tle4998 Infineon Technologies Corporation, tle4998 Datasheet - Page 8

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

2.2
The Hall probe has a higher order behaviour over temperature. Generally, it can be approximated by a sensitivity
where
and
2.3
With the knowledge of the behaviour of DSP and Hall probe, the complete compensated system can be described
as
where the subscript pre refers to precalibration. Inserting
Hall probe behaviour) into
This means that during precalibration at Infineon the parameters
(precalibrated, therefore the subscript pre) to reach an overall “flat” temperature behaviour (constant 100% of
sensitivity over the whole temperature range,
polynomial and calculating its inverse to determine the DSP polynomial.
The measurement during precalibration has a finite accuracy in terms of the applied magnetic fields and
temperatures. This leads to a certain (but small) sensitivity error residue over temperature. Also, the DSP
parameters have some finite quantization. Finally, some minor influences of other parts we neglected might sum
up (e.g. the accuracy of the on-chip temperature). These factors are the main cause for the not 100% perfect
calibration.
2.4
The last step is now to compensate the external magnetic circuitry. Every magnet has some variation in its field
strength over temperature and additional effects of the application (such as thermal expansions) may contribute
to a non-constant magnetic field at one particular position if measured at different temperatures. Modeled as a
sensitivity with respect to temperature changes, we call this application behaviour
allows the user to compensate those effects via a second-order user polynomial
where the three parameters
temperature coefficient),
package a specific thermal resistance
for understanding the principle (based on these explanations) it is not required. Thus, we define
Temperature Coefficient Setup Guide
User’s Manual
S
S
S
S
T
probe
pre
pre
user
is somewhat lower than the junction temperature T
TC3
( )
( )
T
T
T ( )
T
( )
j
j
T
j
probe
j
=
=
is the junction temperature, represented by the
=
=
S
(
⎛
⎝
1
Influence of the Hall Probe
Overall Behaviour of the IC: The Precalibration at IFX
Calibration of the Application Circuit
1
1
probe
1
+
are the linear, quadratic and cubic temperature coefficients of the Hall probe, respectively.
+
+
+
TC1
TC1
TL
------------------------------------------ -
TC1
( ) S
DSP pre
T
user
probe
8 8192
j
probe
⋅
⋅
,
(
T T0
TC2
T
DSP pre
Equation (4)
T
–
j
–
+
j
+
160
user
,
TC2
TC2
user
T0
⎛
⎝
( )
user
probe
TCAL
--------------- -
(quadratic user temperature coefficient) are user selectable. The temperature
T
)
probe
j
16
+
,
TC2
R
T
(Reference temperature for a sensitivity of 1),
(having
thJA
T
⎞
⎠
j
2
j
+
2
+
user
+
TQ
------------------------------------------- -
TC3
. You may want to include this difference later to improve the setup,
TC3
(
1024 8192
T T0
DSP pre
TCAL
probe
S
–
probe
pre
,
⋅
( )
T
j
user
, as the sensor die has a certain power dissipation and the
T
T
j
3
8
–
j
=
Equation (2)
j
)
3
TCAL
)
128
≅
,
16T
2
1
,
⎛
⎝
). This is done by acquiring the probe sensitivity
j
TCAL
--------------- -
–
value used by the DSP, and
16
Temperature Coefficient Setup Guide
768
TR
⎞
⎠
DSP
), we get
2
(the DSP behaviour) and
–
------------------------------ -
32768 8192
,
TT
TL
DSP pre
DSP
⋅
,
S
and
app
Mathematical Background
⎛
⎝
TCAL
--------------- -
T ( )
TQ
16
. The TLE4998 system
DSP
TC1
Rev 1.1, 2008-10-30
TC1
⎞
⎠
3
⎞
⎠
Equation (3)
user
are programmed
T
probe
=
(linear user
TLE4998
T
,
j
TC2
=
T
probe
a
(the
.
(3)
(4)
(5)
(6)