JPS63103978A - Source voltage drop detecting circuit - Google Patents

Abstract

PURPOSE:To obtain extremely small temperature characteristics by using a high resistance polysilicone for the resistance of a source voltage drop detecting circuit. CONSTITUTION:The high-resistance polysilicone is used for the resistance 4 of the source voltage drop detecting circuit. The high-resistance polysilicone has minus temperature characteristics and varies in temperature characteristics based upon sheet resistance, so the resistance is so settable that the temperature characteristic of the threshold voltage of an MOS transistor 3 which is the major part of the temperature characteristic is canceled. Thus, nearly flat temperature characteristics are obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a circuit guard for a power supply voltage reduction circuit.

[Conventional technology]

A conventional power supply voltage reduction circuit is shown in FIG. 0 is the negative potential of the power supply voltage, 1 is the positive potential of the power supply voltage, 2 is the power supply voltage drop detection output, 3 is the channel transistor doped to set the detection voltage, 7 is the P
A P-resistance 5.6 is used to transmit the 0N1OFF state of the channel transistor 1 to the next stage impark, and 5.6 is an inverter used to amplify the state of the previous stage.

When the power supply voltage decreases to below the threshold voltage of the P-channel transistor 3, the off-red drain potential becomes a negative potential, and the output 2 becomes a positive potential, thereby detecting a decrease in the power supply voltage.

The detection voltage is as follows. The symbols are as follows.

vit L I+: Power supply voltage drop detection voltage Vtnn:
MO3) Thresh of Ranjisk "n"; 1. − field voltage βn: MO8) voltage of transistor “n” b) ε amplification factor R:
Resistance value vl of P-resistance 7: Gate potential of the inverter V, .: When the voltage drop detection voltage of the power supply voltage is reached, the gate potential of impark is at the manual logic level of the inverter (V,).

Since this is the case when the voltage becomes L), the transistor 3 works in the saturation region. The voltage drop detection voltage VQL'D is as follows.

■ From ■, VFllJl= (VTl13+C) +((Vtos
+C)”-2C(VTMS -4屓VruJ Vtn
5") number -■""(AR(1+〃qK)-1-■ For example, VT u j = 3VNβ5 = 15μA/V'
, VT II & =Vf II @ , β, = β @,
If R=IMΩ, then Vo Lo' = 3. 48V A configuration diagram of another conventional example is shown in FIG. The configuration is such that a comparator 10 compares the outputs of a reference voltage circuit 8 and a power supply voltage detection circuit 9 to detect a drop in the power supply voltage. FIG. 4 is an example of the battery voltage drop detection circuit having the above configuration. Transistors 12, 17, and 19 are N-channel depressor transistors and are used as current sources. Transistors 11 and 12 form a reference voltage circuit and output the difference between the threshold voltages of both transistors with reference to the plus power supply. Transistors 13-19 form a comparator. Resistors 20 and 21 are formed so that the power supply voltage is divided into resistors, and the divided potential becomes equal to the reference voltage when the power supply voltage drop is detected. The reference voltage and the power supply voltage division potential are input to a comparator, and when the power supply voltage division potential becomes smaller than the reference voltage, the output 2 is inverted,
Detects a drop in power supply voltage.

[Problem that the invention seeks to solve]

However, in the prior art shown in FIG. 2, the temperature characteristics are poor.

The temperature characteristics shown in FIG. 2 will be described below.

At the detection voltage, vTII s ” VTMS @
, βi=β, VIILJ= (VTM!+C) + (C”+2Vt
osC) Officer C=(2AR)-''h'='??'+ N++ (2CVT, ls +
C”)(X (2Vms%+2C'2-+2C!1
- ■ Silence = - (213sR) -” x (2R 掠 + 2A
static) - ■Here, the temperature characteristic of the threshold value 7 is -2 mV/"
The temperature characteristic of C1β is -3000ppm/'C11)-
The temperature characteristic of the resistance is +3000ppm/@C1βs' =
1511 A/V', R= I M Q I
-L, Substitute the above temperature characteristics into ■ and ■.

Blue=C(-(AR)-'X(2R Feng+2A Shizuka))=0"Xf='2f'+(2CVTR1+C")-
'X C%"9-=-2mv/"C,Vt)ls=
3v, then 豐=-2,15mv/''C From the above, the temperature characteristics of the power supply voltage drop detection voltage vn LD are almost equal to the temperature characteristics of the gA value voltage vd II l of the transistor 3. This value is 50@ The detection voltage will fluctuate by about 0.1V with respect to the temperature change of C.

On the other hand, the conventional technique shown in FIG. 4 has a problem in that the number of elements is large. The temperature characteristics of the detection voltage shown in FIG. 4 will be described below.

