JPH0323659A - Substrate potential setting circuit - Google Patents

Abstract

PURPOSE:To keep a substrate potential definite by providing the following: a substrate- potential detection part; an oscillation part whose oscillation frequency is controlled according to the substrate potential; and a substrate-potential generation pumping circuit. CONSTITUTION:When a substrate potential Vsub is changed, a substrate-potential detection part 10 detects this change and gives a signal Vc1 according to the substrate potential to an oscillation part 20. The oscillation part 20 cescades inverters 21 to 23 and feeds back an output to the inverter 21. When the Vc1 is at 'H', the oscillation part is oscillated in a short cycle; when the Vc1 is at 'L', it is oscillated in a long cycle. A waveform of the oscillation part 20 is reshaped by using a waveform-reshaping part 30 which has cascaded inverters 31 to 34. A substrate-potential generation pumping circuit 40 executes a pumping operation according to an output of the waveform- reshaping circuit 30 by using a coupling capacity 43 which has been inserted between series-connected diodes 41, 42 and their connection point and the waveform-reshaping part 30; the substrate potential Vsub is lowered to a threshold value or lower of the Vsub. When it is lower than the threshold value, the oscillation part 20 is oscillated in the long cycle; the pumping circuit 40 maintains the substrate potential Vsub in a present state. By this constitution, the Vsub can always be definite.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a substrate potential setting circuit that is built into a semiconductor integrated circuit and sets a substrate potential to a predetermined potential.

[Prior Art] In semiconductor devices such as dynamic RAM and some static RAM, the substrate potential (P
It has a built-in substrate potential generation circuit that sets the P sub in the case of a type substrate and the N well in the case of an N type substrate to a certain voltage lower than the ground potential.

FIG. 5 is a diagram showing a conventional substrate potential generation circuit of this type. That is, when the chip selection signal CS is input to the substrate potential setting control section 60, the three stages of inverters Ell, 82 .
This signal CS is level-converted via 83 and is applied to the oscillation section 20 as a substrate potential setting control signal. Oscillator 2
0, when the substrate potential setting control signal is input, the inverters 21, 22, and 23 become operational, and by feeding back the output of the inverter 23 to the input of the inverter 21, the signals of these inverters 21 to 23 are Outputs an oscillation signal with a period corresponding to the transmission time. This signal is waveform-shaped by a waveform shaping section 30 consisting of four stages of inverters 31, 32, 38, and 34, and is input to a substrate potential generation pump circuit section 40. This substrate potential generation pump circuit section 40
are diodes 41 and 42 connected in series between the substrate and ground, with the substrate side as the anode and the ground side as the cathode.
and a coupling capacitor 43 connected between the connection point A of these diodes 41 and 42 and the output part of the waveform shaping section 30.
It operates so as to oscillate the potential at the connection point A by the oscillation output output from the waveform shaping section 30 and draw out the charge on the board to the ground side. This allows the substrate potential V tub to be lowered to a predetermined potential.

[Problems to be Solved by the Invention] However, in the conventional substrate potential setting circuit described above, the operating state of the circuit is controlled by a control signal such as a chip selection signal to obtain the substrate potential. will depend on the above control signal. Therefore, if the substrate potential fluctuates for some reason, there is a problem that a stable substrate potential cannot be guaranteed unless a control signal is input.

The present invention has been made in view of such problems, and includes:
An object of the present invention is to provide a substrate potential setting circuit that can always maintain a stable substrate potential.

[Means for Solving the Problems] The substrate potential setting circuit according to the present invention is a semiconductor integrated circuit W!
a substrate potential detection section that detects the substrate potential of the substrate and outputs a signal corresponding to the substrate potential; an oscillation section whose oscillation frequency is controlled by a signal corresponding to the substrate potential output from the substrate potential detection section; The present invention is characterized in that it includes a substrate potential generation pump circuit section that extracts charges from the substrate according to the output from the oscillation section.

[Operations] In the present invention, when the substrate potential fluctuates, the substrate potential detection section detects this fluctuation and outputs a signal corresponding to the substrate potential to the oscillation section. The oscillation section changes the oscillation frequency according to the signal. As a result, the charge extraction ability of the substrate potential generation pump circuit is controlled so that the substrate potential is always kept at a constant potential. Therefore, according to the present invention, the substrate potential can always be kept at a constant potential.

[Example] Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a diagram showing a substrate potential setting circuit according to a first embodiment of the present invention.

That is, this substrate potential generation circuit includes a substrate potential detection section 1 that detects a substrate potential and outputs a signal VOI according to the substrate potential.
0, an oscillation section 20 whose oscillation frequency is controlled based on the output signal VOI of the substrate potential detection section 10, and a waveform shaping section 30 that shapes the waveform of the oscillation output from this oscillation section 20.
and a substrate potential generation pump circuit section 40 that lowers the substrate potential to a predetermined potential in response to the waveform-shaped oscillation output.

