(1) If output current and voltage specifications are exceeded, linearity will be degraded.
(2) If V
OQ
is programmed beyond these limits, the temperature compensation may become a problem at high tem-
peratures. It is not recommended to program values of V
OQ
below 1V or above 4V when sensitivity exceeds 100
mV/mT. Temperature instability can occur on some devices under these conditions.
(3) Bandwidth is inversely proportional to ROUGHGAIN.
(4) Peak to Peak Noise is a function of ROUGHGAIN setting. See page 5, Peak to Peak Noise versus Sensitivity.
(5) Sensitivity drift is independent of other parameters and does not include individual tolerances (∆V
OQ
or
∆V
OQ
/∆T).
The tolerance for sensitivity is + 1% of its initial value. This does not include tolerance stack-up.
(6) If the impulse occurs in the middle of a sample interval, the small signal response delay will double. If a 50% to
100% impulse, slew rate may result in double or triple delay.
(7) 1 mT = 10 Gauss
Melexis Inc. reserves the right to make changes without further notice to any products herein to improve reliability, function, or design. Melexis does
not assume any liability arising from the use of any product or application of any product or circuit described herein.
MLX90215 Programmable Hall Effect Sensor
Rev 4.3
7/6/01
Page 2
Precision Programmable*
Linear Hall Effect Sensor
MLX90215
*Patent Pending
How does it Work?
The MLX90215 programming is done through the
output pin, by changing supply voltage levels. Please
note that the V
DD
is raised to approximately 13V and
18V during programming.
Any connected
components must also tolerate this voltage
excursion.
When the supply voltage is at 4.5V to
5.5V, the output behaves normally. If the supply
voltage is raised to 13V, the output then behaves as an
input, or LOAD mode, allowing the 31-bit word to be
clocked in. All data is loaded through a single line,
with no dedicated clock signal. Clock and data are
integrated into one signal which is initiated with the
beginning of the L
OAD sequence, then clocked with
the positive edge of each bit. Variables are changed
with the PC software and loaded into the temporary
register of the device (RAM) via the timings of the
programmer’s microcontroller. Data can be loaded as
many times as desired while in LOAD mode. Once a
word is loaded, results are checked by observing the
output voltage. This can be done with an external
Voltmeter attached directly to pin 4 of the device, or
with the internal ADC of the programmer. Once the
desired program is loaded, the word can be “Zapped”
permanently into ROM.
This is done when the supply voltage rises above 18V,
or ZAP mode, c
reating enough current to “Zap” 31
zener diodes which correspond to the temporary
register. The ZAP function is a one-time function and
cannot be erased.
The above description is only for reference. The
voltage levels and data transfer rates are completely
controlled by the ASIC programmer. For more
information on the programmer hardware, contact
Melexis and request a datasheet for the SDAP
programmer.
Programming The Quiescent Offset Voltage (V
OQ
)
10 bits, 1024 steps of resolution, are allotted to adjust
the Quiescent Offset Voltage (V
OQ
). By utilizing the
HALFVDD function, the V
OQ
can be set to one of two
ranges. With the HALFVDD function disabled, the
V
OQ
can be programmed within a range of 10% to 90%
V
DD
with about 5mV per step resolution. With the
HALFVDD function enabled, the device may be
programmed within a 2V to 3V window with less than
1mV per step resolution
Programming the Sensitivity (Gain)
The sensitivity is programmed with a ROUGHGAIN
and a FINEGAIN adjustment. The ROUGHGAIN is
adjusted by utilizing three bits, or 8 increments. The
FINEGAIN is programmed with 10 bits or 1024
increments. The sensitivity can be programmed within
a range of 5mV/mT to 140mV/mT. Another 1
-bit
function allows the direction of the sensitivity to be
reversed. The INVERTSLOPE function, when
activated, will cause the Voltage output of the
MLX90215 to decrease in the presence of a South
magnetic field, and to increase in the presence of a
North magnetic field. Table 2 expresses examples of
sensitivity resulting from programming ROUGH
GAIN and FINE GAIN codes, with the INVERT
SLOPE function turned off.
