Patent ID: 8351235
Filing Date: 2013-01-08
Classification: H03K

Abstract:
1. A level shift circuit for transmitting an input signal from a primary-side potential system to a system operating in a secondary-side potential system different from the primary-side potential system, the level shift circuit comprising: a first series circuit which includes a first resistor circuit and a first switching device connected between a high-potential-side power supply potential of the secondary-side potential system and a low-potential-side power supply potential of the primary-side potential system; a second series circuit which includes a second resistor circuit and a second switching device connected between the high-potential-side power supply potential of the secondary-side potential system and the low-potential-side power supply potential of the primary-side potential system; a transmission circuit which operates in the secondary-side potential system and has a first input and a second input, the first input having a potential at a first connection point which is a connection point between the first resistor circuit and the first switching device of the first series circuit, the second input having a potential at a second connection point which is a connection point between the second resistor circuit and the second switching device of the second series circuit; a memory device which operates in the secondary-side potential system and to which an output of the transmission circuit is supplied; and a feedback circuit which pulls one of the first and second connection points up to the high-potential side power supply potential of the secondary-side potential system and pulls the other down to the low-potential-side power supply potential of the secondary-side potential system in accordance with an output of the memory device; wherein signals of the primary-side potential system for controlling on/off of the first and second switching devices are supplied to the first and second switching devices respectively, and the transmission circuit transmits a signal decided based on the first and second inputs to the memory device when only one of the first and second switching devices is turned on while the transmission circuit does not transmit the signal decided based on the first and second inputs to the memory device when the first and second inputs of the transmission circuit turn on the first and second switching devices concurrently or become in the same state as the on-state.