JPH09172324A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow one semiconductor device to have provision for a processing having been conducted by plural semiconductor devices so far and to reduce the power consumption by providing a switch between an output section of a crystal oscillation circuit and an input section of plural frequency divider circuits and between an output section of the plural frequency divider circuits and an input section of an internal circuit. SOLUTION: Respective oscillated clocks are outputted to a node 152 by having only to connect crystal oscillators 113, 114, 115 to oscillation circuit terminals 140, 141 while optimizing power consumption in an oscillation circuit section. Logic circuits 100, 104 select a required frequency divider circuit to frequency-divide the received oscillation clock with a prescribed frequency and to give the frequency-divided clock to an internal circuit 105. A level signal of nodes 150, 151 is decoded to allow a selector to select any frequency divider circuit. A signal of a high or a low level is fed to the nodes 150, 151 via switches 120, 121. The switches 120, 121 are formed by wiring layers of a semiconductor device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator circuit and a frequency divider circuit in a semiconductor device.

[0002]

2. Description of the Related Art In a conventional crystal oscillating circuit, since only one crystal oscillator is operated as shown in FIG. 4, only one frequency divider is required to divide the oscillation frequency. However, when using a crystal unit with a different frequency, the oscillation circuit corresponding to the oscillation frequency was redesigned in another semiconductor. Further, when the internal circuit includes the clock function, the display function, etc., a new frequency divider circuit is created so that the frequency-divided clocks required for the clock function, the display function, etc. can be output.

[0003]

A conventional crystal oscillator circuit,
In the frequency dividing circuit, when using crystal oscillators of different frequencies, each semiconductor was designed with an oscillation circuit corresponding to the oscillation frequency. Further, when the internal circuit includes the clock function, the display function, etc., a new frequency divider circuit is created so that the frequency-divided clocks required for the clock function, the display function, etc. can be output. Therefore, when using a crystal unit with a different frequency, the total development cost of the semiconductor is ( The type of crystal unit) x (development cost of a semiconductor corresponding to one crystal unit) was increasing.

[0004]

