T L E 4 9 9 7

T L E 4 9 9 7
Application Note, V 1.00, December 2007
TLE4997
2-Point Calibration Guide
Sensors
Edition 2007-12
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2007 Infineon Technologies AG
All Rights Reserved.
Legal Disclaimer
The information given in this document shall in no event be regarded as a guarantee of conditions or
characteristics. With respect to any examples or hints given herein, any typical values stated herein and/or any
information regarding the application of the device, Infineon Technologies hereby disclaims any and all warranties
and liabilities of any kind, including without limitation, warranties of non-infringement of intellectual property rights
of any third party.
Information
For further information on technology, delivery terms and conditions and prices, please contact the nearest
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TLE4997-2P Guide
1
1.1
1.2
1.3
1.4
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Concept of TLE4997 2-point calibration setup . . . . . . . . . . . . . . . . . . . . . . .
Principle signal processing operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Signal Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
2.1
2.2
2.3
2.4
2.5
2.5.1
2.5.2
Mathematical background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Influence of the DSP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Influence of the Hall probe and output DAC . . . . . . . . . . . . . . . . . . . . . . . . 7
Calibration of the application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Conversion table for the G and OS value . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Rough manual calculations and simple experiments . . . . . . . . . . . . . . . . . 10
Using pre-calibrated samples to check out an application . . . . . . . . . . . 10
Using pre-calibrated samples to do a rough 2P calibration . . . . . . . . . . 11
3
3.1
3.2
3.3
3.4
3.5
2P setup flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Measurement setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Read out the required data of the magnetic circuit . . . . . . . . . . . . . . . . . .
Determine the exact DAC values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Determine the gain/offset values for programming . . . . . . . . . . . . . . . . . .
Procedure overview as summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application Note
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Revision history
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Application Note
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Overview
1
Overview
1.1
General Information
• This document is valid for all TLE4997 products and derivatives.
• It is intended as add-on to the current available TLE4997 target and/or data sheets.
• It is recommended to read the programming description of this device prior to this
document.
• It gives an overview and detailed description of the 2-point calibration concept (align
magnetic field to output voltage) of the TLE4997.
1.2
Concept of TLE4997 2-point calibration setup
The concept is based on shifting as much as possible of the on-chip sensor signal
processing to the digital domain. This can be achieved by directly converting the output
of the Hall probe, without additional analog pre-processing. The range setup is also done
directly in the first stage of the used sigma-delta analog-to-digital converter (Hall ADC).
This principle we call magnetic-to-digital conversion (MDC).
By doing that, and of course by using an Hall ADC with outstanding performance, the
compensation requirements are mainly reduced to the magnetic circuit or mechanical
behavior of the application and of course the Hall probe itself. All other parts do no longer
have any significant depedency on the temperature.
Figure 1 shows the principle in a simplified block diagram.
Tj
fixed biasing
MAGNETIC
CIRCUIT
(B-Field)
Hall probe
A
D
A
D
DSP
D
A
OUTPUT
VOLTAGE
(ratiometric)
range setup
EEPROM
Figure 1
Simplified Block Diagram
By providing an accurate digital calibration of the sensor temperature behavior (during
pre-calibration by Infineon Technologies), the user setup depends only on analyzing the
application temperature behavior correctly. After this step, the behavior of output voltage
to given magnetic field is easily determined by setting only two parameters. The
TLE4997 incorporates an analog (ratio metric) output stage, but also future derivates
with digital interfaces will build on the same methods to allow seamless transitions.
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Overview
1.3
Principle signal processing operation
Figure 2 show the main data processing steps of the TLE4997 digital part:
Hardware-trigger
(~16kHz)
T_ADC sample
rate ~ 400 SPS
compensate TADC value (IFX),
subtract TR value,
store it toT_CAL
Calculate and
store O_TC out of
TCAL (IFX)
multiply TL value
with TCAL, store it
multiply TQ value
with TCAL*TCAL,
add it to previous
multiply TT value
with TCAL*TCAL²,
add it to previous
and store S_TC
H_ADC sample
rate ~ 16k SPS
Subtract TOFF
from H_ADC
value, mutiply it
with TGAIN and
store it asH_CAL
Multiply GAIN with
HCAL and
subtract OFFSET,
store it to VALUE
Check clamping
limits CH/CL and
set then V_DAC
Wait for next
trigger
Figure 2
Data processing flowchart
As illustrated, the processing occurs with the same data rate as the Hall-ADC update
rate with typical 16k SPS (samples per second). This happens due to a hard link of the
Hall-ADC-value updates from the decimation filters to the DSP data processing.
