JPS60236510A - Voltage limiter circuit - Google Patents

Abstract

PURPOSE:To obtain a voltage limiter circuit which can be set on an integrated circuit together with the controllable limit voltage, the reduced variance of production and the excellent temperature characteristics, by connecting at least a constant voltage diode, an insulated gate type field effect transistor and a constant current circuit successively between an output terminal and an earth terminal. CONSTITUTION:The limit voltage is decided by a circuit where a constant voltage diode 3 and limit voltage controlling insulated gate field effect transistors IGFETs 4 and 5 are connected in series. The diode 3 uses the breakdown voltage adverse to a P-N-junction diode. It is possible to reduce the variance of the breakdown voltage down to several percents or less by putting the N and P type impurity diffusion areas close to each other on a mask centering on a line. While the limit voltage is controlled by the number of IGFETs 4 and 5 which are connected in series.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage limiter circuit that limits and outputs a voltage higher than a certain voltage when an input voltage is higher than that.

1 to 3 show conventional voltage limiter circuits. 1 shows a circuit using a constant voltage diode 3, one end of the resistor 2 is connected to the input terminal 1K, and the other end is connected to the output terminal 9. Figure 2 shows a circuit that utilizes the forward voltage circuit of the diode 10, and Figure 3 shows a circuit that connects a constant voltage diode 3 in parallel to the negative feedback circuit of the operational amplifier 16 so that this constant voltage is limited. This is the circuit. Note that the resistor 12 is connected to one terminal of the operational amplifier 16 in parallel with the resistor 117-j. Both utilize the reverse breakdown voltage of the diode, and the latter utilizes the constant voltage property of the forward voltage. When mounting this on an integrated circuit, it is difficult to adjust the limit voltage to a desired voltage. Namely.

When using the diode's reverse breakdown voltage, KIf is used to change the breakdown voltage itself.
(i) It is necessary to change the concentration of either the P-type impurity or the N-type impurity (or both) in the PM junction; (9) it requires process steps and masks in addition to the normal process; The method of adjusting the limit voltage by connecting diodes in series can only roughly adjust the limit voltage. Furthermore, when using the forward voltage of a diode, this voltage itself is as low as α7 to α8v, so if the limit voltage is set high, the number of diodes connected in series will increase, and the forward characteristics The method of obtaining sharp constant voltage characteristics has drawbacks such as the need to flow a certain amount of current and large temperature characteristics.

The present invention is designed to eliminate the above-mentioned drawbacks.1 According to the present invention, it can be mounted on an integrated circuit by a normal process without adding any special process steps or masks.
The limit voltage is adjustable and due to manufacturing variations,
A limiter with excellent temperature characteristics etc. can be realized.

The present invention will be explained in detail below with reference to the figures.

FIG. 4 clearly shows the principle of the invention.

What determines the limit voltage is a series tangential circuit consisting of a constant voltage diode 3, an insulated gate field effect transistor for limit voltage adjustment (hereinafter referred to as IGF'KT) 4, and an IGPIIIT5. It utilizes the reverse breakdown voltage of a PN junction diode, and by placing an N-type impurity diffusion region and a P-type impurity region close to each other online on a mask, it is possible to suppress variations in breakdown voltage to a few percent or less. is possible. As will be described later, the MAKUKOG GF'1CT4 and GIPICT5rlt are for voltage adjustment, and the limit voltage is adjusted by the number of them connected in series. Here are two simple rounding IGPIIIT
Connect and explain. The conductivity type is n channel, p
It goes without saying that either option is fine, but
In Konin, this will be explained as n-channel. In the circuit of Fig. 4, the voltage between the cathode of the constant voltage diode 5 and the node 6 is Vl)T, the constant current value is VZ, the breakdown voltage of the diode is VZ, and the threshold value i of XCh'FmT4 and 5 is
When VTI and K value are set to 1, VDT = VZ +2VT1 + 2 V'l/Kl
−=(11 also GFKT8(7) threshold value vT!
, K value is 2, gate voltage is vG, input voltage of limiter circuit is Van, output voltage is Vout, value of resistor 2 is R1
Then, "Vout=Vin RiKl(VGVTI)=='V
ln -Rt @= (VG -v'rl)r P
-t@Un↓VT1'P=Vnn+4'4x MuVout=Vin-Seisha(VOut-
VDT v'rz ) Therefore, gmR1/2)) If 1, then Taut" VDT+VT! ・" - (4) From equations (1) and (2), the limit voltage is determined by the threshold value Vτ1 of GFffiT5 and 4 and the constant current. The limit voltage is determined by the value, and the limit voltage can be adjusted by the number of GIPIT stages and the current value. If the value of IGFET8 is large enough, it will not be affected by the current value of the constant current circuit and will simply be
The limit voltage is adjusted depending on the number of T stages. As mentioned above, the variation in the reverse breakdown voltage is very low, so this circuit can suppress the variation in the limit voltage.

