Pll burn-in circuit and semiconductor integrated circuit

A PLL burn-in circuit which applies a burn-in voltage to a voltage-to-current conversion transistor for converting a voltage applied to its gate terminal into a current, said transistor being included in a voltage-controlled oscillator which constitutes a phase locked loop circuit (hereinafter referred to as a PLL) embedded in a semiconductor integrated circuit, said PLL burn-in circuit comprising:

• a current supply having one end connected to a first power supply;
• a first transistor which has the same polarity as the voltage-to-current conversion transistor, and has a drain terminal connected to the other end of the current supply and a source terminal connected to a second power supply;
• and
• a voltage switching means which makes the voltage at the gate terminal of the voltage-controlled oscillator equal to the voltages at the gate terminal and the drain (or source) terminal of the first transistor when performing PLL burn-in, and makes the gate terminal of the voltage-to-current conversion transistor have a high impedance when performing normal operation.