Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob

XENSIV™ current sensors: Frequently asked questions – KBA238402

XENSIV™ current sensors: Frequently asked questions – KBA238402

Infineon_Team
Employee
Employee
50 replies posted 25 likes received 25 replies posted

What is the maximum continuous current measurement using the TLE4972 current sensor?

Since TLE4972 is an external current rail sensor, it is not possible to provide a value for the maximum current that the product can measure. The maximum sensing current depends on the transfer factor of the external conductor (µT/A) and the sensor sensitivity (mV/mT).

The transfer factor of the external conductor depends on the customer system design and specifications. The sensor sensitivity, is specified in  the Analog Output Characteristics table in the TLE4972 datasheet (Rev. 1.02, 21-12-2021). Following are the six different sensitivity and full-scale ranges that can be programmed.

Infineon_Team_0-1692263365705.png

How does the current sensor measuring sensitivity degrade with temperature?

The sensor sensitivity has a ±1.9% variation over temperature and lifetime. If sensitivity changes, the measurable full scale of the current also changes, as described in the Analog Output Characteristics table  in the TLE4972 datasheet (Rev. 1.02, 21-12-2021).

Infineon_Team_1-1692263394381.png

Total error including sensitivity, gain, offset, and linearity error is ±2%.

Infineon_Team_2-1692263407357.png


What are the differences between OCD1 and OCD2 output of the TLE4972 current sensor?

Following are the differences between the OCD1 and OCD2 outputs of TLE4972 current sensor:

  • OCD1 is slightly faster than OCD2, given that the max value of the response time is 1 µs for OCD1 and 1.2 µs for OCD2.
  • OCD2 has lower threshold value options ranging from 0.5 - 1.25 factor for Full-Scale, whereas the OCD1 threshold value options range from 1.25 - 2.25 factor for Full-Scale and it is usually used as a pre-alert function.

 

What is the recommended pull-up resistor or pull-down resistor for the OCD in the TLE4972 current sensor?

It is recommended to use a 4k7-ohm pull-up resistor for the OCD, which is illustrated in the following application circuit figure (you can also refer to the application circuit figures in the TLE4972 Datasheet (Rev. 1.02, 21-12-2021)).

Infineon_Team_3-1692263438969.png

Figure 1  Application circuit for three-phase system in single-ended mode

Infineon_Team_4-1692263470584.png

Figure 2 Application circuit for three-phase system in semi and fully differential mode

How does the TLE4972 current sensor sense the current externally?

The TLE4972 coreless magnetic current sensor measures the differential magnetic field caused by a current flowing in an external conductor. The following formula shows that the magnetic fields, +BIPN and -BIPN, (at the sensor’s Hall cell position) depend on the current, IPN. S refers to the sensitivity and VOQ the quiescent voltage of the sensor. The output voltage function of the magnetic field is expressed as follows:  

Infineon_Team_6-1692263557437.png

Where Bdiff is defined as the average differential magnetic field at the Hall probes location.

Infineon_Team_5-1692263534837.png

The following figures show different package orientations relative to the current direction. If the current IPN is flowing according to the direction shown in the following figure, then the sensor provides an output voltage VO(IPN) with respect to the polarity of the input current, IPN; otherwise, the sensor provides an inverted output voltage, VO(IPN), with in respect to the polarity of the input current IPN.

Infineon_Team_7-1692263590711.png

Figure 3  Lateral insertion for PG-VSON-6 package

Infineon_Team_8-1692263630768.png

Figure 4  Vertical insertion for PG-VSON-6 package

Infineon_Team_9-1692263725789.png

Figure 5  Lateral insertion for PG-TDSO-16 package

What is the immunity level of the TLE4972 current sensor to noise?

Since TLE4972 uses a differential sensing principle, it is able to suppress homogeneous magnetic disturbances nearby. Systematic crosstalk from neighboring lines can also be compensated with calibration at room temperature. It is recommended to not have ferro-magnetic materials below/above the sensing element locations, in order not to influence the shape and amplitude of the magnetic field seen by the sensor.

Which layer should be the current rail with respect to the IC in TLE4972 current sensor?

Usually inner layers are used, in order to have isolation between the current rail and sensor. The top layer cannot be too thick due to the clearance rule of PCB manufacturers. Hence the SMD device with small pins cannot be connected. The top layer is generally 35-µm wide. For the inner layers, depending on the RMS current, 70 µm, 100 µm, and 140 µm are used. The number of inner layers also depend on the application needed.

Is  ground plane required between the current rail and below the IC in the TLE4972 current sensor?

The area below the IC should not have ground planes due to eddy current effects.

What is the dimensionality requirement for the current rail below the IC in the TLE4972 current sensor?

The current rail width depends on the system requirements (maximum current, maximum allowed heating). The relevant factor for the sensor is the magnetic field at the sensing element locations. The optimum is when the maximum magnetic field to be sensed matches the full scale of the sensor (see the Analog Output Characteristics table in TLE4972 Datasheet (Rev. 1.02, 21-12-2021)).

Different current rail geometries based on your system designs can be simulated using Infineon’s Current sensor simulation tool. The result gives the insertion resistance, maximum current for full scale, and corresponding sensitivity ranges and power dissipation.

Does VAOUT drift with VREF?

VAOUT will follow VREF. and VREF must be within ±10% accuracy. 1.65 V is the default setting in EEPROM (the range is 1.485 V-1.815 V).

What is the impact on output if VREF drifts too far from the VREFext defined in EEPROM?

Vout will follow up to ±10% drift of VREF. Drifts exceeding 10% are not characterized.

Is the TLI4971 current sensor UL-1577 certified?

The following versions of TLI4971 current sensors are UL-certified:

  • TLI4971-A120T5-U-E0001
  • TLI4971-A075T5-U-E0001
  • TLI4971-A050T5-U-E0001
  • TLI4971-A025T5-U-E0001

For details, refer to the TLI4971 Datasheet (Rev 1.30, 01-12-2021).

TLI4971 current sensor ISO compliance and other qualifications

The TLI4971 current sensor is not ISO compliant.

But it is qualified according to AEC Q100 grade 2. Following is the list of current sensors qualified according to AEC Q100 grade:

  • TLI4971-A120T5-U-E0001
  • TLI4971-A120T5-E0001
  • TLI4971-A075T5-U-E0001
  • TLI4971-A075T5-E0001
  • TLI4971-A050T5-U-E0001
  • TLI4971-A050T5-E0001
  • TLI4971-A025T5-U-E0001
  • TLI4971-A025T5-E0001

For details, refer to the TLI4971 Datasheet (Rev 1.30, 01-12-2021).

0 Likes
83 Views