An incremental delta-sigma modulator with self-making capacitors for multi-cell battery packs

An incremental delta-sigma modulator with a self-making capacitor having a high voltage operating ability for a 12-cell battery pack is proposed in this paper. The measured voltage range for each battery is from 0 to 5 V, and the maximum input voltage reaches to 60 V. The self-making capacitor adopting a metal over poly silicon with a relatively thin layer of oxide between the two plates is generated. The incremental delta-sigma modulator adopting a second-order CIFB structure is implemented in a 0.25-μm 5 V CMOS process with drain extended MOS high-voltage devices. The modulator consuming a current of approximately 400 μA and with a sampling frequency of 500 kHz completes converting one cell voltage in 790 μs. The schematic and layout simulation results show the modulator with a digital filter achieves a resolution of 12 bits and good linearity.