PLL BURN-IN CIRCUIT AND SEMICONDUCTOR INTEGRATED CIRCUIT

摘要

In a PLL not incorporating a loop filter, an added circuit for performing burn-in test to a voltage controlled oscillator with a suitable oscillation frequency is configured with a small number of circuits. To a gate terminal of a voltage-current conversion transistor (11) in a voltage controlled oscillator (10), a gate of a diode-connected transistor (13) is connected through a switch (12a). The gate has a polarity same as that of the transistor (11). A current source (14) is connected to a drain terminal of the transistor (13), and a value of a current supplied by the current source (14) and the size ratio of the transistor (11) to the transistor (13) are suitably adjusted. Thus, a current required for performing burn-in test to the ring oscillator in the voltage controlled oscillator (10) is supplied.