A1335-DS, Rev. 4
MCO-0000137
• 360° contactless high-resolution angle position sensor
• CVH (Circular Vertical Hall) technology
• Available with either a single die or dual independent die
housed within a single package
• Digital output format selectable among SPI, I2C, and
SENT (Single-Edge Nibble Transmission)
• SENT output is SAEJ2716 JAN2010 compliant, with
Allegro proprietary enhanced programmable features
• Customer-programmable SENT tick times, ranging
from 0.5 to 7.9 µs
• SPI interface allows use of multiple independent sensor
ICs for applications requiring redundancy
• Refresh rate: 32 µs, 12-bit resolution
• Programmable via Manchester encoding on the VCC
line, reducing external wiring
• Automotive temperature range: –40°C to 150°C
• AEC-Q100 automotive qualified
• Two types of linearization algorithms offered: harmonic
linearization and segmented linearization
□Enables off-axis operation
Precision Hall-Effect Angle Sensor IC
with I 2C, SPI, and SENT Interfaces
Functional Block Diagram
A1335
Continued on the next page…
Multisegment
CVH Element
Regulator
Analog Front End
Digital
Subsystem
To all internal circuits
EEPROM
32-bit
Microprocessor
I2C/SPI
Interface
SENT
Interface
Diagnostics
BYP
CBYP(BYP)
VCC (also
programming)
V+
ADC
SA0/CS
SA1/MOSI
SDA/MISO
VCC
(Programming)
SCL/SCLK
CBYP(VCC)
DGND
AGND
SOC Die
SENT
ISEL
The A1335 is a 360° contactless high-resolution programmable
magnetic angle position sensor IC. It is designed for digital
systems and is capable of communicating via an I2C, SPI, or
SENT interface.
This system-on-chip (SoC) architecture includes a front
end based on Circular Vertical Hall (CVH) technology,
programmable microprocessor-based signal processing, and
features an interface capable of supporting I2C, SPI, and SENT.
Besides providing full-turn angular measurement, the A1335
also provides scaling for angle measurement applications less
than 360°. It includes on-chip EEPROM technology, capable of
supporting up to 100 read/write cycles, 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 A1335 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 A1335
linearization schemes were designed with challenging off-axis
applications in mind.
The A1335 is available as a single die in a 14-pin TSSOP, or
dual die in a 24-pin TSSOP. Both packages are lead (Pb) free
with 100% matte-tin leadframe plating.
PACKAGES:
Not to scale
Single SoC, 14-pin TSSOP
(suffix LE)
Dual Independent SoCs, 24-pin
TSSOP (suffix LE)
FEATURES AND BENEFITS DESCRIPTION
Industry-leading linearization
enables off-axis (side-shaft)
operation
July 30, 2018
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
2
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
FEATURES AND BENEFITS (continued)
• Programmable range—can scale 22.5° to full-scale digital
output
• Microprocessor-based output linearization
• EEPROM with Error Correction Control (ECC) for trimming
calibration
• 1 mm thin (TSSOP) package
• Improved air gap performance, based on continuous
background calibration
SELECTION GUIDE
Part Number System Die Package Packing*
A1335LLETR-T Single 14-pin TSSOP 4000 pieces per 13-in. reel
A1335LLETR-DD-T Dual 24-pin TSSOP 4000 pieces per 13-in. reel
*Contact Allegro for additional packing options
ABSOLUTE MAXIMUM RATINGS
Characteristic Symbol Notes Rating Unit
Forward Supply Voltage VCC 24 V
Reverse Supply Voltage VRCC –18 V
All Other Pins VIN –0.5 to 5.5 V
Operating Ambient Temperature TAL temperature range –40 to 150 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
LE-14 package 82 ºC/W
LE-24 package 117 ºC/W
*Additional thermal information available on the Allegro website.
Table of Contents
Features and Benefits ........................................................... 1
Description .......................................................................... 1
Packages ............................................................................ 1
Functional Block Diagram ..................................................... 1
Selection Guide ................................................................... 2
Absolute Maximum Ratings ................................................... 2
Thermal Characteristics ........................................................ 2
Pinout Diagrams and Terminal Lists ........................................ 3
Operating Characteristics ...................................................... 4
Functional Description .......................................................... 7
Overview ......................................................................... 7
Operation ......................................................................... 7
Diagnostic Features ........................................................ 10
Programming Mode ..........................................................11
Manchester Serial Interface ................................................. 12
Entering Manchester Communication Mode ....................... 12
Transaction Types ........................................................... 12
Writing to EEPROM......................................................... 12
Manchester Interface Reference ....................................... 13
SENT Output Mode ......................................................... 14
Application Information ....................................................... 16
Serial Interface Description .............................................. 16
Magnetic Target Requirements ......................................... 17
Calculating Target Zero Degree Angle ............................... 18
Bypass Pin Usage ........................................................... 18
Effect of Orientation on Signal .......................................... 20
Linearization ................................................................... 22
Typical Performance Characteristics ..................................... 25
Package Outline Drawings .................................................. 27
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
3
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
DGND
BYP
DGND
NC
VCC
NC
AGND
1
2
3
4
5
6
7
14
13
12
11
10
9
8
DGND
SA0/CS
SA1/MOSI
SCL/SCLK
SDA/MISO
SENT
ISEL
DGND_1
BYP_1
AGND_1
NC
VCC_1
ISEL_2
SENT_2
SDA_2/MISO_2
SCL_2/SCLK_2
SA1_2/MOSI_2
SA0_2/CS_2
DGND_2
DGND_1
SA0_1/CS_1
SA1_1/MOSI_1
SCL_1/SCLK_1
SDA_1/MISO_1
SENT_1
ISEL_1
VCC_2
NC
AGND_2
BYP_2
DGND_2
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
LE-14 Package
(Single SoC)
LE-24 Package
(Dual SoC)
Terminal List Table
Pin Name [1] Pin Number
LE-14 LE-24 Function
VCC_1 5 5 Device power supply and input for EEPROM writing pulses. Used to enter/exit
Manchester Serial Communication mode; serves as programming data input
once mode has been entered.
