R1205x Series Step-up DC / DC Converter with Overcurrent Protection NO.EA-272-201211 OUTLINE The R1205x is a PWM control type step-up DC/DC converter IC with low supply current. Each of these ICs consists of an NMOS FET, a diode, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier, a current limit circuit, an under voltage lockout circuit (UVLO), an over-voltage protection circuit (OVP), a soft- start circuit, a Maxduty limit circuit, and a thermal shutdown protection circuit. This step-up DC/DC converter can be easily built with a few external components such as a coil, a resistor, and a capacitor. As the protection functions, the R1205x has an Lx peak current limit function, an over voltage protection (OVP) function, an under voltage lock out (UVLO) function and a thermal shutdown function. The R1205x presents the R1205x8xxA version that is optimized for the constant voltage power source, and the R1205x8xxB/C version that is optimized for driving the white LED with the constant current. The R1205x8xxB/C is an adjustable version that can change the LED brightness dynamically by using a 200Hz to 300kHz PWM signal toward the CE pin. The R1205x is available in DFN1616-6B and TSOT-23-6 packages. FEATURES Input Voltage Range ............................................. 2.3V to 5.5V (R1205x8xxA) 1.8V to 5.5V (R1205x8xxB/C) Supply Current ...................................................... Typ. 800 A Standby Current .................................................... Max. 5 A Feedback Voltage ................................................. 1.0V15mV (R1205x8xxA) 0.2V10mV (R1205x8xxB) 0.4V10mV (R1205x8xxC) Oscillator Frequency ............................................. Typ. 1.2MHz Maximum Duty Cycle ............................................ Typ. 91% UVLO Function Typ.2.0V (Hys.Typ.0.2V) (R1205x8xxA) Typ.1.6V (Hys.Typ.0.1V) (R1205x8xxB/C) Selectable Lx Current Limit Function .................... Typ. 350mA / 700mA Over Voltage Protection ........................................ Typ. 25V LED dimming control (R1205x8xxB/C) ............... by external PWM signal (Frequency 200Hz to 300kHz) Thermal Protection Function ................................. Typ.150C(Hys.Typ.50C) Switch ON Resistance .......................................... Typ. 1.35 Packages .............................................................. DFN1616-6B, TSOT-23-6 Ceramic capacitors are recommended APPLICATION Constant Voltage Power Source for portable equipment OLED power supply for portable equipment White LED Backlight for portable equipment 1 R1205x NO.EA-272-201211 SELECTION GUIDE The OVP threshold voltage, current limit, package and VFB/Auto discharge are user-selectable options. Product Name Package Quantity per Reel Pb Free Halogen Free R1205L8x1-TR DFN1616-6B 5,000 pcs Yes Yes TSOT-23-6 3,000 pcs Yes Yes R1205N8x3 -TR-FE x : Designation of current limit. (1) 350mA (2) 700mA : Designation of VFB. (A) 1.0V (B) 0.2V (C) 0.4V 2