Level shift circuit

1. A signal level shifting circuit, comprising:

an input stage circuit, for receiving an input signal, wherein a voltage level of the input signal falls within a first predetermined voltage range; and

an output signal latching circuit, cascoded with the input stage circuit, comprising:

a latching circuit, for generating an output signal according to the input signal, wherein a voltage level of the output signal falls within a second predetermined voltage range, and the second predetermined voltage range is different from the first predetermined voltage range; and

an activating circuit, coupled to the latching circuit for selectively enabling or disabling the latching circuit, wherein when a level transition appears to the input signal, the activating circuit disables the latching circuit.

2. The signal level shifting circuit of claim 1 , wherein the activating circuit disables the latching circuit before the level transition appears to the input signal, and enables the latching circuit after the level transition appears to the input signal.

3. The signal level shifting circuit of claim 1 , wherein the activating circuit comprises:

a switching circuit, for selectively enabling or disabling the latching circuit according to an activating control signal; and

a control circuit, coupled to the switching circuit, for generating the activating control signal.

4. The signal level shifting circuit of claim 3 , wherein the input stage circuit comprises:

a first input transistor, comprising a gate terminal for receiving a first phase input signal of the input signal, and a source terminal coupled to a first reference voltage source; and

a second input transistor, comprising a gate terminal for receiving a second phase input signal of the input signal, and a source terminal coupled to the first reference voltage source, wherein a phase of the second phase input signal is inversed to a phase of the first phase input signal;

the switching circuit comprises:

a first switching transistor, comprising a gate terminal for receiving the activating control signal, and a first connecting terminal coupled to a drain terminal of the first input transistor; and

a second switching transistor, comprising a gate terminal for receiving the activating control signal, and a first connecting terminal coupled to a drain terminal of the second input transistor; and

the latching circuit comprises:

a first latching transistor, comprising a gate terminal coupled to the drain terminal of the second input transistor, a drain terminal coupled to a second connecting terminal of the first switching transistor, and a source terminal coupled to a second reference voltage source; and

a second latching transistor, comprising a gate terminal coupled to the drain terminal of the first input transistor, a drain terminal coupled to a second connecting terminal of the second switching transistor, and a source terminal coupled to the second reference voltage source.

5. The signal level shifting circuit of claim 4 , wherein the first latching transistor, the second latching transistor, the first switching transistor, and the second switching transistor are P-type field effect transistors, and the first input transistor and the second input transistor are N-type field effect transistors.

6. The signal level shifting circuit of claim 4 , wherein the first latching transistor, the second latching transistor, the first switching transistor, and the second switching transistor are N-type field effect transistors, and the first input transistor and the second input transistor are P-type field effect transistors.

7. The signal level shifting circuit of claim 4 , wherein the gate terminal of the first switching transistor receives a first phase activating control signal of the activating control signal, the gate terminal of the second switching transistor receives the first phase activating control signal, and the switching circuit further comprises:

a third switching transistor, comprising a gate terminal for receiving a second phase activating control signal of the activating control signal, a first connecting terminal coupled to the drain terminal of the first input transistor, and a second connecting terminal coupled to the drain terminal of the first latching transistor, wherein a phase of the second phase activating control signal is inversed to a phase of the first phase activating control signal; and

a fourth switching transistor, comprising a gate terminal for receiving the second phase activating control signal, a first connecting terminal coupled to the drain terminal of the second input transistor, and a second connecting terminal coupled to the drain terminal of the second latching transistor, wherein the first and the third switching transistors comprise a P-type field effect transistor and a N-type field effect transistor respectively, and the second and the fourth switching transistors comprise a P-type field effect transistor and a N-type field effect transistor respectively.

8. The signal level shifting circuit of claim 4 , wherein a voltage level generated by the first reference voltage source is higher than the voltage level generated by the second reference voltage source.

9. The signal level shifting circuit of claim 4 , wherein a voltage level generated by the second reference voltage source is higher than the voltage level generated by the first reference voltage source.

10. A signal level shifting circuit, comprising:

an input stage circuit, for receiving an input signal, wherein a voltage level of the input signal falls within a first predetermined voltage range, and the input stage circuit comprises:

a first input transistor, comprising a gate terminal for receiving a first phase input signal of the input signal, and a source terminal coupled to a first reference voltage source; and

a second input transistor, comprising a gate terminal for receiving a second phase input signal of the input signal, and a source terminal coupled to the first reference voltage source, wherein a phase of the second phase input signal is inversed to a phase of the first phase input signal;

an output signal latching circuit, cascoded with the input stage circuit, comprising:

a latching circuit, for generating an output signal according to the input signal, wherein a voltage level of the output signal falls within a second predetermined voltage range, and the second predetermined voltage range is different from the first predetermined voltage range, and the latching circuit comprising:

a first latching transistor, comprising a gate terminal coupled to the drain terminal of the second input transistor, and a source terminal coupled to a second reference voltage source; and

a second latching transistor, comprising a gate terminal coupled to the drain terminal of the first input transistor, and a source terminal coupled to the second reference voltage source; and

a switching circuit, comprising:

a first switching transistor, comprising a gate terminal for receiving an activating control signal, a first connecting terminal coupled to a drain terminal of the first input transistor, and a second connecting terminal coupled to the drain terminal of the first latching transistor, wherein the gate terminal of the first switching transistor does not connect to the first connecting terminal of the first switching transistor;

a second switching transistor, comprising a gate terminal for receiving the activating control signal, a first connecting terminal coupled to a drain terminal of the second input transistor, and a second connecting terminal coupled to the drain terminal of the second latching transistor, wherein the gate terminal of the second switching transistor does not connect to the first connecting terminal of the second switching transistor, wherein the gate terminal of the first switching transistor receives a first phase activating control signal of the activating control signal, the gate terminal of the second switching transistor receives the first phase activating control signal;

a third switching transistor, comprising a gate terminal for receiving a second phase activating control signal of the activating control signal, a first connecting terminal coupled to the drain terminal of the first input transistor, and a second connecting terminal coupled to the drain terminal of the first latching transistor, wherein a phase of the second phase activating control signal is inversed to a phase of the first phase activating control signal; and

a fourth switching transistor, comprising a gate terminal for receiving the second phase activating control signal, a first connecting terminal coupled to the drain terminal of the second input transistor, and a second connecting terminal coupled to the drain terminal of the second latching transistor, wherein the first and the third switching transistors comprise a P-type field effect transistor and an N-type field effect transistor respectively, and the second and the fourth switching transistors comprise a P-type field effect transistor and an N-type field effect transistor respectively.

11. The signal level shifting circuit of claim 10 , wherein the first latching transistor, the second latching transistor, the first switching transistor, and the second switching transistor are P-type field effect transistors, and the first input transistor and the second input transistor are N-type field effect transistors.

12. The signal level shifting circuit of claim 10 , wherein the first latching transistor, the second latching transistor, the first switching transistor, and the second switching transistor are N-type field effect transistors, and the first input transistor and the second input transistor are P-type field effect transistors.

13. The signal level shifting circuit of claim 10 , wherein a voltage level generated by the first reference voltage source is higher than the voltage level generated by the second reference voltage source.

14. The signal level shifting circuit of claim 10 , wherein a voltage level generated by the second reference voltage source is higher than the voltage level generated by the first reference voltage source.