VCC_2 – 17
AGND_1 7 3 Device analog ground terminal.
AGND_2 – 15
BYP_1 2 2 Internal bypass node, connect with bypass capacitor to DGND (die 1).
BYP_2 – 14 Internal bypass node, connect with bypass capacitor to DGND (die 2).
DGND_1 1, 3, 14 1, 24 Device digital ground terminal.
DGND_2 – 12,13
ISEL_1 8 18 Selects between I2C operation (set to logic low)
or SPI operation (set to logic high) (for SENT/Manchester operation set low) (die 1)
ISEL_2 – 6 Selects between I2C operation (set to logic low)
or SPI operation (set to logic high) (for SENT/Manchester operation set low) (die 2).
NC 4, 6 4, 16 Not Connected; connect to GND for optimal ESD performance.
SA0_1/C
¯
¯
S
¯
_1 13 23
I2C: SA0 digital input. Sets slave address bit 0 (LSB) [2]; tie to BYP for 1, tie to
DGND for 0.
SPI: Chip Select input, active low (die 1).
Manchester: LSB of the ID value for Die 1. tie to BYP for 1, to DGND for 0. Must
be in I2C operation (ISEL set to a logic low).
SA0_2/C
¯
¯
S
¯
_2 –11
I2C: SA0 digital input. Sets slave address bit 0 (LSB) [2]; tie to BYP for 1, tie to
DGND for 0.
SPI: Chip Select input, active low (die 2).
Manchester: LSB of the ID value for Die 2. tie to BYP for 1, to DGND for 0. Must
be in I2C operation (ISEL set to a logic low).
SA1_1/
MOSI_1 12 22
I2C: SA1 digital input: Sets slave address bit 1 (LSB) [2]; tie to BYP for 1, tie to
DGND for 0.
SPI: Master Output / Slave Input terminal (die 1).
Manchester: MSB of the ID value for Die 1. tie to BYP for 1, to DGND for 0. Must
be in I2C operation (ISEL set to a logic low).
SA1_2/
MOSI_2 – 10
I2C: SA1 digital input: Sets slave address bit 1 (LSB) [2]; tie to BYP for 1, tie to
DGND for 0.
SPI: Master Output / Slave Input terminal (die 2).
Manchester: MSB of the ID value for Die 2. tie to BYP for 1, to DGND for 0. Must
be in I2C operation (ISEL set to a logic low).
SCL_1/
SCLK_1 11 21 Digital input: Serial clock (I2C: SCL, SPI: SCLK); open drain, pull up externally to
3.3 V (die 1).
SCL_2/
SCLK_2 – 9 Digital input: Serial clock (I2C: SCL, SPI: SCLK); open drain, pull up externally to
3.3 V (die 2).
SDA_1/
MISO_1 10 20
I2C: Digital data terminal: digital output of evaluated target angle, also
programming data input; open drain, pull up externally to 3.3 V (die 1).
SPI: Master Input / Slave Output terminal (die 1).
SDA_2/
MISO_2 – 8
I2C: Digital data terminal: digital output of evaluated target angle, also
programming data input; open drain, pull up externally to 3.3 V (die 2).
SPI: Master Input / Slave Output terminal (die 2).
SENT_1 9 19 SENT transmission output terminal (die 1); Manchester output in Manchester
mode; open drain, pull-up to external supply.
SENT_2 – 7 SENT transmission output terminal (die 2); Manchester output in Manchester
mode; open drain, pull-up to external supply.
[1] The number following the underscore refers to the die number in a dual SOC variant
[2] For additional information, refer to the Programming Reference addendum, EEPROM Description and Programming section, regarding
the INTF register, I2CM field.
PINOUT DIAGRAMS AND TERMINAL LIST
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
4
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Continued on the next page…
OPERATING CHARACTERISTICS: Valid throughout full operating voltage and ambient temperature ranges,
unless otherwise specied
Characteristic Symbol Test Conditions Min. Typ. [1] Max. Unit [2]
ELECTRICAL CHARACTERISTICS
Supply Voltage VCC 4.5 5 5.5 V
Supply Current ICC – 15 20 mA
VCC Low Flag Threshold VCCLOW(TH) 4.4 4.55 4.75 V
Supply Zener Clamp Voltage VZSUP IZCC = ICC + 3 mA, TA = 25°C 26.5 – – V
Reverse Battery Voltage VRCC IRCC = –3 mA, TA = 25°C – – –18 V
Power-On Time [3][4] tPO TA = 25°C 2 – 40 ms
SPI INTERFACE SPECIFICATIONS [5]
Digital Input High Voltage [3] VIH MOSI, SCLK,
¯
C
¯
¯
S
¯
pins 2.8 – 3.63 V
Digital Input Low Voltage [3] VIL MOSI, SCLK,
¯
C
¯
¯
S
¯
pins – – 0.5 V
SPI Output High Voltage VOH MISO pins, TA = 25°C 2.93 3.3 3.69 V
SPI Output Low Voltage VOL MISO pins – 0.3 – V
SPI Clock Frequency [3] fSCLK MISO pins, CL = 50 pF 0.1 – 10 MHz
Chip Select to First SCLK Edge [3] tCS Time from
¯
C
¯
¯
S
¯
going low to SCLK falling edge 50 – – ns
Chip Select Idle Time [3] tCS_IDLE Time CS must be high between SPI message frames 200 – – ns
Data Output Valid Time [3] tDAV Data output valid after SCLK falling edge – 45 – ns
MOSI Setup Time [3] tSU Input setup time before SCLK rising edge 10 – – ns
MOSI Hold Time [3] tHD Input hold time after SCLK rising edge 50 – – ns
SCLK to ¯
C
¯
¯
S
¯
Hold Time [3] tCHD Hold SCLK high time before
¯
C
¯
¯
S
¯
rising edge 5 – – ns
Load Capacitance [3] CLLoading on digital output (MISO) pin – – 50 pF
