A1338
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
FEATURES AND BENEFITS
DESCRIPTION
• Contactless 0° to 360° angle sensor IC, for angular
position and rotation direction measurement
□ Circular Vertical Hall (CVH) technology provides
a single-channel sensor system, with air gap
independence
• 12-bit resolution possible in Low RPM mode, 10-bit
resolution in High RPM mode
• Angle Refresh Rate (output rate) configurable between
25 and 3200 μs through EEPROM programming
□ Capable of sensing magnetic rotational speeds up to
7600 rpm, and up to 30,000 rpm with reduced accuracy
Continued on the next page…
PACKAGES:
14-pin TSSOP (Suffix LE)
Not to scale
The A1338 is a 0° to 360° angle sensor IC that provides
contactless high-resolution angular position information based
on magnetic circular vertical Hall (CVH) technology. It has a
system-on-chip (SoC) architecture that includes: a CVH front
end, digital signal processing, digital SPI, and SENT or PWM
outputs. It also includes on-chip EEPROM technology, capable
of supporting up to 100 read/write cycles, for flexible end of
line programming of calibration and configuration parameters.
The A1338 is ideal for automotive applications requiring 0° to
360° angle measurements, such as electronic power steering
(EPS), seatbelt motor position systems, rotary PRNDLs, and
throttle systems.
The A1338 was designed with safety-critical application
requirements in mind. It includes user-controlled on-chip
logic built-in self-test (LBIST) and full signal path diagnostics
to enable customers to determine if the IC is operating in a
proper manner.
The A1338 supports a Low RPM mode for slower rate
applications and a High RPM mode for high-speed applications.
High RPM mode is for applications that require higher refresh
rates to minimize error due to latency. Low RPM mode is for
applications that require higher resolution operating at lower
angular velocities.
Single SoC
Continued on the next page…
A1338
BYP1_1
BYP2_1
VCC_1 (also
Programming)
SoC
Regulator
To all internal circuits
EEPROM
ECC Error Detection /
Correction
GNDA_1
GNDD_1
CVH Self-Test
CVH Self-Test
Control
Amplifier
ADC
Bandpass
Filter
PWM or SENT
Interface
Angle
Detect
PWM_1/SENT_1
Temp
Sensor
Multi-Segment
Circular Vertical Hall
CS_1/ID0_1
MISO_1
MOSI_1
SCLK_1/ID1_1
BIAS_1
ADC
Digital Processing
SPI
Interface
with
4-bit CRC
Adjustable Rotational
Discontinuity
Direction
Point
(0° Angle) CW /CCW
Data
Registers
TC Segment
Processing
Figure 1: A1338 Magnetic Circuit and IC Diagram
A1338LLE-DS, Rev. 7
MCO-0000279
October 19, 2021
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
FEATURES AND BENEFITS (continued)
• SPI (mode 3), and SENT (Single Edge Nibble Transmission)
or PWM (Pulse-Width Modulation)*
□ SPI interface provides a robust communication protocol for
fast angle readings*
□ SENT output supports four modes: SAEJ2716 (JAN2010)
and Allegro proprietary options of Triggered SENT
(TSENT), Sequential SENT (SSENT), and Addressable
SENT (ASENT)*
□ 4-bit CRC on SPI messages
□ User-Programmable Missing Magnet Error flag for
notifying controller of low magnetic field level
• Diagnostics are initiated over the SPI or SENT interface and
can directly test proper operation of the IC in safety-critical
applications
□ Programmable via Manchester Encoding on the VCC line,
reducing external wiring*
• EEPROM with Error Correction Control (ECC) configuration,
sensor calibration including end-of line adjustments like
programmable angle reference (0°) position and rotation
direction (CW or CCW)
□ SPI and SENT interfaces allows use of multiple independent
sensors for applications requiring redundancy*
• Absolute maximum VCC of 26.5 V for increased robustness
and direct connection to automotive vehicle battery
• Advanced diagnostics to support safety-critical applications,
including:
□ On-chip, user-controlled logic built-in self-test (LBIST) and
signal path diagnostics
*
See Selection Guide for more details.
