Field of the Invention
The present invention relates to a transmitter circuit, a semiconductor apparatus, and data transmission method.
Related Art
In a case where signals are exchanged between a plurality of semiconductor chips differing from each other in power supply voltage, the semiconductor chips must be electrically insulated from each other with insulating coupling elements in exchanging signals. Known insulating coupling elements include an AC coupling element using capacitors, coils and the like, and an optical coupling element (a photocoupler). Japanese Unexamined Patent Application Publication No. 2013-229812 discloses a semiconductor apparatus which exchanges signals using coils as insulating coupling elements, that is, what is called a micro-isolator.
In the disclosure of Japanese Unexamined Patent Application Publication No. 2013-229812, a pulse signal triggered by the edges of a data signal is transmitted from a transmitter circuit. Here, from the transmitter circuit, a pulse signal capable of distinguishing between the rising edge and the falling edge of the data signal is transmitted. Therefore, the data signal can be reconstructed at a receiver circuit.
Meanwhile, Japanese Unexamined Patent Application Publication Nos. 2005-045100 and 2012-253241 and Japanese Patent No. 4750746 each disclose an electrostatic discharge protection circuit provided between the power supply and the ground. The electrostatic discharge protection circuit is mounted for protecting the internal circuitry of a semiconductor apparatus from high voltage pulses generated by electrostatic discharge. The electrostatic discharge protection circuit disclosed in Japanese Unexamined Patent Application Publication Nos. 2005-045100 and 2012-253241 turns on an NMOS transistor upon sensing a sharp increase in the power supply. The electrostatic discharge protection circuit (GGNMOS: Gate Grounded NMOS) disclosed in Japanese Patent No. 4750746 turns on a parasitic bipolar of an NMOS transistor when a power supply potential of a certain level is reached. By the foregoing operations, each electrostatic discharge protection circuit operates before the power supply potential reaches the breakdown voltage of the internal circuitry. Thus, an increase in the power supply voltage is suppressed and the internal circuitry is protected.