I2C INTERFACE SPECIFICATIONS (VPU = 3.3 V on SDA and SCL pins)
Bus Free Time Between Stop
and Start [3] tBUF 1.3 – – µs
Hold Time Start Condition [3] tHD(STA) 0.6 – – µs
Setup Time for Repeated Start
Condition [3] tSU(STA) 0.6 – – µs
SCL Low Time [3] tLOW 1.3 – – µs
SCL High Time [3] tHIGH 0.6 – – µs
Data Setup Time [3] tSU(DAT) 100 – – ns
Data Hold Time [3] tHD(DAT) 0 – 900 ns
Setup Time for Stop Condition [3] tSU(STO) 0.6 – – µs
Logic Input Low Level (SDA and
SCL pins) [13] VIL(I2C) – – 0.9 V
Logic Input High Level (SDA and
SCL pins) VIH(I2C) 2.1 – 3.63 V
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
5
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
OPERATING CHARACTERISTICS (continued): Valid throughout full operating voltage and ambient temperature ranges,
unless otherwise specied
Characteristic Symbol Test Conditions Min. Typ. [1] Max. Unit [2]
I2C INTERFACE SPECIFICATIONS (VPU = 3.3 V on SDA and SCL pins) (continued)
Logic Input Current [3] IIN VIN = 0 V to VCC –1 – 1 µA
Output Voltage (SDA pin) VOL(I2C) RPU = 1 kΩ, CB = 100 pF, TA = 25°C – – 0.6 V
Logic Input Rise Time (SDA and
SCL pins) [3] tr(IN) – – 300 ns
Logic Input Fall Time (SDA and
SCL pins) [3] tf(IN) – – 300 ns
SDA Output Rise Time [3] tr(OUT) RPU = 1 kΩ, CB = 100 pF – – 300 ns
SDA Output Fall Time [3] tF(OUT) RPU = 1 kΩ, CB = 100 pF – – 300 ns
SCL Clock Frequency [13] fCLK – – 400 kHz
SDA and SCL Bus Pull-Up Resistor RPU –1–kΩ
Total Capacitive Load on SDA Line [3] CB– – 100 pF
Pull-Up Voltage [3] VPU RPU = 1 kΩ, CB = 100 pF 2.97 3.3 3.63 V
SENT Interface Specications [3]
SENT Message Duration tSENT Tick time = 3 µs – – 1 ms
Minimum Programmable SENT
Message Duration tSENTMIN
Tick time = 0.5 µs, 3 data nibbles, SCN, and
CRC, nibble length = 27 ticks – 96 – µs
SENT Output Signal
VSENT(L) 5 kΩ ≤ Rpullup ≤ 50 kΩ – – 0.10 V
VSENT(H)
Minimum Rpullup = 5 kΩ 0.9 × VS– – V
Maximum Rpullup = 50 kΩ 0.7 × VS– – V
SENT Trigger Signal VSENTtrig(L) – – 1.4 V
VSENTtrig(H) 2.8 – – V
Minimum Time Frame for SENT
Trigger Signal Ttrig(MIN) 2 – – µs
Triggered Delay Time tdSENT
From end of trigger pulse to beginning of SENT
message frame.
TSENT (SENT_MODE 3 and SENT_MODE 4)
– 7 – tick
Maximum Sink Current ILIMIT Output FET on, TA = 25°C – 30 – mA
Magnetic Characteristics
Magnetic Field [6] B Range of input field – – 1500 G
Continued on the next page…
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
6
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Characteristic Symbol Test Conditions Min. Typ. [1] Max. Unit [2]
ANGLE CHARACTERISTICS
Output [7] RESANGLE – 12 – bit
Effective resolution [8] B = 300 G, TA = 25ºC, ORATE = 0 – 10.8 – bits
B ≥ 700 G, TA = 25ºC, ORATE = 0 – 12 – bits
Angle Refresh Rate [9] tANG ORATE = 0 – 32 – µs
Response Time [10] tRESPONSE
All linearization and computations disabled, see
Figure 1 – 60 – µs
Angle Error [11] ERRANG
TA = 25°C, ideal magnet alignment, B = 300 G,
target rpm = 0, no linearization – ±0.5 – degrees
TA = 25°C, ideal magnet alignment, B = 900 G,
target rpm = 0, no linearization – ±0.2 – degrees
TA = 150°C, ideal magnet alignment, B = 300 G,
target rpm = 0, no linearization –1.3 – +1.3 degrees
TA = 150°C, ideal magnet alignment, B = 900 G,
target rpm = 0, no linearization – ±0.3 – degrees
Angle Noise [11][12] NANG
TA = 25°C, B = 300 G, no internal filtering,
3 sigma value – 0.6 – degrees
TA = 150°C, B = 300 G, no internal filtering,
3 sigma value – 0.8 – degrees
Temperature Drift ANGLEDRIFT
TA = 150°C, B = 300 G –1.4 1.4 degrees
TA = –40°C, B = 300 G – ±1.2 – degrees
Angle Drift Over Lifetime ANGLEDRIFT-
LIFE
B = 300 G, typical maximum drift observed after
AEC-Q100 qualification testing – ±0.5 – degrees
[1] Typical data is at TA = 25°C and VCC = 5 V and it is for design information only.
[2] 1 G (gauss) = 0.1 mT (millitesla).
[3] Parameters for this characteristic are determined by design. They are not measured
at final test.
[4] End user can customize what power-on tests are conducted at each power-on that
causes a range of power-on times. For more information, see the description of the
CFG register.
[5] During the power-on phase, the A1335 SPI transactions are not guaranteed.
[6] The A1335 operates in Magnetic fields lower than 300 G, but with reduced accuracy
and resolution. CVH self-test operation is not guaranteed at field levels above 300 G.
[7] RESANGLE represents the number of bits of data available for reading from the die
registers.
[8] Effective Resolution is calculated using the formula below:
log
22
(360) – log ( )
n
i
i =1
1
n
where σ is the Standard Deviation based on thirty measurements taken at each of the
32 angular positions, I = 11.25, 22.5, … 360.
