FO2203A 1.2MHZ，26V Step-up DC/DC Converter GENERAL DESCRIPTION FEATURES The FO2203A is a high frequency, high efficiency DC to DC converter with an integrated 2.8A, 0.1Ω power switch capable of providing an output voltage up to 26V. The fixed 1.2MHz allows the use of small external inductions and capacitors and provides fast transient response. It integrates Soft start, Comp,. only need few components outside. z z z z z z z z 2.3V to 6V input voltage Rangel Efficiency up to 96% 26V Boost convert er with 2.8A switch current 1.2Mhz fixed Switching Frequency Integrated soft-start Thermal Shutdown Under voltage Lockout SOT23-6 Package APPLICATIONS • • • • • • • Handheld Devices GPS Receiver Digital Still Camera Portable Applications DSL Modem PCMCIA Card TFT LCD Bias Supply Figure 1. Typical Application Circuit 1 FO2203A ORDERING INFORMATION PART NUMBER TEMP RANGE FO2203A -40°C to 85°C SWICHING FREQUENCY OUTPUT VOLTAGE (V) 1.2MHZ ADJ ILIM (A) PACKAGE PINS SOT23-6 6 2.8 PIN CONFIGURATION PIN DESCRIPTION PIN NUMBER PIN NAME 1 SW 2 PGND Power ground 3 FB Feedback pin 4 EN Shutdown control input., Connect this pin to logic high level to enable the device 5 IN Input power supply pin PIN DESCRIPTION Switch pin ABSOLUTE MAXIMUM RATINGS (Note: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.) PARAMETER VALUE UNIT -0.3 to 6.5 V FB, EN Voltage -0.3 to VIN+0.3 V SW Voltage Operating Ambient Temperature Vin+0.3 to 28V V -40 to 85 °C 150 °C Supply Voltage VIN Maximum Junction Temperature REV0.2 FO2203A Storage Temperature -55 to 150 °C 300 °C Lead Temperature (Soldering, 10 sec) ELECTRICAL CHARACTERISTICS (VIN = 3.6V, TA= 25°C unless otherwise specified) PARAMETER Input Voltage Range SYMBOL TEST CONDITIONS MIN VIN 2.3 Boost output voltage range Vout 26 UVLO Threshold VUVLO Operating Supply Current Shutdown Supply Current ISUPPLY 6.0 V V VFB =1.3V，EN=Vin, ILoad =0 75 135 VEN =0V, VIN =4.2V 0.1 1 VFB Peak Inductor Current IPEAK 2.5 Oscillator Frequency FOSC 0.9 1.188 1.2 Rds(ON) of N-channel FET ISW =-100mA Enable Threshold VIN = 2.3V to 5.5V Enable Leakage Current UNIT 2.3 Regulated Feedback Voltage SW Leakage Current MAX 2.2 VHYSTERESIS =100mV 2.1 TYP 0.3 -0.1 VEN = 0V, VSW = 0V or 5V, VIN = 5V V µA 1.212 V 2.8 3.0 A 1.2 1.5 MHz 0.1 0.2 Ohm 1 1.5 V 0.1 µA 1 uA REV0.2 FO2203A Figure 3. Functional Block Diagram FUNCTIONAL DESCRIPTION NORMAL OPERATION The boost converter is designed for output voltage up to 26V with a switch peak current limit of 2.8 A. T he device, which operates in a current mode scheme with quasi-constant frequency, is externally 1.2MHZ and the minimum input voltage is 2.3 V. To control the inrush current at start-up a softstart pin is available. During the on-time, the voltage across the inductor causes the c urrent in it to rise. When the current reaches a threshold value set by the internal GM amplifier, the power transistor is turned off, the energy stored into the inductor is then released and the current flows through the Schottky diode towards the output of the bo ost converter. The offtime is fixed for a c ertain Vin and Vs, and therefore maintains the same frequency when varying these parameters. drop across the Rdson of the p ower transistor which will have an effect on the voltage across the inductor and thus on Ton ( Toff remains fixed). Some slight frequency changes might also a ppear with a fixed output load due to the fact th at the output voltage Vs is not sensed directly but via the SW Pin, which affects accuracy. Because of the q uasi-constant frequency behavior of the device , the FO2203A eliminates the need for an int ernal oscillator and slope compensation, which provides better stability for