Signal conversion using coarse and fine digital to analog converters

A method for providing control commands to a micromirror device, the method comprising:

• generating a digital control command;
• apportioning the digital control command into a digital coarse value and a digital fine value;
• converting the digital coarse value into an analog coarse signal;
• switching on a filter to perform the filtering of the analog coarse signal;
• filtering the analog coarse signal before the summing of the analog coarse and fine signals;
• converting the digital fine value into an analog fine signal;
• summing the analog coarse and fine signals, in accordance with a coarse/fine gain ratio, to generate an analog position signal corresponding to the digital control command;
• and
• providing the analog position signal to a driver element to orient the micromirror device.

A digital to analog converter apparatus for converting a digital signal into an analog signal, the digital to analog converter comprising:

• a coarse input for receiving a coarse digital value;
• a fine input for receiving a fine digital value, wherein the combined coarse and fine digital values represent the digital signal;
• a coarse DAC having an input coupled to the coarse input, and having an analog coarse output;
• a switch disposed between the analog coarse output and a filter, wherein the switch has a first input coupled to the analog coarse output, and an output coupled to the filter;
• a fine DAC having an input coupled to the fine input, and having an analog fine output and
• a summing amplifier having a first input coupled to the analog coarse output and a second input coupled to the analog fine output, and having a summed analog output providing the analog signal.

A method of generating an analog signal from a digital signal, the method comprising:

• apportioning the digital signal into a digital coarse value and a digital fine value;
• converting the digital fine value into an analog fine value;
• converting the digital coarse value into an analog coarse value;
• summing the analog coarse and fine values, in accordance with a coarse/fine gain ratio, to generate the analog signal corresponding to the digital signal;
• and
• switching on a filter coupled to the analog coarse value after a time period during which the analog coarse value remains constant.

A position control circuit for a positioning system, the position control circuit comprising:

• a digital controller, wherein the digital controller generates a digital control command and apportions the digital control command into a digital coarse value and a digital fine value;
• a coarse DAC having an input coupled to the digital controller for receiving the digital coarse value, and having an analog coarse output;
• a fine DAC having an input coupled to the digital controller for receiving the digital fine value, and having an analog fine output;
• a switch having a first input coupled to the analog coarse output;
• a filter having a capacitor coupled to an output of the switch;
• and
• a summing amplifier having a first input coupled to the analog coarse output and a second input coupled to the analog fine output, and having a summed analog output, corresponding to the digital control command, for controlling an actuator in the positioning system.