The basic Kll voltage Vra@ is created by the transistor 11.12, and the value is the threshold voltage VT of the transistor 11.12.
o r I % V d u + * (D difference tare 6°V
r#g:VT1+++-VT11
+ The temperature characteristic of snow V, ;,, is -2mV/''C, but the reference voltage is the threshold voltage V 11VTI
Since the difference is I 1m, there is no temperature characteristic. On the other hand, the resistor-divided potential for power supply voltage detection is determined by a ratio, so there is no temperature characteristic. Since the comparator maintains pairability for both positive input and negative input, there is no temperature characteristic. From the above, ? in Figure 4? Ii When the voltage drop in the source voltage is detected, there is no effect.

However, as mentioned earlier, this requires four times as many elements as the circuit of FIG. This places a large weight on the IC chip size, and the chip size I
It cannot be used unless it is C.

SUMMARY OF THE INVENTION The present invention aims to solve this problem, and its purpose is to provide a method for realizing a power supply voltage drop detection circuit with extremely small temperature characteristics using an extremely small number of elements.

[Means for solving problems]

In the power supply voltage drop detection circuit of the present invention, the source of a MOS transistor is connected to one power supply, the drain of the transistor is connected through a resistor to one power supply that is not at the source potential, and the gate of the transistor is connected to a resistor of v< The method is characterized in that the transistor is connected to the gate of the next-stage inverter, and the resistor is made of high-resistance polysilicon.

[Effect]

According to the above configuration of the present invention, high-resistance polysilicon has negative temperature characteristics, and the temperature characteristics change due to sheet resistance, so MOS
) The resistance can be set so as to cancel out the temperature characteristics of the threshold voltage of the transistor 3, making it possible to obtain a substantially flat temperature characteristic.

〔Example〕

FIG. 1 shows a power supply voltage drop detection circuit in an embodiment of the present invention. The circuit is the same as before.

What has changed is that resistor 4, which used to be P = low resistance, has been changed to high resistance polysilicon. In this circuit,
Assuming that the resistance value of high-resistance polysilicon is R, the power supply voltage drop detection voltage Vnjo can be written as follows, as in the prior art. (Refer to [Prior Art]) Vtu, n= (Vn+3+C)+((Vtus+C)
”-2C(Vtl(s-1p-VTHII) Vt
u3)'-〇C=(AR(1+ 〃qK〉)
−■Below! ! Let's talk about the time characteristics.

At the detection voltage, VTII k = VTII
When g, β, = β, the fourth-order temperature characteristic of the detected voltage is as follows.

'rf' = 'j:? + % + 4 (2CVT
H3+ C") -4X (2VTH3silence+2C4'?
+2Cff) −〇5 = −(2AR)−'
Hari 2R4? -+2A deaf) -〇Here, the temperature characteristic of threshold value VTI+ is -2mV/'C0β, and the temperature characteristic of ゛ is -3000PPm/''C.

Temperature characteristics of high resistance polysilicon -50001) Pm
/ ” Co V t o s
= 3 V S R = 1 to 1
9, β, = 15 μA/V'.

fi=0.26667mv/'C 'at'=0.078mv/"C From the above, the temperature characteristics of the power supply voltage drop detection voltage VnLrl of this embodiment are determined by correcting the temperature characteristics of the threshold voltage ■T113 of the transistor 3. This value only changes the detection voltage by about 4 mV for a temperature change of 50'C.

[Efficacy of invention]

As described above, according to the invention, since high-resistance polysilicon is used for the resistor, it is possible to cancel the temperature characteristic of the threshold voltage of the MOS transistor, which is the main cause of the temperature characteristic of the detected voltage. be. Also, compared to using an I)-resistance as a resistor, there is no need to worry about diffusion spread, distance to the stopper, etc., and the sheet resistance of high-resistance polysilicon is greater than the P-resistance, so the shape ratio is Since it is smaller, the pattern area of the resistor part becomes smaller and the chip size is reduced.
A low-cost power supply voltage drop detection circuit with extremely small temperature characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a four-element power supply voltage drop detection circuit according to the present invention, FIG. 2 is a diagram of a conventional four-element power supply voltage drop detection circuit, and Part 3 is a diagram of a conventional power supply voltage drop detection circuit. Yes, Fig. 4 is a conventional power supply voltage drop detection circuit diagram. 0...Minus power supply 1...Plus power supply 2...Power supply voltage drop detection output 4...High resistance polysilicon resistor 7...・P2 resistance or more Applicant: Seiko Epson Corporation Figure 4

Claims (1)

[Claims] The sources of the MOS transistors are connected to one power supply,
The drain of the transistor is connected to one power source other than the source potential through a resistor, the gate of the transistor requires means for connecting to the power source connected to the resistor, and the transistor is connected to the gate of the next stage inverter. A power supply voltage drop detection circuit characterized in that the resistor is made of high resistance polysilicon.