JPH05235640A - Semiconductor device - Google Patents

Abstract

PURPOSE:To reduce number of externally mounted components mounted at the outside of a chip when an oscillation circuit is formed by devising a transmission gate used to separate the oscillation circuit to act like a damping resistor. CONSTITUTION:A switch 12 and a resistor 11 are shown in an equivalent circuit of a transmission gate (TMG) 9 and the resistance depends on the size of a transistor(TR) of the TMG 9. Thus, the size of the TR of the TMG 9 is manufactured so that the resistance is proper as a damping resistance and the resistor 11 is used for the damping resistor. Thus, an output terminal 3 of an oscillation circuit and an output terminal 3 of a usual port circuit 13 are used in common and the output terminal is selected by TMGs 9,10. Then the TMG 9 acts like the damping resistor acting like a switch to select an oscillation inverter 1. Thus, it is not required to provide the damping resistor at the outside of a chip 20, and its exclusive circuit is not required even in the inside and number of components and output terminals is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device,
In particular, the present invention relates to a semiconductor device having an oscillation circuit in which a ceramic oscillator or a crystal resonator is connected on a chip to form an oscillation circuit.

[0002]

2. Description of the Related Art FIG. 3 is a configuration diagram of an oscillation circuit of a conventional semiconductor device. In the figure, 1 is an inverter for oscillation in a chip 20, 2 is an input terminal of the oscillation circuit, 15 is an output terminal of the oscillation circuit, 4 is a ceramic resonator or crystal resonator, 5 is a feedback resistor, and 6 is a damping resistor. , 7 and 8 are capacitors. Further, 13 is a normal port circuit in the chip 20, and 14 is an output terminal of the normal port circuit.

Inverter 1 in chip 20 is connected to chip 2
A ceramic oscillator or a crystal resonator 4, a feedback resistor 5, a damping resistor 6, and capacitors 7 and 8 outside the device 9.
By connecting as shown in FIG. 3, the oscillation circuit oscillates at the resonance frequency of the ceramic oscillator or the crystal resonator 4.

[0004]

The conventional semiconductor device is constructed as described above, and a damping resistor must be prepared outside the chip 20 when the oscillation circuit is constructed, and the number of external parts is reduced. There was a problem of increasing one point.

The present invention has been made in order to solve the above problems, and it is not necessary to attach a damping resistor to the outside, and the oscillation not having a circuit dedicated to the damping resistor inside the chip is also possible. Aim to get the circuit.

[0006]

A semiconductor device according to the present invention is a chip in which a ceramic oscillator or a crystal resonator is connected to form an oscillation circuit and an oscillation circuit is connected to the ceramic oscillator or the crystal resonator. The transmission gate is provided between the oscillation circuit and the chip terminal and switches between connection and non-connection between the oscillation circuit and the chip terminal and functions as a damping resistor when the oscillation circuit operates.

[0007]

In the present invention, since the transmission gate for disconnecting the oscillation circuit also functions as a damping resistor, no damping resistor is required outside the chip,
Moreover, a circuit dedicated to the damping resistor is not required inside the chip.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an oscillator circuit according to an embodiment of the present invention. In the figure, 1 is an inverter for oscillation in a chip, 2 is an input terminal of the oscillator circuit, 3 is an output terminal of the oscillator circuit Ports 4 are ceramic resonators or crystal resonators, 5 are feedback resistors, 7 and 8 are capacitors, 9 is a transmission gate for disconnecting the oscillating inverter 1, and 10 is a transmission gate for disconnecting the normal port circuit 13. ..

Further, FIG. 2 shows a transmission gate 9
11 is a resistance, and 12 is a switch.

Next, the operation will be described. The transmission gates 9 and 10 are switched between "ON" and "OFF" by a switching signal, and when the transmission gate 9 is in the "ON" state, the transmission gate 10
Is in the "OFF" state and the transmission gate 9
Is in the "OFF" state, transmission gate 10
Becomes the "ON" state.

Therefore, when the transmission gate 9 is in the "ON" state, the output of the inverter 1 for oscillation is connected to the terminal 3 and the terminal 3 becomes the output terminal of the oscillation circuit.
On the contrary, when the transmission gate 10 is in the "ON" state, the normal port circuit is connected to the terminal 3 and the terminal 3 becomes the normal port.

The equivalent circuit of the transmission gate 9 is as shown in FIG. 2, and has a resistor 11 in addition to the switch 12. This resistance value is determined by the transistor size of the transmission gate 9, and the resistance value can be set to a desired value by adjusting the transistor size.

Therefore, in this embodiment, the transistor size of the transmission gate 9 is made so that this resistance value becomes an appropriate value as a damping resistance, and the resistance 11 of the transmission gate 9 is used as a damping resistance.

As described above, in this embodiment, the output terminal of the oscillation circuit and the output terminal of the normal port circuit, which are separately provided in the past, are made common, and these are switched by the transmission gates 9 and 10, and the oscillation inverter is used. Since the transmission gate 9 functioning as a switch for changing over is provided with a function as a damping resistor, it is not necessary to provide a damping resistor outside the chip 20, and a circuit dedicated to the damping resistor is also provided inside the chip 20. There is no need, and the number of external parts and the number of output terminals can be reduced by one as compared with the conventional case.

In the above embodiment, as shown in FIG. 1, the transmission gate 9 is composed of both channel transistors and N-channel transistors.
This may be composed of only P-channel transistors or only N-channel transistors.

Further, in the above embodiment, the case where the output of the normal port circuit is connected to the chip terminal when the oscillation circuit is separated from the chip terminal has been described, but the present invention uses the transmission gate 9 as a damping resistor. If it is also used, any other circuit may be used.

[0017]

As described above, according to the present invention, an oscillation circuit which is connected to a ceramic resonator or a crystal resonator to form an oscillation circuit and a chip terminal to which the ceramic resonator or the crystal resonator is connected. And a connection between the oscillation circuit and the chip terminal, and a transmission gate that functions as a damping resistor when the oscillation circuit operates. There is an effect that the number of external parts can be reduced by 1 without providing a circuit.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a transmission gate of a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional semiconductor device.

[Explanation of symbols]

 1 Inverter for oscillation 2 Input terminal of oscillation circuit 3 Output terminal of oscillation circuit and output terminal of normal port circuit 4 Ceramic oscillator or crystal resonator 5 Feedback resistor 6 Damping resistor 7 Capacitor 8 Capacitor 9 Transmission gate 10 Transmission gate 11 Resistor 12 Switch 13 Normal Port Circuit 14 Output Port of Normal Port Circuit 20 Chip

Claims (2)

[Claims] 1. A semiconductor device having an oscillating circuit in which a ceramic oscillator or a crystal resonator is connected on a chip to form an oscillation circuit, wherein the oscillation circuit is connected to the ceramic oscillator or the crystal resonator. An oscillation circuit comprising a transmission gate provided between the chip terminal and the oscillation circuit and the chip terminal to switch connection / disconnection between the oscillation circuit and the chip terminal and to function as a damping resistor when the oscillation circuit operates. 2. The semiconductor device according to claim 1, further comprising another circuit connected to the chip terminal when the oscillation circuit is not connected to the chip terminal.