Final Datasheet Subject to Change Without Notice September 10, 2014
A1332-DS
• 360° contactless high resolution angle position sensor
• CVH (Circular Vertical Hall) technology
• Digital I2C output
• Refresh Rate: 32 µs, 12-bit resolution
• Automotive temperature range –40°C to 85°C
• Two types of linearization schemes offered: harmonic
linearization and segmented linearization
• Linearization features enable use in off-axis applications
• EEPROM with Error Correction Control (ECC) for
trimming calibration
• 1 mm thin (TSSOP-14) package
• Automatic calibration features maintain angle accuracy
over airgap
Precision Hall Effect Angle Sensor IC with I2C Interface
Functional Block Diagram
A1332
Multisegment
CVH Element
Regulator
Analog Front End
Digital Subsystem
To all internal circuits
EEPROM
32-bit
Microprocessor
I2C
Interface
Diagnostics
BYP
CBYP(BYP)
VCC (also
programming)
V+
ADC
SA0
SA1
SDA
VCC
(Programming)
SCL
CBYP(VCC)
DGND
AGND
SOC Die
TEST
Package: 14-pin TSSOP (LE suffix)
Not to scale
The A1332 is a 360° contactless high resolution programmable
magnetic angle position sensor IC. It is designed for digital
systems using an I2C interface.
This system-on-chip (SoC) architecture includes a front
end based on Circular Vertical Hall (CVH) technology,
programmable microprocessor based signal processing, and
digital I2C interface. Besides providing full-turn angular
measurement, the A1332 also provides scaling for angle
measurement applications less than 360°. It includes on-chip
EEPROM technology for flexible programming of calibration
parameters.
Digital signal processing functions, including temperature
compensation and gain/offset trim, as well as advanced output
linearization algorithms, provide an extremely accurate and
linear output for both end of shaft applications, as well as
off-axis applications.
The A1332 is ideal for automotive applications requiring high
speed 360° angle measurements, such as: electronic power
steering (EPS), transmission, torsion bar, and other systems
that require accurate measurement of angles. The A1332
linearization schemes were designed with challenging off-axis
applications in mind.
The device is offered in a 14-pin TSSOP (LE) package, which
has a single die. The package is lead (Pb) free, with 100%
matte tin leadframe plating.
FEATURES AND BENEFITS DESCRIPTION
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
2
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Table of Contents
Specifications 3
Absolute Maximum Ratings 3
Thermal Characteristics 3
Pin-out Diagram and Terminal List 3
Operating Characteristics Table 4
Functional Description 6
Overview 6
Operation 6
Diagnostic Features 8
Programming Modes 8
Application Information 10
Serial Interface Description 10
Magnetic Target Requirements 11
On-Axis Applications 11
Off-Axis Applications 11
Effect of Orientation on Signal 12
Linearization 13
Correction for Eccentric Orientation 14
Harmonic Coefficients 15
PCB Layout 15
Package Outline Drawing 16
Selection Guide
Part Number Application Package Packing* Operating Ambient Tem-
perature, TA
A1332ELETR-T I2C digital output Single die,
14-pin TSSOP 4000 pieces per 13-in. reel –40°C to 85°C
*Contact Allegro™ for additional packing options
Refer to the Programming Reference addendum for information on programming the device.