DESCRIPTION (continued)
The A1338 is available in a single-die 14-pin TSSOP package. The
package is lead (Pb) free with 100% matte-tin leadframe plating.
SELECTION GUIDE
[1]
Part Number
System Die
Output Protocols
Package
Packing [1]
A1338LLETR-T
Single
SPI and SENT
14-pin TSSOP
4000 pieces per 13-in. reel
A1338LLETR-P-T
Single
SPI and PWM
14-pin TSSOP
4000 pieces per 13-in. reel
Contact Allegro™ for additional packaging options.
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
2
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Table of Contents
Features and Benefits............................................................ 1
Description........................................................................... 1
Packages............................................................................. 1
A1338 Magnetic Circuit and IC Diagram................................... 1
Selection Guide.................................................................... 2
Specifications....................................................................... 3
Absolute Maximum Ratings................................................. 3
Thermal Characteristics...................................................... 3
Typical Application Diagram.................................................... 4
Pinout Diagrams and Terminal List.......................................... 5
Functional Block Diagram...................................................... 6
Operating Characteristics....................................................... 7
Functional Description......................................................... 10
Overview........................................................................ 10
Angle Measurement......................................................... 10
Impact of High-Speed Sensing.......................................... 10
Angle Resolution and Representation..................................11
Programming Modes........................................................ 12
SPI System-Level Timing.................................................. 12
Power-Up....................................................................... 12
PWM Output (“-P” option)................................................. 12
Error Reporting in PWM.................................................... 12
Manchester Serial Interface.................................................. 13
Entering Manchester Communication Mode........................ 13
Transaction Types............................................................ 13
Writing to EEPROM......................................................... 13
Manchester Interface Reference........................................ 14
SENT Output Mode.......................................................... 15
Diagnostics..................................................................... 18
Serial Interface Structure...................................................... 19
Application Information........................................................ 25
Serial Interface Description............................................... 25
Calculating Target Zero-Degree Angle................................ 25
Bypass Pins Usage.......................................................... 25
Changing Sampling Modes............................................... 26
Magnetic Target Requirements.......................................... 26
Redundant Applications and Alignment Error....................... 27
System Timing and Error.................................................. 27
Characteristic Performance Data.......................................... 28
EMC Reduction.................................................................. 30
Package Outline Drawings................................................... 31
ABSOLUTE MAXIMUM RATINGS
Rating
Unit
Forward Supply Voltage
Characteristic
Symbol
VCC
Not sampling angles
26.5
V
Reverse Supply Voltage
VRCC
Not sampling angles
–18
V
5.5
V
All Other Pins Forward Voltage
VIN
All Other Pins Reverse Voltage
VR
Operating Ambient Temperature
TA
Maximum Junction Temperature
Storage Temperature
Notes
0.5
V
–40 to 150
°C
TJ(max)
165
°C
Tstg
–65 to 170
°C
L range
THERMAL CHARACTERISTICS: May require derating at maximum conditions; see application information
Characteristic
Package Thermal Resistance
[1] Additional
Symbol
RθJA
Test Conditions [1]
Value
Unit
82
°C/W
LE-14 package
thermal information available on the Allegro website.
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
3
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
VCC
0.1 µF
0.1 µF
0.1 µF
BYP1_1
BYP2_1* VCC_1
CS_1
SCLK_1
MOSI_1
MISO_1
BIAS_1
Host
Microprocessor
PWM_1/SENT_1
Optional
A1338
GNDA_1
GNDD_1
Figure 2: Typical A1338 Configuration Using SPI Interface
(See “EMC Reduction” Section for application circuits that require a higher level of EMC immunity.)
* Secondary bypass capacitors only required when using Elevated SPI Output Voltage. Contact Allegro for availability.
Vcc
Vs
0.1 µF
RP
Vcc
BYP2*
PWM/SENT
BYP1
0.1 µF
PWM or
SENT Out
A1338
MOSI
MISO
CS/ID0
SCLK/ID1
GND
BIAS
Figure 3: Typical A1338 Configuration Using PWM or SENT Output. ID Value of 002.
