KR100428592B1 - Reference voltage generation circuit - Google Patents

Abstract

PURPOSE: A reference voltage generation circuit is provided to reduce the loss of speed under hot temperature and reduce the current amount under cold temperature by varying a reference voltage level according a variation of temperature. CONSTITUTION: A reference voltage generation circuit includes a reference voltage division circuit, a comparison circuit, and a driving circuit. The reference voltage division circuit(120) includes a first resistor and a second resistor in order to divide the reference voltage according to a resistance ratio between the first and the second resistors. Each resistance value of the first and the second resistors is changed according to the variation of the external temperature. The comparison circuit(100) compares the reference voltage with the divided voltage of the reference voltage division circuit and outputs a comparison signal. The driving circuit(110) supplies the predetermined charges to a reference voltage line in response to the comparison signal.

Description

Reference voltage generator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage conversion circuit, and more particularly, to a reference voltage generating circuit of a semiconductor memory device for converting a power supply voltage into a reference voltage of a predetermined level.

Semiconductor devices vary in characteristics depending on various surrounding environments and their manufacturing processes. The device will change its carrier mobility in the surrounding environment, in particular with the external temperature. The carrier mobility varies with two scattering mechanisms: lattice scattering and ionized impurity scattering. Here, the amount of the ionic impurities is varied by injecting N or P type impurities into the device, and the lattice scattering is varied according to the external temperature.

As the outside temperature decreases, carrier mobility due to the lattice scattering increases. Intuitively, lattice vivrations decrease as the external temperature decreases, suggesting that the likelihood of scattering is reduced. Thus, carrier mobility increases. In addition, semiconductor devices, such as MOS transistors, have the property that, as the carrier mobility increases, the conductivity of the device also increases while its resistivity decreases.

In general, circuits for generating reference voltages in semiconductor devices are widely used. In particular, the reference voltage is applied to a gate of a MOS transistor that operates as a current source in a sense amplification circuit used to read data stored in a memory cell of a static random access memory (SRAM) semiconductor device. Done. A constant reference voltage is applied to the gate of the transistor to operate insensitive to power supply voltage and temperature change.

1 is a reference voltage generation circuit according to the prior art.

In FIG. 1, the reference voltage generator circuit is composed of a comparator 10, a driver 20, and a voltage dividing circuit 30. The voltage dividing circuit 30 divides the voltage REFSA according to the resistance ratio of the first resistor R1 and the second resistor R2 composed of the transistors 1 to 4, and the first resistor R1. (R1) is formed as a material such as polysilicon. The transistors 1 to 4 are formed of PMOS transistors in which a current path is formed in series between the first resistor R1 and ground.

The comparator 10 compares the difference between the voltage REFSA0 divided by the voltage dividing circuit 30 and the voltage REF0 which is a reference of the voltage REFSA. In addition, the driver 20 supplies a predetermined current according to a result of comparing the two voltages REFAS0 and REF0 through the comparator 10. The first resistor R1 of the voltage dividing circuit 30 maintains its resistivity, that is, the resistance value, even if the external temperature increases or decreases. On the other hand, when the external temperature increases or decreases, the transistors 1 to 4 change its resistivity according to the external temperature.

That is, as the temperature changes, the first resistor R1 in the voltage dividing circuit 30 has a constant resistance while the resistance values of the transistors 1 to 4 vary. In this case, the width of the reference voltage REFSA changes narrowly (see FIG. 3) when the external temperature changes from a low temperature to a high temperature or from a high temperature to a low temperature. In other words, when the sense amplification circuit operates at a low temperature, the resistance value of the current source increases to decrease the speed, and when operating at a high temperature, its resistance value decreases to increase the current.

In this way, the transistor of the current source has a characteristic that a current at a low temperature flows more than that at a high temperature and a speed decreases. However, the width of the reference voltage REFSA, which can be varied by the voltage divider circuit, changes in proportion to the width at which the resistors R1 and R2 are variable. However, since the resistance value of the resistor R1 is fixed without being variable with temperature, the change in the reference voltage caused by the resistors R1 and R2 is not large enough to control the characteristics of the transistor. This looks like

Accordingly, it is an object of the present invention to provide a reference voltage generator circuit capable of varying a width in which a reference voltage is varied as the temperature thereof is larger than that of the conventional art.

