JPS63187915A - Reference voltage generating circuit - Google Patents

Abstract

PURPOSE:To constitute a logical LSI having a stable operation margin by providing a ground potential detecting means for detecting a distribution of the ground potential on an integrated circuit substrate loaded with a current switching type logic circuit, and supplying a reference voltage of the current switching type logic circuit in accordance with its potential difference. CONSTITUTION:In a reference voltage generating circuit, when the ground potential GND of a logic circuit of the inside of an LSI is dropped due to a wiring resistance of the inside of the LSI, when the ground potential GND2 is set to a point which is varied by following up the ground potential GND, the ground potential GND2 drops in accordance with the drop quantity of the ground potential GND. Therefore, in proportion thereto, the base potential of a transistor (TR) Q6 becomes lower than the base potential of a TR Q7, a collector current of the TR Q7 increases, and in accordance with the drop of the ground potential GND, the potential of a reference voltage VREF is lowered. Accordingly, in spite of the drop of the ground potential GND, the correction is executed automatically so that the reference voltage VREF always becomes the center of the logical amplitude.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reference voltage generation circuit, and more particularly to a reference voltage generation circuit for supplying various reference voltages required for current switching type logic circuits in semiconductor integrated circuits.

[Conventional technology]

Current switching type logic circuits are integrated circuits as typical logic circuits for high-speed logic operation, and are widely used in various LSIs for high-speed fields such as computers and electronic equipment. A typical circuit configuration example is shown in FIG. This circuit is supplied with a power supply voltage VEE based on the ground potential GND, and performs two-man OR/N O for input signals at input terminals 11 and I2.
Although this is an example in which the R logic operation is performed and output signals are obtained from the output terminals P and R2, various reference voltages are required as a characteristic of the current switching type logic circuit. First, the reference voltage VREP is also called a reference voltage, and its center potential is always supplied to the high or low logic level applied to the input terminal IN/I2.
Transistors Q1 to Q3 are turned on and off depending on the logic level of
It performs an OFF operation, and the current of the constant current circuit constituted by the transistor Q4 and the resistor R3 flows through the resistor R or R2, and the entire circuit performs a logical operation. Further, the reference voltage VC52 provides a bias potential to the base of the transistor Q4 as a reference voltage for the constant current circuit described above.

Normally, these reference voltages vREF-vcs2 are commonly used by all current switching type logic circuits inside the integrated circuit, so all currents from at least one reference voltage generation circuit IC placed around the periphery of the board are The voltage is supplied to the switching type logic circuit, thereby reducing the area occupied by the reference voltage generation circuit IC on the board. Reference voltage■
REF must be in the middle of the internal logic amplitude; any deviation from this will degrade the internal noise margin. Also, the reference voltage V. S□ still determines the internal logic amplitude, and if the logic amplitude is set large, it will be advantageous in terms of internal operation margin, but on the contrary, it will deteriorate in terms of performance such as operation speed.
It is necessary to set the logic amplitude to the minimum while ensuring the necessary operating margin.

Therefore, the reference voltage generation circuit IC according to the conventional technology is composed of transistors Q15 and Q17 and resistors R15 to RI7, the base of transistor Q17 is driven by another reference voltage cs1 prepared in advance, and the collector of transistor Q+7 is driven by another reference voltage cs1 prepared in advance. A constant voltage determined by the ratio of resistors RI5 and R16 can be obtained.

Furthermore, a constant potential shifted by the forward voltage between the base and emitter of transistor Q15 is obtained at the emitter of Qls and is supplied to the current switching type logic circuit as reference voltage VREF.

Reference voltage V. Since s2 is normally driven by another reference voltage generation plane, it is omitted here, but is still supplied with a constant potential. The potential of the reference voltage VREF is at the input terminal 1.・Since it must always be located in the center of the potential of 2, the potential difference between both ends of resistor R15 is usually R1 to
It is set to the potential difference between both ends of 2, that is, half the logic amplitude.

In general, the characteristics of the elements on an integrated circuit board are uniform, so a configuration like this circuit can be used, and even if there are variations in the integrated circuit manufacturing process, the reference voltage VRε
It is possible to set F to the center of the internal logic level.

[Problem that the invention seeks to solve]

The conventional reference voltage generation circuit IC described above is designed on the premise that the potential of its ground terminal is equal to the potential of the ground terminal of the current switching type logic circuit, so if there is a potential difference between the respective ground terminals, However, this has the disadvantage that it directly causes fluctuations in the reference voltage, leading to a reduction in the internal operating margin.

Especially recent LS, 1. The degree of integration in VLSI, etc. has been increasing rapidly, and as the chip size and power consumption have increased, the difference in ground potential distribution inside the substrate tends to widen, so this problem is becoming more and more prominent. It's coming.

The present invention solves the problems of conventional reference voltage generation circuits.

Regarding the ground potential on the LSI board, the system detects the potential difference between the ground potential at the periphery and the ground potential at the center, which is considered to be the lowest, and automatically supplies the optimal reference voltage according to that potential difference. It has original content.

[Means for solving problems]

The reference voltage generation circuit of the present invention detects the distribution of ground potential on an integrated circuit board on which the current switching type logic circuit is mounted, in the reference voltage generation circuit that supplies a necessary preparation voltage to the current switching type logic circuit. The device is configured to include ground potential detection means for supplying a reference voltage for the current switching type logic circuit according to the potential difference.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1 to 3 are circuit diagrams showing the configurations of first to third embodiments including the present invention.

