JPH0260315A - Voltage controlled oscillator circuit - Google Patents

Abstract

PURPOSE:To obtain a VCO circuit which can be oscillated to the wide range capable of extending a variable range by preparing plural voltage controlled oscillators(VCO) with different oscillation frequency and selecting VCO as necessary. CONSTITUTION:When an H level is inputted to an SEL input terminal, a constant current source circuit 3 is operated, an oscillation stopping circuit in a VCO1 is turned OFF, therefore, the VCO1 is oscillated. Then, a constant current circuit 4 is turned OFF, the oscillation stopping circuit in a VCO2 is operated and the VCO2 stops the oscillation. When an L level is inputted to an SEL input terminal, reversely, the constant current source circuit 3 is turned OFF, the oscillation stopping circuit in the VCO1 is operated and the VCO1 stops the oscillation. Then, a constant current source circuit 4 is operated, the oscillation stopping circuit in the VCO2 is turned OFF and therefore, the VCO2 is oscillated. Thus, plural VCO1 and 2 with different oscillation frequencies are selected and can be oscillated to a wide range.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a voltage controlled oscillator (VCO) circuit in a PLL circuit for synchronization extraction of a code conversion circuit used for transmission speeds ranging from low to high speeds. The present invention relates to a voltage controlled oscillator circuit capable of oscillating over a wide range, particularly suitable for use over a wide range of frequencies.

[Conventional technology]

A conventional voltage controlled oscillator (VCO) is, for example,
As described in Publication No. 86509, an odd number of inverters are connected in cascade, and the input of the first stage of the inverter and the output of the last stage of the inverter are connected, and a power supply current of dε is supplied to each stage of the inverter. It was configured to be controlled by a control voltage. In addition, as described in Japanese Patent Application Laid-Open No. 62-107, a related conventional device of this kind has an RC phase in which a load of a series-connected circuit of an internal resistor of a one-heran sister and a capacitor is connected to the output of an inverter. A semiconductor device having a ring oscillator that performs shift oscillation includes a device that includes means for stopping oscillation of the ring oscillator and starting oscillation.

[Problem to be solved by the invention]

When trying to expand the operating frequency range of a PLL using a VCO according to the above-mentioned conventional technology, it is limited by the variable range of the vCO used in the PLL (range from 1/2 to 2 times the center frequency). There was a problem with receiving it.

The purpose of the present invention is to prepare a plurality of n VCOs with different oscillation frequencies, and to select a VCO as necessary, to
An object of the present invention is to provide a voltage controlled oscillator (VCO) circuit that can oscillate over a wide range and can extend the variable range of CO.

[Means to solve the problem]

The above purpose is to connect an odd number of stages of inverters in cascade, connect the input of the first stage of the inverter and the output of the last stage inverter, and control the current flowing into each stage of the inverter using a control voltage. Equipped with two voltage controlled oscillators (VCOs), a constant current source circuit for each vC○ and an oscillation stop circuit without inserting a transistor between the inverter and a VC○ selection circuit to selectively control their operation. This is achieved by a voltage controlled oscillator circuit that can oscillate over a wide range.

[Operation] The above VC○ circuit has multiple VCOs with different oscillation frequencies.
The operation of the constant current source circuit and the oscillation stop circuit connected to the
"When the level is input, the constant current source circuit of the first VCO operates and the oscillation stop circuit turns OFF, so the first VCO
oscillates, the constant current source circuit of the second VCO turns OFF, and the oscillation stop circuit operates, so the first VCO stops oscillating, and when the II L I+ level is input to the SEL input terminal, the reverse occurs. When the sumo wrestler's VCO stops oscillating and the second vCO starts oscillating, a VCO with a different oscillation frequency is selected and can oscillate over a wide range.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a basic block diagram illustrating one embodiment of a 700 circuit according to the present invention. In Figure 1, 1°2 is the 1st. The second VCO, 3 and 4, is a constant current source circuit, and 5 is an inverter. The 1M VCOs 1 and 2 connect odd-numbered stages of inverters (not shown) in cascade, connect the input of the first stage of the inverter and the output of the last stage inverter, and input the current flowing into each stage of the inverter to the control terminal C0NT. The VCOs have different oscillation frequencies and are controlled by control voltages, and are each equipped with an oscillation stop circuit in which no transistor is inserted between the inverters. Constant current source circuits 3 and 4 are connected to the above ■C○1 and 2, respectively, and the constant current source circuit 3゜4 and VCO1 and 2 are connected via the VC○ selection circuit consisting of an inverter 5 according to the SEL input. The configuration allows the operation of the oscillation stop circuit to be selectively controlled.

In the above configuration, when the LL HII level is input to the S E L input terminal, the constant current source circuit 3 operates and the oscillation stop circuit in the VCO1 is turned off, so the VCO1 oscillates and the constant current source circuit 4 is turned off. As a result, the oscillation stop circuit in the VCO2 operates, so the VCO2 stops oscillating. Also SEL
When the rrL" level is input to the input terminal, the constant current source circuit 3 turns OFF and the oscillation stop circuit in the VCO1 operates, so the VCO1 stops oscillating, and the constant current source circuit 4 operates and the VCO2 Since the oscillation stop circuit inside turns off, V
CO2 oscillates, thereby making it possible to oscillate over a wide range by selecting a plurality of VCOs 1 and 2 having different oscillation frequencies.