[9] The rate at which a new angle reading is ready. This value varies with the ORATE
selection.
[10] This value assumes no post-processing and is the response time to read the mag-
netic position with no further computations. Actual response time is dependent on
EEPROM settings. Settings related to filter design, signal path computations, and
linearization will increase the response time.
[11] Error and noise values are with no further signal processing. Angle Error can be cor-
rected with linearization algorithm, and Angle Noise can be reduced with
internal filtering and slower Angle Refresh Rate value.
[12] 3 sigma value at 300 G. Operation with a larger magnetic field results in improved
noise performance. For 600 G operation, noise reduced by 40-50% vs. 300 G.
[13] Parameter is tested at wafer probe only.
OPERATING CHARACTERISTICS (continued): Valid throughout full operating voltage and ambient temperature ranges,
unless otherwise specied
Denition of Response Time
Response Time
t
t
Position 1
Position 2
Output 1
Output 2
Magnet
Position
Sensor
Output
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
7
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
FUNCTIONAL DESCRIPTION
The A1335 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 A1335 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 interface capable of supporting I2C, SPI and SENT, and
digital output of processed angle data.
Advanced linearization, offset, and gain adjustment options
are available in the A1335. 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 1 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
user-selected computations. The type and selection of computa-
tions 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 periodic
stream, 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 (output 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:
Table 1: Refresh Rates of Averaged Samples
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.
P2 Angle Compensation. The A1335 is capable of compensat-
ing for drift in angle readings that result from changes in the
device temperature 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.
P2a Prelinearization Rotation (Optional, but required if lin-
earization used). The linearization algorithms require input func-
tions 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.
Overview
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
8
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
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
P3
P4
P5
P6
P7
P1a
P2a
P4b
P4c
P2b
P4a
P5a
P7a
Angle
Averaging
SRAM
EEPROM
(Optional)
IR Filter
(Optional)
Prelinearization
Rotation
(Optional)
Prelinearization
0 Offset
(Optional)
Segmented
Linearization
(Optional)
Postlinearization
Rotation
Minimum/
Maximum
Angle Check*
* Short Stroke Applications Only
(Optional)
Harmonic
Linearization
Angle Rounding
to 12 Bits
(Optional)
Angle Clamping*
(Optional)
Angle
Inversion
Primary Serial Interface
Microprocessor
(Angle Processing)
Sample Rate
(Resolution)
P2 Angle
Compensation
(Optional)
Gain Offset
(Optional)
Postlinearization
0 Offset
(Optional)
Die Adjust
Gain Adjust*
Figure 1: Signal Processing Flow (refer by index number to text descriptions)
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
9
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
P2b Gain Offset (Optional). Allows zeroing out of the angle
prior to applying Gain. Set via the GAIN_OFFSET field. Angle =
Angle - GAIN_OFFSET.
P3 Minimum/Maximum Angle Check (Short Stroke Appli-
cations Only). 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 violation). This feature is useful for
applications that use angle strokes less than 360 degrees (short
stroke). (Note: This feature is only active if the Short Stroke bit
has been set.)
P4 Gain Adjust (Short Stroke Applications Only). 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 such that a 45-degree angular change would be
distributed across the entire 4095 → 0 code range. Set using the
GAIN field. (Note: This feature is only active if the Short Stroke
bit has been set.)
P4a Harmonic Linearization (Optional). Applies user-pro-
grammed error correction coefficients (set in the LINC registers)
to the raw angle measurements. Use the HL bit to enable har-
monic linearization.
P4b Prelinearization 0 Offset (optional but required if
Segmented Linearization is used). The expected angle values
should be distributed throughout the input dynamic range to opti-
mize angle post-processing. This is mostly needed for applica-
tions that use full 360-degree rotations. This value establishes the
position that will correspond to zero error. This value should be
set such that the 360 ≥ degree range corresponds to the 4095 ≥ 0
code range. Setting this point is critical if segmented linearization
is used. This is required prior to going through linearization, as
the compensation requires a continuous input function to operate
correctly. Set using the LIN_OFFSET field.
P4c Segmented Linearization (Optional). Applies user-pro-
grammed error correction coefficients (set in the LINC registers)
to the raw angle measurements. Use the SL bit to enable seg-
mented linearization.
P5 Postlinearization 0 Offset (Optional). 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_OFF-
SET field.
P5a 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.
P6 Angle Clamping (Short Stroke Applications Only). The
A1335 has the ability to apply digital 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: This feature is only active if the Short Stroke bit
has been set.)
P7 Angle Rounding to 12 Bits. All of the internal calculations
for angle processing in the A1335 take place with 16-bit preci-
sion. This step rounds the data into a 12-bit word for output
through the Primary Serial Interface.
P7a Angle Inversion (Short Stroke Application Only). Rota-
tion within the high and low clamp values. [CLAMP_HI - (Angle
- CLAMP_LO)]. (Note: This feature is only active if the Short
Stroke bit has been set.)
P8 Die Adjust (Optional). Rotates final angle 180 degrees. Used
to compensate for the 180 degree offset between die in dual SoC
packages.
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Diagnostic Features
The A1335 was designed with diagnostic requirements in mind
and supports many on-chip diagnostics as well as error/status
flags, enabling the host microcontroller to assess the operational
status of each die.
In addition, the A1335 supports three different on-chip user-
initiated diagnostics.
USER-INITIATED DIAGNOSTICS
The following three internal self-tests may be configured to run
at power-on, and may also be initiated at any time by the system
microcontroller via Extended Access commands through the
SPI/I2C interface. A failure of any one of the three self-tests will
assert the Self-Test Failure Flag, ST, within the extended error
register. The specific failing test can be identified by performing
an extended address-read (address 0xFFFC).
• CVH Self-Test
The CVH self-test is a signal path diagnostic used to verify
both analog and digital system integrity. Test execution
requires approximately 36 ms, during which time no new
angle measurements will be generated by the sensor. The
test is implemented by changing the transducer switch
configuration from normal mode into a test configuration,
allowing a test current to drive the CVHD in place of the
magnetic field. By changing the direction of the test current
and sequencing different elements within the CVH, the self-
test emulates a changing magnetic field angle. The measured
angle is monitored to determine a passing or failing device.
