Precision 50A current measurement sensor in 7-mm sq. IC-style packaging
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. This allows the error condition detected by the sensor to be processed with an extremely short delay of less than 3 µsec directly in the driver stage or in the microcontroller. To fine-tune the overcurrent threshold to the requirements of the application, the system developer can program both the current value and the subsequent filtering in the sensor.
The integration of the current path in the SMD package permits complete calibration of the sensor on delivery. This also dispenses with the need for a subsequent, time-consuming calibration process by the customer during assembly.
The TLI4970 is one of the first current sensors to transmit the measured values via the digital SPI interface. It integrates differential amplifiers, filters and signal processing and can carry out galvanically isolated measurements up to 600V operating voltage and up to 3,600V test voltage.
SMD package for automatic component placement
The TLI4970 will be offered in a compact TISON (Thin Interstitial Small Outline No leads) SMD package with dimensions of 7 x 7 x 1mm. Samples of the TLI4970 are availablenow; series production is scheduled to begin in May 2014.
The TLI4970 evaluation kit makes evaluation easy. A graphic user interface allows the sensor to be programmed easily and tested out quickly for a whole range of system settings. The evaluation kit also includes an analogue board, which converts the digital SPI output signals into analogue signals. This enables developers to test the performance of the TLI4970 directly for their existing system designs with analogue interfaces – also because Infineon has ensured the analogue board is pin-compatible with conventional current sensors.
Infineon; www.infineon.com/TLI4970 and www.infineon.com/hall-switches
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