Semiconductor device and ultrasonic sensor

A semiconductor device comprising:

• a driving circuit arranged to be capable of supplying a drive signal in an ultrasonic band to a piezoelectric element;
• a damping circuit having a resistance load and an inductive load;
• a control circuit arranged to be capable of controlling the driving circuit, so as to perform a reverberation reduction operation after stopping a supply of the drive signal to the piezoelectric element,
• wherein in the reverberation reduction operation, the control circuit is configured to control the driving circuit to supply the piezoelectric element with a damping signal having a phase different from that of the drive signal, and to enable the damping circuit to connect to the piezoelectric element;
• an adjustment driving circuit arranged to be capable of supplying the piezoelectric element with a second drive signal in the ultrasonic band separately from the drive signal as a first drive signal,
• wherein the control circuit is arranged to be capable of performing an adjustment operation using the adjustment driving circuit, before a normal detection operation including the supply of the first drive signal to the piezoelectric element,
• in the adjustment operation, the control circuit is configured to determine a set physical quantity for an adjustment target based on a reverberation state of the piezoelectric element after supplying the second drive signal to the piezoelectric element,
• in the normal detection operation, the control circuit is configured to control the adjustment target to have the set physical quantity, and
• the adjustment target includes at least one of a resistance value of the resistance load, an inductance value of the inductive load, and the phase of the damping signal,
• wherein the adjustment driving circuit is arranged to be capable of supplying the piezoelectric element with a second damping signal having a phase different from that of the second drive signal, separately from a first damping signal as the damping signal,
• the adjustment operation includes an adjustment unit operation,
• in the adjustment unit operation, the control circuit is configured to supply the second drive signal to the piezoelectric element, stop the supply of the second drive signal, control the adjustment driving circuit to supply the second damping signal to the piezoelectric element, and then connect the damping circuit to the piezoelectric element, and
• in the adjustment operation, the control circuit is capable of performing the adjustment unit operation a plurality of times while changing the adjustment target by a plurality of steps, and in each adjustment unit operation, the control circuit is configured to determine the set physical quantity based on the reverberation state of the piezoelectric element when the damping circuit is connected to the piezoelectric element.