ID0/ID1 brought to BYP or GND to configure Manchester address.
When configuring an IC for address 002, MOSI should be tied to BYP.
* Secondary bypass capacitors only required when using Elevated SPI Output Voltage. Contact Allegro for availability.
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
4
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
PINOUT DIAGRAMS AND TERMINAL LIST
BYP1_1
1
14 GNDD_1
GNDD_1
2
13 CS_1/ID0_1
GNDA_1
3
12 MOSI_1
SENT_1/PWM_1
4
11 SCLK_1/ID1_1
VCC_1
5
10 MISO_1
NC
6
9
BYP2_1
NC
7
8
BIAS_1
14-Pin TSSOP LE Package Pinouts
Terminal List Table
Pin Name
Pin Number
BYP1_1
1
External Bypass Capacitor Terminal for Internal Regulator
Function
BYP2_1
9
External Bypass Capacitor Terminal for Internal Regulator
CS_1 /ID0_1
13
GNDA_1
3
Device Analog Ground Terminal
GNDD_1
2, 14
Device Digital Ground Terminal
MISO_1
10
SPI Master Input/Slave Output
MOSI_1
12
SPI Master Output Slave Input
SLCK_1/ID1_1
11
SENT_1/PWM_1
4
SENT Output; PWM Output; SENT for A1338LLETR-T; PWM for A1338LLETR-P-T
BIAS_1
8
Bias Connection; connect to ground or pull up to 3.3 V
VCC_1
5
Power Supply; also used for EEPROM Programming
NC
6, 7
Option 1: SPI Chip Select Terminal, Active Low Input
Option 2: ID0 bit to indicate Slave Address for SSENT or ASENT communication modes only
Option 1: SPI Clock Terminal
Option 2: ID1 bit to indicate Slave Address for SSENT or ASENT communication modes only
Not internally connected; tie to GNDD
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
5
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
A1338
BYP1_1
BYP2_1
VCC_1 (also
Programming)
SoC
Regulator
To all internal circuits
EEPROM
ECC Error Detection /
Correction
GNDA_1
GNDD_1
CVH Self-Test
CVH Self-Test
Control
Amplifier
ADC
Bandpass
Filter
PWM or SENT
Interface
Angle
Detect
PWM_1/SENT_1
Temperature
Sensor
Multi-Segment
Circular Vertical Hall
CS_1/ID0_1
MISO_1
MOSI_1
SCLK_1/ID1_1
ADC
Digital Processing
SPI
Interface
with
4-bit CRC
Adjustable
Rotational
Discontinuity
Direction
Point
CW/CCW
(0° Angle)
Data
Registers
TC Segment
Processing
BIAS_1
Figure 4: Functional Block Diagram
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
6
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
OPERATING CHARACTERISTICS: Valid over the full operating voltage and ambient temperature ranges, unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ. [1]
Max.
Unit [2]
3.7
–
16
V
ELECTRICAL CHARACTERISTICS
Supply Voltage
VCC
Supply Current
ICC
Undervoltage Lockout Threshold
Voltage [3]
VCC Low Flag Threshold [4]
Supply Zener Clamp Voltage
Reverse-Battery Current
Power-On Time [5]
TA = 150°C
–
8.25
10
mA
VUVLOHI
Maximum VCC , dV/dt = 1V/ms, TA = 25°C
–
–
3.6
V
VUVLOLOW
Maximum VCC , dV/dt = 1V/ms, TA = 25°C
2.9
–
–
V
3.5
–
3.9
V
VUVLOTH
VZSUP
26.5
40
–
V
VRCC = –18 V, TA = 25°C
–5
–
0
mA
–
300
–
µs
VBYP1
TA = 25°C, CBYP = 0.1 µF
2.5
2.7
2.9
V
VBYP2
TA = 25°C, CBYP2 = 0.1 µF;
Contact Allegro for availability
2.9
3.1
3.3
V
IRCC
ICC = ICC(AWAKE) + 3 mA, TA = 25°C
tPO
Bypass1 Pin Output Voltage [6]
Voltage [6]
Bypass2 Pin Output
(Elevated SPI Output Mode)
SPI INTERFACE SPECIFICATIONS
Digital Input High Voltage [7]
VIH
MOSIx, SCLKx, ¯C¯ ¯S¯ x pins
2.4
–
5.5
V
Digital Input Low Voltage [7]
VIL
MOSIx, SCLKx, ¯C¯ ¯S¯ x pins
–
–
0.5
V
CSx Pin Input Bias Current
IBIAS
VCSx = 3.3 V
–
15
–
µA
SPI Output High Level
VOH1
MISOx pins, CL = 20 pF, CBYP1 = 0.1 µF,
CBYP2 grounded
2.5
2.7
2.9
V
SPI Output High Level
(Elevated SPI Output Mode)
VOH2
MISOx pins, CL = 20 pF, CBYP1 = 0.1 µF,
CBYP2 = 0.1 µF. Contact Allegro for availability.
