A Versatile ± 25-A Shunt-Based Current Sensor With ± 0.25% Gain Error From − 40 ∘ C to 85 ∘ C
Zhong Tang (TU Delft - Electronic Instrumentation)
Roger Zamparette (TU Delft - Electronic Instrumentation)
Yoshikazu Furuta (MIRISE Technologies Corporation)
Tomohiro Nezuka (MIRISE Technologies Corporation)
K. A.A. Makinwa (TU Delft - Microelectronics)
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Abstract
This article presents a versatile shunt-based current sensor for battery
management applications. It digitizes the current-induced voltage drop
across an external shunt resistor with the help of a 2
nd
-order delta-sigma (
ΔΣ
) ADC, whose summing node is implemented as a low-noise capacitively
coupled amplifier. To compensate for the shunt’s finite temperature
coefficient (TC), the TC of the ADC on-chip voltage reference can be
tuned. As a result, the sensor maintains high accuracy when used with
low-cost high TC shunts, such as PCB traces, as well as with more
expensive low TC shunts, such as metal-alloy resistors. Optimal gain
flatness over temperature is achieved by a two-current room-temperature
TC tuning scheme, which exploits the shunt’s self-heating at high
current levels. Fabricated in a standard 0.18-
μ
m CMOS process, the current sensor occupies 0.36 mm
2
and draws 265
μ
A from a 1.8-V supply. Over the industrial temperature range (
−
40
∘
C to 85
∘
C) and a
±
25-A current range, it achieves the state-of-the-art gain error (
±
0.25%) with both PCB (1.6 m
Ω
) and metal-alloy (2 m
Ω
) shunts. With these shunts, it achieves 5.3-mA/4.3-mA (rms) resolution in a 10-kHz bandwidth.