loose-electron
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Best Design Tool = Capable Designers
Posts: 1638
San Diego California
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A little piece of trivia. Last I checked, you can get a highly accurate voltage reference on a chip (a good bandgap) but, due to process variance, there is not a straightforward way to get a good accurate absolute current.
Consequently, most prior art in this area has used an external reference resistor (in conjunction with the bandgap reference) to get there, or has used some form of trimming, to adjust for process variance.
So then, the question become, do you want to auto trim with a state machine when the chip power cycles on, or do you want to trim once when the chip is at wafer test (digital coding, fuse link blowing or zener zapping)
The state machine trimming takes some die area, and a little power during the cycle up process, but after you get your trim setting you can turn that part of the chip. Trimming at wafer test takes ATE test time which can be expensive as well.
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