Patent ID: 7557666
Filing Date: 2009-07-07
Classification: G06F,H03K

Abstract:
1. An oscillation circuit comprising: an oscillation unit being configured to generate an internal clock signal having an amplitude corresponding to an internal power supply voltage; a switch being configured to be turned off when an external clock signal having a larger amplitude than said power supply voltage is provided to a clock terminal and be turned on when said oscillation unit oscillates so as to output said internal clock signal generated by said oscillation unit from said clock terminal; a transistor for a tolerant input circuit being configured to include a first electrode being provided with a input clock signal having an amplitude corresponding to input signal from said clock terminal, a second electrode for outputting signals, and a control electrode being provided with a given voltage to change an on-resistance between said first electrode and said second electrode, and said transistor for a tolerant input circuit being configured to change an amplitude of said input clock signal by said on-resistance value and output said input clock signal from said second electrode; a driver being configured to drive an output signal from said second electrode of said transistor and output said output signal as a clock signal; and a first coupling capacitance being configured to be connected between said first electrode and said control electrode, and being configured to change a voltage of said control electrode at a rising edge of said input clock signal so as to keep said on-resistance constant.