tle4998 Infineon Technologies Corporation, tle4998 Datasheet - Page 11

• Manufacturer Part Number: tle4998
• Description: Programmable Linear Hall Sensor
• Manufacturer: Infineon Technologies Corporation

Figure 5
4
There is only one parameter set stored in the TLE4998 to calculate a single implemented polynomial. This means
that the new user polynomial is not stored separately in the sensor, but needs to be combined with the
precalibration polynomial. The new parameter set is then again stored back to the sensor. The reason is simply
that the calculation must only be done once (at start of life). Further advantages are
•
•
•
The user sensitivity
find the final DSP sensitivity
deviation from a constant output over temperature. This means that we want to find
which lead to
where a constant Cst is included, which is independent of temperature and can therefore be accounted for with
the GAIN factor set during the two-point calibration and
function of the temperature and has to be minimized. Due to the fact that a second order (user) and a third order
polynomial (DSP) are multiplied, it is not possible to find an exact final DSP polynomial. Since the second and
especially the third order term are comparably small, it is however possible to find sufficiently accurate parameters
expressed as
User’s Manual
Temperature Coefficient Setup Guide
S
TL
ε T ( )
DSP final
DSP final
It saves required EEPROM bits for the second parameter set
It improves reliability (easier protection of less “influencable” EEPROM bits)
It reduces power consumption for the calculation of this second polynomial
k
1
2
3
4
5
6
7
8
=
,
,
-------------------------------------------------------------------------- - 1
Cst S
T ( )
⋅
T
Example of User Parameter Retrieval Using Microsoft Excel
TC Setup Part 2 - Calculating the New EEPROM Values
and
k
100
120
-40
-20
25
50
75
0
[°C]
DSP pre
=
S
DSP final
Cst S
1,440
1,420
1,400
1,380
1,360
1,340
1,320
1,300
1,280
1,260
TQ
,
S
OUT(T
,
user
⋅
DSP final
-50
T ( ) S
89,0
88,7
88,2
87,8
87,3
86,5
86,0
85,3
DSP pre
k
T ( )
) [%DC] S
,
T ( )
⋅
,
user
must therefore be combined with the precalibration DSP sensitivity
y = 2,135E-06x
S
, in the available parameter space to minimize the error
DSP final
T ( ) S
T ( )
user,unnorm
⋅
,
0
–
1,282
1,292
1,309
1,323
1,340
1,370
1,389
1,416
user
.
(T
T ( )
k
) [-]
T ( )
2
+ 6,550E-04x + 1,305E+00
, which must be chosen such as to minimize the overall system
⋅
(
T (°C)
1
50
+
ε T ( )
TC Setup Part 2 - Calculating the New EEPROM Values
11
)
ε T ( )
,
100
is the residual error of the calculation, which is a
y = a + bx + cx
a =
b =
c =
S
T0
TC1
TC2
Temperature Coefficient Setup Guide
user
user
user
user
= 1 + TC1
=
=
=
2
user
150
(T-T0
user
TL
1,31E+00 [-]
6,55E-04 [°C
2,14E-06 [°C
) + TC2
DSP final
1,64 [ppm/°C
502 [ppm/°C]
0 [°C]
,
user
Suser,unnorm(Tk) [-]
Quadratic fit
(T-T0
ε T ( )
Rev 1.1, 2008-10-30
-1
-2
]
]
and
user
2
, which can be
S
]
)
2
DSP pre
TQ
TLE4998
,
DSP final
T ( )
,
(13)
(14)
to
,