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
3
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Absolute Maximum Ratings
Characteristic Symbol Notes Rating Unit
Forward Supply Voltage VCC 24 V
Reverse Supply Voltage VRCC –18 V
Logic Input Voltage for I2C Pins VIN –0.5 to 5.5 V
Operating Ambient Temperature TAE temperature range –40 to 85 ºC
Maximum Junction Temperature TJ(max) 165 ºC
Storage Temperature Tstg –65 to 170 ºC
Thermal Characteristics may require derating at maximum conditions, see application information
Characteristic Symbol Test Conditions* Value Unit
Package Thermal Resistance RθJA On 4-layer PCB based on JEDEC standard 82 ºC/W
*Additional thermal information available on the Allegro website
SPECIFICATIONS
1
2
3
4
5
6
7
14
13
12
11
10
9
8
DGND
BYP
DGND
AGND
VCC
VCC
AGND
DGND
SA0
SA1
SCL
SDA
DGND
TEST
Package LE, 14-Pin
TSSOP Pin-out Diagram
Terminal List Table
Pin-
Name
Pin Num-
ber Function
AGND 4, 7 Device analog ground terminal
BYP 2 Internal bypass node, connect with bypass capacitor to DGND
DGND 1, 3, 9,
14 Device digital ground terminal
SA0 13 Digital input: Sets slave address bit 0 (LSB)*; tie to BYP for 1, tie to DGND for 0
SA1 12 Digital input: Sets slave address bit 0 (LSB)*; tie to BYP for 1, tie to DGND for 0
SCL 11 Digital input: Serial clock; open drain, pull up externally to 3.3 V
SDA 10
Digital control output: digital output of evaluated target angle, also programming data
input
I2C data terminal; open drain, pull up externally to 3.3 V
TEST 8 Test terminal, must be tied to DGND for correct operation
VCC 5, 6 Device power supply; also input for EEPROM writing pulse
*For additional information, refer to the Programming Reference addendum, EEPROM Description
and Programming section, regarding the INTF register, I2CM field.
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
4
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Continued on the next page…
Characteristic Symbol Test Conditions Min. Typ.1Max. Unit2
Electrical Characteristics
Supply Voltage VCC 4.5 5 5.5 V
Supply Current ICC – 16 20 mA
VCC Low Flag Threshold3VCCLOW(TH) 4.4 4.55 4.75 V
Supply Zener Clamp Voltage6VZSUP IZCC = ICC + 3 mA, TA = 25°C 26.5 – – V
Reverse Battery Voltage VRCC IRCC = –3 mA, TA = 25°C – – –18 V
Power-On Time4,5 tPO TA = 25°C 2 – 40 ms
I2C Interface Specication (VPU = 3.3 V on SDA and SCL pins)
Bus Free Time Between Stop
and Start4tBUF 1.3 – – µs
Hold Time Start Condition4tHD(STA) 0.6 – – µs
Setup Time for Repeated Start
Condition4tSU(STA) 0.6 – – µs
SCL Low Time4tLOW 1.3 – – µs
SCL High Time4tHIGH 0.6 – – µs
Data Setup Time4tSU(DAT) 100 – – ns
Data Hold Time4tHD(DAT) 0 – 900 ns
Setup Time for Stop Condition4tSU(STO) 0.6 – – µs
Logic Input Low Level (SDA and
SCL pins)6VIL(I2C) TA = 25ºC – – 0.9 V
Logic Input High Level (SDA and
SCL pins)6VIH(I2C) TA = 25ºC 2.1 – 3.63 V
Logic Input Current6IIN VIN = 0 V to VCC, TA = 25ºC –1 – 1 µA
Output Voltage (SDA pin)6VOL(I2C) RPU = 1 kΩ, CB = 100 pF, TA = 25ºC – – 0.6 V
Logic Input Rise Time (SDA and
SCL pins)4tr(IN) – – 300 ns
Logic Input Fall time (SDA and
SCL pins)4tf(IN) – – 300 ns
SDA Output Rise Time4tr(OUT) RPU = 1 kΩ, CB = 100 pF – – 300 ns
SDA Output Fall Time4tF(OUT) RPU = 1 kΩ, CB = 100 pF – – 300 ns
SCL Clock Frequency 6fCLK TA = 25ºC – – 400 kHz
SDA and SCL Bus Pull-Up Resistor RPU –1–kΩ
Total Capacitive Load for Each of SDA
and SCL buses 6CB TA = 25ºC – – 100 pF
Pull-Up Voltage VPU RPU = 1 kΩ, CB = 100 pF 2.97 3.3 3.63 V
1Typical data is at TA = 25°C and VCC = 5 V and it is for design information only.
21 G (gauss) = 0.1 mT (millitesla).
3VCC Low Threshold Flag will be sent via the I2C interface as part of the angle measurement. When VCC goes below the minimum value of VCCLOW(TH)
. the VCC Low Flag is
set. See programming manual for details.
4Min. and Max. parameters for this characteristic are determined by design. They are not measured at nal test.
5End user can customize what power-on tests are conducted at each power-on that causes a wide range of power-on times. For more information, see the description of the
CFG register, which is available in the programming manual.
