A ramp generator includes a plurality of switched current sources coupled in parallel between a resistor and ground. A digital ramp control signal generator includes a counter to generate a ramp control signal in response to a clock signal. Each bit of the ramp control signal is coupled to control switching of a respective one of the plurality of switched current sources to generate a ramp signal at an output of the ramp generator. The digital ramp control signal generator is coupled to receive a reset signal to zero the ramp control signal. The digital ramp control signal generator is further coupled to receive a set bits signal to initialize the ramp signal to a preset value after every reset of the ramp control signal to add a DC offset compensation current determined by the preset value to the ramp signal.

A ramp generator includes a plurality of switched current sources coupled in parallel between a resistor and ground. A digital ramp control signal generator includes a counter to generate a ramp control signal in response to a clock signal. Each bit of the ramp control signal is coupled to control switching of a respective one of the plurality of switched current sources to generate a ramp signal at an output of the ramp generator. The digital ramp control signal generator is coupled to receive a reset signal to zero the ramp control signal. The digital ramp control signal generator is further coupled to receive a set bits signal to initialize the ramp signal to a preset value after every reset of the ramp control signal to add a DC offset compensation current determined by the preset value to the ramp signal.

A ramp generator includes a plurality of switched current sources coupled in parallel between a resistor and ground. A digital ramp control signal generator includes a counter to generate a ramp control signal in response to a clock signal. Each bit of the ramp control signal is coupled to control switching of a respective one of the plurality of switched current sources to generate a ramp signal at an output of the ramp generator. The digital ramp control signal generator is coupled to receive a reset signal to zero the ramp control signal. The digital ramp control signal generator is further coupled to receive a set bits signal to initialize the ramp signal to a preset value after every reset of the ramp control signal to add a DC offset compensation current determined by the preset value to the ramp signal.

A ramp generator includes a plurality of switched current sources coupled in parallel between a resistor and ground. A digital ramp control signal generator includes a counter to generate a ramp control signal in response to a clock signal. Each bit of the ramp control signal is coupled to control switching of a respective one of the plurality of switched current sources to generate a ramp signal at an output of the ramp generator. The digital ramp control signal generator is coupled to receive a reset signal to zero the ramp control signal. The digital ramp control signal generator is further coupled to receive a set bits signal to initialize the ramp signal to a preset value after every reset of the ramp control signal to add a DC offset compensation current determined by the preset value to the ramp signal.

The present invention provides an output buffer including a first transistor, a second transistor and a pad-tracking circuit is disclosed. The first transistor is coupled between a supply voltage and an output node, wherein the output node is coupled to a pad. The second transistor is coupled between the output node and a reference voltage. The pad-tracking circuit is coupled to the control circuit and the first transistor, and is configured to generate a gate control signal to a gate electrode of the first transistor. The output buffer is selectively operated in an input mode and a fail-safe mode, and when the output buffer switches between the input mode and the fail-safe mode and the supply voltage of the first transistor ramps up or ramps down, the pad-tracking circuit generates the gate control signal to the gate electrode of the first transistor according to the voltage of the pad.

The present invention provides an output buffer including a first transistor, a second transistor and a pad-tracking circuit is disclosed. The first transistor is coupled between a supply voltage and an output node, wherein the output node is coupled to a pad. The second transistor is coupled between the output node and a reference voltage. The pad-tracking circuit is coupled to the control circuit and the first transistor, and is configured to generate a gate control signal to a gate electrode of the first transistor. The output buffer is selectively operated in an input mode and a fail-safe mode, and when the output buffer switches between the input mode and the fail-safe mode and the supply voltage of the first transistor ramps up or ramps down, the pad-tracking circuit generates the gate control signal to the gate electrode of the first transistor according to the voltage of the pad.

A signal generator includes a processing unit. The signal generator is configured to generate at least one periodic output signal. The output signal comprises a triangular-waveform signal. A frequency and an amplitude of the output signal are adjustable. The signal generator is configured to receive an input parameter. The input parameter comprises at least one piece of information about a setpoint amplitude and a setpoint frequency of the output signal. The processing unit is configured to determine a signal direction of the output signal. The processing unit is configured to determine a step size. The processing unit is configured to apply the step size to an actual amplitude based on the signal direction for a number of clock cycles. The number of clock cycles is dependent on the setpoint frequency of the output signal.

A signal generator includes a processing unit. The signal generator is configured to generate at least one periodic output signal. The output signal comprises a triangular-waveform signal. A frequency and an amplitude of the output signal are adjustable. The signal generator is configured to receive an input parameter. The input parameter comprises at least one piece of information about a setpoint amplitude and a setpoint frequency of the output signal. The processing unit is configured to determine a signal direction of the output signal. The processing unit is configured to determine a step size. The processing unit is configured to apply the step size to an actual amplitude based on the signal direction for a number of clock cycles. The number of clock cycles is dependent on the setpoint frequency of the output signal.

A spread spectrum clock generator includes a phase comparator that compares a reference clock with a feedback clock, a low-pass filter that passes a predetermined low-frequency component, a phase lock loop that includes a voltage-controlled oscillator generating an output clock whose frequency corresponds to the filtered signal, a triangular wave controller that generates a triangular wave signal for frequency-modulating the spread spectrum clock based on the output clock, a delay controller that generates the feedback clock by controlling delay of the output clock based on the triangular wave signal, a first counter that counts the output clock and output a first count value, a second counter that counts the reference clock and output a second count value, and a phase error correction circuit that compares the first count value with the second count value and corrects phase error of the output clock.

A spread spectrum clock generator includes a phase comparator that compares a reference clock with a feedback clock, a low-pass filter that passes a predetermined low-frequency component, a phase lock loop that includes a voltage-controlled oscillator generating an output clock whose frequency corresponds to the filtered signal, a triangular wave controller that generates a triangular wave signal for frequency-modulating the spread spectrum clock based on the output clock, a delay controller that generates the feedback clock by controlling delay of the output clock based on the triangular wave signal, a first counter that counts the output clock and output a first count value, a second counter that counts the reference clock and output a second count value, and a phase error correction circuit that compares the first count value with the second count value and corrects phase error of the output clock.