Sensors feature voltage isolation
Allegro Microsystems Europe is launching new ACS714 and ACS715 automotive-grade Hall-effect linear current sensors that combine high accuracy with excellent voltage isolation.
The new devices are designed to provide economical and precise sensing of ac and dc currents in automotive applications such as motor control, load detection and management, switched-mode power supply control, and overcurrent fault protection.
Each of the new products consists of a precise, low-offset, linear Hall sensor circuit with a copper conduction path located near the surface of the die. Applied current flowing through this copper conduction path generates a magnetic field that is sensed by the integrated Hall IC and converted into a proportional voltage. Device accuracy is optimised through the close proximity of the magnetic signal to the Hall transducer.
A precise proportional voltage is provided by the low-offset, chopper-stabilised BiCMOS Hall IC, which is programmed for accuracy after packaging. Total output error is 1.5 per cent at +25 degrees C and 5 per cent over the range -40 to +150 deg C; the risetime in response to a step input current is only 6us.
The internal resistance of the conductive path is typically 1.2 milliohms, which leads to low power losses, and the thickness of the copper conductor enables the device to survive up to five times overcurrent conditions.
By electrically isolating the terminals of the conductive path from the sensor leads with an isolation voltage of 2.1 kV RMS, the ACS714 and ACS715 current sensors can be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques.
The conductive shield across the face of the ACS714/15 is connected to ground, so that, in the presence of high dV/dt events on the device conductor, it will shunt the resultant capacitively coupled energy to ground. This prevents output voltage disturbances in the presence of very high conductor dV/dt events, which are often present in motor control and switched-mode power supply applications.
Both devices are supplied in a small, surface-mount SOIC8 package. The leadframe is plated with 100 per cent matt tin, which is compatible with standard lead-free printed circuit board assembly processes. Internally, the device is lead-free, except for flip-chip high-temperature lead-based solder balls, currently exempt from RoHS.
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