Oscillation circuit and phase synchronization circuit

摘要

An oscillation circuit includes a ring oscillator and a current generating circuit. The ring oscillator includes a control terminal. The current generating circuit generates a current according to a voltage of the control terminal in the ring oscillator, and supplies the current to the control terminal. The ring oscillator includes a plurality of delay stages connected to each other in a ring shape. Each of the delay stages includes an inverter and a capacitance element. The inverter includes a power source side node, an input node, and an output node. The power source side node is connected to the control terminal. The capacitance element is connected as a load for the inverter. The capacitance value of the capacitance element is larger than a parasitic capacitance at the output node.

主权项

1. An oscillation circuit comprising:
a ring oscillator having a control terminal, an oscillation frequency of the ring oscillator being controllable by a drive current supplied to the control terminal; and a current generating circuit configured to adjust the drive current to a level corresponding to a voltage of the control terminal and supply the drive current to the control terminal, wherein the ring oscillator includes at least three delay elements connected in a ring shape, wherein each delay element includes:
an inverter having a power source side node connected to the control terminal, an input node, and an output node; anda capacitance element connected to the output node of the inverter and having a capacitance larger than a parasitic capacitance of the inverter at the output node, wherein the input node of the inverter in each delay element is connected to the output node of the inverter in a different delay element, wherein the current generating circuit includes a current setting resistor and the drive current is controlled to be proportional to a voltage across the current setting resistor, wherein the current generating circuit further includes:
a compensation current generating section configured to generate a compensation current that is equivalent to a leakage current which does not contribute to oscillation in the ring oscillator; anda current generating section configured to generate the drive current by adding the compensating current to a current proportional to the voltage across the current setting resistor, wherein each inverter includes a first PMOS transistor and a first NMOS transistor, and wherein the compensation current generating section includes:
a second PMOS transistor that corresponds in operational characteristics to the first PMOS transistor;a second NMOS transistor that corresponds in operational characteristics to the first NMOS transistor;a third PMOS transistor that corresponds in operational characteristics to the first PMOS transistor; anda third NMOS transistor that corresponds in operational characteristics to the first NMOS transistor.