A failure of the CVH self-test will assert the ST flag. If the
self-test was initiated via the Extended Access Command, test
results for the individual Hall elements will be stored in the
SRAM CmdStatus field (0x00) and the primary serial interface
ERD register (0x0E through 0x11).
Due to the sensitivity of the self-test, test results are only valid
at field levels equal to or less than 300 G and temperatures at
or above 25°C.
• SRAM BIST
The SRAM Built-In Self-Test (BIST) verifies proper
functionality of the SRAM. The test may be run in either long
or short mode, and can be configured to halt on error. A failure
of the SRAM BIST will assert the ST flag. When enabled
to run on power-up, the short test mode is used, requiring
approximately 100 µs to complete. For more information on
SRAM BIST options, consult the A1335 programming guide.
Table 2: Status and Error Flags
Fault Condition Description Sensor Response
VCC < VCCLOW(TH)(min) Indicates potential for reduced angle accuracy UV error flag is set
VCC > 8.8 V Indicates possible system level power supply failure OV error flag is set*
Field > MAG_HIGH MAG_HIGH programmable from 0-1240 G in 40 G steps. Monitors Mag Field
level in case of mechanical failure MH flag is set
Field < MAG_LOW MAG_LOW programmable from 0-620 G in 20 G steps. Monitors Mag Field
level in case of mechanical failure ML flag is set
–60°C > TA > 180°C Ambient temperature beyond maximum rating detected TR flag is set
Processor Halt Monitors digital logic for proper functionality WT and WC Flags set
Single-Bit EEPROM Error (correctable) Detects and corrects a single-bit EEPROM Error ES error flag is set
Multi-Bit EEPROM Error (uncorrectable) Detects a multi-bit uncorrectable EEPROM ERROR EU error flag is set
Single-Bit SRAM Error (correctable) Detects and corrects a single-bit SRAM Error SS Error flag is set
Multi-Bit SRAM Error (uncorrectable) Detects a multi-bit uncorrectable SRAM ERROR SU Error flag is set
Angle-Processing Errors New angle measurement did not occur within the maximum time allotted. AT flag is set
Angle Out of Range Angle value (prior to scaling by Gain) is outside the range set by MIN_ANGLE
and MAX_ANGLE. Short Stroke only. The AL or AH flag is set
Loss of VCC
Determine if system power was lost. Also detects a reset of the internal
microprocessor POR and RC flags are set
Self-Test Failure
Indicates a failure of one of the three internal self-tests. SRAM BIST, ROM
Checksum Verification, and CVH self-test. Tests can be individually configured
to run at power-up and may also be user initiated.
ST flag set
* EEPROM programming pulses result in OV flag assertion.
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Programming Modes
The EEPROM can be written through the dedicated I2C or SPI
interface pins or via Manchester encoding on the VCC pin, allow-
ing process coefficients to be entered and options selected. (Note:
programming EEPROM also requires the VCC line to be pulsed,
which could adversely affect other devices if powered from the
same line). Certain operating commands also are available by
writing directly to SRAM. The EEPROM and SRAM provide
parallel data structures for operating parameters. The SRAM
provides a rapid test and measurement environment for applica-
tion development and bench-testing. The EEPROM provides
persistent storage at end of line for final parameters. At Power-on
initialization, the EEPROM contents are read into the correspond-
ing SRAM. Provided the Lock Microprocessor [LM] bit within
EEPROM is not set, SRAM can be overwritten during operation
(Use Caution). The EEPROM is permanently locked by setting
the lock EEPROM [LE] bit in the EEPROM.
The A1335 EEPROM is programmed via either the I2C, the SPI,
or the VCC pin Serial Interface, with additional power provided
by pulses on the VCC pin to set the EEPROM bit fields.
4.4
t
V (V)
CC
High
Impedance
High
Impedance
Accurate
Angle Output
UV
Error
Flag
Set
Angle
Output
Accuracy
Reduced
UV
Error
Flag
Set
Angle
Output
Accuracy
Reduced
State of SDA/MISO
and SENT Pins
3.8 POR
CCLOW(TH)
VCC Low Flag Threshold, V
POR
3.7
Figure 2: Relationship of VCC and Output
• ROM Checksum
Verification of the ROM checksum may be configured to take
place at power-on. In addition, the checksum is continuously
recalculated in the background during normal operation
(independent of power-on configuration). This test may be
initiated at any time by the system microcontroller via an
Extended Access Command (0xFFE0). If the self-test was
initiated via the Extended Access Command, the failing
checksum is stored in the CmdStatus SRAM register (0x00). A
bad ROM checksum asserts the Self-Test Failure Flag, ST.
LOW VOLTAGE DETECTION
In addition to setting the undervoltage (UV) flag, a VCC ramp will
also change the state of the output pins (SDA/MISO and SENT)
as the part enters and exits the reset condition. This is shown in
Figure 2.
For more information on diagnostic features and flags, refer to
the programmers guide for a more complete description of the
available flags and settings.
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MANCHESTER SERIAL INTERFACE
To facilitate addressable device programming when using the
unidirectional SENT output mode with no need for additional
wiring, the A1335 incorporates a serial interface on the VCC
line. (Note: The A1335 may be programmed via the SPI or I2C
interfaces, with additional wiring connections. For detailed
information on part programming, refer to the A1335 program-
ming manual). This interface allows an external controller to read
and write registers in the A1335 EEPROM and volatile memory.
The device uses a point-to-point communication protocol, based
on Manchester encoding per G.E. Thomas (a rising edge indi-
cates a 0 and a falling edge indicates a 1), with address and data
transmitted MSB first. The addressable Manchester code imple-
mentation uses the logic states of the SA0/SA1 pins to set address
values for each die. In this way, individual communication with
up to four A1335 die is possible.
To prevent any undesired programming of the A1335, the serial
interface can be disabled by setting the Disable Manchester bit.
