| 摘要 |
PROBLEM TO BE SOLVED: To confirm the precision of a bait-in A/D converter in an LSI even if an inexpensive tester is used. SOLUTION: An A/D converter 5 of 8 bits, for example, digitally converts an input ramp wave and supplies the output codes of 0 to 255 steps in resolution to a matching detection circuit 9. A reference value setting circuit 7 supplies one value to the matching detection circuit 9 for every ramp wave input period based on a reference setting signal from a tester 21 which does not incorporate DSP. The reference value setting circuit 7 sequentially supplies the values of 1-254 to the matching detection circuit 9 in accordance with 254 ramp wave inputs. The matching detection circuit 9 supplies detection period signals (continuous high signals) of a period when the output code from the A/D converter 5 is matched with a value from the reference value setting circuit 7 at every ramp wave input to the tester 21. The tester 21 counts to how many clocks the detection period signal continues.
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