CT405x: Contactless Sensor Performance

Crocus Technology has expanded its contactless current sensing product offering with two new contactless, coreless current sensors CT4051 and CT4052. These contactless sensors that measure current via the magnetic field generated by flowing current, are coreless (with no ferromagnetic core), non-intrusive (they don’t cut the current path), and differential (in the case of CT4052), which enables immunity to external magnetic field disturbance.

The CT405x line up completes the current CT45x contactless current sensor lineup from Crocus Technology. Leveraging ten years of deep XtremeSense® TMR R&D. They are available to all markets — especially high volume and price sensitive ones that were stuck with low performance, legacy Hall sensors. (Figure 1)

Figure 1: Contactless Sensors
Contactless CT4051 and CT4052 deliver a much better device solution than typical hall sensors, with better performance and cost basis. (Figure 2)
Figure 2

CT4051 and CT4052

Each new sensor is designed for specific requirements.

CT4051 is designed to measure uniform magnetic fields, while the CT4052 is a differential sensor, measuring differential fields.

While the CT4051 can be used with practically any busbar (as it simply picks up the magnetic field generated by flowing current), the CT4052 requires an S-shaped busbar to generate the differential magnetic field shape necessary for its immunity to external magnetic fields.

The CT4051 is ideal when high resolution is necessary, as a straight busbar will typically generate a higher amplitude magnetic field per 1 Amp (i.e. higher coupling coefficient). Conversely, the CT4052 requires an S-shaped busbar, which enables external magnetic field immunity, but has a negative impact on the coupling coefficient.

This is also the reason the CT4051’s magnetic range can go up to 26mT, as it has to allow for higher coupling coefficients so it doesn’t saturate too quickly. Conversely the CT4052’s lower magnetic range up to 4mT, is due to the lower coupling coefficient of its S-shaped busbar configuration.

A look at the features:

  • Supports AC & DC magnetic fields
  • Measurement range ±4 mT to ±26.0 mT
  • Ratiometric analog output
  • Factory-trimmed sensitivity and quiescent output voltage • 3.3V to 5V single supply operation
  • Immunity to common mode fields (only on CT4052)
  • DC to 500 kHz Bandwidth
  • Max. Total Error: ±3% FS (-40 ̊C to 125 ̊C)
  • 7mA current draw
  • Operating Temperature:
  • -40°C to +125°C
Figure 3: CT4051 (left) and CT4052 (right) busbars

As you can see in figure 4, the features of each sensor affect their performance in terms of sensitivity, signal-to -noise ratio, cross-talk, etc. In this table we also see CT4051 and CT4052’s superior SNR performance, better resolution, and less noise compared to Hall sensor solutions.

Figure 4

Applications

When the powerful performance of these contactless sensors is targeted at high- volume, cost-constrained segments, the applications are numerous. (figure 5)

Figure 5

Contactless CT4051 and CT4052 deliver an ideal device solution for high volume, lower cost automotive and industrial market applications (optimal when nominal current is >100A.)

This includes applications like High Voltage Traction Inverters (HVTI) and Solar and Power inverters.

The CT4051 and CT4052 deliver accuracy specifications of less than 3% over the full temperature range and a high bandwidth specification of 500kHz, since they are contactless sensors designed for specific applications. For example, an automotivinverter application typically requires 100kHz to 200kHz capable sensors, so the CT4051/2 500kHz bandwidth specification is sufficient.

And both new sensors have distinct advantages: To meet automotive HVN (harshness vibration and noise) requirements, CT4051 is suitable as it is less sensitive to mechanical displacement, while CT4052’s benefit is its immunity to magnetic field changes.

The Crocus Technology Sensor Portfolio

Figure 6: The Sensor Portfolio
These new contactless, coreless, differential sensors complete Crocus technology’s comprehensive portfolio of contactless TMR Current Sensors (figure 6). With the CT4051 and CT4052, high performance is available at every price point.

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