Note:
Tables 1 and 2 are examples how various codes affect the
Table 2 - Programming Sensitivity
RoughGain
0
0
1
1
2
2
3
3
FineGain
0
1023
0
1023
0
1023
0
1023
0
1023
0
1023
0
1023
0
1023
7/6/01
Output
4.1
9.4
6.2
14.6
9.5
22.4
14.2
33.1
21.5
50.4
31.3
72.5
46.2
107
68.9
140
Units
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
mV/mT
Table 1 - Programming Offset Voltage (V
OQ
)
HalfVDD
0
0
0
1
1
1
OffsetDAC
0
512
1023
0
512
1023
Output
4.97
2.47
0.03
3.07
2.45
1.83
Units
V
V
V
V
V
V
Rev 4.3
4
4
5
5
6
6
7
7
MLX90215 Programmable Hall Effect Sensor
Page 3
Precision Programmable*
Linear Hall Effect Sensor
*Patent Pending
MLX90215
Temperature Compensation
Temperature compensation (TC) is defined as the
change in sensitivity over temperature. Expressed in
(Parts Per Million per Degree Celcius) ppm/
o
C.
TC
=
Sens
T
1
−
Sens
T
2
1
ppm
∗
∗
10
6
o
Sens
25
T
1
−
T
2
C
Sens
T1
= Sensitivity measured at Temperature 1 (T1)
Sens
T2
= Sensitivity measured at Temperature 2 (T2)
Sens
25
= Initial Sensitivity measured at 25
o
C
Table 3 - Temperature Compensation
TC Code
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Min
-600
-535
-465
-390
-300
-235
-150
-85
125
125
210
285
450
535
600
680
1150
1230
1320
1405
1490
1575
1665
1750
2165
2340
2425
2500
2595
2680
2710
2775
Typical
-450
-385
-315
-240
-150
-85
0
65
275
360
435
515
600
685
750
830
1300
1380
1470
1555
1640
1725
1815
1900
2365
2490
2575
2650
2745
2830
2910
2975
Max
-300
-235
-165
-90
0
65
150
215
425
510
585
665
750
835
900
980
1450
1530
1620
1705
1790
1875
1965
2950
2565
2640
2725
2800
2895
2980
3110
3175
Units
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
ppm/
o
C
Programming the Temperature Compensation
The MLX90215 has a 5-bit (32 step) programmable
adjustment that changes it’s sensitivity drift over a
given temperature range. By adjusting the TC code
the sensitivity can be programmed to increase as
temperature increases to counteract the decrease in
magnetic flux most magnets display over temperature.
For example a SmCo (Samarium Cobalt) magnet has a
temperature coefficient of approximately – 300 ppm/
o
C. The MLX90215 can be programmed with a TC of
300 ppm/
o
C to counteract the TC of the magnet and
greatly improve linearity over temperature.
Table 3
(left) illustrates the way the TC code affects
the sensitivity temperature drift. Also note in Table 3,
the overlap in TC codes. The numbers in the table
represent typical results and are for reference only.
For accurate results the TC code must be determined
experimentally. This Tc code map applies to
MLX90215’s with a second line brand showing
“15DXX”
Special Note
The MLX90215 programmed with a zero TC code
(default) has a typical TC value between the range of –
300 to –600 ppm/
o
C. This means sensitivity will
decrease slightly as temperature increases. The
slightly negative initial TC value allows the
MLX90215 to be accurately programmed up to 0 TC.
Almost all magnets have a naturally negative TC code.
The natural TC of a magnet added with the initial
negative TC value of the MLX90215 could degrade
linearity over a large temperature span. Using a TC
code of 6, 7, or 8 will give the MLX90215 a slightly
positive TC code.
Early revisions of the MLX90215 with second line
brand of “15AXX” should refer to factory for Tc code
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