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

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-<inline-formula> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> offset, which is significantly better than the state-of-the-art systems. The heart of the system is a robust 260-<inline-formula> <tex-math notation="LaTeX">$\mu \Omega $ </tex-math></inline-formula> shunt resistor made from the lead frame of a standard HVQFN plastic package. The resulting voltage drop is then digitized by a precision <inline-formula> <tex-math notation="LaTeX">$\Delta \Sigma $ </tex-math></inline-formula> ADC and a bandgap reference (BGR). At the expense of current handling capability, a ±5-A version of the CSS uses a 10-<inline-formula> <tex-math notation="LaTeX">$\text{m}\Omega $ </tex-math></inline-formula> on-chip metal shunt to achieve just a 4-<inline-formula> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> offset. Both designs are realized in a standard 0.13-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process and draw 13 <inline-formula> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> from a 1.5-V supply. Compensation of the spread and nonlinear temperature dependency of the shunt resistor <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm {shunt}}$ </tex-math></inline-formula> 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.

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