Therefore it needs to process the new output data within that time frame.
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Overview
1.4
Signal Flow
Figure 3 shows a the signal flow diagram including important internal data values.
Range
LP
H_ADC
V_DAC
Limiter
Gain
(Clamp)
Hall
Sensor
Temperature
Sensor
T_ADC
A
D
P
-T0
A
P
D
X
X
D
A
TC 2
X
+
DAC_SET
H_CAL
X
1
TC1
out
LP DAC
Offset
X
+
Stored in
EEPROM
Memory
internal device
pre-calibration
P
T_CAL
Temperature
Compensation
Figure 3
+
Block Diagram
Note: This is just given as reference - please check out the programming description
(application note) for details about how to access and use this values.
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Mathematical background
2
Mathematical background
To describe the overall behavior of the IC, we need to separate now between the
calculated temperature behavior of the DSP and the natural (physical) temperature
behavior of the Hall probe.
2.1
Influence of the DSP
All processing happens in a deterministic way using integer operations. To reconstruct
this behavior in a simulation model, this needs to be considered. Otherwise (when using
just simple models using floating point operations e.g. in tools like SimulinkTM) some
notifiable truncation effects could lead to small inconsistencies between the reality and
the model. Nevertheless the system is designed in a way that this error should be always
less than one LSB for the resulting output value V_DAC.
Therefore it is necessary to know that the calculations within one line shown in the table
below use 20bit (signed) integers and that the results itself are stored in 16bit (signed)
integers. All combined “multiply and shift right” operations use virtually a broader integer
width (20bit plus the amount of bits shifted right) due to the used mechanism in the
processor.
When storing a value, a proper saturation is taking place, so that there is no clipping for
too big/small results of any calculation. On the other hand, when using a value in an other
equation, a proper sign extension is performed.
Table 1
Equations performed
Internal value (16bit)
Calculation (20bit integer operations)
Tint
Tj*16 (IFX calibrated junction temperature from T_ADC in °C)
T_CAL
Tint + 768 - TR*256 (Tint is already truncated as integer value)
O_TC
IFX calibrated (and T dependent) offset value
S_TC1
8192 + ((TL-160)*T_CAL)>>7
VALUE1
(T_CAL*T_CAL)>>10
S_TC2
((TQ-128)*VALUE1)>>8 + S_TC1
VALUE2
(T_CAL*VALUE1)>>11
S_TC
((TT-64)*VALUE2)>>8 + S_TC2
H_CAL
((((H_ADC*3)>>1) + O_TC)*S_TC)>>13
VALUE
((G-16384)*H_CAL)>>15 + OS - 16384
V_DAC
VALUE
(but limited to given CL and CH values)
Note: This document describes only the bold lines above. The temperature
compensation calculation is described in a separate application note.
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Mathematical background
For a better overview, the calculation of the output value can be also written simplified as:
V _ DAC =
( G − 16384 ) ⋅ H _ CAL
+ OS − 16384
32768
To get a voltage for the output value, it needs to be divided by 4095 and multiplied by the
Vdd value. Of course, if a clamping limit is set, the output value would be limited to it, too.
Note: Please remember that the ratiometric output has also physical limitations, which
reduces the possible range of the V_DAC value. See specification for details.
2.2
Influence of the Hall probe and output DAC
The precalibrated Hall sensor has a typical sensitivity of about 60mV/mT in the 100mT
range and a zero-field offset voltage of 2.5V at 5V Vdd (not guaranteed). This
sensitivity/offset values need to be adopted to the application by performing a magnetic
field to output voltage calibration.
Nevertheless some typical values of such a precalibration are shown in Table 2 - please
note that this values of course vary from part to part:.
Table 2
Typical system values
System value
Value range in 100mT range
Applied field
-100mT ... +100mT
H_ADC (ADC REG.)
