A Digitally Calibrated Bandgap Reference With 0.06% Error for Low-Side Current Sensing Application

Abstract

Accurate current and voltage measurements are essential for estimating the state of charge of an automotive battery. Typically, circuits are designed to measure low-side current of lead-acid battery. These circuits, however, require a precision reference voltage across a temperature range. In this paper, a design of an on-chip precision bandgap reference with a digitally calibrated technique is described. The bandgap is trimmed for temperature and magnitude and is calibrated digitally. Experimental results show that a maximum of 0.06% variation in the bandgap output for a temperature range of −40 °C–100 °C at a power supply voltage of 3.3 V is achieved. The integrated circuit is fabricated in 0.35- $\mu \text{m}$ standard CMOS technology and occupies an area of 0.23 mm2.