MLX91220KDF-ABF-117-SP Integrated Current Sensor IC Comprehensive Guide

Features and Benefits

▪ Factory trimmed AC and DC current sensor

▪ Analog ratiometric or fixed output voltage

▪ Combining sensing element, signal conditioning & isolation in SOIC package

▪ No application programming required

▪ High speed sensing

▪ DC to 300kHz bandwidth

▪ 2µs response time

▪ Robust against external magnetic fields

▪ No magnetic hysteresis

▪ Double overcurrent detection (SOIC-16)

▪ Low ohmic losses of integrated conductor

▪ 1.09mΩ SOIC-8 / 0.89mΩ SOIC-16

▪ SOIC-8 narrow body and SOIC-16 wide body package, RoHS compliant

▪ Lead free component, suitable for lead free soldering profile up to 260°C, MSL3

▪ Rated voltage isolation

▪ 3550 VRMS for SOIC-8

▪ 5400 VRMS for SOIC-16

▪ Suitable for Basic and Reinforced voltage isolation

 


Applications

▪ AC and DC Chargers

▪ Electric Drives

▪ DCDC converters

▪ Solar

▪ Power Supplies

▪ Demand/Load control

 

Description

The MLX91220 is an Isolated Integrated Current Sensor that senses the current flowing through the low impedance leadframe of the SOIC package. By virtue of fixing the current conductor position with respect to the monolithic CMOS sensor, a fully integrated Hall-effect current sensor is obtained, that is factory calibrated.

 

Inside the package, the magnetic flux densitygenerated by the current flow is sensed differentially by two sets of Hall plates. As a result the influence of external disturbing fields is minimized in the fast analog front-end. The residual signal is amplified to provide a high-speed linear analog output voltage.

 

The close proximity of the Hall plates to the current conductor ensures a high signal-to-noise ratio and an accurate signal over temperature. Even with this miniaturization, high voltage isolation ratings are still maintained between the primary and the opposing secondary side.

 

 


The sensor can be used in 2 different modes, depending on the application. Both modes rely on the output voltage of the sensor being proportional to the flow of current, but the difference resides in the signal reconstruction.

 

No matter if the VDD line is at 5V or deviating +/-10%, the ADC code for a given measured current will always be the same as the ADC is supplied by the same voltage as the sensor. The sensor has a sensitivity expressed in %VDD/A.

 

In this particular case the ADC does not necessarily share the same supply voltage with the sensor. For this reason, the sensor is calibrated with an absolute sensitivity regardless of the actual supply voltage. The output signal can be reconstructed by taking the difference between the output and the reference voltage from the IC. The ADC gets these two signals as inputs for establishing the sensed current accurately, and is not influenced by the supply voltage differences between both sensor and microcontroller, if applicable.

 


 

MLX91220 General Electrical Specifications

DC Operating Parameters at VDD = 5V (unless otherwise specified) and for TA as specified by the Temperature suffix (K)

 

MLX91220 General Current Specifications

DC Operating Parameters at VDD = 5V (unless otherwise specified) and for TA as specified by the Temperature suffix (K)

 

MLX91220 Timing Specifications

DC Operating Parameters at VDD = 5V (unless otherwise specified) and for TA as specified by the Temperature suffix (K)

 

Diagnostics

It is possible to take advantage of diagnostic features, with the help of adding a pull-down resistor (see Section 16).

If a failure event occurs, the measured output will be set to ground. This can be interpreted as failure by the microcontroller unit.

 

MLX91220KDx-ABF-117 Specifications

DC Operating Parameters at VDD = 5V (unless otherwise specified), for TA as specified by the Temperature suffix (K) and for TJ < 150 °C

 

MLX91220KDx-ABR-025 Specifications

DC Operating Parameters at VDD = 5V (unless otherwise specified), for TA as specified by the Temperature suffix (K) and for TJ < 150 °C.

 

MLX91220 Overcurrent Detection

The MLX91220 provides two OCD features that allow detecting overcurrent applied on the integrated sensor primary. In case of OCD detection, the OCDINT or OCDEXT is pulled to ground. During normal operation the OCD voltage remains at VDD. This OCD feature is available for SOIC16 version only.

 

The two OCD functions are able to react to an overcurrent event within few us of response time. To avoid false alarm, the overcurrent has to be maintained at least 1µs for the detection to occur. After detection by the sensor the output flag is maintained for 10µs of dwell time. This allows the overcurrent to be easily detected at microcontroller level.

 

Internal Overcurrent Detection Principle

The internal OCD takes fixed threshold voltage values predefined in the EEPROM and do not require any extra components. The OCDINT implementation allows detecting overcurrent outside of the output measurement range of the sensor and is therefore suitable for large current peaks as occurring during short-circuit. If the theoretical sensor output overcomes the OCDINT voltage threshold, the overcurrent event is flagged on OCDINT pin. The default OCD threshold voltages are defined as follow, but other values can be set on request. The overcurrent threshold in ampere is deduced from the sensitivity of the sensor [mV/A] and the OCDINT threshold voltage.

 

External Overcurrent Detection Principle

The external OCD uses the voltage applied on VOCEXT pin as threshold voltage. This translates into an overcurrent threshold in ampere depending on the sensitivity of the sensor. A voltage divider on VOCEXT allows defining the threshold voltage in a custom way. Depending on the voltage divider configuration, the OCDEXT can be used either in bidirectional or unidirectional mode. The External OCD threshold is defined within the measurement range of the sensor output. This feature is then suitable for out-of-range detection where the OCD threshold remains close to the nominal current. It offers a better accuracy than OCDINT but the response is slower. The below table presents the unidirectional and bidirectional external OCD configurations. Please refer to section 13.1 and 13.3 for more details about the application diagram and the recommended resistances.

 

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