Datasheet BL8531 (Belling) - 4

BL8531 BLOCK DIAGRAM Note: CE pin is only available on 5 pins packages. DETAILED DESCRIPTION The BL8531 series are boost structure, voltage- inside BL8531 provides fixed frequency and pulse type Pulse-Frequency Modulation (PFM) step-up width wave. DC-DC converter. Only three external The reference circuit provides stable reference components are necessary: an inductor, an voltage to output stable output voltage. Because output filter capacitor and a schottky diode. And internal trimming technology is used, The chip the converter’s low noise and low ripple output output change less than ±2%. At the same time， voltage can be adjusted from 2.5V to 5.0V, 0.1V the problem of temperature-drift coefficient of step. By using the depletion technics, the output voltage is considered in design, so quiescent current drawn from power source is temperature-drift coefficient of output voltage is lower than 7uA. The high efficiency device less than 100ppm/℃。 consists of resistors for output voltage detection and trimming, a start-up voltage circuit, an High-gain differential error amplifier guarantees oscillator, a reference circuit, a PFM control stable output voltage at difference input voltage circuit, a switch protection circuit and a driver and load. In order to reduce ripple and noise, the transistor. error amplifier is designed with high band-with. The PFM control circuit is the core of the BL8531 Though at very low load condition, the quiescent IC. This block controls power switch on duty cycle current of chip do effect efficiency certainly. The to stabilize output voltage by calculating results four main energy loss of Boost structure DC-DC of other blocks which sense input voltage, output converter in full load are the ESR of inductor, the voltage, output current and load conditions. In voltage of Schottky diode, on resistor of internal PFM modulation system, the frequency and pulse N-channel MOSFET and its driver. In order to width is fixed. The duty cycle is adjusted by improve the efficiency, BL8531 integrates low on- skipping pulses, so that switch on-time is changed resistor N-channel MOSFET and well design driver based on the conditions such as input voltage, circuits. The switch energy loss is limited at very output current and load. The oscillate block low level. www.belling.com.cn 4