High-Precision Current Sensing: Diodes’ Shunt Series for Auto Apps

Accurate current measurement is essential in modern applications for power estimation, regulation, and diagnostics. In automotive and industrial systems, it helps maintain reliability, safety, and energy efficiency for mission-critical power systems. However, traditional current measurement methods often face challenges such as fluctuating common-mode voltages, rapid current transients, and environmental noise. These challenges are particularly acute in high-performance automotive settings, where systems must function reliably under varying loads and extreme temperatures.

Diodes Incorporated has launched the ZXCT18xQ series as a solution. Diodes’ latest products integrate many desirable specifications in a single package.

The ZXCT 18XQ series. Image used courtesy of Diodes Incorporated

Reviewing the Basics

Current shunt monitors use Ohm’s Law to measure small voltage drops across a shunt resistor and calculate current. Generally, dedicated shunt-current sense ICs will incorporate internal operational amplifiers that provide a gain to the input voltage (across shunt resistor) for easy measurement by microcontrollers.

An important parameter to consider when selecting a current shunt monitor is its slew rate, the maximum rate at which the output voltage changes when responding to a rapid change in input current. It is measured in volts per microsecond (V/µs). A high slew rate is needed in fault-detection applications because it enables the monitor to respond quickly to sudden current spikes or drops. Consider applications like battery management and power systems, where delays in detecting and addressing faults can lead to system damage or failure.

These devices are expected to operate over extensive common-mode voltage ranges, which can be particularly challenging because common-mode voltages in automotive and industrial environments can fluctuate drastically due to dynamic operating conditions, such as varying loads or transient events.

Diodes High-Precision Current Shunt Monitors

Diodes Incorporated has introduced its ZXCT18xQ series as a high-precision solution for current sensing in automotive applications.

These current shunt monitors are single-stage instrumentation amplifiers capable of measuring minimal sense voltages across shunts with a common-mode voltage range of -0.3 V to 26 V, independent of the supply voltage (2.7 V to 5.5 V). Designed for accuracy and flexibility, the series offers four fixed voltage gain options (20 V/V, 50 V/V, 100 V/V, and 200 V/V) for compatibility with diverse system requirements. Operating with a maximum supply current of 370 µA, the devices deliver small-signal bandwidths up to 400 kHz and a large-signal slew rate of 2 V/µs.

Application circuits of ZXCT180Q and ZXCT181Q. Image used courtesy of Diodes Incorporated

The series includes unidirectional and bidirectional variants. The ZXCT181Q supports bidirectional current sensing by introducing an offset voltage at the REF pin, whereas the ZXCT180Q provides configurations optimized for unidirectional flow.

Overall, by integrating precise current sensing across low-sense voltages down to 10 mV and supporting high- and low-side sensing, the ZXCT18xQ series hopes to improve fault detection accuracy and speed in systems such as battery management and body control modules.

Future Applications

In demanding and dynamic fields like automotive, systems will require more reliable and efficient designs, and precise current sensing will remain a central piece of the puzzle. Adopting advanced sensing solutions enables faster fault detection, improved energy management, and seamless operation in challenging environments.