the system over a wide of input and output voltages range, and more stable and accurate current limiting operation compared to boost converters operating with a con ventional PWM scheme .The FO2203A topology has also the benefits of providing very good load and line regu lations, and excellent load transient response. However, for d ifferent output loads, the frequency may slightly change due to the voltage REV0.2 FO2203A UNDERVOLTAGE LOCKOUT (UVLO) THERMAL SHUTDOWN To avoid mis-operation of the device at low input voltages an under voltage lockout is i ncluded that disables the dev ice, if the input voltage falls belo w 2.2V A thermal shutdown is imp lemented to prevent damages due to excessive heat and power dissipation. Typically the thermal shutdown threshold is 150℃ .When the thermal shutdown is triggered the device stops switching until the temperature falls below typically 136 ℃ .Then the device starts switching again. APPLICATION INFORMATION INDUCTOR SELECTION In normal operation, the inductor maintains continuous current to the output. The inductor current has a ripple that is dependent on the inductance value. The high inductance reduces the ripple current. Selected inductor by actual application: Manu Part Indu DRC Dimensio factu Numb ctanc max ns rer er e(uH) (Oh L*W*H(m ms) m3) Murat LQH44 a PN LQH5 BP Sumi CDRH da 6D23 3.3 0.065 4*4*1.7 4.7 0.08 10 0.16 22 0.37 3.3 0.044 5*5*2 4.7 0.058 10 0.106 22 0.259 3.3 0.11 4.7 0.16 5*5*2.4 Table 1. Recommend Surface Mount Inductors If output voltage is 5V or 12V，you can use 3.3uH or 4.7uH, or 10uH is OK，if 24V ,maybe need 10uH Normal application: Input 3.3V (3.6V or 4.2V) to Output 5V 9V 12V 24V； Input 5V Output 9V 12V 24V to INPUT CAPACITOR SELECTION The input capacitor reduces input voltage ripple to the converter, low ESR ceramic capacitor is highly recommended. For most applications, a 10uF capacitor is used. The input capacitor should be placed as close as possible to VIN and GND. REV0.2 FO2203A OUTPUT CAPACITOR SELECTION A low ESR output capacitor is required in order to maintain low output voltage ripple. In the case of ceramic output capacitors, capacitor ESR is ver y small and does not contribute to the rip ple, so a lower capacitance value is acceptable when ceramic capacitors are used. A 10uF or two 10uF ceramic output capacitor is suitable for most applications. OUTPUT VOLTAGE PROGRAMMING In the adjustable version, the output voltage is set by a resistive divider according to the following equation: Typically choose R2=10K and determine R1 from the following equation: DIODE SELECTION According to max Iout an d max Vout, you can select suitable diode. Normally we select di ode If= (1.5~2)*Ioutmax and VR= (1.5~2)*Voutmax. For high efficiency，suggest that you sele ct low Vf Schottky diode. For example, 3.3V~4.2Vin 5V 1Aout,you can select MBRA210 or SS34. REV0.2 FO2203A TYPICAL PERFORMANCE CHARACTERISTICS (L=4.7uH, CIN=10uF, COUT=2*10uF,if not mentioned) Efficiency vs. Output Current (Vout=5V) Efficiency vs. Output Current(Vout=9V) Efficiency vs. Output Current(Vout=12V) REV0.2 FO2203A STARTUP (3.3V IN 5V 500MA OUT) STARTUP(3.3V IN 9V 500MA OUT) PWM SWITCHING CONTINUOUS CONDUCTION MODE PWM SWITCHING DISCONTINUOUS CONDUCTION MODE NOTES: The efficiency is tested under normal temperature, the actual current driver capability is 70% ~80% of the max current in sheet consider of high temperature surrounding status. REV0.2 FO2203A PACKAGE OUTLINE SOT23-6 PACKAGE OUTLINE AND DIMENSIONS REV0.2 FO2203A PROUCT CHANGE NOTICE LIST NO 1 2 Updated date 2012-2-1 2012-3-5 Version update Rev 0.1 Rev 0.2 Update content Create FO2203A datasheet Modify Typical schematic REV0.2