An Active-Passive 2nd-order CT Sigma Delta Using Single FIR Feedback for Battery Monitoring

P. Peres, N. Paulino (NOVA School of Science and Techn., Portugal), B. Nowacki (Renesas, Portugal)

This paper presents a 2nd-order hybrid (active-passive) CTΔΣM for battery monitoring. The ΔΣM uses a single 4-tap FIR DAC feedback path and adds zeros to each RC integrator for stabilization. This modulator was designed in 65nm CMOS technology. It dissipates 237uW from a 1.2V supply with a clock of 20MHz. The modulator occupies an estimated area of 0.209mm2. Electrical transient noise simulations show, that for a signal bandwidth of 20KHz, 10KHz and 5KHz the modulator has a maximum SNDR of 93.29dB, 96.75dB and 99.52dB, respectively, under typical conditions, with minimums of 89.28dB, 92.35dB and 94.53dB and maximums of 94.61dB, 99.25dB and 101.3dB. The modulator has a DR of 95.3dB, 97.1dB and 100.1dB, under typical conditions, with minimums of 89.3dB, 91.6dB and 94.6dB and maximums of 97.5dB, 99.5dB, 102.5dB, for 20KHz, 10KHz and 5KHz bandwidths, respectively. FOMW of 157.2, 211.3 and 306.7 fJ/conv.-step, for typical conditions, with minimums of 67.8, 95.8 and 151.9fJ/conv.-step and maximums of 618.2, 565.3 and 896.9fJ/conv.-step, for bandwidths of 20KHz, 10KHz and 5KHz, respectively.