Programmable integrating ramp generator and method of operating the same

A ramp generator, comprising:

• control logic for generating a plurality of control signals during the production of one of a rising edge or a falling edge of a ramp signal;
• a falling ramp portion, wherein said falling ramp portion comprises a first operational amplifier comprising:
• a first input for receiving a high reference voltage;
• and
• second input connected to a first current source and a first side of a first variable capacitance, said first variable capacitance being responsive to said control logic;
• and
• an output connected to a second side of said first capacitance;
• and
• a rising ramp portion, wherein said rising ramp portion comprises a second operational amplifier comprising:
• a first input for receiving a low reference voltage;
• a second input connected to a second current source and a first side of a second variable capacitance, said second variable capacitance being responsive to said control logic;
• and
• an output connected to a second side of said second capacitance.

A method for operating a ramp generator having an array of capacitors each controlled by a switch, comprising:

• resetting said ramp generator;
• generating a plurality of control signals during the production of a ramp signal comprised of a plurality of discrete segments;
• enabling a current generator, said current generator charging connected capacitors within said array;
• controlling the state of one or more switches with said control signals, wherein said switches are operable to control which of said capacitors are connected in parallel within said array;
• and
• changing the state of one or more of said plurality of control signals during the production of said ramp signal.

An analog-to-digital converter, comprising:

• a ramp generator for producing a ramp signal output wherein said ramp signal output has a linear portion and a portion comprised of a plurality of discrete segments;
• said ramp generator comprising:
• control logic configured for producing a plurality of control signals during the production of said ramp signal output;
• said control logic being further configured for changing the state of one or more of said plurality of control signals during the production of said ramp signal;
• an array of parallel connected capacitors each controlled by a switch operable to connect/disconnect that switch's capacitor to/from said other capacitors within said array, wherein said switches are responsive to one or more of said plurality of control signals;
• and
• a current source for charging at least one of said capacitors within said array;
• and
• a comparator producing a comparator output responsive to an analog input and said ramp signal output.

An analog-to-digital converter, comprising:

• control logic for generating a plurality of control signals during the production of one of a rising edge or a falling edge a ramp signal;
• a ramp generator, comprising:
• a falling ramp portion operable to produce a falling ramp signal, wherein said falling ramp portion comprises a first operational amplifier comprising:
• a first input for receiving a high reference voltage;
• and
• a second input connected to a first current source and a first side of a first variable capacitance, said first variable capacitance being responsive to said control logic;
• and
• an output connected to a second side of said first capacitance;
• and
• a rising ramp portion operable to produce a rising ramp signal, wherein said rising ramp portion comprises a second operational amplifier comprising:
• a first input for receiving a low reference voltage;
• a second input connected to a second current source and a first side of a second variable capacitance, said second variable capacitance being responsive to said control logic;
• and
• an output connected to a second side of said second capacitance;
• and a conversion circuit, comprising:
• a differential amplifier operable to produce an amplified differential signal responsive to two or more input signals;
• a comparator operable to compare said amplified differential signal to the difference of said falling ramp signal and said rising ramp signal;
• and
• a logic circuit operable to produce a digital output responsive to an output of said comparator.

A nonlinear, programmable ramp generator, comprising:

• control logic configured for generating a plurality of control signals during the production of a ramp signal, having a linear portion and a compressed portion;
• said control logic being further configured for changing the state of one or more of said plurality of control signals during the production of said ramp signal;
• said control signals representing programmable points at which the slope of the ramp signal changes;
• a variable capacitance responsive to said plurality of control signals;
• and
• a current source for charging said variable capacitance.

A method of operating a nonlinear, programmable ramp generator, comprising:

• generating a plurality of control signals during the production of a ramp signal having a linear portion and a compressed portion;
• said control signals representing programmable points at which the slope of the ramp signal changes;
• controlling the capacitance of a variable capacitance in response to said plurality of control signals;
• changing the state of one or more of said plurality of control signals during the production of said ramp signal;
• and
• charging said variable capacitance.