With this bit set, the A1335 will ignore any Manchester input on
VCC.
Entering Manchester Communication Mode
Provided the Disable Manchester bit is not set in EEPROM, the
A1335 continuously monitors the VCC line for valid Manchester
commands. The part takes no action until a valid Manchester
Access Code is received.
There are two special Manchester code commands used to
activate or deactivate the serial interface and specify the output
format used during Read operations:
1. Manchester Access Code: Enters Manchester Communica-
tion Mode; Manchester code output on the SENT pin.
2. Manchester Exit Code; returns the SENT pin to normal
(angle data) output format.
Once the Manchester Communication Mode is entered, the SENT
output pin will cease providing angle data, interrupting any data
transmission in progress.
Transaction Types
As shown in Figure 3, the A1335 receives all commands via the
VCC pin, and responds to Read commands via the SENT pin.
This implementation of Manchester encoding requires the com-
munication pulses be within a high (VMAN(H)) and low (VMAN(L))
range of voltages on the VCC line. Writing to EEPROM is sup-
ported by two high voltage pulses on the VCC line.
Each transaction is initiated by a command from the controller;
the A1335 does not initiate any transactions. Two commands are
recognized by the A1335: Write and Read.
Writing to EEPROM
When a Write command requires writing to non-volatile
EEPROM, after the Write command, the controller must also
send two Programming pulses, high-voltage strobes via the VCC
pin. These strobes are detected internally, allowing the A1335
to boost the voltage on the EEPROM gates. Refer to the A1335
programming manual for specifics on sensor programming and
protocol details.
Figure 3: Top-Level Programming Interface
A1335
ECU
GND
Read Manchester Code
Write/Read Command -
Manchester Code
VCC
SENT
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Manchester Interface Reference
Table 3: Manchester Interface Protocol Characteristics [1]
Characteristics Symbol Note Min. Typ. Max. Unit
INPUT/OUTPUT SIGNAL TIMING
Bit Rate Defined by the input message bit rate sent from
the external controller 4 – 100 kbps
Bit Time tBIT
Data bit pulse width at 4 kbps 243 250 257 µs
Data bit pulse width at 100 kbps 9.5 10 10.5 µs
Bit Time Error errTBIT Deviation in tBIT during one command frame –11 –+11 %
Write Delay tWRITE(E)
Required delay from the end of the second
EEPROM Program pulse to the leading edge of
a following command frame
VCC <
6.0 V – – –
Read Delay tSTART
_
READ
Delay from the trailing edge of a Read
command frame to the leading edge of the Read
Acknowledge frame
¼ × tbit – ¾ × tbit µs
EEPROM PROGRAMMING PULSE
EEPROM Programming Pulse
Setup Time tsPULSE(E)
Delay from last bit cell of write command to start
of EEPROM programming pulse 40 – – μs
INPUT SIGNAL VOLTAGE
Manchester Code High Voltage VMAN(H) Applied to VCC line 7.8 – – V
Manchester Code Low Voltage VMAN(L) Applied to VCC line – – 5.7 V
OUTPUT SIGNAL VOLTAGE (Applied on SENT Line)
Manchester Code High Voltage VMAN(H)
Minimum Rpullup = 5 kΩ 0.9 × VS– – V
Maximum Rpullup = 50 kΩ 0.7 × VS– – V
Manchester Code Low Voltage VMAN(L) 5 kΩ ≤ Rpullup ≤ 50 kΩ – – 0.1 V
[1] Determined by design.
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0000
4095
2048
SENT Data Value
(LSB)
(1111 1111 1111)
(0000 0000 0000)
(1000 0000 0000)
Angle (°)
Figure 4: Angle is Represented as a 12-bit Digital Value
The SENT output converts the measured magnetic field angle to
a binary value mapped to the Full-Scale Output (FSO) range of
0 to 4095, shown in Figure 4. This data is inserted into a binary
pulse message, referred to as a frame, that conforms to the SENT
data transmission specification (SAEJ2716 JAN2010).
The SENT frame may be configured via EEPROM. The A1335
may operate in one of three broadly defined SENT modes (see
the A1335 programming manual for details on SENT modes and
settings).
• SAE J2716 SENT: free-streaming SENT frame in accordance
with industry specification. Additional programmability allows
Tick time adjustment from 0.5 µs to 7.9 µs.
• Triggered SENT (TSENT): User-defined sampling and
retrieval.
• Shared SENT: Allows multiple devices to share a common
SENT line. Devices may either be directly addressed
(Addressable SENT or ASENT) or sequentially polled
(Sequential SENT or SSENT).
SENT Output Mode
Sensor
ID = 0
Sensor
ID = 1
Sensor
ID = 2
Sensor
ID = 3
Host
(ECU)
VCC 5 V Max
R
C
Bus Capacitance
Figure 5: Allegro’s proprietary SENT protocol allows
multiple parts to share one common output bus.
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The duration of a nibble is denominated in ticks. The period of
a tick is set by the SENT_TICK parameter. The duration of the
nibble is the sum of the low-voltage interval plus the high-voltage
interval.
The parts of a SENT message are arranged in the following
required sequence (see Figure 7):
1. Synchronization and Calibration: Flags the start of the
SENT message.
2. Status and Communication Nibble: Provides A1335 status
and the optional serial data determined by the setting of the
SENT_SERIAL parameter.
3. Data: Angle information and optional data.
4. CRC: Error checking.
5. Pause Pulse (optional): Fill pulse between SENT message
frames.
SENT MESSAGE STRUCTURE
Data within a SENT message frame is represented as a series of
nibbles, with the following characteristics:
• Each nibble is an ordered pair of a low-voltage interval
followed by a high-voltage interval
• The low-voltage interval acts as the delimiting state which acts
as a boundary between each nibble. The length of this low-
voltage interval is fixed at 5 ticks.
• The high-voltage interval performs the job of the information
state and is variable in duration in order to contain the data
payload of the nibble
• The slew rate of the falling edge may be adjusted using the
SENT_DRIVER parameter.