1 is a circuit diagram showing a reference voltage generating circuit according to the prior art;

2 is a circuit diagram showing a reference voltage generating circuit according to the present invention;

3 is a view showing that the level of reference voltages REFSA changes according to the conventional and the present invention when a temperature is changed;

* Description of symbols on the main parts of the drawings *

100: comparator 110: driver

120: voltage divider circuit 130: MOS capacitor

According to one aspect of the present invention for achieving the above object, in the voltage conversion circuit for converting the power supply voltage to a reference voltage of a predetermined level when the power supply voltage is applied, the first resistance means and the second resistance means Means for dividing the reference voltage according to a resistance ratio of the first and second resistance means; The first and second resistance means vary their resistance values as the external temperature changes; Means for receiving a voltage that is a reference of the reference voltage and a voltage divided by the voltage dividing means and comparing the two voltages to generate a comparison signal; And driving means for supplying a predetermined amount of charge to a reference voltage line for transferring the reference voltage from a power supply terminal to which the power supply voltage is applied in response to the comparison signal.

In this embodiment, the first resistance means comprises a PMOS transistor having a current path formed between the reference voltage line and the second resistance means and a gate to ground.

In this embodiment, the first resistance means comprises an NMOS transistor having a current path formed between the reference voltage line and the second resistance means and a gate to which the power supply voltage is applied.

In this embodiment, the second resistance means comprises a plurality of PMOS transistors having current paths sequentially formed in series between the first resistance means and ground, and gates that are commonly grounded.

In this embodiment, in order to remove noise on the reference voltage line when a predetermined electric charge is supplied to the reference voltage line by the driving means, it is common to the gate connected to the output terminal of the comparing means and the reference voltage line. And a Morse capacitor having a source and a drain connected thereto.

By such a circuit, by implementing the resistors in the voltage divider circuit as MOS transistors, its resistance ratio is changed greatly with temperature change.

Reference to the drawings according to an embodiment of the present invention will be described in detail with reference to Figs.

Referring to FIG. 2, the novel reference voltage generator circuit of the present invention is adapted to adjust the first and second resistors R1 and R2 in the distribution circuit 120 to divide the reference voltage REFSA according to temperature. MOS transistors whose resistance, i.e., carrier mobility, is variable. As a result, when the temperature is changed, the values of the resistors R1 and R2 in the voltage dividing circuit 120 are also varied, thereby increasing the variable width of the reference voltage REFSA according to the temperature.

That is, while the sensing operation is performed at a cold temperature (e.g. -10 DEG C), the level of the reference voltage applied to the current source of the sense amplifier circuit is lowered than that of the conventional one to be applied to the transistor operating as the current source. The amount of current flowing can be reduced than that of the conventional one. At a high temperature (eg, 80 ° C.), the level of the reference voltage is increased and applied to the transistor, so that the amount of current flowing through its channel, that is, the speed, can be faster than that of the conventional one.

2 is a reference voltage generating circuit according to a preferred embodiment of the present invention.

Referring to FIG. 2, the comparator 100 is a circuit for comparing the difference between the voltage REF0 and the voltage REFSA0, and a current path between the terminal 201 and the connection point 203 to which the power supply voltage VCC is applied. PMOS transistors 202 and 204 and PMOS transistors 206 and 208 in which the transistors are formed in series are connected to the junction 205 with their gates in common. NMOS transistors 210-220, in which current paths are formed in series between the connection point 203 and ground, are applied with voltages REF0 to their gates, respectively. Here, the transistors 214 to 220 operate as a current source that is activated when a voltage REF0 is applied. In addition, the NMOS transistors 222 and 224, in which current paths are formed in series between the connection point 205 and the connection point 207, have their gates commonly connected to the output terminal 209 of the voltage dividing circuit 120. .

When the voltage REF0 is at a level higher than the voltage REFSA0, the transistors 210 and 212 are turned on and the transistors 222 and 224 are turned off. As a result, the level of the connection point 203 becomes lower than the level of the connection point 205, thereby outputting the low level signal COMP. On the other hand, when the voltage REF0 is lower than the voltage REFSA0, the transistors 210 and 212 are turned on and the transistors 222 and 224 are turned off. Thereby, the level of the connection point 203 becomes higher than the level of the connection point 205, and outputs the high level signal COMP.