According to the present invention, there is provided a semiconductor device comprising:
A crystal oscillation circuit for oscillating a plurality of crystal oscillators having different oscillation frequencies, a plurality of frequency dividing circuits for dividing the oscillation output of the crystal oscillation circuit, and a divided clock output by the frequency dividing circuit are input. And a switch between the output section of the crystal oscillation circuit and the input sections of the plurality of frequency dividing circuits, and between the output section of the plurality of frequency dividing circuits and the input section of the internal circuit. The oscillation circuit is an oscillation inverter,
It is composed of a drain resistance and a feedback resistance, and can switch the circuit constant or the power supply voltage supplied to the oscillating circuit section for each connected crystal unit in the wiring layer of the semiconductor, and the switch is composed of a logic circuit, The output of the crystal oscillator circuit can be input to any one input unit of the plurality of frequency dividing circuits, and the output of any one of the plurality of frequency dividing circuits can be input to the input unit of the internal circuit, The logic circuit is characterized in that it can be controlled by an external terminal or a semiconductor wiring layer.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
A circuit diagram of the crystal oscillation circuit and the frequency dividing circuit is shown in FIG. In FIG. 1, the drive capacity of the oscillation inverter 110 can be adjusted to be optimum for each crystal unit used. Adjustment can be performed using the semiconductor wiring layer. However, if the crystal oscillator circuit is set to optimally oscillate with the oscillator having the maximum oscillation frequency among the oscillators to be used, all often oscillates without problems. Especially, when there is not much difference between the oscillation frequencies of the oscillators or the types of oscillators are the same, no adjustment is necessary. Even if the oscillation circuit needs to be adjusted depending on the oscillation frequency,
In a chip microcomputer or the like, a program ROM is created for each application. Therefore, if the oscillation circuit is optimized in the same wiring layer as the ROM change, there is no difference in development cost with / without adjustment of the crystal oscillation circuit. Also,
The drain resistance 111 and the feedback resistance 112 can be adjusted in resistance value in the wiring layer of the semiconductor similarly to the drive capacity adjustment of the oscillation inverter. FIG. 3 shows an embodiment in which the drive capacity, drain resistance, feedback resistance, power supply for driving the oscillation circuit section, etc. of the oscillation inverter can be switched in the semiconductor wiring layer. To increase the drive capability of the oscillation inverter, the switches 311, 314, 312, 315, 313, 31 are used.
To turn on 6 and lower it, for example, switches 311 and 31
Only 4 is turned on. The drain resistance and the feedback resistance are also switches 317, 318, 319, 320, 32.
By turning 1 on, the resistance value can be lowered. The switch 310 is a switch that can switch between the internal power supplies 301 and 302, and if a power supply with a low power supply voltage can be used, low power consumption can be achieved. In this way, if the oscillation circuit section can be adjusted in the wiring layer, the drive capacity, drain resistance, feedback resistance, or oscillation circuit section of the oscillation inverter can be taken into consideration while minimizing the power consumption in the oscillation circuit section. It is possible to set the power source and the like for driving each of the oscillating frequencies. As a result, in FIG. 1, the crystal oscillators 113 and 11 are optimized while optimizing the power consumption in the oscillator circuit section.
It is possible to output the respective oscillation clocks to the node 152 simply by connecting Nos. 4 and 115 to the oscillation circuit terminals 140 and 141. A frequency divider circuit necessary for the logic circuit 100 and the logic circuit 104 is selected in order to send the output oscillation clock to the internal circuit 105 as a clock whose frequency is divided into a constant frequency. An example of the logic circuit here is a selector. The level signals of the node 150 and the node 151 are decoded and the selector selects the frequency dividing circuit. Switch 120, switch 121 to HIGH or L
An OW level signal is sent to the nodes 150 and 151. The switches 120 and 121 are formed in a semiconductor wiring layer. Switching is possible according to the crystal oscillator to be used in the same manner as the adjustment of the oscillation circuit described above. When it is possible to oscillate a plurality of crystal oscillators without adjustment of the crystal oscillator circuit, and when the semiconductor wiring layer cannot be changed like in a one-chip microcomputer, the example of the present invention shown in FIG. Can be used. The terminals 220 and 221 shown in FIG. 2 are terminals outside the semiconductor chip, and by applying a level signal to these terminals, it is possible to select a frequency divider circuit suitable for the crystal oscillator to be used. The example of the invention shown in FIG. 2 is an invention that can deal with a plurality of crystal oscillators simply by applying a level signal to the terminals 220 and 221 without changing the wiring layer. However, the number of terminals of the semiconductor chip is increased as compared with the example of the invention shown in FIG. In FIG. 1, the frequency dividing circuits 101, 102, and 103 are individually connected in parallel, but, for example, among a plurality of crystal oscillators to be used, those of 38.4 KHz and 76.8 K, for example.
If the frequency range of Hz is included, first, 76.8KH
38.4KH after dividing the oscillation clock of z by 1/2
A method such as using the dividing stage used in z is adopted. This is a natural method for designing a circuit with a minimum. The example of the invention shown in FIG. 1 does not have a configuration in which the number of circuits in the case of supporting various oscillation frequencies is minimized. Therefore, depending on the oscillator used, the logic circuit and the frequency dividing circuit are complicated. The internal circuit 105 uses a signal divided into a certain frequency. For example, in the case of a clock function or the like, there are many circuit functions that require a constant signal, such as using a 1 Hz signal or using a 256 Hz signal for a frame frequency such as an LCD display function. Also, it is possible to use the oscillation clock as it is in the internal circuit,
It is also possible to use a frequency-divided clock that has been frequency-divided halfway through the frequency dividing circuit.

