Abstract: A signal from a crystal resonator or an external clock signal are input from terminals xta1 or exta1, and the signal from the crystal resonator or external clock signal are selected by mode terminal mod8 and input to an oscillator OSC. An input clock signal ckl1 is frequency-divided to desired values by a divider DIV1. A divided clock signal clk2 is input as the reference clock of a phase-locked loop PLL1 or delay-locked loop DLL1, and a clock signal output by a circuit selected by a selector SEL3 passes via a divider DIV2 to be distributed to an LSI. The phase-locked loop PLL1 has a clock settling time of at least 40 clock periods, whereas the clock settling time of the delay-locked loop DLL1 is 2-3 periods.

Abstract: A filter that can achieve miniaturization and low power consumption at the same time without reducing operation precision, and a modulation semiconductor integrated circuit suitable for a wireless communication system using the filter are realized. In a modulation semiconductor integrated circuit including a digital filter that sample a digital transmission data signal an odd number of times for each two symbol cycles to perform product-sum operations, and a DA conversion circuit that subjects the output of the digital filter to DA conversion, a compensating circuit is provided which inserts predetermined values different from two types of symbols to the input of the digital filter.

Abstract: A timing-control circuit device, which uses a synchronous mirror delay circuit, for keeping the synchronization between clock signals in phase even at a load change. A reference clock signal (clkin 11) is entered to a timing-control circuit (SMDF 14) and used to generate an internal clock (dclk 12), then generates an external clock (clkout 13) through a buffer (BUF 15). The external clock signal is fed back to the timing-control circuit (SMDF 14) and used to generate an internal clock signal so as to synchronize the external clock signal in phase with the reference clock signal. The timing-control circuit is provided with a circuit (FDA 21, MCC 22) for detecting a phase difference between the internal clock signal and the external clock signal, as well as a delay circuit (DCL 24) for controlling a delay time, so that the delay circuit (DCL 24) can change the delay time according to the detected phase difference.

Abstract: A clock-generating circuit for forming internal clock signals by comparing a signal obtained by delaying, through a variable delay circuit, an input clock signal input through an external terminal with the input clock signal through a phase comparator circuit, and so controlling the delay time of the variable delay circuit that they are brought into agreement with each other, wherein the clock-generating circuit and an internal circuit to be operated by the clock signals formed thereby are formed on a common semiconductor substrate, and an element-forming region in which the clock-generating circuit is formed is electrically isolated from an element-forming region in which the digital circuit is constituted on the semiconductor substrate relying upon the element-isolation technology. The power-source passages, too, are formed independently of other digital circuits.

Abstract: An FM transmitter that can control start/idle of each of such devices as a buffer amplifier without using a sample-and-hold circuit for moving a PLL into open loop control, wherein a controller that controls a charging pump in the PLL to start/idle the FM modulation is controlled with use of a closed/open loop select signal of the PLL, a start/idle signal of the buffer amplifier, and a preamble detection signal. The power consumption of the FM transmission can be reduced, since both the buffer amplifier and the PLL in the FM transmitter can be started/idled together in a ganged manner.

Abstract: A clock-generating circuit for forming internal clock signals by comparing a signal obtained by delaying, through a variable delay circuit, an input clock signal input through an external terminal with the input clock signal through a phase comparator circuit, and so controlling the delay time of the variable delay circuit that they are brought into agreement with each other, wherein the clock-generating circuit and an internal circuit to be operated by the clock signals formed thereby are formed on a common semiconductor substrate, and an element-forming region in which the clock-generating circuit is formed is electrically isolated from an element-forming region in which the digital circuit is constituted on the semiconductor substrate relying upon the element-isolation technology. The power-source passages, too, are formed independently of other digital circuits.

Abstract: A clock-generating circuit for forming internal clock signals by comparing a signal obtained by delaying, through a variable delay circuit, an input clock signal input through an external terminal with the input clock signal through a phase comparator circuit, and so controlling the delay time of the variable delay circuit that they are brought into agreement with each other, wherein the clock-generating circuit and an internal circuit to be operated by the clock signals formed thereby are formed on a common semiconductor substrate, and an element-forming region in which the clock-generating circuit is formed is electrically isolated from an element-forming region in which the digital circuit is constituted on the semiconductor substrate relying upon the element-isolation technology. The power-source passages, too, are formed independently of other digital circuits.

Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts it into an output signal having a transmission frequency, and includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter, the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal, and a current source which supplies a current to an input of the low pass filter.

Abstract: A timing-control circuit device, which uses a synchronous mirror delay circuit, for keeping the synchronization between clock signals in phase even at a load change. A reference clock signal (clkin 11) is entered to a timing-control circuit (SMDF 14) and used to generate an internal clock (dclk 12), then generates an external clock (clkout 13) through a buffer (BUF 15). The external clock signal is fed back to the timing-control circuit (SMDF 14) and used to generate an internal clock signal so as to synchronize the external clock signal in phase with the reference clock signal. The timing-control circuit is provided with a circuit (FDA 21, MCC 22) for detecting a phase difference between the internal clock signal and the external clock signal, as well as a delay circuit (DCL 24) for controlling a delay time, so that the delay circuit (DCL 24) can change the delay time according to the detected phase difference.

Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts the first signal into an output signal having a transmission frequency. The phase-locked loop circuit includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter, the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, and a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal.

Abstract: A timing-control circuit device, which uses a synchronous mirror delay circuit, for keeping the synchronization between clock signals in phase even at a load change. A reference clock signal (clkin 11) is entered to a timing-control circuit (SMDF 14) and used to generate an internal clock (dclk 12), then generates an external clock (clkout 13) through a buffer (BUF 15). The external clock signal is fed back to the timing-control circuit (SMDF 14) and used to generate an internal clock signal so as to synchronize the external clock signal in phase with the reference clock signal. The timing-control circuit is provided with a circuit (FDA 21, MCC 22) for detecting a phase difference between the internal clock signal and the external clock signal, as well as a delay circuit (DCL 24) for controlling a delay time, so that the delay circuit (DCL 24) can change the delay time according to the detected phase difference.

Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts the first signal into an output signal having a transmission frequency. The phase-locked loop circuit includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter, the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, and a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal.

Abstract: It is an object of the present invention to provide a variable frequency oscillator capable of operating at low power supply voltage and oscillating at high frequency as well as a phase locked loop and a clock synchronizer using thereof and having a wide oscillation frequency range.

Abstract: The variable frequency oscillator is capable of operation at a low power supply voltage and oscillating at a high frequency. A phase locked loop and a clock synchronizer use the variable frequency oscillator and have a wide oscillation frequency range. The variable frequency oscillator has plural delay cells which are cascaded and the output of the final stage delay cell is fed back to the input of the first stage delay cell. Each of the delay cells includes a differential amplifier and a positive feedback circuit, connected with input and output terminals intersecting with each other. The feedback circuit has complementary amplifiers each having an input terminal formed by connecting together gates of a pMOS and an nMOS transistor and an output terminal formed by connecting together the drains thereof.

Abstract: A phase-locked loop circuit includes a current output type phase comparator for converting a phase difference between a first signal and a second signal into a current signal to be outputted, a low pass filter for filtering the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator for producing an output signal having a frequency corresponding to the output signal of the low pass filter, a current source for supplying a current to an input of the low pass filter, a reset switch for applying to the voltage controlled oscillator a reset voltage for canceling a phase-locked state of the phase-locked loop, and a frequency converter for frequency-converting the output signal of the voltage controlled oscillator to produce the second signal.

Abstract: A bus driving system includes n bus wires having data signal wires and control signal wires, (n-1) switching circuits constituting driver circuits at a transmitting end, a precharge circuitry for precharging (n-2) bus wires and (n-1)-th bus wire with a control circuit for redistributing wire capacitances of transmission lines formed by the bus wires, and a predischarge circuitry for predischarging n-th bus wire. The switching circuits control conduction and non-conduction between (n-2) bus wires, (n-1)-th bus wire and n-th bus wire, wherein the (n-2) switching circuits respond to (n-2) bit signals and a control signal, while the (n-1)-th switching circuit responds to the control signal. The signal from the transmitting end is detected by a detection circuit at a receiving end via the transmission lines.

Abstract: A digital to analog converter which includes a delta-sigma modulator for transforming the lower n bits of an input digital signal of N bits by delta-sigma modulation; first and second signal output devices for outputting first and second signals which are used for selecting current cells of a current cell array according to the higher bits and the higher bits+one LSB of the input digital signal, and a selector for selecting either of the first and second signals in accordance with the change of the output of the delta-sigma modulator. A filter is provided for smoothing the total of the currents output from the current cells which are in the output state corresponding to the first or second signal selected by the signal selector.

Abstract: A frequency synthesizer which comprises a voltage controlled oscillator; a unit for outputting a value corresponding to a differential phase of a reference signal at a predetermined frequency as a first differential phase; a unit for sampling an oscillating signal corresponding to an output of the voltage controlled oscillator K times per period of a repeating frequency f.sub.r (f.sub.

Abstract: A filter processing unit 2 receives the output of an oversampling-type analog/digital (A/D) converter circuit 1. Predetermined information is acquired by a compensation circuit 3-1 with predetermined timing from the filter processing unit 2 in the course of processing for producing a filter output for a predetermined integration-phase state and the predetermined information is fed back to the filter processing unit 2 as compensation information representing a difference in magnitude between a filter output with an integration phase lagging behind or leading ahead of the predetermined integration-phase state and a filter output with an unchanged integration phase in order to produce a controllable-phase filter output DMout. The timing for the acquisition of the compensation information by the compensation circuit 3-1 is controlled by a control circuit 7-1.

Abstract: An automatic equalizer is capable of updating tap coefficients and constituted to vary the frequency at which to update the tap coefficients depending on the magnitude thereof. There are provided a plurality of ways to vary the frequency at which to update the tap coefficients. One way is to divide the taps into two groups, one group having its tap coefficients updated at a relatively high frequency, the other group having its tap coefficients updated at a relatively low frequency. Another way is to vary the frequency at which to update the tap frequency based on the result of suitably judging the magnitude thereof.