Precision 50A current measurement sensor in 7-mm sq. IC-style packaging

March 12, 2014 // By Graham Prophet
TLI4970 from Infineon is a high-precision, AC/DC, ±50A current sensor that claims to resolve many compromises in today’s current measurement circuitry, and which requires only a sixth of the board space taken up by existing sensors on the market today.

The fully digital sensor does not require external calibration. Thanks to the stray-field suppression it incorporates the sensor is extremely robust against external magnetic fields. It continues to measure with absolute precision even after years of continuous operation. It also provides additional functions such as fast overcurrent detection at a pre-configurable level. The TLI4970 is suited for use in solar inverters, charging devices and power supplies as well as for electric drives and for controlling energy-saving LED lighting units. Samples of the TLI4970 are already available. Series production is due to commence in May 2014.

The measuring principle of the TLI4970 is based on Infineon’s implementation of Hall effect technology. This involves using integral Hall probes to detect the magnetic field of a current-carrying conductor. The TLI4970 dispenses with the field concentrators that other designs require and, as a result, avoids hysteresis effects, which can lead to measuring inaccuracies.

The differential measuring principle integrated in the TLI4970 suppresses interference caused by external magnetic fields, achieving an extremely low offset of just 25 mA. With conventional current measurement principles, the measuring accuracy is always governed by the ambient conditions (e.g. the temperature). In addition, substantial, non-deterministic drifts and ageing phenomena are encountered. These can have a negative impact on the accuracy of the current measuring, which needs to be compensated. The TLI4970 avoids such dependencies due to the fact that it incorporates separate structures for measuring the temperature and the mechanical stress. By measuring both variables separately during operation, it is possible to constantly ensure effective compensation – the foundation for long-term measurement stability and, as such, for highly efficient, reliable and cost-optimised inverters and motors.

Fast overcurrent detection

Besides high-precision current measurement, it is also possible to implement highly efficient protection of a power output stage. In the event of external short circuits, critical overcurrents can occur. To keep the latency extremely short, the TLI4970 provides a parallel signal path.