Abstract: A low-side off-detection signal compares the gate signal of a low-side transistor with a predetermined first level to generate a low-side off-detection signal indicating that the low-side transistor is off. The low-side detection transistor is of the same type as the low-side transistor, with the source connected to the ground terminal, and the gate receiving the low-side transistor gate signal. A first resistor is arranged between the drain of the low-side detection transistor and the power supply terminal. A first bypass circuit is arranged in parallel with the first resistor, and is configured to switch to the conduction state when a control signal is a level which instructs the low-side transistor to switch off, and to switch to the cut-off state when the control signal level instructs the low-side transistor to switch on. The drain signal of the low-side detection transistor is output as the low-side off-detection signal.

Abstract: A power transistor is arranged between an output terminal and a power supply terminal. A pre-driver includes a high-side transistor and a low-side transistor connected in series between the power supply terminal and a second terminal, and the ON/OFF operations of which are controlled in a complementary manner according to a control signal. The electric potential at a connection node between the two transistors is output to a control terminal of the power transistor. A constant voltage circuit stabilizes the second terminal to a predetermined voltage. An output transistor for the constant voltage circuit is provided between the second terminal and the ground terminal. A differential amplifier adjusts the voltage applied to the control terminal of the output transistor such that the electric potential at the second terminal approaches a predetermined target value. A feedback capacitor is provided between the second terminal and the control terminal of the output transistor.

Abstract: A motor driving circuit drives a motor on receipt of an error signal having a digital value corresponding to a deviation between a current rotation speed of the motor, which is the subject to be driven, and its target value. A digital filter eliminates a high-frequency component of the error signal. A driving unit controls an electric current flowing through the motor in accordance with the digital value of the error signal from which the high-frequency component is eliminated by the digital filter. An upper-limit value setting unit sets an upper limit value to the digital value of the error signal input to the digital filter. The upper-limit value setting unit is configured to be capable of changing the upper limit value in accordance with a setting signal from the outside.

Abstract: In a motor driving apparatus, a control unit detects a rotation frequency of a motor to be driven and generates a control voltage Vcnt in a manner such that the rotation frequency thereof is brought close to a desired rotation frequency. A clamping circuit sets an upper limit Vcu and a lower limit Vcl of the control voltage Vcnt. A drive unit drives the motor based on the control voltage Vcnt generated by the control unit. A start circuit fixes the control voltage Vcnt to a predetermined initial voltage Vinit at the start of driving the motor.

Abstract: At an occasion of a level transition when a second periodic voltage becomes equal to a main reference voltage a first periodic voltage generating circuit starts a first monotonically changing time-period in which a voltage value of a first periodic voltage increases monotonically from 0, which is an initial value, towards a voltage value of the main reference voltage. At an occasion of a level transition of a first main switching signal when the first periodic voltage becomes equal to the main reference voltage, a second periodic voltage generating circuit starts a second monotonically changing time-period in which a voltage value of the second periodic voltage increases monotonically from 0, which is an initial value, towards a voltage value of the main reference voltage.

Abstract: When the bit number of an error signal ERR2 is n and the magnitude of the error signal ERR2 is “a” (a is an integer) in decimal notation, a pulse-width modulator generates a PWM signal Spwm as a set of k (k is an integer of 2 or more) continuous sub-pulses. Further, the pulse-width modulator generates k sub-pulses in such a manner that the average value of the duty ratios of the sub-pulses becomes approximately a/2n.

Abstract: A motor drive method which supplies a drive current in a pulse form to a multiphase motor, to drive the motor. The motor drive method includes the steps of: generating a pulse signal having a duty ratio in accordance with torque, alternately repeating an ON time-period and an OFF time-period in accordance with the pulse signal, to supply a drive current in a pulse form to a phase coil currently driving, interpolating back electromotive voltage of the OFF time-period (Toff), using a back electromotive voltage (Vu) of the ON time-period (Ton), with respect to the back electromotive voltage (Vu) occurring in at least one coil of the multiphase motor, to generate an interpolated virtual back electromotive voltage (Vu?), detecting a zero-cross point, by comparing the interpolated virtual back electromotive voltage (Vu?) with a midpoint voltage (Vcom) of the coil, to generate a BEMF detection signal (BEMF_EDGE), and switching a phase to be driven, based on the BEMF signal (BEMF_EDGE).

Abstract: A stable high-precision current detection circuit capable of continuously detecting load current through a load with extremely reduced power loss. The current detection circuit has a power transistor and a current detection transistor that are fed with a common power supply voltage and a common switching signal. A buffer circuit is provided for supplying an idling current to the output node of the current detection transistor while realizing the same virtual potential at the output terminals of these transistors. Thus, the buffer circuit always functions as a class-A amplifier.

Abstract: A motor drive method which supplies a drive current in a pulse form to a multiphase motor, to drive the motor. The motor drive method includes the steps of: generating a pulse signal having a duty ratio in accordance with torque, alternately repeating an ON time-period and an OFF time-period in accordance with the pulse signal, to supply a drive current in a pulse form to a phase coil currently driving, interpolating back electromotive voltage of the OFF time-period (Toff), using a back electromotive voltage (Vu) of the ON time-period (Ton), with respect to the back electromotive voltage (Vu) occurring in at least one coil of the multiphase motor, to generate an interpolated virtual back electromotive voltage (Vu?), detecting a zero-cross point, by comparing the interpolated virtual back electromotive voltage (Vu?) with a midpoint voltage (Vcom) of the coil, to generate a BEMF detection signal (BEMF_EDGE), and switching a phase to be driven, based on the BEMF signal (BEMF_EDGE).

Abstract: A motor driving circuit drives a motor on receipt of an error signal having a digital value corresponding to a deviation between a current rotation speed of the motor, which is the subject to be driven, and its target value. A digital filter eliminates a high-frequency component of the error signal. A driving unit controls an electric current flowing through the motor in accordance with the digital value of the error signal from which the high-frequency component is eliminated by the digital filter. An upper-limit value setting unit sets an upper limit value to the digital value of the error signal input to the digital filter. The upper-limit value setting unit is configured to be capable of changing the upper limit value in accordance with a setting signal from the outside.

Abstract: A stable high-precision current detection circuit capable of continuously detecting load current through a load with extremely reduced power loss. The current detection circuit has a power transistor and a current detection transistor that are fed with a common power supply voltage and a common switching signal. A buffer circuit is provided for supplying an idling current to the output node of the current detection transistor while realizing the same virtual potential at the output terminals of these transistors. Thus, the buffer circuit always functions as a class-A amplifier.

Abstract: In a motor driving apparatus, a control unit detects a rotation frequency of a motor to be driven and generates a control voltage Vcnt in a manner such that the rotation frequency thereof is brought close to a desired rotation frequency. A clamping circuit sets an upper limit Vcu and a lower limit Vcl of the control voltage Vcnt. A drive unit drives the motor based on the control voltage Vcnt generated by the control unit. A start circuit fixes the control voltage Vcnt to a predetermined initial voltage Vinit at the start of driving the motor.