-17519 ... +17519 (independent of LP setting, in 100mT range)
S_TC (DSP REG.)
~ 8192 ... S(T)=S_TC/8192=1, dep. on TC setup (±30% max.)
O_TC (DSP REG.)
~ 0 ... varies over T to compensate for Hall probe/ADC offset
H_CAL (DSP REG.)
-26278 ... +26278 (limits at -32768...32767 as it is 16bit)
GAIN (EEPROM)
~ 22500 (this is approx. a factor of 1.5 to set 60mV/mT)
OFFSET (EEPROM)
~ 18432 (this delivers approx. 2,[email protected] Vdd at zero field)
VALUE (DSP REG.)
-4914 ... 4914 (internal calculation result)
V_DAC (DSP REG.)
0 ... 4095 (and possibly limited to given CL and CH values)
For full range, the H_ADC has a typical allowed dynamic range of up to 2/3 of the
maximum possible range represented by a 16 bit integer value (-32768...+32767) in the
H_ADC register (which means approximately +/- 20000 max.). Above this point, the
H_ADC will start to saturate. A certain production spread is needed to be covered, too
(+/-15% are used as savety margin). So the typical seen H_ADC values at the required
full-range magnetic input (flux density value) applied to the sensor will be approximately
15% below the considered ADC limit (see table above). It is important to note that the
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Mathematical background
ADC value is 100% independent of the lowpass filter setting (the lowpass filter has only
effect on the noise of the signal, not its value directly).
Saturating the H_ADC input is seen as a nonlinear behavior and an increase of noise in
the signal. This saturation is a smooth process, but finally the H_ADC value saturates at
the (lower or upper) numeric limit. During calibration, it is important to check that the
H_ADC value is always within the decimal range of -20000 to +20000. Otherwise the flux
density of the application is outside the allowed limit and it is recommended to use the
next lower magnetic field range to fully avoid any saturation problems.
The sensitivity temperature compensation of the Hall probe introduces a fixed gain factor
of 1.5 which is temperature dependent (see temperature compensation application
note). This increases the dynamic range to fit the 16 bit representation in the H_CAL
register more ideal (approx. +/-30000 max., again the typical values seen are 15%
smaller to cover production spreads). This is done not directly for accuracy increase, but
for minimizing truncation effects of the digital signal processing itself.
Finally, the output related sensitivity and offset setup is done. The result is kept in a 16
bit integer register called VALUE. The relation between VALUE and H_CAL is as follows:
when setting the gain register to 1.0 (which means G=16384+4096 decimal, according
to the product specification), the resulting VALUE is 1/8 smaller than the H_CAL register.
For a maximum gain of +3.999 or -4.0 (this is G=32767 or G=0 decimal) the final VALUE
is 4/8 (= half) of the H_CAL value. The purpose of that is removing the “noisy LSBs” of
the H_CAL signal.
However, at the end the 12 bit positive integer range (0 to 4095) of VALUE is used for
the output DAC value in the V_DAC register, everything outside is clamped to the
nearest maximum border value (0 or 4095). Of cause for OBD functionality the ranges
can be restricted even more using the digital clamping value registers (both are again 12
bit).
Figure 4 shows the calculation procedure from the H_CAL value to the V_DAC value in
a simplified flow diagram.
-4.0 … +3.999
-400% to 399.9%
0%...100%
EEPROM:
Gain
EEPROM:
VOS
EEPROM:
VCLH
Vdd
Usable range:
5%...95%
X
H_CAL
gain setup
:8
+
VALUE
V_DAC
A
clamping
Vout
(ratiometric)
offset setup
-30000…+30000
(maximum
allowed)
EEPROM:
V CLL
0%...100%
Figure 4
D
0…+4095
(maximum
possible)
0%…100%
(theoretical,
without el.
saturation)
Simplified Calculation Flow Diagram
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Mathematical background
2.3
Calibration of the application circuit
For a complete calibration procedure, five steps need to be performed:
1. Read-out the EEPROM and setup the temperature compensation parameters using
the temporary EEPROM registers - this is the base for the 2P calibration.
