Integrated circuit

An integrated circuit that detects a pen signal transmitted from an active pen, the integrated circuit comprising:

• a delta-sigma modulation circuit including:
• a subtractor that, in operation, subtracts a feedback signal from the pen signal that is input from a sensor,
• an integrator that, in operation, integrates an output signal of the subtractor,
• a quantizer that, in operation, quantizes an output signal of the integrator, and
• a digital analog converter that, in operation, generates the feedback signal based on an output value of the quantizer;
• a processor that, in operation, detects a level of the pen signal based on an output value of the delta-sigma modulation circuit;
• and
• a gain controller that, in operation, controls a level of the feedback signal based on the level of the pen signal detected by the processor,
• wherein the processor includes a low-pass filter that, in operation, restores the pen signal based on the output value of the delta-sigma modulation circuit and a quadrature demodulation circuit that, in operation, performs quadrature detection of the pen signal restored by the low-pass filter,
• wherein the processor, in operation, detects the level by using a result of the quadrature detection, and
• wherein the processor, in operation, detects the level by performing statistical processing of a level derived using the result of the quadrature detection.

An integrated circuit that detects a pen signal transmitted from an active pen, the integrated circuit comprising:

• a delta-sigma modulation circuit including:
• a subtractor that, in operation, subtracts a feedback signal from the pen signal that is input from a sensor,
• an integrator that, in operation, integrates an output signal of the subtractor,
• a quantizer that, in operation, quantizes an output signal of the integrator,
• a digital analog converter that, in operation, generates the feedback signal based on an output value of the quantizer,
• a comparator that, in operation, detects that an absolute value of a level of the output signal of the integrator exceeds a predetermined value, and
• an adder that, in operation, controls the level of the feedback signal in a case where the comparator detects that the absolute value of the level of the output signal of the integrator exceeds the predetermined value;
• a processor that, in operation, detects a level of the pen signal based on an output value of the delta-sigma modulation circuit;
• and
• a gain controller that, in operation, controls a level of the feedback signal based on the level of the pen signal detected by the processor.