MLX90277

Dual Programmable Linear Hall Effect Sensor

3901090277

Page 13 of 21

Data Sheet

Rev 004

Nov/06

The value of TempCo is often determined by the magnet. In the application the TempCo is adjusted to

compensate for the temperature coefficient of the magnet. To adjust the value the look up table is read from

the device. The parameters are then calculated to match the desired value. The Melexis PTC hardware and

software tools contain built in functions for programming the TempCo.

TempCo Range (ppm / °C)

Accuracy (ppm / °C)

0 to 500

± 100

500 to 1200

± 150

1200 to 2000

± 200

Table 12: TempCo Accuracy

Note: The budget error of the whole system, the compensation mismatch (system vs. IC) tolerance should be

taken into consideration during the design. Table 11 is valid for Rough Gain within the specified option code.

See section 10.4 for information on selecting the option code.

10.9 Diagnostic Output Level (FAULTLEV)

The MLX90277 sensors' EEPROM memory content is secured through a parity check. This self-diagnostic

feature brings the output to a defined range in case of a parity error. The parameter, FAULTLEV, is used to

define the parity error diagnostic state. With the FAULTLEV set to 0 a parity error event will result in an

output diagnostic voltage low. With the FAULTLEV set to 1 a parity error event will result in an output

diagnostic voltage high. To get rid of the output load influence the output diagnostic voltage level can be

software and hardware tools have built in functions for calculating and programming the parity.

Note: The MLX90277 sensors' EEPROM is also redundant. Each parameter bit is written in three separate

cells and a “majority voting” is applied to determine its status. A parity error is detected only if two out of the

three cells unexpectedly change state. The bits available for the customer ID are not redundant.

10.10 The EEPROM, Parity and Melexis CRC

The memory cells of the EEPROM are arranged in a table of four columns and one hundred twenty eight

rows. This configuration gives redundancy to the parameters stored in the EEPROM. Each parameter bit is

written in three separate cells in an individual row. A majority voting applied to the three cells determines the

logic status of the bit.

A parameter bit only toggles state in error if two out of three memory cells, within a row, unexpectedly

change. If this happens the feature, PARITY, forces the output voltage to the FAULTLEV diagnostic level.

This ensures the device does not operate with a critical memory fault.

The remaining memory cells are used for data storage. The status of these cells does not effect the device

operation. For example the Customer ID, CUSTID, is stored in this area. Melexis stores the device ID

information, TempCo look-up table and CRC bits in the extra cells. The CRC bits ensure the integrity of the

Melexis data.

Note: To avoid parity and CRC errors, the entire contents of the EEPROM must be read before

programming. Melexis PTC software and hardware tools have built in functions for reading the EEPROM and

handling parity.