Daily Archives: November 3, 2022

AC-DC Core-Less Magnetic Current Sensor

Infineon has a new high-precision core-less magnetic current sensor, the TLI4971. It has an analog interface for measuring both AC and DC currents. This QFN leadless package is only 8x8x1 mm in physical size. The output has dual fast over-current detection. The new sensor from Infineon is UL certified, but a non-UL version is also available.

Current sensors are devices that generate a signal proportional to the amount of current flowing using a magnetic core. The core-less current sensor does not have a magnetic core. Rather, they use magnetic sensors like a Hall element to sense the current flow and generate a proportional voltage output.

Made with the robust and well-established Hall technology of Infineon, the TLI4971 allows highly linear and accurate measurements of current. The full measurement range covers ±120 A. Infineon has managed to avoid all negative effects that plague sensors using flux concentration techniques. This includes saturation and hysteresis. The TLI4971 has internal features for self-diagnostics.

Infineon has added its proprietary digital temperature and stress compensation to provide superior stability to the TLI4971. The analog concept of the sensor along with the digital assistance provides it with excellent stability over lifetime and temperature excursions. For operating in harsh environments, Infineon has provided the sensor with a differential measurement principle that allows substantial suppression of stray fields.

The insertion resistance of the integrated current rail sensor is typically 225 µΩ, enabling ultra-low power loss in the circuit. The small form factor of the SMD package makes it easy to integrate and saves real estate on the board. The sensor accepts a single supply voltage ranging from 3.1 VDC to 3.5 VDC. It is highly accurate and scalable, with the capability to sense and measure both AC and DC currents. The sensor supports a wide range of applications, as its bandwidth is greater than 120 kHz. Its sensitivity error over temperature is very low, typically a 2.5% maximum. Offset over temperature and lifetime is very stable. Voltage slew rates are highly robust up to 10 V/ns.

Infineon has provided galvanic isolation for TLI4971 up to 1150 V peak VIORM. The sensor has a partial discharge capacity of greater than 1200 V. The creepage and clearance distances available are 4 mm. With the application of the differential sensor principle, Infineon has ensured superior suppression of magnetic stray fields. They have also provided two independent fast OCD or Over-Current Detection pins on the sensor. These have configurable thresholds to allow protection for power circuitry of typically 0.7 µs. The operating temperature range is -40 °C to +105 °C. Infineon has precalibrated its sensor, which means it does not require calibration in the field.

There are several potential applications for this core-less magnetic current sensor. Primarily, it is useful in electrical drives up to 690 V, photovoltaic inverters, and other general purpose inverters that require AC/DC current sensing and measurement. The sensor is extremely helpful in detecting the overload and over-current situations. It is applicable in all types of current monitoring, and its huge range is a definite advantage in these situations. It is applicable to all types of power supplies and battery chargers where current measurement is necessary.