An 18-Bit Incremental Zoom ADC with Reduced Delay Overhead Data Weighted Averaging for Battery Measurement Systems

The paper presents a systematic implementation of 18-bit incremental zoom ADC for stacked lithium-ion battery voltage monitoring system with a reduced dynamic range analog front-end that comprises a resistive level shifter. A comparative study of the incremental zoom ADC and its incremental ADC counterpart, for a given modulator order, is presented in detail. The choice of incremental zoom ADC is demonstrated to be a best fit for an 18-bit resolution of the target application. Multi-bit DAC non-linearity is proven to be major bottleneck for the ADC performance. The performance of data weighted averaging (DWA) dynamic element matching (DEM) technique for improvising modulator linearity with 0.1 percent DAC component mismatch is analyzed. DWA DEM is confirmed to meet an in-band SNDR of 108 dB, operating on a 250 kHz oversampled clock frequency, required for 18-bit modulator linearity with a 5-bit DAC. An SNR of 114 dB is achieved with the first-stage integrator thermal noise limited to 3.3 µVrms over process voltage and temperature variations (PVT) using 0.35 µm CMOS process.