A built-in self-test technique for load inductance and lossless current sensing of DC-DC converters

One of the major problems associated with integrated DC-DC converters used in state of the art Power Management ICs (PMICs) is dynamic performance and stability degradation due to off-chip component and output current variations. A high accuracy built-in self-test (BIST) architecture measuring load inductance and DC resistance (DCR) of DC-DC converters is presented. The DCR measurement of the inductor also enables continuous, lossless average load current sensing of the DC-DC converter across the inductor. Both the BIST circuit and the primary signal chain utilize low analog complexity frequency-domain ΔΣADC. The ΔΣADC decimation filter nulls also provide current ripple cancellation and average current extraction. The BIST module can measure filter inductance values ranging from 3.6μH to 22.3μH range with average 2.0% error and inductor DCR 13mΩto 68mΩ range with average 2.1% error. The average current sensing enabled by the BIST technique achieves current measurement accuracy with average 2.3% error for 0.1A-1A range load current. BIST and current sensing modules occupy less than 6% of total chip area. The BIST circuitry is fabricated and tested with a 12V input, 1V-11.5V output range, for a 3W output power digital DC-DC converter.