Abstract: Disclosed is a DC-DC converter, including: a switch unit configured to generate output voltage for driving a load; an output voltage monitoring unit including a reference voltage generator generating reference voltage and a reference voltage capacitor maintaining the reference voltage when power of the reference voltage generator is interrupted and configured to generate a signal for setting the output voltage as the reference voltage; a switch controlling unit configured to control the switch unit by being operated in a pulse width modulation (PWM) mode or a pulse frequency modulation (PFM) mode by using the signal of the output voltage monitoring unit; and a mode determining and power interrupting unit configured to set an operating mode of the switch controlling unit as the PWM mode or the PFM mode according to a magnitude of the load and interrupt power of the reference voltage generator when operated in the PFM mode.

Abstract: Provided is an apparatus for calculating an absolute difference capable of efficiently performing an absolute difference using an adder. The apparatus for calculating an absolute difference includes a comparator comparing values of two integers, first and second selectors each selecting and outputting one of the two integers according to the comparison results of the comparator, an inverter complementing the result value selected by the second selector; and an adder adding up the result value selected by the first selector, the value complemented by the inverter, and 1.

Abstract: The present inventive concept relates to an analog-digital converter. The analog-digital converter includes a clock generating unit generating a clock signal; a clock delay adjusting unit outputting one of a first clock signal to a Kth clock signal according to a control signal; a capacitive digital-analog converting unit outputting a difference between the analog signal and a reference signal; a comparison unit judging whether an output of the capacitive digital-analog converting unit is 0, a positive number, or a negative number, in response to an output of the clock delay adjusting unit; and an SAR logic unit transferring an output of the comparison unit to the capacitive digital-analog converting unit in response to an output of the clock delay adjusting unit and performing a successive approximation operation to output the N-bit digital signal.

Abstract: Disclosed is a DC-DC converter including: a switch unit controlling a flow of a current based on a buck-boost topology; a short circuit unit short circuited or opened according to an external setting to change a topology of the switch unit; an inductor storing a current induced by the switch unit; a topology selecting unit selecting a topology in response to an external input signal and generating a signal corresponding to the selected topology; a pulse width modulating unit generating a signal for determining an operation time of the switch unit; a reverse flow detecting unit detecting a reverse flow of a current flowing through the switch unit to generate a signal; and a switch control unit controlling the switch unit in response to signals of the topology selecting unit, the pulse width modulating unit and the reverse flow detecting unit.

Abstract: Disclosed is a triangular wave generator which includes a square wave signal generating unit configured to output a first signal transitioning to a high level from a low level via an output terminal in response to a first transition of a clock signal and to transition the first signal to a low level from a high level in response to a reset signal; a resistance unit configured to adjust a voltage level of a the square wave signal; and a capacitance unit configured to receive an output signal of the resistance unit to generate a second signal rising to a high level from a low level with a slope, to provide the reset signal to the square wave signal generating unit, and to output a triangular signal by falling the second signal to a low level from a high level with a slope.

Abstract: Provided is an analog digital converting device which consumes a low power and guarantees fast operation characteristic. The analog digital converting device includes a sub-ADC and a successive approximation ADC. The sub-ADC converts an external analog signal into a first digital signal by using first and second reference voltages. The successive approximation ADC comprises a plurality of bit streams, and converts the external analog signal into a second digital signal according to a successive approximation operation using the first and second reference voltages. The successive approximation ADC receives the first digital signal, and converts the second digital signal in a state where one of the first and second reference voltages has been applied to the bit streams based on the first digital signal.

Abstract: Provided is a PLL circuit including automatic frequency control circuit and an operating method thereof. The voltage controlled oscillator is primarily controlled by an automatic frequency control circuit, and is secondarily controlled by a loop filter. The voltage controlled oscillator outputs a coarsely-tuned oscillation signal when primarily controlled, and outputs a finely-tuned oscillation signal when secondarily controlled. The PLL circuit can have a quick frequency fixing time, and output the oscillation signal having a broad and stable frequency. Moreover, the noise characteristic of the PLL circuit is enhanced.

Abstract: Provided is a read-out circuit that is connected to a microphone and configured to linearly amplify a current signal generated by the microphone and output the amplified current signal. The read-out circuit includes an amplification unit and a feedback resistor. The amplification unit has an amplification gain between 0 and 1. The feedback resistor is connected between input and output terminals of the amplification unit. As the amplification gain of the amplification unit becomes closer to 1, an input impedance becomes higher. A preamp of the read-out circuit can have a high input impedance due to the amplification gain, and the read-out circuit can be manufactured using a CMOS process.

Abstract: A motor control device including a preprocessing portion calculating a counter electromotive force using an analog operation is provided. The motor control device may include an offset compensation portion and a counter electromotive force measuring portion. The offset compensation portion receives a three-phase current signal from the motor and compensates an offset of the three-phase current signal. The counter electromotive force measuring portion receives the compensated current signal and a three-phase voltage signal from the motor and calculates the received current signal and the received voltage signal using an analog operation to provide the calculated result.