6This Parameter is tested at wafer probe only.
OPERATING CHARACTERISTICS: valid throughout full operating voltage and ambient temperature ranges, unless other-
wise specied
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
5
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Transducer Output
50
0
Response Time, tRESPONSE
t
Angle
(Degrees)
Applied Magnetic Field
Figure 1: Denition of Response Time
Characteristic Symbol Test Conditions Min. Typ.1Max. Unit2
Magnetic Characteristics
Magnetic Field9B Range of input field 300 – 1000 G
Angle Characteristics
Output10 RESANGLE – 12 – bits
Effective resolution11 B = 300 G, TA = 25ºC, ORATE = 0 – 10.1 – bits
Angle Refresh Rate12 tANG ORATE = 0 – 32 – µs
Response Time13 tRESPONSE
All linearization and computations disabled, see
figure 1, note 12 – 68 – µs
Angle Error TA = 25 to 85°C, ideal magnet alignment, B =
300 G, target rpm = 0, no linearization –2 – 2 deg.
Angle Noise14,15 NANG3Σ
TA = 25°C, 30 samples, B = 300 G, no internal
filtering. – 0.6 – deg.
TA = 85°C, 30 samples, B = 300 G, no internal
filtering – 0.8 – deg.
Temperature Drift ANGLEDRIFT
TA = –40°C, B = 300 G, drift measured relative
to TA = 25°C –2 – 2 deg.
TA = 85°C, B = 300 G, drift measured relative to
TA = 25°C –1.5 – 1.5 deg.
Angle Drift over Life-Time16 ANGLEDRIFT-
LIFE
B = 300G, drift observed after AEC-Q100
qualification testing – ±1 – deg.
7Typical data is at TA = 25°C and VCC = 5 V and it is for design information only.
81 G (gauss) = 0.1 mT (millitesla).
9This represents a typical input range.
10RESANGLE represents the number of bits of data available for reading from the device registers.
11Effective Resolution is calculated using the formula below:
log22
(360) - log (3 X )
32
l
l = 1
where σ is the Standard Deviation based on thirty measurements taken at each of the 32 angular positions, I = 11.25, 22.5, … 360.
12The rate at which a new angle reading is ready. This value varies with the ORATE selection.
13This value assumes no linearization, (harmonic, or segmented) , no IIR or ORATE ltering, and no short-stroke features enabled. This number also does not account for
the added latency associated with the I2C interface sampling rate. This value only represents the time to read the magnetic position with no further computations made.
Actual response time is dependent on EEPROM settings. Settings related to lter design, signal path computations, and linearization will increase the response time.
14Error and noise values are with no further signal processing. Angle Error can be corrected with linearization algorithm, and Angle Noise can be reduced with internal lter-
ing and slower Angle Refresh Rate value. The parameters are characterized, but not measured at nal test.
15This value represents 3-sigma or thrice the standard deviation of the measured samples.
16The Angle Error of most devices tested did not shift appreciably after AEC-Q100 qualication testing. However, the Angle Error of some devices was observed to drift by
approximately 2 degrees after AEC-Q100 (grade 1) testing.
OPERATING CHARACTERISTICS (continued): valid throughout full operating voltage and ambient temperature ranges,
unless otherwise specied
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
6
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
FUNCTIONAL DESCRIPTION
Overview
The A1332 incorporates a Hall sensor IC that measures the direc-
tion of the magnetic field vector through 360° in the x-y plane
(parallel to the branded face of the device). The A1332 computes
the angle based on the actual physical reading, as well as any
internal parameters that have been set by the user. The end user
can configure the output dynamic range, output scaling, and
filtering.
This device is an advanced, programmable internal microproces-
sor-driven system-on-chip (SoC). It includes a Circular Vertical
Hall (CVH) analog front end, a high speed sampling A-to-D con-
verter, digital filtering, a 32-bit custom microprocessor, a digital
control I2C interface, and digital output of processed angle data.
Advanced linearization, offset, and gain adjustment options
are available in the A1332. These options can be configured in
onboard EEPROM providing a wide range of sensing solutions
in the same device. Device performance can be optimized by
enabling individual functions or disabling them in EEPROM to
minimize latency.
