Method and apparatus for trimming high-resolution digital-to-analog converter

A digital-to-analog converter (DAC), comprising:

• a digital input;
• a current-source element responsive to the digital input sourcing a current having a total current magnitude;
• and
• a memory associated with the current-source element,
• wherein the total current magnitude sourced by said current source element is responsive to said memory,
• wherein said total current magnitude comprises a first current magnitude and a second current magnitude, said first current magnitude being sourced by a first transistor and said second current magnitude being sourced by a second transistor, and
• wherein said second current magnitude is responsive to said memory and said first current magnitude is not.

A method for trimming a current-steering-type digital-to-analog converter (DAC), the DAC including an input codeword register and a plurality of trimmable current-source elements each having:

• a current source transistor having a source and drain;
• a trim device having a floating gate, a source and a drain, said source and drain of said trim device coupled in parallel with said source and drain of said current-source transistor;
• an injection device coupled to inject electrons onto said floating gate in response to application of an injection control voltage to said injection device;
• a tunneling device coupled to remove electrons from said floating gate in response to application of a tunneling control voltage to said tunneling device;
• and
• an output node coupled to said drain of said current source transistor and said drain of said trim device;
• said method comprising the steps of:
• erasing the floating gates of all trim devices by applying a relatively high tunneling control voltage to said tunneling devices;
• and
• trimming each current-source element using electron injection by applying a negative voltage to each trim device's drain.