ACE701C
High Efficiency Low Noise PFM Boost DC/DC Converter
Typical Application Circuit
D 1N5819
Vin
L 27uH
LX
LX OUT
ACE701C
GND
Iout
Cout
100uF
Rload
Tan
Vout
Cin 47uF
Detailed Description
The ACE701C series are boost structure, voltage-type pulse-frequency modulation(PFM) step-up
DC-DC converter. Only three external components are necessary: an inductor, an output filter capacitor
and a schottky diode. And the converter’s low noise and low ripple output voltage can be adjusted from
2.5V to 5.0V, 0.1V step. By using the depletion technics, the quiescent current drawn from power source
is lower than 7uA. The high efficiency device consists of resistors for output voltage detection and
trimming, a start-up voltage circuit, an oscillator, a reference circuit, a PFM control circuit, a switch
protection circuit and a driver transistor.
The PFM control circuit is the core of the ACE701C IC. This block controls power switch on duty cycle to
stabilize output voltage by calculating results of other blocks which sense input voltage, output voltage,
output current and load conditions. In PFM modulation system, the frequency and pulse width is fixed.
The duty cycle is adjusted by skipping pulses, so that switch on-time is changed based on the conditions
such as input voltage, output current and load. The oscillate block inside ACE701C provides fixed
frequency and pulse width wave.
The reference circuit provides stable reference voltage to output stable output voltage. Because internal
trimming technology is used, The chip output change less than ±2%. At the same time，the problem of
temperature-drift coefficient of output voltage is considered in design, so temperature-drift coefficient of
output voltage is less than 100ppm/℃。
High-gain differential error amplifier guarantees stable output voltage at difference input voltage
and load. In order to reduce ripple and noise, the error amplifier is designed with high band-with.
Though at very low load condition, the quiescent current of chip do effect efficiency certainly. The four
main energy loss of Boost structure DC-DC converter in full load are the ESR of inductor, the voltage of
Schottky diode, on resistor of internal N-channel MOSFET and its driver. In order to improve the efficiency,
ACE701C integrates low on-resistor N-channel MOSFET and well design driver circuits. The switch
energy loss is limited at very low level.
VER 1.3
4
ACE [ ACE TECHNOLOGY CO., LTD. ]
