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A double edge clipping technique is proposed for at-speed BIST testing. It differs from traditional circuit delay testing techniques by changing the clock rate using external ATE. This method uses lower-speed input clock frequency, then applies internal BIST circuit to adjust clock edges for circuit at-speed delay testing and speed binning. This built-in at-speed delay test with calibration mechanism named as double edge clipping (DEC) technique. DEC is based on the lunch on shift (LOC) scheme by precisely controlling the launch and capture edges during delay test operation. Two wide-range (26% -80%), fine-scale (16ps) duty cycle adjustment circuits with high-precision (28ps) calibration mechanism are effective applied for at-speed delay testing and performance binning. The key to DEC testing technique is to generate a pair of clock pulses for the launch and capture events. Two DCPG provide adjusted positive clock edge during test operation. DEC uses 500kHz low speed input clock then provides working clock frequency from 197MHz to 932MHz.