摘要:
The invention provides a low-pass filter suitably used as a loop filter for a PLL or a DLL that has a filtering characteristic equivalent to that of a conventional one and can be realized in a smaller circuit area. The low-pass filter includes first filtering means (31) for accepting, as an input, an input signal to the low-pass filter and outputting a first voltage; a circuit element (311) included in the first filtering means (31) for allowing a first current to flow in accordance with the first voltage; current generating means (32) for generating a second current at a given rate to the first current; second filtering means (33) for accepting, as an input, the second current and outputting a second voltage; and adding means (34) for adding the first voltage and the second voltage and outputting an output signal of the low-pass filter, in which the second current is set to be smaller than the first current.
摘要:
The invention provides a low-pass filter suitably used as a loop filter for a PLL or a DLL that has a filtering characteristic equivalent to that of a conventional one and can be realized in a smaller circuit area. The low-pass filter includes first filtering means (31) for accepting, as an input, an input signal to the low-pass filter and outputting a first voltage; a circuit element (311) included in the first filtering means (31) for allowing a first current to flow in accordance with the first voltage; current generating means (32) for generating a second current at a given rate to the first current; second filtering means (33) for accepting, as an input, the second current and outputting a second voltage; and adding means (34) for adding the first voltage and the second voltage and outputting an output signal of the low-pass filter, in which the second current is set to be smaller than the first current.
摘要:
In order to correct the duty cycle of a given clock signal to produce a clock signal with a 50% duty cycle, a duty cycle correction circuit includes a delay unit for delaying a first clock signal to output a second clock signal and a clock-signal output unit. The clock-signal output unit includes two transistors which use the first and second clock signals as the inputs of respective gates and an inverter circuit for inverting a signal output from a common drain of the transistors to output a third clock signal. The delay unit delays the first clock signal so that the first clock signal falling appears at a timing at which the duty cycle thereof becomes 50%. The two transistors in the clock-signal output unit output, as the third clock signal, a ground voltage and a source voltage as the signal from the common drain in response to the rising of the first clock signal and the falling of the second clock signal, respectively.
摘要:
An analog circuit automatic calibration system for calibrating an object circuit that is an analog circuit having a characteristic changing with an input set value. The system includes: a set value storage section for storing a value and outputting the value to the object circuit as the set value; a characteristic detection section for detecting the characteristic of the object circuit; a first characteristic change section for determining the set value so that the characteristic of the object circuit is optimized; a second characteristic change section for updating the set value so that the characteristic of the object circuit is maintained, using an algorithm different from that used in the first characteristic change section; and a selector for selecting either one of the outputs of the first and second characteristic sections to enable the selected one to be stored in the set value storage section.
摘要:
An analog circuit automatic calibration system for calibrating an object circuit that is an analog circuit having a characteristic changing with an input set value. The system includes: a set value storage section for storing a value and outputting the value to the object circuit as the set value; a characteristic detection section for detecting the characteristic of the object circuit; a first characteristic change section for determining the set value so that the characteristic of the object circuit is optimized; a second characteristic change section for updating the set value so that the characteristic of the object circuit is maintained, using an algorithm different from that used in the first characteristic change section; and a selector for selecting either one of the outputs of the first and second characteristic sections to enable the selected one to be stored in the set value storage section.
摘要:
A semiconductor integrated circuit includes a plurality of units. Each of the units includes a power supply pad, a function circuit, and a power supply control circuit. The plurality of units each have a first state in which the function circuit is in an operating state by the power supply pad being at a prescribed operating potential and a second state in which the function circuit is in a non-operating state by the power supply pad being at a prescribed non-operating potential. The power supply control circuit includes a switching circuit for connecting the power supply pad to the prescribed non-operating potential. The power supply control circuit in each of the plurality of units closes the switching circuit when at least one of the other units is in the first state and opens the switching circuit otherwise.
摘要:
A three-state phase detector, including two latches and one NAND gate, is provided with two additional latches. To detect a phase difference between first and second input clock signals R and V, the phase detector alternates among three states responsive to a rising edge of the input R or V signal. Each of the two additional latches and an associated latch in the phase detector together constitute one shift register. When the phase detector gets back to its neutral state, the NAND gate generates a reset signal, thereby resetting all of these four latches. Two isolated pulse generators are further provided. Each of the pulse generators makes the pulse width of a frequency difference pulse signal, output from associated one of the additional latches, constant and then outputs the pulse signal with the constant width.
摘要:
A constant determination unit (90) determines various constants, that are the magnitude of a charge current outputted from a charge pump circuit (30), the time constant of a loop filter (40), and the gain of a voltage controlled oscillator (50), so as to make the proportionality constant of a natural frequency of a phase locked loop circuit for the input frequency of the phase locked loop circuit and the damping factor to be predetermined values, and outputs various control signals based on the determined constants. The charge pump circuit (30), the loop filter (40), and the voltage controlled oscillator (50) modify the magnitude of the charge current, the time constant, and the gain, respectively, in accordance with control signals outputted from the constant determination unit (90).
摘要:
Fixed pattern noise of an analog memory is reduced. Transfer paths of an address selection signal (SL) between an address generation unit (10) and respective storage elements (21) for storing an analog signal are constructed to have a substantially uniform electric characteristic in driving the storage elements (21) by the address selection signal (SL) to such an extent that the output signal of the analog memory is free from fixed pattern noise. A buffer unit (50) for temporarily storing and outputting the address selection signal is provided between the address generation unit (10) and the respective storage elements (21), and the buffer unit (50) is constructed to have an output characteristic substantially uniform between the storage elements (21). Also, lines between the buffer unit (50) and the storage elements (21) are constructed to have substantially the same electric characteristic. In this manner, charge feed through noise of the respective storage elements (21) are made substantially uniform, resulting in suppressing the fixed pattern noise.
摘要:
The invention provides an analog FIFO memory from which a written analog signal can be accurately read by eliminating errors in the analog signal between the write operation and the read operation. Prior to the read operation for reading the analog signal from a memory cell through a memory bus, a reset operation for setting the memory bus at a predetermined potential is conducted so as to remove a charge stored in a parasitic capacitance of the memory bus. The input terminal of a read circuit is set at a predetermined potential, with a write circuit disconnected from the memory bus by using an input circuit and with the read circuit connected with the memory bus by using an output circuit. In this manner, the memory bus is set at the predetermined potential, and the charge stored in the parasitic capacitance is discharged. At this point, a switch in each memory cell is in an off-state, and hence, a charge corresponding to the analog signal can be retained in the memory cell.