Abstract: Provided is a sensorless BLDC motor system. The sensorless BLDC motor system includes a BLDC motor, a comparator, a motor controller, a three-phase inverter, and a mode selector. The BLDC motor includes first to third coils. The comparator compares a voltage of a specific coil of the first to third coils with a neutral-point voltage to output the compared result. The voltage of the specific coil becomes equal to the neutral-point voltage and a specific time elapses, and then the motor controller generates first and second coil control signals based on the compared result. The three-phase inverter supplies a source voltage or ground voltage to the specific coil, or floats the specific coil, in response to the first and second coil control signals. The mode selector selects a driving mode of the BLDC motor by adjusting the specific time.

Abstract: A phase-locked loop (PLL) circuit including a voltage-controlled oscillator (VCO) with a variable gain is provided. A phase frequency detector (PFD) detects a phase difference between a reference signal and a PLL feedback signal. A charge pump and a loop filter sequentially process an output signal of the PFD. A VCO has different gains according to a mode transition. A control voltage applied to the VCO is selected from an output signal of the loop filter and an additional control signal according to the mode transition.

Abstract: Provided are a switching circuit and a small-size high-efficiency direct current-to-direct current (DC-DC) converter for portable devices including the same. Using dynamic threshold-complementary metal oxide semiconductor (DT-CMOS) transistors having dynamic threshold voltages as a switching device, the switching circuit maintains a low threshold voltage in a normal mode to improve current drivability while reducing conduction loss, and maintains a high threshold voltage in a standby mode to minimize power consumption. When the switching circuit is employed in a DC-DC converter, power conversion efficiency can be improved by reducing conduction loss in the normal mode, and power consumption can be minimized in the standby mode. Consequently, the DC-DC converter can maximize a use time of a battery of a portable device and can be useful in power supplies of portable devices that are gradually being miniaturized.

Abstract: Provided is a transformer-based oscillator which is suited to oscillate frequencies in multiple bands. An oscillator includes a transformer resonance unit and a plurality of complementary transistors. The transformer resonance unit includes a primary coil and a secondary coil corresponding to the primary coil. The plurality of complementary transistors have gates and drains between which both ends of the transformer resonance unit are respectively connected. Thus, the oscillator may operate in a differential mode or common mode according to the phase of the transformer resonance unit. Also, a complementary transistor constituting a multiband oscillation loop may be independently connected to both ends of the transformer resonance unit, and an oscillation loop of at least one band may be selected out of a multiband oscillation loop using a switch unit. Thus, the oscillator may be suited to oscillate resonance frequencies in multiple bands.

Abstract: Provided is an offset-voltage calibration circuit. The circuit includes a comparator configured to receive at least two comparison voltages and output a result of a comparison between the comparison voltages, an up/down counter (UDC) configured to output an up-counting or down-counting output signal in response to an output signal of the comparator, and a current digital-to-analog converter (DAC) configured to control the amount of current supplied from a node to which the comparison voltage is applied, in response to the output signal of the UDC and control the magnitude of the comparison voltage.

Abstract: Provided are a memory system and an integrated management method for a plurality of direct memory access (DMA) channels. The memory system includes a memory controller exchanging data with a memory and having a plurality of channels physically separated from each other, and a DMA controller having a plurality of DMA channels physically separated from each other and in contact with the plurality of channels of the memory controller, and exchanging data with the memory via the plurality of DMA channels and the memory controller.

Abstract: An LC voltage-controlled oscillator (VCO) is provided. The LC VCO includes an LC resonant circuit including at least one inductor whose both terminals are connected to output nodes and at least one capacitor connected in parallel with the inductor, and an amplifier circuit including at least one pair of switching transistors. Here, drains of the pair of switching transistors are connected to the output nodes respectively, and gates of the switching transistors are connected with the drains through a variable capacitance block exhibiting different characteristics according to an input signal.

Abstract: Provided are a current switch driving circuit generating a signal for driving a current switch, and a digital-to-analog converter using the same. The current switch driving circuit includes a first PMOS transistor in which a source terminal is connected to a power supply terminal, a gate terminal receives an input signal, and a drain terminal outputs a driving signal, an NMOS transistor in which a drain terminal is connected to the drain terminal of the first PMOS transistor, and a gate terminal receives the input signal, a second PMOS transistor in which a source terminal is connected to a source terminal of the NMOS transistor, a gate terminal is connected to a bias voltage terminal, and a drain terminal is connected to a ground terminal, and a control current source allowing the second PMOS transistor to be maintained constantly in an ON state.

Abstract: Disclosed is a bias circuit which includes a bias voltage generating part configured to generate a bias voltage using a reference current and a variable current; a reference current source part configured to provide the reference current to the bias voltage generating part; and a current adjusting part configured to provide the variable current to the bias voltage generating part and to adjust the amount of the variable current according to voltage levels of at least two input signals. The bias circuit prevents an increase in power consumption and improves a slew rate at the same time.

Abstract: Provided are a memory system and an integrated management method for a plurality of direct memory access (DMA) channels. The memory system includes a memory controller exchanging data with a memory and having a plurality of channels physically separated from each other, and a DMA controller having a plurality of DMA channels physically separated from each other and in contact with the plurality of channels of the memory controller, and exchanging data with the memory via the plurality of DMA channels and the memory controller.

Abstract: Provided is an analog digital converter (ADC). The ADC includes: a capacitor array generating a level voltage; a comparator outputting a compare signal by comparing the level voltage; and a logic circuit determining digital bits of an analog signal based on the compare signal, wherein the logic circuit determines at least one digital bit among digital bits of the analog signal while a sampling operation of the analog signal is performed in the capacitor array.