Output buffer for reducing slew rate variation

A method for buffering output data, the method comprising:

• generating first and second bias voltages responsive to a reference voltage;
• driving an output in response to said generated voltages;
• controlling a pull-up slew rate of said driven output in response to said output data and said first bias voltage;
• controlling a pull-down slew rate of said driven output in response to said output data and said second bias voltage;
• compensating for slew rate variation in response to a change in the load capacitance of said driven output;
• applying said driven output to said output terminal;
• dropping a voltage applied to said output terminal;
• and
• detecting if a voltage higher than a power supply voltage is applied to said output terminal.

An output buffer circuit for buffering output data, the circuit comprising:

• means for generating first and second bias voltages responsive to a reference voltage;
• means for driving an output in response to said generated voltages;
• means for controlling a pull-up slew rate of said driven output in response to said output data and said first bias voltage;
• means for controlling a pull-down slew rate of said driven output in response to said output data and said second bias voltage;
• means for compensating for slew rate variation in response to a change in the load capacitance of said driven output;
• means for applying said driven output to an output terminal;
• means for dropping a voltage applied to said output terminal;
• and
• means for detecting if a voltage higher than a power supply voltage is applied to said output terminal.

A semiconductor integrated circuit comprising an output buffer circuit for buffering output data, the output buffer circuit comprising:

• a bias voltage generator for generating first and second bias voltages responsive to a reference voltage;
• an output driver in signal communication with said bias voltage generator for driving an output terminal;
• a first slew rate controller in signal communication with said output driver for controlling a pull-up slew rate of said output driver in response to said output data and said first bias voltage;
• a second slew rate controller in signal communication with said output driver for controlling a pull-down slew rate of said output driver in response to said output data and said second bias voltage;
• a slew rate compensator in signal communication with the output ends of said first and second slew rate controllers and said output terminal for compensating for slew rate variation in response to a change in the load capacitance of the output terminal;
• and
• a high voltage protector for dropping a voltage applied to the output terminal and providing the dropped voltage to the output driver and the slew rate compensator if a voltage higher than a power supply voltage is applied to the output terminal.