[0006]

As described above, according to the present invention, a plurality of crystal oscillators having different oscillation frequencies can be oscillated by one crystal oscillating circuit, and the oscillation output corresponding to each crystal oscillator can be obtained. By using a plurality of frequency dividing circuits for frequency division, it is possible to realize in a single semiconductor device what has been handled by a plurality of semiconductor devices so far. When a plurality of crystal oscillators having different oscillation frequencies are handled by one crystal oscillation circuit, if the highest oscillation frequency among them can be oscillated, all other crystal oscillators oscillate. However, in the present invention in which the circuit constants of the oscillation circuit and the internal power source for driving the oscillation circuit can be switched, it is possible to change to a circuit suitable for each oscillation frequency in consideration of low power consumption.
It is also possible to achieve low power consumption. Further, it is necessary to select the frequency dividing circuit corresponding to the oscillation frequency from among the plurality of frequency dividing circuits, which can be realized by the logic circuit of the present invention. The control of this logic circuit is made possible by an external terminal or a semiconductor wiring layer. The number of types of crystal units supported by these is n
Then, the development cost can be reduced to 1 / n and the development period can be shortened to 1 / n, as compared with the conventional development cost and development period. This is reflected in the unit price of the semiconductor device itself, and an inexpensive semiconductor device can be provided to the customer with a short delivery time. Moreover, it is possible to provide a semiconductor device in which power consumption is optimized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a semiconductor device showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a semiconductor device showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a semiconductor device showing a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a semiconductor device showing a first conventional example.

[Explanation of symbols]

100, 104, 200, 204, 300 Logic circuits 101, 102, 103, 201, 202, 203, 4
00, 420, 440 divider circuit 105, 205, 401, 421, 441 Internal circuit 110, 210, 410, 430, 450 Oscillation inverter 111, 211, 343, 344, 345, 346, 4
11, 431, 451 Oscillation circuit drain resistance 112, 212, 340, 341, 342, 412, 4
32, 452 Oscillation circuit feedback resistors 140, 141, 222, 223, 350, 351, 4
14, 415, 434, 435, 454, 455 Crystal oscillator external terminals 220, 221 Logic circuit control external terminals 113, 114, 115, 213, 214, 215, 4
13, 433, 453 Crystal oscillator 150, 151, 152 Signal line 120, 121, 310, 311, 312, 313, 3
14, 315, 316, 317, 318, 319, 32
0, 321 Switch by semiconductor wiring layer 130 Pull-up resistor 131 Pull-down resistor 301, 302 Internal power supply 330, 331, 332 P-channel MOS transistor 333, 334, 335 N-channel MOS transistor 160, 230, 416, 436, 437 Semiconductor device

Claims (4)

[Claims] 1. A crystal oscillation circuit for oscillating a plurality of crystal oscillators having different oscillation frequencies, a plurality of frequency dividing circuits for dividing the oscillation output of the crystal oscillation circuit, and an output by the frequency dividing circuit. A switch is provided between an internal circuit that receives a divided clock, an output section of the crystal oscillation circuit and an input section of the plurality of frequency dividing circuits, and an output section of the plurality of frequency dividing circuits and an input section of the internal circuit. A semiconductor device having. 2. The crystal oscillation circuit is an oscillation inverter,
2. The semiconductor device according to claim 1, wherein the semiconductor constant is configured by a drain resistance and a feedback resistance, and a circuit constant or a power supply voltage supplied to the oscillation circuit unit can be switched by a semiconductor wiring layer for each connected crystal unit. . 3. The switch comprises a logic circuit,
The output of the crystal oscillator circuit can be input to any one input unit of the plurality of frequency dividing circuits, and the output of any one of the plurality of frequency dividing circuits can be input to the input unit of the internal circuit. The semiconductor device according to claim 1 or 2. 4. The semiconductor device according to claim 1, wherein the logic circuit can be controlled by an external terminal or a semiconductor wiring layer.