Operation
The device is designed to acquire angular position data by sam-
pling a rotating bipolar magnetic target using a multi-segmented
circular vertical Hall effect (CVH) detector. The analog output
is processed, and then digitized, and compensated before being
loaded into the output register. Refer to figure 2 for a depiction of
the signal process flow described here.
• Analog Front End In this stage, the applied magnetic signal is
detected and digitized for more advanced processing.
A1 CVH Element. The CVH is the actual magnetic sensing ele-
ment that measures the direction of the applied magnetic vector.
A2 Analog Signal Conditioning. The signal acquired by the
CVH is sampled.
A3 A to D Converter. The analog signal is digitized and handed
off to the Digital Front End stage.
• Digital Front End In this preprocessing stage, the digitized
signal is conditioned for analysis.
D1 Digital Signal Conditioning. The digitized signal is deci-
mated and band pass filtered.
D2 Raw Angle Computation. For each sample, the raw angle
value is calculated.
• Microprocessor The preprocess signal is subjected to various
standard and user-selected computations. The type and selection
of computations used involves a trade-off between precision and
increased response time in producing the final output.
P1 Angle Averaging. The raw angle data is received in a peri-
odic stream (every 32 µs), and several samples are accumulated
and averaged, based on user selected output rate. This feature
increases the effective resolution of the system. The amount of
averaging is determined by the user-programmable ORATE (out-
put rate) field. The user can configure the quantity of averaged
samples by powers of two to determine the refresh rate, the rate
at which successive averaged angle values are fed into the post
processing stages. The available rates are set as follows:
ORATE
[2:0]
Quantity of Samples
Averaged
Refresh Rate
(µs)
000 1 32
001 2 64
010 4 128
011 8 256
100 16 512
101 32 1024
110 64 2048
111 128 4096
P1a IIR Filter (Optional) The optional IIR filter can provide
more advanced multi-order filtering of the input signal. Filter
coefficients can be user-programmed, and the FI bit can be pro-
grammed by the user to enable or disable this feature.
P1b Angle Compensation over Temperature and Magnetic
Field (Optional) The A1332 is capable of compensating for drift
in angle readings that result from changes in the device tempera-
ture through the operating ambient temperature range. The device
comes from the factory pre-programmed with coefficient settings
to allow compensation of linear shifts of angle with temperature.
The TC bit can be programmed by the user to enable or disable
this feature. The default value from Allegro factory is “enabled”.
Please note, this bit must be set, to meet specifications on angle
error related items in the data-sheet.
P1c Prelinearization 0 Offset (Optional, but required if linear-
ization used.) The expected angle values should be distributed
throughout the input dynamic range to optimize angle post-
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
7
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
CVH
Element
Analog Signal
Conditioning
A to D
Converter
Digital Signal
Conditioning
Raw Angle
Computation
Digital
Front End
(Digital Logic for
Processing)
Analog
Front End
(Applied Magnetic
Signal Detection)
A1
A2
A3
D1
D2
P1
P2
P3
P4
P5
P6
P1a
P1b
P1c
P1d
P3a
P4a
P6a
Angle
Averaging
SRAM
EEPROM
(Optional)
IR Filter
Angle
Compensation
(Optional)
Prelinearization
0 Offset
(Optional)
Prelinearization
Rotation
(Optional)
Postlinearization
Rotation
Minimum/
Maximum
Angle Check*
Gain Adjust*
* Short Stroke Applications Only
(Optional)
Linearization
Segmented or
Harmonic
Postlinearization
0 Offset
Angle Rounding
to 12 Bits
(Optional)
Angle Clamping*
(Optional)
Angle
Inversion Primary Serial Interface
Microprocessor
(Angle Processing)
Sample Rate
(Resolution)
Figure 2: Signal Processing Flow
(refer by index number to text descriptions)
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
8
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
processing. This is mostly needed for applications that utilize
full 360-degree rotations. This value establishes the position
that will correspond to zero error. This value should be set such
that the 360 → 0 degree range corresponds to the 4095 → 0
code range. Setting this point is critical if linearization is used,
whether segmented or harmonic. This is required, prior to going
through linearization, because both linearization methods require
a continuous input function to operate correctly. Set using the
LIN_OFFSET field.
