Level shift circuit
View Patent ↗In a level shift circuit allows satisfactory operation with short delay time in the case of low-voltage setting of a low-voltage source, for example, when a state of an input signal IN transitions from a H (VDD) level to a L level, a node W 2 precharged to a H (VDD 3 ) level is discharged to ground (VSS) by a discharge circuit N 2 , and decreases in potential. The decrease in potential propagates to a latch circuit LA, and an output of the latch circuit LA propagates to an output circuit OC. Further, an inversion signal of the node W 2 is input to the output circuit OC by bypassing the latch circuit LA. Thus, the output circuit OC starts operating prior to operation based on an output of the latch circuit LA.
1. A level shift circuit which includes an input terminal and an output terminal, converts an input signal input to the input terminal and having a first voltage amplitude into an output signal having a second voltage amplitude, and outputs the output signal from the output terminal, the level shift circuit comprising:
a precharge circuit;
a first node and a second node which are precharged to a high level in a stably operating state by the precharge circuit;
a first discharge circuit configured to discharge the first node to a low level upon transition of the input signal from the low level to the high level;
a second discharge circuit configured to discharge the second node to the low level upon transition of the input signal from the high level to the low level;
a latch circuit connected to the first node and the second node, an output of the latch circuit being reset to the low level by the transition of the first node to the low level, and the output of the latch circuit being set to the high level by the transition of the second node to the low level to control the precharge circuit; and
an output circuit configured to receive the output of the latch circuit, wherein
the output circuit further receives a signal from the first node and an inversion signal from the second node, or an inversion signal from the first node and a signal from the second node.
2. The level shift circuit of claim 1 , wherein
in the output circuit, a node configured to receive the inversion signal from the first or second node has a load capacitance which is smaller than a load capacitance of an output node of the latch circuit.
3. The level shift circuit of claim 1 , wherein
in the output circuit, transistors connected to a node configured to receive the inversion signal from the first or second node are fewer than transistors connected to an output node of the latch circuit.
4. The level shift circuit of claim 1 , wherein
the output circuit starts inversion operation upon reception of both the signals from the first and second nodes, and after that, the output circuit holds the inversion operation when the output circuit receives the output of the latch circuit.
5. The level shift circuit of claim 1 , wherein
the latch circuit includes a precharge control circuit configured to control precharge operation of the precharge circuit based on latch operation.
6. The level shift circuit of claim 1 , further comprising:
a pull-up device, wherein
while any one of the first or second node is precharged by the precharge circuit, the other of the first or second node is pulled up to the high level by the pull-up device.
7. The level shift circuit of claim 1 , wherein
the first and second discharge circuits include transistors, and
a voltage source configured to generate a voltage having the first voltage amplitude is set to a generation voltage which is equal to a voltage close to a threshold voltage of the transistors.
8. The level shift circuit of claim 1 , wherein
the first and second discharge circuits include transistors, and
a voltage source configured to generate a voltage having the first voltage amplitude is set to a generation voltage which is higher than a voltage close to a threshold voltage of the transistors.
9. The level shift circuit of claim 5 , wherein
when voltage supply from a voltage source configured to generate a voltage having the first voltage amplitude is stopped, the precharge control circuit receives a control signal to control and force the precharge circuit to perform the precharge operation.
10. The level shift circuit of claim 9 , wherein
when the voltage supply from the voltage source configured to generate the voltage having the first voltage amplitude is stopped, the latch circuit receives another control signal to determine the output signal from the output terminal to be at the high or low level.