2. Find the ideal DAC values (of both positions and if required of both clamping limits) by
measuring the voltage output while testing several V_DAC vaues using a special DAC
test mode (overrides the actual V_DAC value calculated by the DSP).
Optionally it is possibly just to take the simple equation:
DAC = 4095 * required_voltage / vdd_voltage
In this simplified way a possible residual output gain/offset error from the analog
output stage of the sensor is not canceled out. Nevertheless it also removes the
requirement to measure the output voltage for calibration. Of course in this case the
specified limits as defined in the 2-point calibration specification of the datasheet can
not be fulfilled anymore.
3. Acquire the H_CAL values at (at least) two magnetic flux density values (positions) via
the sensor interface (see application note for programming).
4. Calculate the corresponding G and OS values (which fit to the determined V_DAC
values and measured H_CAL values).
5. Setup, program (and possibly lock) the EEPROM.
This document describes the items 2-4, the first and last item are described in separate
documents.
2.4
Conversion table for the G and OS value
This table should help when mapping different notations for the H_CAL value, V_DAC
value, G parameter and OS parameter for the 2-point calibration:
Table 3
Mapping between important 2P values/parameters
Definition
Description
Range
Corresponds to
H_CAL
Calibrated Hall ADC
value as the input
value for the linear
field-to-output
mapping.
-30000 to +30000
maximum allowed otherwise use next
range setup
-FSR to +FSR (full scale
range) of Hall probe and Hall
ADC (temperature
calibrated), e.g. -100mT to
+100mT in the middle range.
V_DAC
Corresponding
output DAC value
for the linear fieldto-output mapping.
0 to 4095 max. nevertheless
values may be
possible clamped
(clamping registers)
0 % to 100% (theoretical) of
the ratiometric output voltage
(= Vout / Vdd [%] ), note that
the output is saturating at
upper/lower limits.
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Mathematical background
Table 3
Mapping between important 2P values/parameters
Definition
Description
Range
Corresponds to
G
Defines the
amplification factor
from the input value
to the output value.
0 to 32767 max. value is shifted in
the DSP by 16384
to generate +/integer values
-4.0 to +3.999 max. a gain of 0.0 corresponds to
a value of 16384. See
datasheet for this mapping.
OS
Defines the offset
shift for the output
value.
0 to 32767 max. value is shifted in
the DSP by 16384
to generate +/integer values
-400.0% to +399.9% of the
output ratio Vdd/Vout - a offset
of 0.0% corresponds to a
value of 16384. See
datasheet for this mapping.
2.5
Rough manual calculations and simple experiments
For first checks it makes sometimes sense to verify if a certain setup is feasible or
plausible. Here some examples for hand calculations are given for demonstration.
2.5.1
Using pre-calibrated samples to check out an application
When using pre-calibrated samples, it is possible to roughly estimate the flux density
values directly - even without programming, as long as it is within the default setup range.
Example:
An application using the pre-calibrated TLE4997 delivers following values:
- Vdd (the supply of the sensor) is set to 5V.
- At the first position of the application setup the output measured is Vout = 1.7V.
- At the second position of the application setup the sensor output given is Vout = 4.1V.
As the output values are far within the allowed output range from 5% to 95% of Vdd
(which is in this case - at 5V supply - a range of 0.25V to 4.75V), we can assume that the
sensor is not saturated. As the sensitivity Sprecal of a precalibrated samples is roughly
60mV/mT and the zero field offset is 2.5V, the two field values can be calculated:
Vout1 = 1.7V, so the sensor sees a magnetic flux of Bin1 = (Vout1 - Vout_zero) / Sprecal = (1.72.5)/0.06 = -13.33 mT.
Vout2 = 4.1V, so the sensor sees a magnetic flux of Bin2 = (Vout2 - Vout_zero) / Sprecal = (4.12.5)/0.06 = +26.67 mT.
Using this method, magnetic flux values within (0.25-2.5)/0.06=-37.5mT and (4.752.5)/0.06=+37.5mT can be measured and evaluated roughly without any programming.
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Mathematical background
In case of saturating the sensor, it is required to adjust the sensor RANGE to do allow
other measurement limits:
- using the smaller range setting (+/- 50mT) doubles the sensitivity (measures magnetic
flux from -18.75mT to +18.75mT).
