin Description NO. Pin Name Pin Function Description
1 SW Switch Output Pin
2 GND Ground Pin
3 FB Feedback Pin; Put a Resistor to GND to Setting the Current
4 EN Enable with Dimming Pin; Internal Pull-Low; Logic High Active
5 OV OVP Sense Pin
6 VCC Power Input Pin
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 4 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver Functional Block Diagram
Ordering Information
Part Number Marking Information Package Remarks SE3505-LF SE3505 YYWW--LF SOT-23-6 YYWW means Production batch LF means Lead Free Absolute Maximum Ratings Symbol Parameter Maximum Units VCC VCC Pin Voltage GND - 0.3 to GND + 6 V EN,FB, OV Pin Voltage GND - 0.3 to VCC + 0.3 V VSW SW, OV Pin Voltage 30 V PD Power Dissipation (TJ-TA)/θJA mW TST Storage Temperature Range -65 to +150 ℃ TOP Operating Junction Temperature Range -40 to +125 ℃ θJC Thermal Resistance from Junction to case 180 ℃/W θJA Thermal Resistance from Junction to ambient 250 ℃/W Note: ΘJA is measured with the PCB copper area of approximately 1 in2(Multi-layer).
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 5 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver
Electrical Characteristics
（Vcc =5V ;Iout=20mA ;Tj=25℃ unless otherwise specified） Characteristics Symbol Conditions Min Typ Max Uints Input Voltage Range VCC 2.5 - 5.5 V Step-Up Voltage Range VOUT 3 - 27 V OV Sense Voltage VOV 27.5 29 30.5 V Under Voltage Lockout UVLOV Rising - 2.25 2.45 V UVLO Hysteresis -- 100 - mV Feedback Voltage VFB 285 300 315 mV EN Threshold Logic-High Voltage VIH 1.4 - - V Logic-Low Voltage VIL - - 0.4 V EN Hysteresis 200 - mV Operating Quiescent Current ICCQ IOUT =0mA,VFB =0.5V - 170 - uA Shutdown Current ISD VEN=0V,tEN>20ms - - 1 uA N-Channel MOSFET Current Limit ILIM Duty=50% - 1.9 - A MOSFET On-Resistance RDS(on) VCC=3V,ISW=1A - 0.6 - Ω VCC=5V,ISW=1A - 0.45 - Maximum Duty Cycle DMAX 85 90 - % Line Regulation VCC=3V to 5V - 1 - % Switching Frequency FOSC 0.9 1.2 1.5 MHz Dimming Clock Rate FDIM 0.2 - 200 KHz FB Input Leakage Current IFB-LKG VFB = 0.5V - 0.01 100 nA SW Leakage Current ISWL Vsw=27V,VFB =0.5V - - 1 uA EN Input Leakage Current IEN -LKG1 VEN = VCC - 1.5 3 uA IEN -LKG2 VEN = GND - 0.01 0.1 uA Shutdown Delay TSHDN - 10 - ms Thermal Shutdown TSD - 150 - Thermal Shutdown Hysteresis TSH - 30 -
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 6 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver Typical Performance Characteristics Efficiency vs. Output Current Efficiency vs. Input Voltage Output Voltage vs. Output Current Quiescent Current vs. Input Voltage Frequency vs. Input Voltage Frequency vs. Temperature
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 7 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver Typical Performance Characteristics (Continuous) Reference Voltage vs. Input Voltage Reference Voltage vs. Temperature LED Current vs. Duty Enable Threshold vs. Input Voltage
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 8 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver Typical Performance Characteristics (Continuous) Power ON from VIN Power ON from EN Steady State Operation Normal Operation into OVP PWM Dimming from EN (200Hz) PWM Dimming from EN (20KHz)
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 9 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver Applications Information Setting the ILED Current Application circuit item shows the basic application circuit with SE3505 adjustable output version. The external resistor sets the LED output current according to the following equation: ILED R3 20mA 15Ω 6mW 350mA 0.857Ω 105mW Over Voltage Protection OV measure the output voltage for open circuit protection. Connect OV pin to the output at the top of the LED string. If V OUT above 29V, the OVP protection is happened that stops the internal driver until VOUT below 29V. Under Voltage Lockout (UVLO) To avoid mis-operation of the device at low input voltages an under voltage lockout is included that disables the device, if the input voltage falls below (2.25V-100mV). Input Capacitor Selection The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. A low ESR input capacitor sized for maximum RMS current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. A 4.7µF ceramic capacitor for most applications is sufficient. For a lower output power requirement application, this value can be decreased. Output Capacitor Selection The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. A 1uF ceramic capacitors works for most of the applications. Higher capacitor values can be used to improve the load transient response.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com • Page 10 9/4/2012 SE3505 1.9A Fixed Frequency White LED Driver Outline Drawing For SE3505 联系方式： 北京思旺电子技术有限公司–中国总部 地址：中国北京市海淀区信息路 22 号上地科技综合楼 B 座二层 邮编：100085 电话:010-82895700/1/5 传真:010-82895706 Seaward Electronics Corporation – 台湾办事处 2F, #181, Sec. 3, Minquan East Rd, Taipei, Taiwan R.O.C 电话: 886-2-2712-0307 传真: 886-2-2712-0191 Seaward Electronics Incorporated – 北美办事处 1512 Centre Pointe Dr. Milpitas, CA95035, USA 电话: 1-408-821-6600