FIG. 2 is a circuit diagram showing one embodiment of the 700 circuit according to the present invention. In FIG. 2, 6 to 23 are P-MOS transistors, 24 to 54 are N-MOS transistors, and R1
, R2 are resistors, and C1 and C2 are capacitors. The first VCO1 from the P-MO8I range resistor ~13 and the N-MO3I range resistor 24~29.38-41 in Figure 2.
is configured, and P-MOS transistors 14 to 23 and N-
A second VCO is constructed from MOS1 transistors 3o to 37, 4.2 to 47, VCOL and VCO2 are VCOs with different oscillation frequencies, and the C0NT input terminal is connected to a control voltage (DC voltage) for changing the oscillation frequency. ) is input. VCO1 P, N-MO8+-Lancistalo and 24
, 7 and 25, and 8 and 26 odd stages of CMOS inverters constitute a linked oscillation circuit, and the oscillation frequency is CMOS inverters.
N-Mo according to the control voltage input to the 0NT input terminal.
8+- transistors 38-40. Next stage P.

11-Mo8 transistors 9 and 27.41.10 and 2
8. An amplifier circuit is constructed with IL and the CMOS inverter 29. Here, the resistor R1 is used to center the DC level of the CMOS inverter, so that even if the amplitude is small, it can be amplified to 1 minute ( DC is uH
This prevents it from sticking to the n level or II L II level. ) P-MO31 to transistors 12 and 13 constitute an oscillation stop circuit, and N-Mo8 +- transistor 48
, 49.50 constitute the constant current source circuit 3, and both SE
Driven by L input. Similarly, P, N-M of VCO2
OS transistors 14-18.c of odd stages of 30-34
A ring-shaped oscillation circuit is configured by an MOS inverter, and its oscillation frequency is determined by the N-Mo8+-Rancistor 42 to 4G according to the control voltage input to the C0NT input terminal.
can be changed by The next stage I), NMOS transistors 19-21.35-37°47 CMOS inverter, etc. constitute an increase 1 limiter circuit, where resistor R2 is a CMOS transistor.
Used to center the DC level of the S inverter. The PMOS transistors 22 and 23 constitute an oscillation stop circuit, and the MOS transistors 51 to 54 constitute a constant current source circuit 4.
○It is driven via an inverter 5 forming a selection circuit.

In the above circuit configuration, first, S E T, and II are connected to the input terminals.
When the IT II level is input, the N-Mo5t-run transistors 48 to 50 of the constant current source circuit 3 on the VCO2 side are turned on, and the P-Mo8 transistor 1- of the oscillation stop circuit is turned on.
In order to pad 2゜13 or ○■, a link-shaped oscillation circuit consisting of CM OS inverters C3-8. , OS inverter 9-11-
．． It is increased by an amplifier circuit consisting of 27 to 29.41 and is output from the CO output. At this time, whether the N-MOS transistors 51 to 54 of the constant current source circuit 4 on the VCO2 side
F and oscillation stop circuit I)-Mo8I-Runsistor 22
, 23 are turned ON, VCO2 stops oscillating and VCO
2 output becomes high impedance state. I want to V
When CO1 is oscillating, VCO2 stops oscillating and the output of VCO2 is in a high impedance state.
■It becomes possible to output the oscillation output of the CO board normally without receiving interference from the VCO2.

Next, when the II L I+ level is input to the SEL input terminal, the N-Mo8 I- transistors 51 to 54 of the constant current source circuit 4 on the VCOZ side are turned on, contrary to the above, and the P- of the oscillation stop circuit is turned on. MOS transistor 22.23 or OF
For F, CMOS inverter 4-18 of VCO2.
A link-shaped oscillation circuit consisting of 30 to 34 allows
Oscillates at different oscillation frequencies depending on the control voltage of the T input,
Next stage CMOS inverter 19-21.35-37,4
．． The signal is amplified by an amplifier circuit consisting of 7, etc., and outputted from the VC○ output.

At this time, the N-Mo81 transistors 48 to 50 of the constant current circuit 3 on the VCO1 side are turned OFF, and the P of the oscillation stop circuit is turned OFF.
-Since MOS transistors 2, 1.3 are turned on, V
Since oscillation is stopped and the output of VCO1 becomes a high impedance state, it is possible to output the oscillation output of VCO2 normally.

In addition, by using only a plurality of SEL large inputs and creating the logic of the VC○ selection circuit appropriately, by selecting a plurality of n VCOs with different oscillation frequencies, the VCO
It is possible to further expand the range of 1liJ variation.

〔Effect of the invention〕

According to the present invention, since a plurality of VCOs having different oscillation frequencies can be selected and output, a VCO circuit capable of oscillating over a wide range can be provided.

[Brief explanation of the drawing]

FIG. 1 is a basic block diagram showing an embodiment of the ■C○ circuit according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the ■C○ circuit according to the present invention. 1, 2-...VCO1,2,3,4 constant current source circuit, 5...Inverter, 6-23 24-54 R1, R2 C1, C2 P-MOS transistor, ・N-MO8t-transistor, resistor, capacitor .

Claims (1)

[Claims] 1. Connect odd-numbered stages of inverters in cascade, and connect the input of the first stage of the inverter and the output of the last stage of inverter,
The voltage controlled oscillator has a plurality of voltage controlled oscillators having different oscillation frequencies that control the current flowing into each stage of the inverter using a control voltage, and the voltage controlled oscillator is provided with a constant current source circuit and an oscillation stop circuit. A voltage controlled oscillator circuit configured to select an operation of a constant current source circuit and an oscillation stop circuit of each voltage controlled oscillator by a selection circuit to obtain an oscillation output of the voltage controlled oscillator.