The temperature characteristics of the limit voltage of this circuit are (1), (
2) From the formula, Nout &vTl! 1 (II Knee”) −・−(
3) at = 'W' (in 'I', 'a'I',
aVz/θ'r=o θVT, /θT; θV T, 2
/aT Therefore, by changing the temperature characteristic of the constant current, the temperature characteristic θVout/aT of the limit voltage can also be optimized. Figure 5 shows IGfPg7 operating the constant current circuit in Figure 4 in the saturation region.
15 and Teflation mold GFKT 14. It is realized by a constant pressure circuit consisting of enhancement mold (FBT15) and has nine circuits. This constant voltage, constant current circuit can be constructed by changing the K value of the depression type GFKT14(7) and the values of the enhancement QIGFET 15, that is, the channel width W and the channel length, and also by changing the threshold value of the IGFET'IM3. Since the temperature cooling property of the constant current can be adjusted by changing the value, the temperature characteristics of the limit voltage can be optimized using equation (3).

As described above, according to the present invention, the specific voltage limiter circuit can be integrated into a circuit with a relatively simple circuit configuration, without the need for special process steps, masks, etc. using normal processes, and with excellent buffiness and m-degree characteristics. can be realized on-chip.

[Brief explanation of the drawing]

Figures 1, 2, and 5 are conventional voltage limiter circuit diagrams, Figure 4 is a circuit diagram for explaining the present invention in detail, and Figure 5 is a diagram for mounting the present invention on an integrated circuit. This is an example of a specific circuit diagram. 1... Input terminal 2... Resistor 3...
... Constant voltage diode 4.5, 8. L5, 14.15... Engineering GFIC
T6... Circuit node 7... Constant current source 9... Output terminal 10... Diode 11.12... Resistor 16...・Operational amplifier and above Applicant Seiko Electronic Industries Co., Ltd. Agent Patent attorney Top Sections Figure 1 Figure 2: Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) At least one voltage regulator diode and at least one
One insulated gate field effect transistor and a constant current circuit are sequentially connected between an output and a ground terminal, and the source and drain of another insulated gate field effect transistor are connected between the output and the ground terminal, and the gate is connected between the output and the ground terminal. A voltage limiter circuit, characterized in that it is connected to a high potential side terminal of the constant current circuit. (2) The voltage limiter circuit according to claim 1, wherein the constant current circuit is an insulated gate field effect transistor whose gate terminal is biased with a constant voltage. (3) The constant voltage bias circuit of the constant current circuit is constituted by a depression type insulated gate field effect transistor. The drain of the depletion type insulated gate field effect transistor is connected to a power supply terminal, the gate and source are connected to the gate and drain of the enhancement type insulated gate field effect transistor, and the source of the enhancement type insulated gate field effect transistor is connected to a power supply terminal. 2. The voltage limiter circuit according to claim 1, wherein the voltage limiter circuit is connected to a ground terminal.