P1d Prelinearization Rotation (Optional, but required if linear-
ization used). The linearization algorithms require input functions
that are both continuous and monotonically increasing. The LR
bit sets which relative direction of target rotation results in an
increasing angle value. The bit must be set such that the input to
the linearization algorithm is increasing.
P2 Minimum/Maximum Angle Check. The device compares
the raw angle value to the angle value boundaries set by the
user programming the MIN_ANGLE_S or MAX_ANGLE_S
fields. If the angle is excessive, an error flag is set at ERR[AH]
(high boundary violation) or ERR[AL] (low boundary viola-
tion). (Note: To bypass this feature, set MIN_ANGLE_S to 0 and
MAX_ANGLE_S to 4095.)
P3 Gain Adjust. This bit adjusts the output dynamic range of the
device. For example, if the application only requires 45 degrees
of stroke, the user can set this field (to 8 in this example) such
that a 45-degree angular change would be distributed across the
entire 4095 → 0 code range. Set using the GAIN field.
P3a Linearization (Optional). Applies user-programmed error
correction coefficients (set in the LINC registers) to the raw angle
measurements. Use the HL bit to enable harmonic linearization
and the SL bit to enable segmented linearization (along with the
LIN_SEL field to select the type of segmented linearization).
P4 Postlinearization 0 Offset. This computation assigns the final
angle offset value, to set the low expected angle value to code 0
in the output dynamic range, after all linearization and processing
has been completed. Set using the ZERO_OFFSET field.
P4a Postlinearization Rotation (Optional). This feature allows
the user to chose the polarity of the final angle output, relative to
the result of the Prelinearization Rotation direction setting (LR
bit, described above). Set using the RO bit.
P5 Angle Rounding to 12 Bits. All of the internal calculations
for angle processing in the A1332 take place with 16-bit preci-
sion. This step truncates the data into a 12 bit word for output
through the Primary Serial Interface.
P6 Angle Clamping. The A1332 has the ability to apply digi-
tal clamps to the output signal. This feature is most useful for
applications that use angle strokes less than 360 degrees. If the
output signal exceeds the upper clamp, the output will stay at
the clamped value. If the output signal is lower than the lower
clamp, the output will stay at the low clamp value. Set using
the CLAMP_HI] and CLAMP_LO fields. (Note: To bypass this
feature, set CLAMP_HI to 4095 and CLAMP_LO to 0.)
P6a Angle Inversion (Optional). This calculation subtracts the
angle from the high clamp.
Diagnostic Features
The A1332 features several diagnostic features and status flags
to let the user know if any issues are present with the A1332 or
associated magnetic system:
Condition Diagnostic Response
VCC < VCCLOW(TH)(min) UV error flag is set
VCC > 8.8 V OV error flag is set
Field > MAG_HIGH MH flag is set
Field < MAG_LOW ML flag is set
Angle processing errors AT flag is set
Angle out of range AHF, ALF flags are set
System status ALIVE always counting indicating
angles being processed
The SDA pin state changes according to the state of the VCC
ramp, as shown in Figure 3.
For more information on diagnostic features and flags, please
refer to the programmers guide for a more complete description
of the available flags and settings.
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
9
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Programming Modes
The EEPROM can be written through the primary serial interface
to enter process coefficients and select options. Certain operating
commands also are available by writing directly to SRAM. The
EEPROM and SRAM provide parallel data structures for operat-
ing parameters. The SRAM provides a rapid test and measure-
ment environment for application development and bench testing.
The EEPROM provides persistent storage at end of line for final
parameters. At initialization, the EEPROM contents are read into
the corresponding SRAM. The SRAM can be overwritten during
operation (although it is not recommended). the EEPROM is
permanently locked by setting the lock EEPROM [LE] bit in the
EEPROM.
The A1332 is programmed through the primary serial interface,
an I2C interface receiving pulses through the SDA and SCL pins,
with additional power provided by pulses on the VCC pin to set
the EEPROM bit fields.