Looking at Figure 1, transistors Q1 to Q4 and resistors R1 to
The circuit composed of R3 is a typical current switching type logic circuit, and has a power supply voltage VER based on the ground potential GND,
A reference voltage VREF as a reference voltage indicating the center value of the operation of the logic circuit and a reference voltage VC8 corresponding to the amplitude of the operation of the logic circuit are supplied, and a two-manpower OR/NOR logic operation is performed.

In the present invention, when supplying the power supply voltage and reference voltage to the above-mentioned current switching type logic circuit, 1. By detecting the ground potential of the current switching type logic circuit mounted on the LSI at two locations, for example,
Among them, the power supply voltage V is the highest.

The reference voltage V REF-V is based on the ground potential close to
cc.

It is designed to supply In particular, when several reference voltage generation circuits are placed around the LSI, current flows at two locations: the periphery, where almost no voltage drop occurs, and the center of the LSI, where the voltage drop is expected to be the largest. Detects the ground potentials GND1 and GND2 of the switching type logic circuit.

Next, the configuration and operation of each embodiment will be described.

First, a first example will be described. Referring to FIG. 1, the reference voltage generating circuit 1 of the first embodiment includes a ground potential detection means 2, a portion for processing the detected ground potential consisting of transistors Q6 to Q8 and resistors R4 to R6, and a transistor QsA. -Q5a-Q+, and a part that outputs a reference voltage consisting of resistors R7A-R7B.

The operation of this will be described below. First, the ground potential G N
Assuming that D1 and GND2 are at the same potential, the base potentials of transistors Q6 and Q7 that compare the ground potentials will be completely equal, and the currents of transistors Q4 and Q8 will be equal.
Further, when the values of the resistors R4 and R5 are set to half of the resistor R+ -Rz, the reference voltage VBp is set to the center of the internal logic amplitude. Next, the ground potential GND of the logic circuit inside the LSI
Consider a case where the resistance decreases due to wiring resistance inside the LSI.

In this case, the ground potential GND2 is set to the ground voltage G inside the LSI.
If the ground potential GND2 is set to a point that changes according to the ground potential GND, the base potential of the transistor Q6 decreases in proportion to the amount of decrease in the ground potential GND, and the base potential of the transistor Q6 decreases in proportion to the base potential of the transistor Q7. The collector current of Q7 increases, that is, the voltage across resistor R5 increases, and as the ground potential GND decreases, the reference voltage V
The potential of REF is lowered. Therefore, despite the drop in ground potential GND, reference voltage VREF is automatically corrected so as to always be at the center of the logic amplitude. On the other hand, since the collector current of the transistor Q6 decreases, the potential across the resistor R4 decreases, and the potential of the reference voltage VC5 increases.
It increases the logic amplitude and acts in the direction of compensating for the decrease in noise margin caused by the decrease in the reference voltage VREP.

Therefore, as the ground potential GND of the logic circuit inside the LSI decreases, the optimum reference voltage VREF/VO2 is automatically adjusted.
is generated, ensuring stable operation and sufficient noise margin that cannot be obtained with conventional circuits.

Next, a second embodiment will be described.

As shown in FIG. 2, the second embodiment is an example in which optimization is focused only on the control of the reference voltage VBHp, compared to the first embodiment shown in FIG. In this case, although the internal logic amplitude is a constant value determined by the reference voltage VC52, it has the advantage that the control method and the configuration of the reference voltage generation circuit are simplified. However, on the other hand, the reference voltage VC3
Regarding this, it has the disadvantage that a decrease in the reference potential GND is not reflected.

Next, a third embodiment will be described. The third example is
Looking at FIG. 3, compared to the first embodiment shown in FIG.
This is an example of optimization focusing only on O2 control. In this case, there is an advantage that the control method and the configuration of the reference voltage generation circuit are simplified, but there is a disadvantage that the reference voltage VREFI is a constant value and does not reflect the decrease in the reference potential GND.

Note that although the above explanation has been made regarding the ground potential, the present invention can also be applied to other power sources. In addition, in gate arrays and the like that use a common base wafer and are designed to accommodate different types only in the wiring process, there is a large difference in ground potential depending on the number of gates used. The application is particularly effective.

〔Effect of the invention〕

As explained above, the present invention provides a reference voltage generation circuit for a current switching type logic circuit, in which a reference circuit is arranged.
Provides a reference voltage generation circuit that detects the potential difference between the ground potential at the periphery of the I-board and the ground potential at the center of the board, where the potential has dropped the most, and generates the optimal reference voltage for the operation of the logic circuit section according to the potential difference. By doing so, it is possible to construct a logic LSI that always has a stable operating margin regardless of the magnitude of the ground potential difference inside the substrate.

FIG. 4 is a circuit diagram including a reference voltage generating circuit according to the prior art.

1.IA.IB.IC...Reference voltage generation circuit, 2..
・Ground potential detection means, GND -GND 1/GND2
...Ground potential, VIE...Power supply voltage, VREF'
VREFI・■o5・Vosl・■cs2...Reference voltage, 1. -I2...input terminal, P, -P2...output terminal.

Q list

Claims (1)

[Claims] In a reference voltage generation circuit that supplies a reference voltage necessary for a current switching type logic circuit, the distribution of the ground potential on an integrated circuit board on which the current switching type logic circuit is mounted is detected, and the current switching type A reference voltage generation circuit comprising ground potential detection means for supplying a reference voltage to a logic circuit.