JP2000261317A - PLL circuit device - Google Patents

Abstract

[PROBLEMS] To provide a PLL circuit device having a VCO circuit in which the number of components is reduced by omitting a capacitor. A VCO circuit in which a charge pump output (3) of a PLL is connected to a base terminal of an oscillation transistor (6) through an LC resonance circuit (5) and an output is output from an emitter or a collector of the transistor (6).
No capacitor is connected between the collector and the emitter and / or between the base and the emitter, and the floating capacitance of the transistor is used instead.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PLL (Phase Locked Loop) circuit device having a VCO circuit (Voltage Controlled Oscillator), and more particularly to a PLL circuit device suitably used for local oscillation of a high-frequency unit for a vehicle. .

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing an example of a conventional Colpitts oscillation circuit. When configuring a PLL circuit, PL
The charge pump output 3 of the L-IC 2 is connected to a low-pass filter 4 and connected to a base terminal of an oscillation transistor 6 of the VCO circuit 1 through a variable voltage LC resonance circuit 5 using a varactor diode or the like. The oscillator circuit includes a capacitor 7 between the collector and the emitter of the transistor 6,
The capacitor 8 between the base and the emic is externally provided.
Although the output of the oscillation circuit is the emitter output of the transistor 6, it may be the collector output. Also,
A conventional PLL circuit device includes the VCO circuit 1 and a PLL-
The power and ground (GND) of IC 2 are connected to VCO circuit 1 and P
In general, the LL-IC2 is connected on a pattern of a substrate provided with the LL-IC2.

[0003]

In recent automotive high-frequency units, it is required to reduce the size of the PLL circuit device. However, since the VCO circuit 1 is determined as described above, the number of components is inevitably reduced. It will be decided. That is,
Since a certain number of components must be mounted, it is difficult to reduce the mounting area. Also,
Switching noise of PLL-IC2 (logic noise of frequency divider, phase comparator, charge pump) is always VC
O deteriorates the performance of O, but this noise flows into the VCO circuit through the power supply and GND especially in the substrate pattern,
Designers' experience and intuition are needed to significantly change the actual circuit layout and pattern characteristics. Therefore, V
There is a problem that it is difficult to theoretically predict whether or not the characteristics of CO appear.

The present invention has been made in view of such a problem, and has as its first object to provide a PLL circuit device in which the number of components is reduced. PLL-
Prevents noise from flowing into the VCO circuit from the IC
It is a second object of the present invention to provide a PLL circuit device with an improved circuit performance.

[0005]

According to a PLL circuit device of the present invention, a charge pump output of a PLL is connected to a base terminal of an oscillation transistor through an LC resonance circuit, and a VCO output from an emitter or a collector of the transistor is output.
A circuit having a circuit, wherein a capacitor is not connected between a collector and an emitter and / or between a base and an emitter of the transistor, and a stray capacitance of the transistor is used instead.

Further, the PLL circuit device of the present invention comprises a VCO
A circuit and a PLL-IC provided on a substrate,
Power supply and / or GND for the VCO circuit and PLL-IC
Are separated from each other on the substrate. As a result, switching noise from the PLL-IC can be prevented from being mixed into the VCO circuit. For this reason, the phase noise of the VCO circuit is reduced without actually confirming the operation on the substrate. Even a designer with little experience in the circuit can design a PLL circuit with good characteristics.

Further, since the power supply and / or GND separated from each other on the substrate are connected via a connector, the isolation between the VCO circuit and the PLL-IC can be improved with a simple configuration. . Further, since the GNDs separated from each other on the substrate are connected via a chassis, the VCO circuit and the PCO can be connected with a simple configuration.
LL-IC isolation can be improved.

[0008]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The components having the same functions as those in FIG. 5 are denoted by the same reference numerals. FIG. 1 is a circuit diagram of a PLL circuit device according to a first embodiment of the present invention. The VCO circuit 1 connects the output 3 of the charge pump of the PLL-IC 2 to a low-pass filter 4 and connects to a base terminal of an oscillation transistor 6 through a variable voltage LC resonance circuit 5 using a varactor diode or the like. This configuration is the same as the conventional configuration shown in FIG. The output of the oscillation circuit is often the emitter output of the transistor 6, but may be the collector output (shown by a chain line in FIG. 1).