The substrate potential detection unit 10 includes a resistor 11 and a P-channel MOS connected in series between a reference voltage terminal and a ground terminal.
It is composed of a transistor 12 and an amplifier 13 that amplifies the potential of these connection points B. A substrate potential V sum is input to the gate electrode of the transistor 12, and this substrate potential V m. b changes the resistance value between the source and drain, and the potential at the connection point B changes to the reference potential V r a f by resistance division with the fixed resistor 11.
Varies between ground potential and ground potential. Note that the reference potential V r
As at, for example, an arbitrary constant voltage of about 3 to 5 V is applied. The potential at the connection point B is amplified by the amplifier 13, and a full swing signal VCt from the ground potential to the power supply potential is generated.
is output as This substrate potential detection section 10 is designed to have various DC transfer characteristics as shown in FIG. 2, for example. That is, when the substrate potential Vsub becomes higher than the predetermined threshold potential V@sob-th, the output Vc1
becomes high level, and the threshold potential V. .

−. When the value becomes lower than , the output Vat becomes a low level.

The oscillation unit 20 includes inverters 21, 22 .
23 are connected in cascade, and the output of the inverter 23 is feedback-connected to the input of the inverter 21. This oscillator 20 outputs the output signal VOI of the substrate potential detector 10.
The oscillation period changes depending on the level. That is,
When the output VOs is at a high level, it oscillates in a short period,
When the output Vat is at a low level, it oscillates with a long period.

The waveform shaping section 30 includes four inverters 31, 32, 33.
．． 34 connected in cascade, and shapes the waveform of the output from the oscillation section 20.

The substrate potential generation pump circuit section 40 also includes diodes 41 and 42, each of which is made of, for example, a MOS transistor, connected in series between the substrate and the ground terminal, with the substrate side as an anode and the ground side as a cand. 42
A coupling capacitor 43 is inserted between the connection point A of the waveform shaping section 30 and the output section of the waveform shaping section 30.
Pumping operation is performed according to the output of 0, and the substrate potential V
It has the function of pulling down the sub.

According to the substrate potential setting circuit according to the present embodiment configured as described above, the substrate potential V mu b is set to a predetermined threshold potential V. . -th, the oscillation unit 20 performs an oscillation operation in a short period, so the substrate potential generation pump circuit unit 40 rapidly lowers the substrate potential to reduce the substrate potential Vsub to Vmum-. lower to a lower level.

Substrate potential v. Is ub a predetermined threshold potential? ．． ub
When the voltage falls below -■, the oscillation section 20 performs an oscillation operation in a long period, so the substrate potential generation pump circuit section 40 maintains the substrate potential V■ at the current potential.

In this way, according to the circuit of this embodiment, the substrate potential can always be maintained at a constant potential.

FIG. 3 is a diagram showing a substrate potential setting circuit according to a second embodiment of the present invention.

This circuit differs from the circuit shown in FIG. 1 in the configuration of the substrate potential detection section 50. That is, in the substrate potential detection section 50 of this embodiment, instead of the output stage amplifier 13,
A CMOS inverter circuit consisting of a P-channel MOS transistor 51 and an N-channel MOS transistor 52 with connection point B as an input, an inverter 53 provided on its output side, and an input terminal and a ground terminal of this inverter 53. an N-channel MOS} transistor 64 inserted between the
and.

According to this circuit, the DC transfer characteristic of the substrate potential detection section 50 is as shown in FIG. ■ゎ-. It will have a hysteresis characteristic of ±ΔV around .
The substrate potential vllub is a preset potential Vsub-
. Even if a small fluctuation occurs around , the output VO1 will not oscillate, and the operation of the entire substrate potential setting circuit can be stabilized.

[Effects of the Invention] As described above, according to the present invention, the substrate potential of the semiconductor integrated circuit is detected by the substrate potential detection section, and the pumping operation is controlled based on the detection result. This has the effect that the potential can always be fixed at a constant potential, and the operation of the semiconductor integrated circuit can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a substrate potential setting circuit according to the first embodiment of the present invention, FIG. 2 is a characteristic diagram showing the DC transfer characteristics of the substrate potential detection section in the same substrate potential setting circuit, and FIG. 3 is a diagram of the present invention. A block diagram of a substrate potential setting circuit according to a second embodiment of the invention, FIG. 4 is a characteristic diagram showing the DC transfer characteristics of the substrate potential detection section in the same substrate potential setting circuit, and FIG. 5 is a diagram showing a conventional substrate potential setting circuit. It is a block diagram of a circuit. 10.50; Substrate potential detection unit, 11; Resistance, 12.51
; P-channel type MOS} transistor, 13; amplifier,
20; Oscillation section, 21 to 23.31 to 34, 53.8
1 to 63; Inverter, 30; Waveform shaping section, 40; Substrate potential generation pump circuit section, 41.42; Diode, 4
3; Coupling capacitor, 60; Substrate potential setting control section

Claims (1)

[Claims] (1) The oscillation frequency is controlled by a substrate potential detection section that detects the substrate potential of the semiconductor integrated circuit device and outputs a signal corresponding to the substrate potential, and a signal corresponding to the substrate potential output from this substrate potential detection section. 1. A substrate potential setting circuit comprising: an oscillating section; and a substrate potential generating pump circuit section that extracts charge from the substrate in accordance with an output from the oscillating section.