- using the larger range setting (+/- 200mT) halves the sensitivity (measures magnetic
flux from -75mT to +75mT).
If this is not sufficient, also the G parameter setting can be modified by useful factors.
E.g. doubling the gain value (multiply by 2) doubles again the sensitivity (and so on).
2.5.2
Using pre-calibrated samples to do a rough 2P calibration
The method explained in the last section can be also used to do a coarse or preliminary
2P calibration without any measurement. Sometimes this might be useful to be done with
just the sensor alone (before the module is set up), as it does not require any further
measurement or programming after the module assembly. Of course this method does
not provide the accuracy as given with a full-featured calibration, but it might be useful
to do a first assembly check before continuing with the final calibration.
Example:
A module provides a magnetic flux of +75mT and -25mT which needs to be mapped to
4.5V and 0.5V, the clamping levels must be set to 4.7V and 0.3V. The precalibrated gain
value is 1.62 and the precalibrated offset value is 50% (sensor read-out).
The +/- 100mT default range is well suited, as both magnetic flux values are well within
the allowed range.
The sensitivity needs to be set in that way that the magnetic flux change from
Bin2 = -25mT to Bin1 = +75mT results in a voltage change from Vout2 = 0.5V to Vout1 = 4.5V.
So the required sensitivity is (Vout1 - Vout2)/(Bin1 - Bin2) = (4.5-0.5) / (+75-(-25)) = 0.04 V/mT
= 40mV/mT.
As the default sensitivity is about 60mV/mT, the gain value needs to be lowered by a
factor of (40 / 60) = 0.667. So the gain must be reprogrammed to (1.62 x 0.667) = 1.08.
For the offset setup, we can proceed as follows:
A magnetic flux of 75mT will cause with the new sensitivity value of 40mV/mT a output
change of (75 x 40) = 3000 mV = 3V. With the default offset setup of 2.5V we would see
on the output (only theoretically) 5.5V, but we need 4.5V. So the offset value needs to
be lowered by (5.5-4.5) = 1V. This corresponds to an ratiometric percentage of (1/5) x
100% = 20%. So it is necessary to set the new offset to (50 - 20) = 30 %. The clamping
parameters need to be set to (0.3 / 5) x 100% = 6% and (4.7 / 5) x 100% = 94% to provide
the required output limits.
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2P setup flow
3
2P setup flow
The previous chapter gave already some examples to demonstrate how the calibration
works basically. Now the generic basic algorithm for the two point setup is shown which
allows the accuracy as specified in the datasheet.
To find a certain gain/offset setup, even more sofisticated methods may be used than
that one described here. Especially if the magnetic field to be measured is not exactly
linear, it might be useful to aquire more points and to do a best fit through all this values.
After describing the basic principle here, it should be easily to enhance this routine for
such purposes.
3.1
Measurement setup
We assume a magnetic circuit setup with a TLE4997 device as illustrated in below figure.
magnetic circuit
(temperature dep.)
T
B(T)
5V
GND
Vout(T)
TLE4997
Figure 5
Principle of a magnetic circuit setup
A stable and accurate 5V DC source (accuracy/stability better +/-0.5 mV) and a good
voltmeter (accuracy better +/-0.1mV) is required. In case of a less reliable DC source, a
second voltmeter (accuracy better +/-0.1mV) measuring the 5V source should be used
(to fetch an accurate ratiometric output value).
Furthermore some programming tool is required to access the TLE4997 using a digital
protocol. This protocol is described in a separate programming application note.
Beside that, the temperature during the setup must kept stable, otherwise the measured
voltage is a mix of the given application setup (e.g. the flux density at a certain position)
and the temperature behavior of the whole system (e.g. used magnet).
When using the PGSISI programmer/demonstration kit for the TLE4997 the ratiometric
output value is directly measured and the temperature is correctly read and displayed.
With this configuration no further measurement equipment is required, but as it is a low
cost device (for a first evaluation only) it does not (and can not) unveil the full
performance of the TLE4997.