VCC (V)
4.4
3.8
SDA Pin
State
t
3.7
VCC Low Flag Threshold, VCCLOW(TH)
POR
POR
High
Impedance
Accurate
Angle Output
High
Impedance
Error
Flag Set
Error
Flag Set
Angle
output
accuracy
reduced
Angle
output
accuracy
reduced
Figure 3: Relationship of VCC and SDA output
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
10
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
APPLICATION INFORMATION
The A1332 features an I2C compliant interface for communica-
tion with a host microcontroller, or Master. A basic circuit for
configuring the A1332 package is shown in Figure 4. It is recom-
mended that both the SCL and SDA lines be tied to 3.3 V via a
1 kΩ pull-up resistor. If using a Pull-Up voltage of 5 V, it is
recommended to limit current by using a higher value pull-up
resistance that 1 K.
Serial Interface Description
If the SDA pin is tied to 5 V, instead of 3.3 V, this results in the
forward biasing of an internal diode in the A1332 which could
conduct current into the digital voltage regulator internal to the
device. This may result in degraded voltage regulation per-
formance. Current- limiting resistors have been implemented
on-chip to limit this effect. Measurements show that exposure to
this condition does not damage the IC in any permanent manner.
However, for best results, it is recommended that the Serial Logic
pins SDA and SCL be tied to 3.3 V and not 5 V VCC.
3.3 V Internal Regulator 3.3 V Internal Regulator
3.3 V External Supply 5 V External Supply
SDA
Pin
SDA
Pin
Pull-Up
Resistor
Pull-Up
Resistor
Internal
Resistor
Internal
Resistor
Digital Sub-System Digital Sub-System
Current Flows from VCC into
3.3 V Internal Regulator.
Regulator may suffer some
degradation in performance.
A1332 will continue to function
with the 5 V SDA Pull-Up, but
this is not a desirable conigur-
ation.
Internal
Diode:
OFF
Internal
Diode:
ON
+
+
+
+
-
-
-
-
SDA Pull-Up = 3.3 V SDA Pull-Up = 5 V
Figure 4: SDA Pin Schematic
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
11
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Magnetic Target Requirements
There are two main sensing configurations for magnetic angle
sensing, on axis and off axis. On-axis (end of shaft) refers to
when the center axis of a magnet lines up with the center of the
sensing element. Off-axis (side shaft) refers to when the angle
sensor is mounted along the edge of a magnet. Figure 9 illustrates
on and off axis sensing configurations.
ON-AXIS APPLICATIONS
Some common on-axis applications for the device include digital
potentiometer, motor sensing, power steering, and throttle sens-
ing. The A1332 is designed to operate with magnets constructed
with a variety of magnetic materials, cylindrical geometries, and
field strengths, as shown in Table 1. The device has two internal
linearization algorithms that can compensate for much of the
error due to alignment. Contact Allegro for more detailed infor-
mation on magnet selection and theoretical error.
OFF-AXIS APPLICATIONS
There are two major challenges with off axis angle sensing
applications. The first is field strength. All efforts should be
conducted to maximize magnetic signal strength as seen by the
device. The goal is a minimum of 300 G. Field strength can be
maximized by using high quality magnetic material, and by mini-
mizing the distance between the sensor and the magnet. Another
challenge is overcoming the inherent non-linearity of the mag-
netic field vector generated at the edge of a magnet. The device
has two linearization algorithms that can compensate for much of
the geometric error. Harmonic linearization is recommended for
off-axis applications.
Figure 5: Typical A1332 Conguration
A1332 set up for serial address 0xC
Host/Master
Microprocessor
A1332
TEST
SA0
SA1
SDA
AGND
AGND
AGND
DGND
DGND
DGND
SCL
VCCVCC
0.1 µF
1 kΩ
1 kΩ
0.1 µF
3.3 V
VCC = 5 V
BYP
14
13
12
11
10
9
8
7
6
5
4
3
2
1
00 0.5 1.0 1.5
Eccentricity of SOC Chip Relative to Magnet Rotation Axis (mm)
Angle Error (±°)
2.5
3.5
2.0 3.0
Table 1: Target Magnet Parameters
Magnetic Material Diameter
(mm)
Thickness
(mm)
Neodymium (bonded) 15 4
Neodymium (sintered)* 10 4
Neodymium (sintered) 8 3
Neodymium / SmCo 6 2.5
NS
Thickness
Diameter
*A sintered Neodymium magnet with 10 mm (or greater) diameter and 4 mm thick-
ness is the recommended magnet for redundant applications.
