JP3766948B2 - Power down circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply drop circuit that is formed on a semiconductor substrate and supplies a circuit element as an internal power supply voltage obtained by stepping down a power supply voltage supplied from the outside to a plurality of voltages.
[0002]
[Prior art]
In general, various circuit elements are formed on a semiconductor substrate, and as the circuit elements are required to be miniaturized, the elements themselves are downsized, the relationship with reduced withstand voltage due to the narrowing of the wiring width, and the current consumption Therefore, it is necessary to lower the voltage, and a power supply voltage supplied from the outside, for example, 5 V is stepped down to 3 to 4 V by a step-down circuit provided on the substrate and supplied to each circuit element.
[0003]
However, if the design has only a low-voltage power supply voltage, when a large voltage is required in tests such as burn-in and aging, it must be separately supplied from the outside each time.
[0004]
Therefore, a technique for switching between an external power supply voltage and a low power supply voltage generated by internally stepping down, for example, Japanese Patent Application Laid-Open No. 7-57472 discloses a low power supply voltage used for driving circuit elements by stepping down the external power supply voltage. A semiconductor integrated circuit provided with a step-down circuit having a voltage dividing function for newly generating a power supply voltage and switching it to either a low power supply voltage or an original external power supply voltage by a switch circuit and supplying the same to an internal circuit element A device has been proposed.
[0005]
[Problems to be solved by the invention]
However, the step-down circuit in the above-mentioned publication inputs a signal with an input level different from the normal signal level given from the external terminal, and the power supply voltage supplied to the circuit element is set during normal operation and during test operation such as burn-in. Therefore, the switching control becomes complicated.
[0006]
In addition, since the normal drive voltage and the test voltage such as burn-in can be selected from only two voltage values, the normal drive level voltage is maintained and the DC current path is wasted even when the circuit is on standby. Consuming.
[0007]
Therefore, the present invention makes it possible to switch the internal power supply voltage generated from the external power supply voltage to a plurality of voltage values of three or more, thereby stably driving the circuit elements, reducing the current consumption during standby, and reducing the DC current leakage. An object of the present invention is to provide a power down circuit.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a power drop circuit that is formed on a semiconductor substrate, steps down an external power supply voltage supplied from the outside, and supplies a predetermined internal power supply voltage to circuit elements on the semiconductor substrate. A series of resistors connected in series based on a desired voltage dividing ratio, generating a fixed voltage dividing level signal from the external power supply voltage, and inputting the divided voltage level signal, and operating according to a first instruction signal from the control unit And a first transistor that outputs a power supply voltage for normal driving of the circuit element, and a power supply voltage for performing burn-in or aging of the circuit element by a second instruction signal from the control unit. The circuit element is kept in a standby state when the first transistor and the second transistor are not supplied with power while maintaining the conduction state with the second transistor for output at all times. Comprising a third transistor which outputs a power supply for maintaining the said first and the second indication signal, the power-down circuit for supplying the internal power supply voltage to the circuit element by driving one of the transistors I will provide a.
[0009]
The power supply voltage drop circuit having the above-described configuration is a drive power supply voltage VDD for performing normal driving in response to an instruction signal from a control unit from a constant external power supply voltage supplied from the outside, for burn-in or aging. testing power supply voltage Vtest or generate Sutanban supply voltage Vst by either Ranaru internal supply voltage VDDin during standby as a low current consumption, stably driven to supply the circuit elements internal power supply voltage to be desired.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 shows and describes the configuration of a power supply dropping circuit according to a first embodiment of the present invention.
[0024]
This power supply drop circuit inputs a voltage dividing unit 21 that divides a power supply voltage VDD supplied from the outside by a ratio of the resistors R1 and R2, and a divided voltage level signal, and receives an instruction from a control unit (not shown). An amplifier unit 22 that feedback-controls the level of the internal power supply voltage VDDin output from the Pch transistor Tr1 that drops the voltage to a normal drive voltage by the signal CTL1, and an external power source by an instruction signal CTL2 from a control unit (not shown). a Pch transistor Tr2 for outputting the test supply voltage Vtest the same voltage value as voltage V DD as the internal power supply voltage VDDin, is composed of a Pch transistor Tr3 functioning as a keeper circuit for generating a standby voltage Vstby maintains the always-on state The