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2P setup flow
3.2
Read out the required data of the magnetic circuit
It is necessary to apply the two magnetic flux values to the sensor, which should be later
mapped to the desired output voltages. For current sensing applications this means to
apply two currents, for a positional detection two positions need to be set or for a angular
detection two angles must be applied.
For these two magnetic flux values, the corresponding H_CAL values need to be read.
To reduce errors possibly caused by noise or environmental distortions, it is
recommended to read out the H_CAL value several times and average it. This gives two
values, H_CAL1 and H_CAL2. Check that the values are within the allowed range to
avoid calibration while the ADC might be saturated.
3.3
Determine the exact DAC values
In the next step, the V_DAC values need to be determined for the required output
voltages (we call Vout1 and Vout2). This is done by switching the sensor to the DAC test
mode. Now several DAC values can be applied and the resulting output voltages can be
measured. It is recommended to do this setup with the pull-up/down load applied to
include any voltage drops caused by this resistive currents flowing in/out of the sensor
output. A simple iteration allows determining the exact DAC value of a required output
voltage within a few steps only. The following visual basic code example illustrates this:
’ Vout ... required output voltage (input)
’ Vdd ... given supply voltage (input)
’ Vdac ... determined DAC value (result)
’ SensorDACset() ... routine setting the DAC of the sensor
’ MeasureDeviceOut() ... routine measuring the ratimetric result
’
in percent (0...100)
’ dac, err ... helper values
’ -------------------------------------------------------’ setting up a good DAC starting point
dac = Math.Round ( 4095 * Vout/Vdd )
’ iterate to find the best DAC value
For i = 1 To 10
’ set the sensor dac value using the special test mode
SensorDACset(dac)
’ we calculate, how far we are away from the measured output value
’ we need to stay in the LSB region
err = Math.Round ( MeasureDeviceOut()*4095/100 - 4095 * Vout/Vdd)
If err = 0 Then : Exit For : End If
’ we have a hit -> exit
’ correct the used DAC value
dac -= err
Next
’ we are finished!
Vdac = dac
We end up with two DAC values we call V_DAC1 and V_DAC2.
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2P setup flow
3.4
Determine the gain/offset values for programming
Mathematically, we need to remember the equation how V_DAC is calculated using
H_CAL and the GAIN/OFFSET value stored in the EEPROM.
V _ DAC =
(GAIN − 16384) ⋅ H _ CAL
+ OFFSET − 16384
32768
With the given relations of the internal value V_DAC to the ratiometric output voltage Vout
and the application setup (like a position) to the flux density value B, the relation of
V_DAC to the B value can be shown as a line defined by two points, as shown in
Figure 6.
V_DAC
~ Vout [%]
V_DAC1
~ Vout1
V_DAC2
~ Vout2
H_CAL1
H_CAL2
~ Pos2 (Bin2 )
Figure 6
H_CAL
~ Position (Bin )
~ Pos1 (Bin1 )
Principle of the 2P setup
With these 2 value-pairs and the above equation we can easily calculate the G and the
OS values, again illustrated using avisual basic code example:
’ check if the input values are different to avoid a division by zero
If ( (H_CAL2 - H_CAL1) != 0 ) Then
G = Math.Round(32768 * (V_DAC2 - V_DAC1) / (H_CAL2 - H_CAL1))
OS = Math.Round(V_DAC1 - (GAIN * H_CAL1) / 32768) + 16384
G = G + 16384
Else
’ throw an error message (division by zero, no field applied)!
End If
Application Note
14
V 1.00, 2007-12
TLE4997-2P Guide
2P setup flow
Now we determined the values for the G and OS parameter. Check that they are within
the specified limits before updating the EEPROM parameters settings. You may perform
a temporary setup first, check the result and finally program the data to the EEPROM.
3.5
Procedure overview as summary
To program a new gain and offset parameter for a two-point setup, perform these steps:
– acquire the H_CAL values for two magnetic flux setups
– determine the exact V_DAC values for the two required output voltages
– calculate the G/OS parameters and program the new EEPROM values
The first two steps may be performed in opposite order, it has no impact if the H_CAL
values are read from the sensor after determining the exact V_DAC values.
Application Note
15
V 1.00, 2007-12
w w w . i n f i n e o n . c o m
Published by Infineon Technologies AG
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