A ±36-A Integrated Current-Sensing System With a 0.3% Gain Error and a 400- $\mu \text{A}$ Offset From −55 °C to +85 °C

Abstract

This paper presents an integrated shunt-based current-sensing system (CSS) capable of handling ±36-A currents, the highest ever reported. It also achieves a 0.3% gain error and a 400- $\mu \text{A}$ offset, which is significantly better than the state-of-the-art systems. The heart of the system is a robust 260- $\mu \Omega $ shunt resistor made from the lead frame of a standard HVQFN plastic package. The resulting voltage drop is then digitized by a precision $\Delta \Sigma $ ADC and a bandgap reference (BGR). At the expense of current handling capability, a ±5-A version of the CSS uses a 10- $\text{m}\Omega $ on-chip metal shunt to achieve just a 4- $\mu \text{A}$ offset. Both designs are realized in a standard 0.13- $\mu \text{m}$ CMOS process and draw 13 $\mu \text{A}$ from a 1.5-V supply. Compensation of the spread and nonlinear temperature dependency of the shunt resistor $R_{\mathrm {shunt}}$ is accomplished by the use of a fixed polynomial master curve and a single room temperature calibration. This procedure also effectively compensates for the residual spread and nonlinearity of the ADC and the BGR.