CDT series : Automotive Residual Current Monitoring type B Sensors

CDT is an automotive grade leakage current sensor family also called Residual Current Monitoring (RCM) or Residual Current Detection (RCD) class B and B+, dedicated to DC, AC and AC+DC leakage current measurement.

CDT Series - Accurate leakage current measurement

The CDT series is the LEM RCM type B current sensor family designed to measure and protect from AC and DC fault current (leakage current). Our proprietary fluxgate architecture allows the sensor to have best in class accuracy hence protection from potential fire hazards and electrical shocks. The package is configurable up to 4 conductors 48Arms capable, allowing 1 and 3 phases systems and offering an optimized leakage measurement of configurations by design.

The CDT series sensors provide a tripping fault current output and an SPI bus enabling fast response time and detailed fault information. For automotive applications, such as bidirectional On-Board Chargers, an ISO26262 ASIL B compliant version offers additional safety diagnostics.

CDT series - Features and benefits


CDT Residual Current Sensor has been designed to achieved best in class performances, measuring and detecting as low as 5 mA DC or AC leakage. Sensor family is suitable for various AC charging applications:

  • AC wallbox
  • ICCPD (charging cable)
  • On Board Charger (bidirectionnal) 

The CDT sensor family is configurable up to 4 conductors 48Arms capable. It allows 1 and 3 phases systems which offers an optimized leakage current measurement of configurations by design. 

Main features and technical advantages

  • Automotive qualified  -40 to +125 °C (AEC-Q100 and 200 components) 
  • Up to 48 A RMS current per primary conductor 
  • Primary current measurement range: ±300 mA DC 
  • External test via dedicated pin 
  • SPI and digital tripping outputs 
  • Compact design for PCB mounting 
  • Excellent accuracy ±0.5 mA 
  • Fast Tripping 
  • Reinforced galvanic insulation. 

Typical applications

  • On Board Charger:
    • Automotive OBC up to 22 kW
  • Off board Charging:
    • Mode 2: In Cord – Control and Protection Device (IC-CPD)
    • Mode 3: Wall box chargers

Functional safety (SF version only)

  • ISO26262 ASIL B.


  • IEC 62752
  • UL 2231

CDT Series - Download & Technical characteristics

ProductDocumentStandardMax primary
current (ARMS)
Range (ADC)
Tripping signal
(leakage threshold)
Application note
SPI Specification
3D Blackbox
40/80±300 mA DCup to 4DC - 2 kHzAdjustable / Factory set
Application note
SPI Specification
3D Blackbox
VDE 0664-400,
40/80±300 mA DCup to 4DC - 2kHz
Adjustable / Factory set

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