COMPARISON BULLETIN

The NVE SM225 and Melexis MLX90288 are both programmable linear magnetic sensors. The advantages of NVE’s groundbreaking SM225 Smart TMR Magnetometer over the Melexis part are summarized below:

	Technology	Programming	Accuracy  % of full-scale; 0–125°C	Conversion  Rate	Power Supply	Package
Melexis MLX90288	Old-fashioned  Hall-effect	Proprietary off-line Programmer	±2.9%	6.33 kHz	4.5 to 5.5V  55 mW	5 x 4 mm  SOIC8
NVE SM225	TMR	SPI Interface	±2%	7.5 kHz	2.2 to 3.6V 25 mW	2.5 x 2.5 mm   leadless TDFN6

Convenient Magnetic Orientation
Unlike Melexis’s awkward, old-fashioned Hall-effect sensor elements, the SM225 uses TMR, which is sensitive in-plane for optimal current sensing and easy mechanical interfaces.

More Accurate
The SM225 accuracy is ±2% for 0 to 125°C and ±4% for the full –40 to 125°C range. That covers all error sources, including sensitivity, offset, nonlinearity, hysteresis, noise, and supply variation.

If you need even more accuracy, you can use our ultraprecise SM324.

The MLX90288 has a sensitivity drift of ±150 ppm/°C, or ±1.9% over 0 to 125°C, a sensitivity thermal hystersis of ±0.5%, and an offset drift of ±20 LSB or ±0.5%. That’s a total of ±2.9%, compared to 2% for the SM225. The total of just those errors over the full –40 to 125°C range is 4% for the MLX90288, but it has additional errors including DAC linearity, ratiometric error, and output noise, plus an ADC required to redigitize its analog output adds another layer of errorm, meaning the SM225 is also more accurate over –40 to 125°C.

Faster
The SM225 minimum conversion rate is 7.5 kHz compared to 6.33 kHz for the MLX90288.

In-Circuit Programmability
The SM225 has a fast, reliable SPI microcontroller interface. The sensor can be zeroed, calibrated, or parameters other changed in the application.

Digital Interface
The SM225’s SPI interface allows fast polling of digital field and temperature data from one or more sensors using ubiquitous SPI hardware and software support for virtually any microcontroller. The MLX90288’s analog output requires an ADC input for a microcontroller, which adds expense to the microcontroller and another layer of error sources..

The nonstandard Melexis programming interface requires a Melexis programmer and a PC, which is not practical in production.

3V Supply; Lower Power
The SM225 has a modern, versatile 2.2 to 3.6 volt supply and 25 milliwatts or less, compared to 5 volts and 44 milliwatts for the Melexis part. Less self-heating means less temperature drift and more accuracy.

No “Absolute Maximum” Field
There is no field that will permanently damage NVE sensors. The MLX90288 specifies a 2 tesla absolute maximum field, and exceeding it “may cause permanent damage.” That seems dangerous for a device that’s designed to be around permanent magnets.

Smaller
The MLX90288 is in a SOIC8 with a 5 x 4 mm body and a 6 x 4 mm footprint. The SM225 has one-fourth the footprint area with its 2.5 x 2.5 mm leadless TDFN.

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