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ACE708
Technology Description
300mA Iout, 0.85V startup, 1MHz, Synchronous Boost Converter
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 1MHz 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 1MHz 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) Available in SOT-23-5
Application
One to Three Cell Battery Operated Devices Medical Instruments Bluetooth Headsets Flash-Based MP3 Players Noise Canceling Headphones
Absolute Maximum Ratings
Parameter SW Voltage EN, FB, OUT Voltage Junction to Ambient Thermal Resistance Maximum Power Dissipation Operating Temperature Range Storage Temperature Symbol VIN Max -0.3~6 -0.3~6 190 0.45 -40~150 -55~150
O
Unit V V C/ W W
O O
C C
VER 1.2
1

Technology Packaging Type
SOT-23-5
5 4
ACE708
300mA Iout, 0.85V startup, 1MHz, Synchronous Boost Converter
1
2
3
Pin SOT-23-5 FB 1 GND 2 EN 3 SW 4 OUT 5
Ordering information
Selection Guide ACE708 XX + H Halogen - free Pb - free BN : SOT-23-5
Block Diagram
VER 1.2
2

Technology Detail Description
ACE708
300mA Iout, 0.85V startup, 1MHz, Synchronous Boost Converter
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 FB=OUT FB to resistor divider VOUT=5.0V VOUT=3.3V 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 1.2
3

Technology Electrical Characteristics
ACE708
300mA Iout, 0.85V startup, 1MHz, Synchronous Boost Converter
Test condition: Vin=1.8V, Vout=3.3V, TA=25 OC, unless otherwise specified.
Parameter Minimum Input Voltage Startup Voltage Dropout Voltage, Vout2.8V
Test Conditions
Min
FB Feedback Voltage FB Input Current Output Voltage Range External divider Quiescent Current at OUT VFB=0.7V Shutdown Supply Current at OUT EN=G NMOS Switch On Resistance Isw=100mA PMOS Switch On Resistance Isw=100mA NMOS Switch Current Limit SW Leakage Current Vout=5.5V, Vsw=0 or 5.5V, EN=G EN Input Current EN Input Voltage for "Low" EN Input Voltage for "High"
FB=OUT FB=G Vout=2.5 to 5V
25
1
0.6
Typ Max Unit 0.7 V 0.85 1.1 V 3.3 V 5 V 0.6 V 50 nA 5 V 25 uA 0.1 1 uA 0.3 0.7 A 1 uA 1 uA 0.3 V V
Typical Application Circuit
SW
ACE708
OUT EN GND
VER 1.2
4

Technology Typical Performance Characteristics
ACE708
300mA Iout, 0.85V startup, 1MHz, Synchronous Boost Converter
Typical values are tested at TA=25 OC, unless otherwise specified.
VER 1.2
5

Technology
ACE708
300mA Iout, 0.85V startup, 1MHz, Synchronous Boost Converter
VER 1.2
6

Technology Packing Information
SOT-23-5
ACE708
300mA Iout, 0.85V startup, 1MHz, Synchronous Boost Converter
VER 1.2
7

Technology
ACE708
300mA Iout, 0.85V startup, 1MHz, 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 1.2
8

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