OSCILLATION CIRCUIT DEVICE

• US 20170134029A1
• Filed: 11/09/2016
• Published: 05/11/2017
• Est. Priority Date: 11/11/2015
• Status: Active Grant

• Current Assignee: Ablic Inc. (MinebeaMitsumi Inc.)
• Original Assignee: SII Semiconductor Corporation
• Inventors: TAKADA, Kosuke
• Granted Patent: US 10,056,910 B2
• Time in Patent Office: Days
• CPC Class Codes: H03L 7/0891 the up-down pulses controlling source and sink current generators, e.g. a charge pump
• CPC Class Codes: H03L 7/093 using special filtering or amplification characteristics in the loop H03L7/087 - H03L7/091 take precedence
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• CPC Class Codes: H03L 7/1075 by changing characteristics of the loop filter, e.g. changing the gain, changing the bandwidth H03L7/1072 takes precedence
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

To provide an oscillation circuit device capable of when detecting an input reference signal and making a transition from a self-running state to a PLL operation, suppressing a fluctuation in the frequency of an output signal CLK to thereby obtain a smoothly-synchronized and stable output signal CLK. There is provided an oscillation circuit device which is adapted to configure a negative feedback circuit by a V/I conversion element to which one end of a filter circuit is connected, and a buffer circuit in a self-running state, and has a configuration which enables a capacitance in the filter circuit to be charged rapidly in such a manner that an output signal CLK can be started from a frequency equal to that in the self-running state immediately after a transition to a PLL operation.

Claims

1. An oscillation circuit device comprising:

an oscillator including;

a first constant current circuit which causes a first constant current to flow,

a second constant current circuit which causes a second constant current to flow,

a current mirror circuit which causes an oscillating current proportional to the first constant current or the second constant current to flow, and

a current control oscillator configured to change a frequency of an oscillation signal outputted according to a current value of the oscillating current inputted thereto;

a PLL circuit including;

a phase frequency comparator which compares the phase of a reference signal inputted from the outside and the phase of the oscillation signal,

a charge pump circuit which inputs an output of the phase frequency comparator therein,

a filter circuit including a capacitance which inputs an output of the charge pump circuit therein, and

a frequency division circuit which divides the output of the current control oscillator,

the PLL circuit controlling the second constant current by the output voltage of the charge pump circuit; and

a buffer circuit which receives an output voltage of the second constant current circuit as an input voltage and charges the capacitance of the filter circuit through a first switch,

wherein the oscillation circuit device is configured to output an oscillation signal based on the first constant current of the oscillator in a first mode in which the reference signal is not inputted, and output an oscillation signal based on the second constant current of the oscillator in a second mode in which the reference signal is inputted,

wherein in the first mode, the oscillation circuit device is configured to turn ON the first switch and thereby charge the capacitance by an output voltage of the buffer circuit, and

wherein in the second mode, the oscillation circuit device is configured to turn OFF the first switch.

2. The oscillation circuit device according to claim 1, wherein the first constant current circuit comprises a first PMOS transistor and a constant current element connected in series,

wherein the second constant current circuit comprises a second PMOS transistor and a first NMOS transistor connected in series,

wherein a gate of the first PMOS transistor is connected to the second PMOS transistor through a second switch, and a gate of the first NMOS transistor is connected to the filter circuit,

wherein in the first mode, the second switch is turned ON to cause the second constant current circuit to generate a current proportional to the current of the first constant current circuit, and

wherein in the second mode, the second switch is turned OFF to generate a current based on a phase difference between the frequency of the reference signal and the frequency of the oscillation signal.

3. The oscillation circuit device according to claim 2, comprising:

a pulse detection circuit which detects that the reference signal is inputted,

wherein the pulse detection circuit controls the first switch and the second switch according to an output signal thereof.