Figure 6: Simulated Error versus Eccentricity for a
10 mm x 4 mm Neodymium Magnet at a 2.7 mm Air
Gap.
Typical Systemic Error versus magnet to sensor eccentricity (daxial),
Note: “Systemic Error” refers to application errors in alignment and
system timing. It does not refer to sensor IC device errors. The data
in this graph is simulated with ideal magnetization.
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
12
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Hall element
Figure 9: Centering the Axis of Magnet Rotation on
the Hall Element
Centering the axis of magnet rotation on the Hall element pro-
vides the strongest signal in all degrees of rotation.
Figure 7: Magnetic Field Flux Lines
The magnetic field flux lines run fixed field lines coming out of
the north pole and going into the south pole of the magnet. The
peak flux densities are between the poles.
daxial(off-axis)daxial(on-axis)
AG
(off axis)
AG (on axis)
Magnetic
Flux Lines
Axis of
Rotation
AG (on axis, centered)
Figure 10: Rapid Degeneration of Magnetic Flux Density
The magnetic flux density degenerates rapidly away from the plane of
peak north-south polarity. When the axis of rotation is placed away from
the Hall element, the device must be placed closer to the magnetic poles
to maintain an adequate level of flux at the Hall element.
+|B|
0 G
Effect of Orientation on Signal
Figure 8: Hall Element Detects Rotating Relative Polarity
of Magnetic Field
As the magnet rotates, the Hall element detects the rotating relative
polarity of the magnetic field (solid line); when the center of rotation is
centered on the Hall element, the magnetic flux amplitude is constant
(dashed line).
+|B|
0 G 0°
360°
Zero
Crossing
Magnetic
Flux
Detected
Rotation
90° 180° 270° 360°
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
13
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Linearization
Magnetic fields are generally not completely linear throughout
the full range of target positions. This can be the result of non-
uniformities in mechanical motion or of material composition.
In some applications, it may be required to apply a mathematical
transfer function to the angle that is reported by the A1332.
The A1332 has built-in functions for performing linearization on
the acquired angle data. It is capable of performing one of two
different linearization methods: harmonic linearization and piece-
wise (segmented) linearization.
Segmented linearization breaks up the output dynamic range
into 16 equal segments. Each segment is then represented by the
equation of a straight line between the two endpoints of the seg-
ment. Using this basic principle, it is possible to tailor the output
response to compensate for mechanical non-linearity.
One example is a fluid level detector in a vehicle fuel tank.
Because of requirements to conform the tank and to provide
stiffening, fuel tanks often do not have a uniform shape. A level
detector with a linear sensor in this application would not cor-
rectly indicate the remaining volume of fuel in the tank without
some mathematical conversion. Figure 11 graphically illustrates
the general concept.
Harmonic linearization utilizes the Fourier series in order to
compensate for periodic error components. In the most basic of
terms, the Fourier series is used to represent a periodic signal
using a sum of ideal periodic waveforms. The A1332 is capable
of utilizing up to 15 Fourier series components to linearize the
output transfer function.
While it can be used for many applications, harmonic lineariza-
tion is most useful for 360-degree applications. The error curve
for a rotating magnet that is not perfectly aligned will most often
have an error waveform that is periodic. This is phenomenon is
especially true for systems where the sensor is mounted off-axis
relative to the magnet. Figure 12 illustrates this periodic error.
An initial set of linearization coefficients is created by character-
izing the application experimentally. With all signal processing
options configured, the device is used to sense the applied mag-
netic field, B: at a target zero-degrees of rotation reference angle
and at regular intervals. For segmented linearization, 16 samples
are taken: at nominal zero degrees and every 1/16 interval (22.5°)
of the full 360° rotational input range. Each angle is read from
the ANG[ANGLE] register and recorded.
These values are loaded into the Allegro ASEK programming
utility for the device, or an equivalent customer software pro-
gram, and to generate coefficients corresponding to the values.
The user then uses the software load function to transmit the
coefficients to the EEPROM. Each of the coefficient values can
be individually overwritten during normal operation by writing
directly to the corresponding SRAM.
