Current limit circuit and semiconductor memory device
View Patent ↗A current limit circuit comprising: a current limit element for limiting an output current level to within a predetermined range of a limiting current and including a first PMOS transistor having a source to which a predetermined voltage is applied and a drain through which the output current is supplied; and a gate voltage generating circuit for generating a gate voltage by a feedback control such that a difference between the predetermined voltage and a gate voltage of the first PMOS transistor coincides with a threshold voltage of a second PMOS transistor having approximately the same characteristic as that of the first PMOS transistor in a state in which a predetermined current is flowing through the second PMOS transistor.
1. A current limit circuit comprising:
a first MOS transistor to be supplied with a predetermined voltage for outputting a current having a level limited within a predetermined range; and
a gate voltage generating circuit for supplying a gate voltage to a gate of said first MOS transistor,
wherein said gate voltage generating circuit includes a level detection circuit for detecting a voltage level at an intermediate node of a series circuit of a second MOS transistor having approximately the same characteristic as that of said first MOS transistor and a resistor, and generates said gate voltage controlled in accordance with a detection output of said level detection circuit, and
said level detection circuit includes a comparator having one input terminal to which said intermediate node is connected.
2. The current limit circuit according to claim 1 , wherein said first and second MOS transistors are PMOS transistors.
3. The current limit circuit according to claim 1 , wherein said resistor includes one or more variable resistors connected in series.
4. The current limit circuit according to claim 1 , wherein said comparator has the other input terminal to which said predetermined voltage is applied.
5. The current limit circuit according to claim 4 , wherein said first and second MOS transistors are PMOS transistors, and said gate voltage is applied to a drain and a gate of said second MOS transistor, a source of said second MOS transistor is connected to said resistor, and a constant voltage having a higher level than that of said predetermined voltage is applied to said series circuit at an end of a resistor side thereof.
6. The current limit circuit according to claim 1 , wherein said comparator has the other input terminal to which said gate voltage is applied.
7. The current limit circuit according to claim 6 , wherein said first and second MOS transistors are PMOS transistors, and said predetermined voltage is applied to a source of said second MOS transistor, a drain and a gate of said second MOS transistor are connected to said resistor.
8. A current limit circuit comprising:
a first transistor connected between a first power supply node and a second node and having a control node receiving a control voltage; and
a voltage generating circuit connected to said control node, including a second transistor having approximately the same characteristics as that of said first transistor, and generating said control voltage in response to a threshold voltage of said first transistor,
wherein said gate voltage generating circuit includes a level detecting circuit including a comparator having a first input terminal connected to said second transistor.
9. The current limit circuit according to claim 8 , wherein said comparator has a second input terminal connected to said first power supply node.
10. The current limit circuit according to claim 8 , wherein said second transistor and a resistor connected between said control node of said first transistor and a node supplying a reference voltage in series.
11. The current limit circuit according to claim 8 , wherein said comparator has a second input terminal connected to said control node of said first transistor.
12. The current limit circuit according to claim 11 , wherein said second transistor and a resistor are connected between said first power supply node and a second power supply node in series.
13. The current limit circuit according to claim 8 , wherein said gate voltage generating circuit includes a ring oscillator controlled in response to a detection output of said level detection circuit and a charge pump circuit generating said control voltage based on an output of said oscillator.