On-chip digital Idn and Idp measurement by 65 nm CMOS speed monitor circuit

An on-chip digital I<sub>ds</sub> measurement method is proposed in this report. In the proposed method, I<sub>ds</sub> is digitally derived from the two values measured by three ring oscillators with PN balanced, N-rich, and P-rich inverters. The first value is the frequency of the PN balanced inverter ring. The second value is the frequency difference between the N-rich and the P-rich inverter rings. The post-digital processing derives NMOS I<sub>ds</sub> (I<sub>dn</sub>) and PMOS I<sub>ds</sub> (I<sub>dp</sub>) separately. The monitor circuit was implemented by 65 nm CMOS technology. The mismatch error between the first I<sub>ds</sub> calculated from measured frequencies, and the second I<sub>ds</sub> directly measured for reference, was analyzed. The standard deviations of the mismatch error in I<sub>dn</sub> and I<sub>dp</sub> are 1.64% and 1.09%, respectively. The margin of 3sigma is within 5% which is our target tolerance for a practical application.

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