In the present invention, both the capacitor 7 between the collector and the emitter and the capacitor 8 between the base and the emitter of the transistor 6 in the conventional circuit configuration of FIG. 5 are removed. . Note that a configuration in which one of the capacitors 7 and 8 is removed may be adopted. Which of the capacitors 7 and 8 in FIG. 5 should be removed, or both, can be properly used depending on the oscillation frequency band and oscillation stability. Also, by removing the capacitors 7 and 8, the Q value (quality f
In some cases, it is difficult to control the actor), so that it may be difficult to suppress the harmonic component. However, this point does not pose a problem when connecting to a frequency multiplier. Therefore, the PLL circuit device of the present invention is suitable for the case where the output of the VCO circuit is connected to the frequency multiplier circuit for the purpose of obtaining higher harmonic components, but is not limited to this.

In general, in a high-frequency oscillation circuit, the time constant of the LC resonance circuit is small, so that the capacitance of the capacitor is also small. In the present invention, focusing on this point, the transistor 6
The capacitance between the collector and the emitter and the capacitance between the base and the emitter are replaced by the stray capacitance of the transistor 6 originally. This allows
The number of components can be reduced by the external capacitors 7 and 8. 2 to 4 show a VCO circuit and a PLL-I
1 shows an embodiment of a PLL circuit device in which a power supply pattern of C is separated.

FIG. 2 is a diagram showing a wiring structure of a power supply.
The power supply patterns of the VCO circuit 1 and the PLL-IC 2 in the substrate 10 are separated (FIG. 2 is a schematic diagram and has no particular significance in shape, size, etc .; FIG. 3 and FIG. 4 are the same). . As a means for connecting the two patterns, a connector 11 is used, and the _Vcc 12 of the power supply and the two patterns are connected only via the connector 11. FIG. 3 is a diagram showing a GND wiring structure.
Similarly, the VCO circuit 1 and the GND pattern of the PLL-IC 2 in the substrate 10 are separated. As a means for connecting these two patterns, a connector 11 is used, and the main body or the power supply GND 14 and the two patterns are connected only via the connector 11.

FIG. 4 is a diagram showing another wiring structure of GND. As means for connecting the two patterns, it is also possible to use the chassis 15 of the substrate 10 and connect the chassis 15 to the main body or the GND 14 of the power supply. When the chassis 15 is used, the caulking portion 16 and the like of the chassis 15 are soldered to the pattern to electrically connect the chassis 15 to the pattern. As described above, by connecting the VCO circuit and the two patterns of the PLL-IC and the power supply V _CC 12 or the main body or the power supply GND 14 only through the connectors 11 and 13 or the chassis 15, switching from the PLL-IC 2 is performed. Noise can be prevented from entering the VCO circuit 1.

[0013]

As described above in detail, according to the first aspect of the present invention, the number of components in the VCO circuit can be reduced and the mounting area can be reduced, so that the present invention is applied to, for example, a high-frequency RF unit. In this case, the size of the VCO circuit can be reduced, which leads to a reduction in the size of the high-frequency RF unit itself. According to the invention of claim 2, the PLL
-It is possible to prevent the switching noise from the IC from being mixed into the VCO circuit, so that the phase noise of the VCO circuit can be reduced without actually confirming the operation on the board. PL with good characteristics even for shallow designers
It becomes possible to design an L circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a PLL circuit device of the present invention.

FIG. 2 is a schematic diagram showing another embodiment of the PLL circuit device of the present invention.

FIG. 3 is a schematic diagram showing still another embodiment of the PLL circuit device of the present invention.

FIG. 4 is a schematic diagram showing still another embodiment of the PLL circuit device of the present invention.

FIG. 5 is a circuit diagram illustrating a conventional modified Colpitts type VCO circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 VCO circuit 2 PLL-IC 3 Charge pump output 5 LC resonance circuit 6 Transistor 10 Substrate 11, 13 Connector 12 Power supply V _CC 13 Body or power supply GND 15 Chassis

Claims (4)

[Claims] 1. A PLL circuit device comprising: a VCO circuit for connecting a charge pump output of a PLL to a base terminal of an oscillation transistor through an LC resonance circuit and outputting the output from an emitter or a collector of the transistor. Wherein the capacitor is not connected between the collector and the emitter and / or between the base and the emic and is replaced by the stray capacitance of the transistor. 2. A PLL circuit device comprising a VCO circuit and a PLL-IC provided on a substrate, wherein the power supply and / or GND of the VCO circuit and the PLL-IC are provided.
Are separated from each other on the substrate,
L circuit device. 3. The PLL circuit device according to claim 2, wherein the power supply and / or GND separated from each other on the substrate are connected via a connector. 4. The GN separated from each other on a substrate
3. The PLL circuit device according to claim 2, wherein D is connected via a chassis.