Pause
Pulse
(optional)
CRC
tSENT
Data 6
Data 1
(MSB)
Status and
Commun-
ication
Synchronization
and Calibration
12 to 27
ticks
12 to 27
ticks
12 to 27
ticks
56 ticks
Nibble Name
SENT_FIXEDSENT_FIXED SENT_FIXEDSENT_FIXED SENT_FIXEDSENT_FIXED
12 to 27
ticks
Table 4: Nibble Composition and Value
Quantity of Ticks Binary
(4-bit)
Value
Decimal
Equivalent
Value
Low-
Voltage
Interval
High-
Voltage
Interval
Total
5 7 12 0000 0
5 8 13 0001 1
5 9 14 0002 2
5 21 26 1110 14
5 22 27 1111 15
Ticks
0512
Message
Signal
Voltage
Low
Interval
High
Interval
Nibble Data Value = 0000
Ticks
0527
Message
Signal
Voltage
Low
Interval
High
Interval
Nibble Data Value = 1111
Figure 6: General Value Formation for SENT
0000 (left), 1111 (right)
Figure 7: General Format for SENT Message Frame
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APPLICATION INFORMATION
The A1335 features I2C-, SPI-, and SENT-compliant interfaces
for communication with a host microcontroller, or Master. A basic
circuit for configuring the A1335 package is shown in Figure 8.
Serial Interface Description
(A) Typical A1335 conguration using I2C interface;
A1335 set up for serial address 0xC
(B) Typical A1335 conguration using SPI interface
Figure 8: Typical A1335 conguration
Host/Master
Microprocessor
A1335
ISEL
SA0
SA1
SDA
AGND
AGND
DGND
DGND
DGND
SCL
VCC
0.1 µF
1 kΩ
1 kΩ
0.1 µF
3.3 V
V= 5 V
CC
BYP
(C) Typical A1335 conguration using SENT interface (SA0/SA1 may be brought
to BYP or GND to congure Manchester/Shared SENT address)
Host/Master
Microprocessor A1335
SCLK
MOSI
MISO
VCC
VCC
0.1 µF
BYP
ISEL
CS
AGND
AGND
DGND
DGND
DGND
0.1 µF
Host/Master
Microprocessor
A1335
ISEL
AGND
AGND
DGND
DGND
DGND
SENT
VCC
0.1 µF
0.1 µF
V= 5 V
CC
BYP
SA0
SA1
SCLK
MISO
3.3 V
5 kΩ
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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 14 to Fig-
ure 17 illustrate on- and off-axis sensing configurations.
FIELD STRENGTH
The A1335 actively measures and adapts to its magnetic environ-
ment. This allows operation throughout a large range of field
strengths (recommended range is 300 to 1000 G, operation beyond
this range is allowed with no long-term impact). Due to the greater
signal-to-noise ratio provided at higher field strengths, perfor-
mance inherently increases with increasing field strength. Typical
angle performance over applied field strength is shown in Figure 9
and Figure 10.
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 3.52.0 3.0
Table 5: 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.
Magnetic Target Requirements
Figure 9: Typical Maximum Angle Error
Over Field Strength
Figure 10: Typical One Sigma Angle Noise
Over Field Strength
0
0.5
1
1.5
100 200 300 400 500 600 700 800 900
Field Strength in Gauss
Angle Error in Degrees
1000
25ºC
150ºC
Recommended Operating Range
(300 to 1000 G)
25ºC
150ºC
Noise in Degrees
Field Strength in Gauss
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
100 200 300 400 500 600 700 800 900 1000
Recommended Operating Range
(300 to 1000 G)
Figure 11: Simulated Error versus Eccentricity for a
10 mm × 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.
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Figure 12: Orientation of Magnet Relative to Primary Die and Secondary Die
NS
arget alignment for default angle setting
arget rotation axis intersects primary die
• Primary die 0° default point
•Secondary die 180° default point
e
)
Target poles aligned with
A1335 elements
E1
Pin 1
E1
E2
E2
SN
Calculating Target Zero Degree Angle
When shipped from the factory, the default angle value when
oriented as shown in Figure 12, is approximately 0º (180º on sec-
ondary die). In some cases, the end user may want to program an
angle offset in the A1335 to compensate for variation in magnetic
assemblies, or for applications where absolute system level read-
ings are required.
The internal algorithm for computing the output angle is as fol-
lows:
AngleOUT = AnglepostLin – Zero Oset . (1)
The procedure to “zero out” the A1335 is as follows.
During final application calibration, position the magnet above
the sensor in the required zero-degree position and record the
angle reading from the device. Program the Zero Offset field in
EEPROM (0x306 bits 12:0) with this value (reference the A1335
programming manual for additional details).
It is important to keep in mind that the Zero Offset adjustment
occurs after linearization within the A1335’s signal path (see
Figure 1). As a result, the zero offset adjustment should be done
following end-of-line linearization.
Bypass Pin Usage
The Bypass pin is required for proper device operation and is
intended to bypass internal IC nodes of the A1335. A 0.1 µF
capacitor must be placed in close proximity to the Bypass pin. It
is not intended to be used to source external components.
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ON-AXIS APPLICATIONS
Some common on-axis applications for the device include digital
potentiometer, motor sensing, power steering, and throttle sens-
ing. The A1335 is designed to operate with magnets constructed
with a variety of magnetic materials, cylindrical geometries, and
field strengths, as shown in Table 5. 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 appli-
cations. 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 minimizing the
distance between the sensor and the magnet. Another challenge
is overcoming the inherent nonlinearity of the magnetic field
vector generated at the edge of a magnet. The device has two
linearization algorithms that can compensate for much of the geo-
metric error. Harmonic linearization is recommended for off-axis
applications.
N
S
Figure 13: Typical On-Axis (a) and
O󰀨-Axis (b) Orientation
(a)
(b)
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Figure 14: The magnetic eld ux lines run between the north pole and south pole of the magnet. The peak ux
densities are between the poles.
