Slew rate adjusting circuit and slew rate adjusting method

A slew rate adjusting method for adjusting a slew rate of an output buffer unit configured to amplify an output of a signal source and output a resulting signal,

• the slew rate adjusting method comprising:
• through a use of a first feedback delay amount and a second feedback delay amount that determine a time of the slew rate, adjusting a delay difference created by a difference in a plurality of reference voltages for the slew rate in such a way that the delay difference is substantially equal to a difference between the first feedback delay amount and the second feedback delay amount,
• wherein the slew rate adjusting method uses a slew rate adjusting circuit including a variable delay unit configured to delay an output of a signal source in response to a first control signal, which is input to the variable delay unit and output a delayed signal, the output buffer unit configured to adjust a slew rate in response to a second control signal input to the output buffer unit, and output a resulting signal, a differential buffer unit configured to compare the resulting signal output from the output buffer unit with a reference voltage and output a comparison result, a first phase comparison unit configured to compare a phase of the output of the signal source with a phase of a signal obtained by delaying an output from the differential buffer unit by a first feedback delay amount and output a signal base on a phase difference, a first count unit configured to count the signal output from the first phase comparison unit and output the first control signal based on a count result, a second phase comparison unit configured to compare the phase of the output of the signal source with a signal obtained by delaying an output from the differential buffer unit by a second feedback delay amount and output a signal based on a phase difference, and a second count unit configured to count the signal output from the second phase comparison unit and output the second control signal based on a count result, and
• wherein a delay amount of the variable delay unit is adjusted in response to the first feedback delay amount, and the slew rate of the output buffer is adjusted in response to the second feedback delay amount.