JPH0529360A - Boosting device - Google Patents

Abstract

PURPOSE:To prevent a latched-up sate generated usually when a boosted voltage is required in an electric circuit and so on. CONSTITUTION:A boosting device comprises a charging pump circuit 18, which receives a control signal and generates a boosted voltage, and an n-channel MOSFET 11 consisting of a gate 11a and a drain 11b for receiving the input from the charging pump circuit 18, and a source 11c associated with a rectifying device for rectifying the output from the source 11c. Moreover, a traditional n-type diffused part, which often causes unstable potential, is omitted so that a latched-up state can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a booster used in an electric circuit or the like, and more particularly to a latch-up countermeasure.

[0002]

2. Description of the Related Art Conventionally, in an analog signal processing circuit, a charge transfer device has been used to obtain an analog signal delayed by a predetermined time. In order to widen the output dynamic range of this charge transfer device, the output of the booster device may be used as the reset power supply. In such a case, a rectifying element is provided so that the charge does not flow backward from the reset power supply to the output side of the charge pump circuit. Less than,
A booster equipped with such a rectifying element will be described.

FIG. 2 shows a booster having a conventional rectifying element. In FIG. 2, reference numeral 21 is a P-channel type MOS field effect transistor (hereinafter referred to as P-channel MOS).
It is called FET21. ), 21a is a gate electrode (hereinafter referred to as a gate 21a), 21b and 21c are P-type diffusion portions (hereinafter referred to as source 21b and drain 21c, respectively), and 22 is an N-type diffusion portion (hereinafter referred to as N well 22). , 23 is an N-type diffusion unit, 24 is a reset voltage line, and 25 is a reset power supply diffusion unit of the charge transfer device (hereinafter,
It is called the reset diffusion unit 25. ), 26 is a P-type substrate, 27
Is a substrate potential input terminal, 28 is a charge pump circuit, 2
Reference numeral 8a is a control signal input terminal, and 29 is a capacitor having a predetermined capacity.

In FIG. 2, the P channel MOSFE is used.
If the threshold voltage of T21 is Vtp, the gate 2
Since 1a and the drain 21c are connected, when the voltage Vsp applied to the source 21b and the voltage Vdp applied to the drain 21c are Vsp ≧ Vdp + Vtp (1), the P-channel MOSFET 21 becomes conductive, When Vsp <Vdp + Vtp (2), the P-channel MOSFET 21 is cut off. That is, the P-channel MOSFET 21 of FIG. 2 forms a rectifying element.

On the other hand, the charge pump circuit 2 in FIG.
8 outputs a boosted voltage when the control signal is at a high level (hereinafter, referred to as H), and the control signal is at a low level (hereinafter, referred to as H).
It is called L. ) Has a function to output the power supply voltage, but the current capability is not high.

Next, the boosting operation of the booster configured as described above will be described below.

First, when the control signal is L, the charge pump circuit 28 outputs the power supply voltage, and the voltage is applied to the reset diffusion section 25 and the capacitor 29 through the P-channel MOSFET 21 forming the rectifying element. Next, when the control signal is set to H, the charge pump circuit 28 outputs the boosted voltage, and the voltage is applied to the reset diffusion unit 25 and the capacitor 29 through the P-channel MOSFET 21 forming the rectifying element, and this reset diffusion is performed. The potentials of the portion 25 and the capacitor 29 are higher than the power supply voltage.

Next, when the control signal is set to L, the charge pump circuit 28 outputs the power supply voltage, but the P-channel MOSFET 21 forming the rectifying element is turned off (see the above equation (2)). , The reset diffusion unit 2
5 and the potential of the capacitor 29 hold a voltage higher than the power supply voltage. In this way, the potential of the reset diffusion section 25 becomes a boosted potential, so that the output dynamic range of the charge transfer device is widened.

[0009]

However, in the booster having the above-mentioned conventional structure, the P-channel MOSF is used.
Since it is necessary to connect the drain 21c to the N well 22 of the ET 21 via the N type diffusion portion 23, the N well 22 of the ET 21 is not operated until the charge pump circuit 28 completely starts its operation after the power is turned on. The potential becomes unstable. Therefore, there is a problem that a so-called latch-up phenomenon is likely to occur, which operates like a parasitic thyristor in the complementary MOS field effect transistor circuit and leads to the destruction of the circuit.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a booster device which outputs a boosted voltage without causing latch-up.

[0011]

To achieve this object, the means taken by the present invention is to form a rectifying element by an N-channel type MOS field effect transistor.