+|B|
0 G
Effect of Orientation on Signal
Figure 15: As the magnet rotates, the Hall element detects the rotating relative polarity of the magnetic eld
(solid line). When the center of rotation is centered on the Hall element, the magnetic ux amplitude is constant
(dashed line).
+|B|
0 G 0°
360°
Zero
Crossing
Magnetic
Flux
Detected
Rotation
90° 180° 270° 360°
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Hall element
Figure 16: Centering the axis of magnet rotation on the Hall element provides the strongest signal in all degrees
of rotation.
daxial(off-axis)daxial(on-axis)
AG (off axis)
AG (on axis)
Magnetic
Flux Lines
Axis of
Rotation
AG (on axis, centered)
Figure 17: The magnetic ux 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 ux at the Hall element.
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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 A1335.
The A1335 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 18 graphically illustrates
the general concept.
Harmonic linearization uses the Fourier series in order to com-
pensate 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 A1335 is capable of using
up to 11 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 19 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 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, to generate coefficients corresponding to the values. The
user then uses the software load function to transmit the coef-
ficients 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 18: 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.
Linearization
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
23
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
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 19a: With the axis of
rotation aligned with the Hall
element, linearization coe󰀩-
cients are a simple inversion
of the input.
Figure 19b: Any eccentric-
ity is evaluated as an error.
Systematic eccentricity can
be factored out by appropri-
ate linearization coe󰀩cients.
For o󰀨-axis applications,
the harmonic linearization
method is recommended.
Figure 19: Correction for Eccentric Orientation
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
24
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Figure 20: Sample of Linearization Function Transfer Characteristic
HARMONIC COEFFICIENTS
The device supports up to 11 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 osets.
3. Calculates the linearization factor as:
An × sin(n × t + φn )
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
x
LIN_10
–x
LIN_3
B
IN16
B
IN10
Maximum Full Scale Input
Coefficients stored in
EEPROM
Input function
Input function
Output function Output function
A
A
A
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
25
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
TYPICAL PERFORMANCE CHARACTERISTICS
0 50 100 150 200 250 300 350
−1
−0.8
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
Encoder Position
Angle Error
Figure 21: Typical Angle Error versus Encoder Position
(300 G, 25ºC)
−40 −20 0 20 40 60 80 100 120 140
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Temperature (ºC)
Angle Error in Degrees
Mean
±3 Sigma
Figure 22: Peak Angle Error over Temperature
(300 G)
−40 −20 0 20 40 60 80 100 120 140
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Temperature (ºC)
Drift in Degrees
Mean
±3 Sigma
Figure 23: Maximum Absolute Drift from 25ºC Reading
(300 G)
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
26
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Figure 24: Noise Distribution over Temperature
(3 Sigma, 300 G)
-40 -20 100 120 140
Ambient Temperature in Degrees C
0
0.5
1
1.5
A1335 Noise in degrees
0 20 40 60 80
Mean
±3 Sigma
Figure 25: Noise Performance over Temperature
(3 Sigma, 300 G)
0 0.5 1 1.5
Noise in degrees
0
1
2
3
4
5
6
7
Frequency (%)
150ºC
25ºC
–40ºC
150ºC
25ºC
–40ºC
18
12
10
8
6
4
2
0
Count (%)
14
16
12 13 14 15 16 17 18 19 20
ICC in mA
Figure 26: ICC Distribution over Temperature
(VCC = 5.5 V)
0 50 100 150
12
13
14
15
16
17
18
19
20
Ambient Temperature (ºC)
A1335 ICC in mA
Mean
±3 Sigma
Figure 27: ICC over Temperature
(VCC = 5.5 V)
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
27
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
For Reference Only – Not for Tooling Use
(Reference MO-153 AB-1)
NOTTO 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
16
X
0.65 BSC
0.25 BSC
21
14
1.59
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 Vi
ew
= 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 28: Package LE, 14-Pin TSSOP (Single Die Version)
PACKAGE OUTLINE DRAWINGS
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
28
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A
1.20 MAX
0.025
0.05
0.30
0.19
0.20
0.09
+0.15
–0.10
8º
0º
0.60
1.00 REF
C
SEATING
PLANE
C0.10
X
0.65 BSC
0.25 BSC
2
2
1
1
24
24
7.80 ±0.10
4.40 ±0.10
2.20
6.40 BSC
GAUGE PLANE
SEATING PLANE
A
B
B
0.65
1.65
0.45
D
D
D
D
DD
Hall elements (E1, E2), corresponding to respective die; not to scale
1.00
3.40
E1 E2
C Branding scale and appearance at supplier discretion
E
E
C
PCB Layout Reference View
(Reference MO-153 AD)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
Terminal #1 mark area
Reference land pattern layout (reference IPC7351 TSOP65P640X120-25M);
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 can improve thermal dissipation
(reference EIA/JEDEC Standard JESD51-5)
Active Area Depth 0.36 mm REF
1
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
NNNNNNNNNN
YYWW
LLLLLLLLLL
Figure 29: Package LE, 24-Pin TSSOP (Dual Die Version)
Precision Hall-Effect Angle Sensor IC
with I2C, SPI, and SENT Interfaces
A1335
29
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
I2C™ is a trademark of Philips Semiconductors.
Revision Change Pages Responsible Date
– Initial release All W. Wilkinson September 21, 2015
1
Updated Angle Characteristics; reduced SENT and Manchester information
redundant with A1335 programming guide; added Field Strength section and
charts; added on-axis and off-axis figures; corrected CVH location in single-die
package outline drawing.
1, 7,
19, 20,
27
W. Wilkinson December 17, 2015
2 Corrected LE-24 Package Outline Drawing dimensions 28 W. Wilkinson April 15, 2016
3 Updated Magnetic Field values in Operating Characteristics table 6 W. Wilkinson July 5, 2016
4
Added description of zero degree position, CS_idle time parameter;
CVH self-test operation restricted to field ≤ 300 G, temperature ≥ 25°C;
Noise plots and table entry updated with 3 sigma values.
4, 6, 10,
18, 24,
26
W. Wilkinson July 30, 2018
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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.
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