JPS62134959A - Semiconductor device - Google Patents

Abstract

PURPOSE:To compose a semiconductor device which can operate at a high speed and has small power consumption by altering the output frequency of an oscillator corresponding to the potential of a substrate. CONSTITUTION:Relationship between a threshold value VT of IGFETMX for forming a detector 300 and a substrate voltage VBB is such that the threshold value when the substrate voltage is, for example, VBB1 becomes VX as shown. Accordingly, when a voltage MX is applied to the gate of IGFETMX, and essential circuit of a semiconductor device becomes active. Since the threshold value of IGFETMX drops when the absolute value of the substrate voltage drops, IGFETMX is turned ON. As a result, the output voltage VSTOP of the detector becomes a low level, this low level output voltage switches the resistance value of a variable resistor of a variable frequency oscillator 200 to increase the frequency of an output pulse phi output from the oscillator 200. When the frequency of the pulse phi increases in this manner, a negative power supplied to a common drain (a) increases, and the absolute value of the substrate voltage VBB increases, thereby enabling an essential circuit to be operated at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a semiconductor device in which a voltage applied to a semiconductor substrate is made variable to reduce power consumption.

[Conventional technology]

In general, using a semiconductor substrate with a predetermined voltage applied to it reduces the diffusion capacitance of the pn junction formed in the semiconductor substrate, allowing the transistor to operate in a region with good back gate characteristics. , enabling high-speed fabrication of transistors. Therefore, in a semiconductor device that requires high-speed operation, a predetermined voltage is applied to the semiconductor substrate, and FIG. 3 shows an example of a substrate voltage generation circuit that generates the predetermined voltage based on an external power supply. In the figure, the circuit osc outputs a pulse φ of a constant frequency, and this pulse φ is passed through a capacitor C3 to insulated gate field effect transistors (hereinafter referred to as IGFETs) Ml, M2.
is applied to the common drain a of the two. In a conventional substrate voltage generation circuit having such a configuration.

A circuit output VBB K negative voltage (typically -2V) is constantly generated, and this negative voltage is applied to the semiconductor substrate, contributing to the high speed operation of the transistor as described above.

[Problem to be solved by the invention]

However, in the conventional semiconductor device described above, since a negative voltage is constantly applied to the semiconductor substrate, the power consumption due to the negative voltage applied to the substrate is high.
In a semiconductor device configured with 0MO8, which consumes less power in the circuit, there is a problem in that the power consumption based on the substrate voltage accounts for a large proportion of the total oil i9R power.

In order to solve this problem, it may be possible to drive the substrate voltage generation circuit only when the main circuit is active, and to stop the substrate voltage generation circuit when the main circuit is stopped. It takes a considerable amount of time to generate a voltage, so it cannot be used in semiconductor devices that require high-speed operation.

Therefore, it is an object of the present invention to provide a semiconductor device equipped with a substrate voltage generation circuit capable of high-speed operation and reducing power consumption.

[Means for solving problems]

The present invention includes a detection circuit that detects the potential of a semiconductor substrate and outputs a control signal corresponding to the potential, and an oscillation frequency changing means that changes the frequency of a pulse signal output from an oscillation circuit based on the control signal. The gist of this invention is to make the substrate potential variable and to switch the substrate potential between when the main circuits of the semiconductor device are in an active state and when they are in a stopped state.

〔Example〕

FIG. 1 is a circuit diagram showing one embodiment of the present invention, in which a capacitor C1, IGFET MI, and M2 constitute a substrate voltage generation circuit 100. 200 is a variable frequency oscillation circuit (
OSC)), the variable frequency oscillation circuit 200 is
Connect multiple stages of inverters in series through variable resistors,
It can be configured by feeding back the final stage inverter output to the first stage inverter input, placing a capacitor in parallel with the variable resistor interposed between the inverters, and grounding one electrode of the capacitor.

On the other hand, there is a resistor R1 and IG between the power supply voltage VCC and the ground.
FETMX are connected in series, and these resistors k
Ll and IGFETMX constitute a detection circuit 300. IGFETMX constituting this detection circuit 300
The relationship between the threshold value ■T and the substrate voltage VBB is as shown in FIG. 2. For example, when the substrate voltage is VBBI, the threshold value is vx.

Therefore, if voltage Mx is applied to the gate of IGFET Mx, the main circuits of the semiconductor device become active, and when the absolute value of the substrate voltage decreases, the threshold of IGFET Mx decreases and IGFET Mx turns on. As a result, the output voltage vs'rop of the detection circuit becomes a low level, and the low level output voltage switches the resistance value of the variable resistor of the variable frequency oscillation circuit 200, and the frequency of the output pulse φ output from the excavation circuit 200 is (Figure 4(a)
). Thus, as the frequency of the output pulse φ increases,
The negative power supplied to the common drain a also increases, the absolute value of the substrate voltage VBH increases, and high-speed operation of the main circuit becomes possible.

However, when the main circuit is stopped and the absolute value of the substrate voltage increases beyond VBBI, I G F ETI
'11 has a threshold value of ■, which makes it more dog-like, so IGFETM
Engineering is yr7. As a result, the output voltage vsTop becomes high level, and the variable resistor to which the high level output voltage is supplied changes its resistance value, decreasing the frequency of the output pulse φ of the oscillation circuit 200 (Fig. 4(b) )). Therefore, the negative power supplied to the common drain a is also small, and power consumption is reduced (about 1/4 compared to FIG. 4(a)). When the main circuit goes from a stopped state to an active state again, the detection circuit 300 detects a change in the substrate potential VBB and immediately changes the resistance value of the variable resistor, making it suitable for semiconductor devices that require high-speed operation. is also applicable.

In the above embodiment, the output frequency of the oscillation circuit 200 was changed by changing the resistance value, but since the output frequency is inversely proportional to the product of the resistor's 0 and the capacitor's capacitance value (q), the capacitor should be a variable capacitor. You can also change the output frequency.

〔effect〕

As explained above, according to the present invention, since the output frequency of the excavation circuit is changed in accordance with the potential of the substrate, a semiconductor device that can operate at high speed and has low power consumption can be constructed. You can get the effect of being able to do it.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an IG
A graph showing the relationship between the threshold value of the FET and the substrate voltage, FIG. 3 is a circuit diagram of a conventional example, and FIG. 4 is a waveform diagram showing output pulses of the oscillation circuit. 100... Substrate voltage generation circuit, 200...
...Variable frequency oscillation circuit, 300...Detection circuit. Agent Patent Attorney Susumu Uchihara 3QOi#daag4Rohi1Figure2

Claims (1)

[Claims] In a semiconductor device having an oscillation circuit and a substrate potential generation circuit that applies a voltage corresponding to the frequency of a pulse signal output from the oscillation circuit to a semiconductor substrate, the potential of the semiconductor substrate is detected and a control signal corresponding to the potential is provided. A semiconductor device further comprising: a detection circuit that outputs a pulse signal; and an oscillation frequency changing means that changes the frequency of the pulse signal based on the control signal.