Online Built-In Self-Test of High Switching Frequency DC-DC Converters Using Model Reference Based System Identification Techniques

A built-in self-test (BIST) technique that enables tracking of loop parameters of integrated DC-DC converters without affecting the normal mode of operation is presented. A digital pseudo-noise based stimulus and a mixed signal cross-correlation based analysis technique is used to derive on-chip impulse response, with minimum computational requirements in comparison to a digital correlator approach. Using measured impulse response, open-loop phase margin and closed-loop unity-gain frequency are estimated within 5.2% and 4.1% error, respectively, for the load current range of 30 mA to 200 mA. Converter parameters, such as natural frequency, Q-factor, and center frequency are estimated within 3.6%, 4.7%, and 3.8% error, respectively, over load inductance of 4.7 μH to 10.3 μH, and filter capacitance of 200 nF to 400 nF. A 5 MHz switching frequency, 5 V to 8.125 V input voltage range, voltage-mode controlled DC-DC buck converter is designed for the proposed model reference based parametric and non-parametric BIST analysis. The converter output voltage range is 3.3 V to 5 V and supported maximum load current is 450 mA with a peak efficiency of 87.93%. The proposed converter is fabricated on a 0.6 μm 6 layer-metal SOI technology with a die area of 9 mm². The system identification circuitry occupies 3.8% of the converter area with 530 μA quiescent current during operation.