ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Description The ACE708 is a step-up converter that provides a boosted output voltage from a low voltage source. Because of its proprietary design, it starts up at a very low input voltage down to 850mV, making it an ideal choice for single cell alkaline/NiMH battery operations. A switching frequency of 1.2MHz minimizes solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. The current mode PWM design is internally compensated, reducing external parts count. Features Up to 95% Efficiency 1.2MHz Switching Frequency allows small inductor and output cap Input boost-strapping allows using small or no input cap Low Vin Start-up Voltage down to 850mV Ideal for Single Alkaline Cell operations Maximum Output Current up to 300mA Low Noise PWM control Internally Compensated Current Mode Control Internal Synchronous Rectifier Logic Control Shutdown (IQ<1uA) Application One to Three Cell Battery Operated Devices Medical Instruments Bluetooth Headsets Flash-Based MP3 Players Noise Canceling Headphones Absolute Maximum Ratings Parameter Max Unit SW Voltage -0.3~6 V EN, FB, OUT Voltage -0.3~6 Junction to Ambient Thermal Resistance 190 Maximum Power Dissipation 0.45 V O C/ W W Operating Temperature Range -40~150 O Storage Temperature -55~150 O C C Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. VER 1.4 1 ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Packaging Type SOT-23-5 5 1 SOT-23-5 Description 4 2 3 1 FB 2 GND 3 EN 4 SW 5 OUT Ordering information ACE708 XX + H Halogen - free Pb - free BN : SOT-23-5 Block Diagram VER 1.4 2 ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Detail Description ACE708 is a low input voltage start up, current mode dc-dc step up converter. It’s operation can be best understood by referring to the block diagram. Upon starting up, the low voltage startup circuitry drives SW with on-off cycles, transferring energy from input to OUT by storing energy in the inductor during on-time and releasing it to the output during off-time. When OUT reaches 2V, the startup circuit turns off and the main controller takes over. The main control loop consists of a reference, a GM error amplifier, a PWM controller, a current sense amplifier, an oscillator, a PWM logic control, and it is power stage including its driver. The main control loop is a classic current mode control loop. The GM stage integrates the error between FB and REF, and its output is used to compare with a triangular wave which the summing result of the current sense amplifier output and a slope compensation voltage. The output of the comparator is used to drive the power stage to reach regulation. Application Information Output Voltage selection The output voltages can be set by connecting FB to OUT, to G or to the midpoint of a resistor divider connected to OUT. See below table for details. FB=G VOUT=5.0V FB=OUT VOUT=3.3V FB to resistor divider VOUT=0.6V(1+R1/R2) Inductor selection With switching frequency up to 1MHz, small surface mount inductors can be used with values from 2.2uH to 4.7uH. For a given chosen inductor value and application conditions make sure the peak inductor current does not exceed the maximum current rating of the selected vendor's inductor. Input and output capacitor selection The ACE708's bootstrap architecture allows the use of very small input capacitor. For applications that only need to drive small output load current, the input capacitor is optional, because once output is started up, the IC's is powered by OUT, a quiet power supply. The output capacitor is used to stabilize the loop and provide ac current to the load. A low ESR ceramic cap with values from 2.2uF to 22uF can be used. Smaller value capacitors are generally cheaper with small footprints, while larger capacitor provides lower ripples and better transient load responses. Also, when extreme low startup voltage is needed, larger output capacitors are needed for the part to startup under heavy load condition. VER 1.4 3 ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Electrical Characteristics O Test condition: Vin=1.8V, Vout=3.3V, T A=25 C, unless otherwise specified. Parameter Test Conditions Minimum Input Voltage 0.7 Max Unit V Startup Voltage 0.85 1.1 Dropout Voltage, Vout≧2.8V FB Feedback Voltage Min Typ V FB=OUT 3.3 V FB=G 5 V Vout=2.5 to 5V 0.6 V FB Input Current nA 5 V Output Voltage Range External divider Quiescent Current at OUT VFB=0.7V 35 Shutdown Supply Current at OUT EN=G 0.1 NMOS Switch On Resistance Isw=100mA 0.3 uA Ω PMOS Switch On Resistance Isw=100mA 0.7 Ω NMOS Switch Current Limit 2.5 50 uA 1 1 A uA EN Input Current 1 uA EN Input Voltage for “Low” 0.3 V SW Leakage Current 1 Vout=5.5V, Vsw=0 or 5.5V, EN=G EN Input Voltage for “High” 0.6 V Typical Application Circuit SW ACE708 OUT EN GND FB VER 1.4 4 ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Typical Performance Characteristics O Typical values are tested at TA=25 C, unless otherwise specified. VER 1.4 5 ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Typical Performance Characteristics O Typical values are tested at TA=25 C, unless otherwise specified. VER 1.4 6 ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Packing Information SOT-23-5 VER 1.4 7 ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter Notes ACE does not assume any responsibility for use as critical components in life support devices or systems without the express written approval of the president and general counsel of ACE Electronics Co., LTD. As sued herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and shoes failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. ACE Technology Co., LTD. http://www.ace-ele.com/ VER 1.4 8