BL8531CB5TR60

BL8531C series are boost structure, voltage-type pulse-frequency modulation(PFM) step-up DC-DC controller. Only four external components are necessary: an inductor, a schottky diode, an output filter capacitor and a NMOSFET or a NPN transistor. The step-up DC-DC converter, constructed by BL8531C, can be adjusted from 2.5V to 6.0V, 0.1V step. By using the depletion technics, the quiescent current drawn from power source is lower than 8uA. 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. BL8531C integrates PFM control system. This system controls fixed power switch on duty cycle frequency 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 ontime is changed based on the conditions such as input voltage, output current and load. The oscillate block inside BL8531C 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. BL8531C has a drive pin (EXT) for external transistor. So it is possible to load a large output current with a power transistor and a low saturation voltage. At very light load condition, the switch current and quiescent current of chip will effect efficiency certainly. So in very light load condition, the efficiency will drop. Therefore, it is recommended that user use BL8531C in the condition of load current as large as several tens of mA to several hundreds of mA.

Applications

• Power source for PDA, DSC, MP3 Player, electronic toy and wireless mouse
• Power source for a single or dual-cell battery powered equipments
• Power source for LED

Key features

• Deliver 500mA at 4.0V Output voltage with 2V input Voltage
• The controller output voltage can be adjusted from 2.5V to 6.0V (in 0.1V step)
• Output voltage accuracy: ±2%
• Low temperature-drift coefficient of the output voltage: ±100ppm/℃
• Only four external components are necessary: An inductor, a Schottky diode, an output filter capacitor and a NMOSFET or a NPN transistor
• High power conversion efficiency: 90%
• Low quiescent current drawn from power source: 6uA
• Small package: SOT-23-3, SOT-23-5, SOT-89-3