[0025]
Note that the standby voltage Vstby by the Pch transistor Tr3, by further series transistors as shown in FIG. 2, it is possible to adjust the voltage value.
[0027]
With reference to FIG. 3 , the operation of the power drop circuit configured as in the first embodiment will be described. In this embodiment, as the internal power supply voltage value to be generated, for example, a normal drive power supply voltage (2.5 V), a test power supply voltage for performing burn-in, aging, etc., an external power supply voltage VDD, and a circuit element in a standby state In this case, the standby power supply voltage Vstby having a relatively low voltage will be described.
[0028]
First, when the instruction signal CTL1 is at the H level, the Pch transistor Tr1 outputs a normal drive power supply voltage according to the output signal based on the divided voltage level signal by the amplifier unit 22. At this time, the instruction signal CTL2 is at the H level, and the transistor Tr2 is in the off state.
[0029]
Further, when the instruction signal CTL2 becomes L level, the transistor Tr2 is turned on and outputs the external power supply voltage VDD as the internal power supply voltage VDDin. At this time, since the normal drive power supply voltage VDDin output from the Pch transistor Tr1 is lower than the external power supply voltage VDD, the Pch transistor Tr1 may be in an on / off state.
[0030]
When the instruction signal CTL1 is at L level, the amplifier unit 22 outputs H level, and the Pch transistor Tr1 is in an off state. Further, when the instruction signal CTL2 is at the H level, the transistor Tr2 is in an off state. Therefore, the standby voltage Vstby is output as the internal power supply voltage VDDin from the Pch transistor Tr3 that is always on.
[0031]
In this embodiment, the Pch transistor is described as an example. However, the present invention is not limited to this, and other drive elements may be used.
[0032]
As described above, according to the embodiment, the drive power supply voltage VDD, the burn-in, etc. for performing the normal drive according to the instruction signal from the control unit while maintaining the constant external power supply voltage supplied from the outside. Is set to a desired internal power supply voltage VDDin, such as a test power supply voltage Vtest or a standby power supply voltage Vstby during standby. As a result, the power supply voltage change required when switching the internal power supply voltage as in the prior art is eliminated, and the amplifier unit incorporated in the power supply voltage drop circuit can be stably driven under a constant voltage environment. .
[0033]
【The invention's effect】
As described above in detail, according to the present invention, the internal power supply voltage generated from the external power supply voltage can be switched to a plurality of voltage values of three or more, thereby stably driving the circuit elements and reducing the current consumption during standby. Also, it is possible to provide a power supply dropping circuit that reduces DC current leakage.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a power supply dropping circuit according to a first embodiment.
FIG. 2 is a configuration example of a keeper circuit that generates a standby voltage V stby .
FIG. 3 is a diagram for explaining the operation of the power supply dropping circuit according to the first embodiment;
[Explanation of symbols]
21 partial pressure section
22 Amplifier section
R1, R2 resistance
CTL1 , CTL2 instruction signal
T r1 ~T r3 P ch transistor
V DD External power supply voltage
V DDin internal power supply voltage

Claims (2)

In a power supply dropping circuit formed on a semiconductor substrate and stepping down an external power supply voltage supplied from the outside and supplying a predetermined internal power supply voltage to a circuit element on the semiconductor substrate,
A resistor string that is connected in series based on a desired voltage division ratio and generates a voltage division level signal fixed from the external power supply voltage, and the voltage division level signal are input, and the first instruction signal from the control unit operates. A first transistor controlled by an amplifier to output a power supply voltage for normal driving of the circuit element;
A second transistor that outputs a power supply voltage for performing burn-in or aging of the circuit element in accordance with a second instruction signal from the control unit;
A third transistor that maintains a constant conduction state and outputs a power supply for maintaining the circuit element in a standby state when both the first and second transistors do not supply power; and
A power supply voltage drop circuit, wherein one of the transistors is driven by the first and second instruction signals to supply an internal power supply voltage to the circuit element. It said third transistor, a power supply voltage applied to the circuit element functions as a keeper circuit that prevents become 0, according to claim 1, characterized in that it consists of one or multiple stages in series connected transistors Power down circuit.

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