Wall stiffener cavities
Uniform walls
Angled walls
Angled walls, uneven bottom
Fill pipe
Linear Depth
Fuel Volume
Linearized rate
0
Meter and
Sender
Figure 11: Varying Volumes in an Integrated Vehicle Fuel Tank
An integrated vehicle fuel tank has varying volumes according to depth due to structural elements. As shown in the chart, this results in a
variable rate of fuel level change, depending on volume at the given depth, and a linearized transfer function can be used against the integral
volume.
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
14
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
+V
0 90 180 270 360
0
∆daxial Correction
Inversion Result
Detected Angle (°)Error Correction (V)
Magnetic Input
Linearization Target
Inversion Function
Device Output Position (°)
360
270
180
90
0
0 90 180 270 360
Target Rotational Position (°)
Corrected Angle Output
∆daxial =
+ phase,
+ amplitude
∆daxial ∆daxial ∆daxial ∆daxial
∆daxial =
+ phase,
– amplitude
∆daxial =
+ phase,
+ + amplitude
∆daxial =
+ phase,
– – amplitude
Figure 12a: Linear-
ization Coefcients
With the axis of rotation
aligned with the Hall
element, linearization
coefficients are a simple
inversion of the input.
Figure 12b: Any Eccen-
tricity is Evaluated as
an Error.
Systematic eccentricity can
be factored out by appropri-
ate linearization coefficients.
For off-axis applications,
the harmonic linearization
method is recommended.
Correction for Eccentric Orientation
Final Datasheet
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September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
15
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Figure 13: Sample of Linearization Function Transfer Characteristic.
HARMONIC COEFFICIENTS
The device supports up to 15 harmonics. Each harmonic is char-
acterized by an amplitude and a phase coefficient.
To apply harmonic linearization, the device:
1. Calculates the error factors.
2. Applies any programmed offsets.
3. Calculates the linearization factor as:
An × sin(n × t + φn )
PCB Layout
Bypass and decoupling capacitor should be placed as close as
possible to corresponding pins, with low impedance traces.
Capacitors should be tied to a low impedance ground plane when-
ever possible.
Interpolated Linear Position
(y-axis values represent
16 equal intervals)
Magnetic Input Values
(15 x-axis values read
and used to calculate
coefficients)
Minimum Full Scale Input
B
IN0
B
IN1
B
IN2
B
IN3
0
–640
2432
4095
xLIN_10
–xLIN_3
B
IN16
B
IN10
Maximum Full Scale Input
Coefficients stored in
EEPROM
Input function
Input function
Output function Output function
A
A
A
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
16
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
For Reference Only – Not for Tooling Use
(Reference MO-153 AB-1)
NOT TO SCALE
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A
1.10 MAX
0.15
0.00
0.30
0.19
0.20
0.09
8º
0º
0.60
1.00 REF
C
SEATING
PLANE
C0.10
16X
0.65 BSC
0.25 BSC
21
14
1.12
5.00 ±0.10
4.40 ±0.10 6.40 BSC
GAUGE PLANE
SEATING PLANE
A
B
B
D
DE
Branding scale and appearance at supplier discretion
Hall element, not to scale
Active Area Depth = 0.36 mm (Ref)
C
D
E
6.00
0.65
0.45
1.70
14
21
1
C
Branded Face PCB Layout Reference View
Standard Branding Reference View
= Device part number
= Supplier emblem
= Last two digits of year of manufacture
= Week of manufacture
= Lot number
N
Y
W
L
Terminal #1 mark area
Reference land pattern layout (reference IPC7351 TSOP65P640X120-14M);
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances; when
mounting on a multilayer PCB, thermal vias at the exposed thermal pad land
can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
NNNNNNNNNNNN
YYWW
LLLLLLLLLLLL
+0.15
–0.10
Figure 14: Package LE, 14-Pin TSSOP (Single Die Version)
PACKAGE OUTLINE DRAWING
Final Datasheet
Subject to Change Without Notice
September 10, 2014
Precision Hall Effect Angle Sensor IC with I2C Interface
A1332
17
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Copyright ©2011-2014, Allegro MicroSystems, LLC
I2C™ is a trademark of Philips Semiconductors.
Allegro MicroSystems, LLC reserves the right to make, from time to time, such departures from the detail specifications as may be required to
permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that
the information being relied upon is current.
Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its
use; nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com
Revision History
Revision No. Revision Date Description
– September 11, 2014 Initial release