Specifically, the means taken by the invention according to claim 1 is a charge pump circuit capable of outputting a boosted voltage when a control signal is input, and an output of the charge pump circuit is an N-type one of which is a gate electrode. N for forming a rectifying element that is input to the diffusion unit and takes out the output from the other N-type diffusion unit.
A channel type MOS field effect transistor is provided.

[0013]

According to the present invention, according to the present invention, the output of the charge pump circuit is an N-channel type MO that forms a rectifying element.
While being output through the S field effect transistor, the N
When the channel type MOS field effect transistor is turned off, the backflow to the charge pump circuit is blocked. This widens the output dynamic range of the charge transfer device. In addition, since there is no N well in which the potential becomes unstable and the voltage becomes lower than that of the P-type diffusion portion, latch-up is prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of a booster having a rectifying element according to an embodiment of the present invention. In FIG. 1, 11 is an N-channel MOS field effect transistor (hereinafter referred to as N-channel MOSFET 11), 1
1a is a gate electrode (hereinafter referred to as a gate 11a), 1
1b and 11c are N-type diffusion portions (hereinafter, drain 1
1b and source 11c. ), 14 is a reset voltage line, 15 is a reset power source diffusion unit (hereinafter referred to as reset diffusion unit 15) of the charge transfer device, 16 is a P-type substrate,
Reference numeral 17 is a substrate potential input terminal, 18 is a charge pump circuit, 18a is a control signal input terminal, and 19 is a capacitor having a predetermined capacity.

In FIG. 1, the N-channel MOSFE is used.
If the threshold voltage of T11 is Vtn, the gate 1
Since 1a and drain 11b are connected, voltage Vdn applied to drain 11b and voltage Vd applied to source 11c
When sn and Vdn ≧ Vsn + Vtn ... (3), the N-channel MOSFET 11 becomes conductive, and when Vdn <Vsn + Vtn ... (4), the N-channel MOSFET 11 becomes cut-off state. That is, the N-channel MOSFET 11 in FIG. 1 forms a rectifying element.

On the other hand, the charge pump circuit 1 in FIG.
8 has exactly the same function as the conventional charge pump circuit 28 of FIG. 2, outputs a boosted voltage when the control signal is at a high level (hereinafter, referred to as H), and outputs the control signal at a low level (hereinafter, referred to as H). It has a function of outputting a power supply voltage at the time of L), but the current capacity is not high.

Next, the boosting operation of the booster configured as above will be described below.

First, when the control signal is L, the charge pump circuit 18 outputs the power supply voltage, and the voltage is applied to the reset diffusion section 15 and the capacitor 19 through the N-channel MOSFET 11 forming the rectifying element. Next, when the control signal is set to H, the charge pump circuit 18 outputs the boosted voltage, and the voltage is applied to the reset diffusion section 15 and the capacitor 19 through the N-channel MOSFET 11 forming the rectifying element, and this reset diffusion is performed. The potentials of the portion 15 and the capacitor 19 are higher than the power supply voltage.

Next, when the control signal is set to L, the charge pump circuit 18 outputs the power supply voltage, but the N-channel MOSFET 11 forming the rectifying element is turned off (see the above equation (4)). The potentials of the portion 15 and the capacitor 19 hold a voltage higher than the power supply voltage. In this way, the output dynamic range of the charge transfer device is widened as in the conventional example.

As described above, according to this embodiment, since the rectifying element is formed by using the N-channel MOSFET 11, there is no N well in which the potential becomes unstable as in the conventional case, so that the latch-up is prevented. Will be prevented.

[0022]

Therefore, according to the booster of the present invention,
Since the N-channel MOS field effect transistor is used as the rectifying element, the potential is unstable between the time when the power supply is turned on and the charge pump circuit operates stably like the conventional P-channel MOS field effect transistor. Since it is not necessary to form the N-type diffused portion (N well) that becomes, it is possible to reliably suppress the latch-up.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a booster device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional booster device.

[Explanation of symbols]

11 N-Channel MOS Field Effect Transistor 11a Gate Electrodes 11b, 11c N-Type Diffusion Part 14 Reset Voltage Line 15 Reset Power Supply Diffusion Part 16 P-type Substrate 17 Substrate Potential Input Terminal 18 Charge Pump Circuit 18a Control Signal Input Terminal 19 Capacitor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication H01L 27/04 B 8427-4M 27/06 H02M 3/00 C 8726-5H

Claims (1)

Claim: What is claimed is: 1. A control signal is input to a charge pump circuit capable of outputting a boosted voltage, and an output of the charge pump circuit is input to a gate electrode and one N-type diffusion portion. , A N-channel MOS field effect transistor forming a rectifying element for extracting an output from the other N-type diffusion section.