Modulation semiconductor integrated circuit device and testing method for oscillation circuit

A method of testing a semiconductor integrated circuit device which includes a voltage-controlled oscillation circuit having its oscillation frequency controlled by a first control voltage and a second control voltage individually, a phase comparison circuit which compares in phase the oscillation output of said voltage-controlled oscillation circuit with a reference clock signal, and a control voltage generation circuit which generates, in accordance with the phase difference detected by said phase comparison circuit, such a voltage that the phase difference dissolves and applies as the first control voltage to said voltage-controlled oscillation circuit, with said voltage-controlled oscillation circuit, said voltage-controlled oscillation circuit, said phase comparison circuit and said control voltage generation circuit being connected to form a phase-locked loop, said second control voltage being supplied to said voltage-controlled oscillation circuit through a path separate from the path of said phase-locked loop, said method by includes the steps of:

• applying the second control voltage in the test operation the second control voltage being made higher than the voltage for normal operation,
• counting the output of said voltage-controlled oscillation circuit with a counter, and
• determining any variation of the output frequency of said voltage-controlled oscillation circuit caused by the second control voltage, by making reference to the count value of said counter in a predetermined time duration.

A modulation semiconductor integrated circuit device comprising:

• a first circuit, including a voltage-controlled oscillation circuit having first and second inputs, arranged to receive a reference signal and to provide a first voltage control signal to the first input of the voltage-controlled oscillation circuit;
• and
• a second circuit arranged to receive data for transmission and to provide a second voltage control signal to the second input of said voltage-controlled oscillation circuit,
• wherein said first circuit is a phase-locked loop circuit further including a demultiplier arranged to receive an output from said voltage-controlled oscillation circuit, a counter arranged to receive an output of the demultiplier, a phase comparator arranged to receive the reference signal and an output from the counter, a charge pump arranged to receive an output of the phase comparator, and a loop filter arranged to receive an output of the charge pump and to output the first voltage control signal to the first input of the voltage-controlled oscillation circuit.