In addition, the driver 110 is connected between the power supply terminal 201 and the connection point 211 and is activated or deactivated according to the output COMP of the comparator 200 to provide a constant current from the terminal 201 to the connection point 211. That is, it serves to supply or block charge. The current path and the resistor 228 of the PMOS transistor 228 are formed in series between the power supply terminal 201 and the connection point 211, and the gate of the transistor 228 is connected to the connection point 203. In addition, the MOS capacitor 130 connected between the connection points 203 and 211 receives noise included in the connection point 211, that is, the voltage REFSA supplied with a constant current by the driver 110. It is to remove.

The voltage dividing circuit 120 includes first and second resistors R1 and R2, and divides the voltage REFSA according to a resistance ratio of the first and second resistors R1 and R2. It is for partial pressure. The first resistor R1 includes a PMOS transistor 230 having a gate connected to ground and a current path formed between the connection points 211 and 209. The second resistor R2 includes PMOS transistors 232 to 238 having current paths sequentially formed in series between the connection point 209 and ground and gates respectively grounded.

The transistors 230 to 238 have a property in that carrier mobility decreases as temperature increases. As the carrier mobility decreases, conductivity decreases and resistance increases. Conversely, if the temperature decreases, the result is the opposite of those when the temperature increases. That is, since the value of the resistor R1 increases at a high temperature, the level of the voltage REFSA can be adjusted high. In addition, since the value of the resistor R1 becomes small at a cold temperature, the level of the voltage REFSA can be adjusted low.

3 is a view showing the level change of the reference voltage REFSA according to the conventional and the present invention when the temperature changes.

Referring to FIG. 3, the X axis represents the power supply voltage and the Y axis represents the voltage level of the output REFSA of the reference voltage generator circuit. The voltage applied to the gate of an NMOS transistor operating as a current source in the sense amplifier circuit (not shown) is typically designed to have a constant level in response to changes in temperature and power supply voltage.

Accordingly, in FIG. 3, it can be seen that the reference voltage old REFSA according to the related art has a small change A even when the temperature is changed (80 ° C. to −10 ° C.). On the other hand, it can be seen that the reference voltage new REFSA according to the present invention changes its level to a width B larger than the change width A when the temperature (80 ° C to -10 ° C) changes.

As such, when the temperature is cold, the value of the resistor R1 of the voltage dividing circuit 120 decreases because the electron mobility of the device increases. This lowers the level of the voltage REFSA and reduces the amount of current flowing through its channel than conventional by applying the voltage REFSA to the transistor of the current source of the sense amplifier circuit. On the other hand, when the temperature is high (hot temperature), the electron mobility of the device decreases, so that the value of the resistor R1 of the voltage divider circuit 120 increases. This raises the level of the voltage REFSA as opposed to the former, and by applying the voltage REFSA to the transistor, the amount of current flowing through its channel, i.

As mentioned above, as the temperature is varied, the level of the reference voltage is varied accordingly, thereby preventing the loss of speed at hot temperature by a transistor operating as a current source in the sense amplification circuit and at the same time. Current at cold temperature can be reduced.

Claims (5)

In the voltage conversion circuit for converting the power supply voltage to a reference voltage of a predetermined level when a power supply voltage is applied, Means for dividing the reference voltage according to a resistance ratio of the first and second resistance means, comprising first and second resistance means; The first and second resistance means vary their resistance values as the external temperature changes; Means for receiving a voltage that is a reference of the reference voltage and a voltage divided by the voltage dividing means and comparing the two voltages to generate a comparison signal; And driving means for supplying a predetermined amount of charge to a reference voltage line for transferring the reference voltage from a power supply terminal to which the power supply voltage is applied in response to the comparison signal. The method of claim 1, And the first resistance means comprises a PMOS transistor having a current path formed between the reference voltage line and the second resistance means and a gate to ground. The method of claim 2, And the first resistance means includes an NMOS transistor having a current path formed between the reference voltage line and the second resistance means and a gate to which the power supply voltage is applied. The method of claim 2 or 3, And the second resistance means comprises a plurality of PMOS transistors having current paths sequentially formed in series between the first resistance means and ground, and gates that are commonly grounded. The method of claim 1, Source and drain commonly connected to the reference voltage line and the gate connected to the output terminal of the comparison means for removing noise on the reference voltage line when a predetermined charge is supplied to the reference voltage line by the driving means. A voltage conversion circuit further comprising a MOS capacitor having a.

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