2.9
3.1
3.3
V
SPI Output Low Voltage
VOL
MISOx pins, CL = 20 pF
–
0.3
–
V
SPI Clock Frequency [7]
fSCLK
MISOx pins, CL = 20 pF
0.1
–
10
MHz
SPI Clock Duty Cycle [7]
DfSCLK
SPICLKDC, 5 V compliant
40
–
60
%
tSPI
5 V compliant
5.8
–
588
kHz
Chip-Select to First SCLK Edge [7]
tCS
¯ x going low to SCLKx falling edge
Time from ¯C¯ ¯S
50
–
–
ns
Data Output Valid Time [7]
tDAV
Data output valid after SCLKx falling edge
–
–
40
ns
SPI Frame Rate [7]
MOSI Setup
Time [7]
MOSI Hold Time [7]
SCLK to CS Hold
Time [7]
Capacitive Load [7]
tSU
Input setup time before SCLKx rising edge
25
–
–
ns
tHD
Input hold time after SCLKx rising edge
40
–
–
ns
tCHD
¯ x rising edge
Hold SCLKx high time before ¯C¯ ¯S
5
–
–
ns
Loading on digital output (MISOx) pin
with SPI Clock Frequency = 10 MHz
–
–
20
pF
CL
Continued on the next page…
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
7
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
OPERATING CHARACTERISTICS (continued): Valid over the full operating voltage and ambient temperature ranges,
unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ. [1]
Max.
Unit [2]
PWM Frequency Code = 00
–
122
–
Hz
PWM Frequency Code = 01
–
1.024
–
kHz
PWM Frequency Code = 10
–
2.048
–
kHz
PWM INTERFACE SPECIFICATIONS (A1338LLETR-P-T variants only)
PWM Carrier Frequency
fPWM
PWM Duty Cycle Minimum
DPWM(min)
–
5
–
%
PWM Duty Cycle Maximum
DPWM(max)
–
95
–
%
5 kΩ ≤ Rpullup ≤ 50 kΩ
–
–
0.2
V
2 kΩ ≤ Rpullup < 5 kΩ
–
–
0.4
V
Minimum Rpullup = 2 kΩ
0.9 × VS
–
–
V
Maximum Rpullup = 50 kΩ
0.7 × VS
–
–
V
–
30
–
mA
–10
–
10
%
VPWM(L)
PWM Output Signal [8]
VPWM(H)
Maximum Sink Current
ILIMIT
Output FET on, TA = 25°C
PWM Carrier Frequency Tolerance [7]
–
Deviation from expected fPWM
PWM Resolution
–
12-bit angle value
0.022
–
%DC/LSB
1σ, TA = 25°C, fPWM = 2 kHz
0.18
–
Hz
1σ, TA = 25°C, fPWM = 1 kHz
0.11
–
Hz
1σ, TA = 25°C, fPWM = 124 Hz
0.01
–
Hz
3σ, 300 G, TA = 25°C, no AVG
0.095
–
%DC
3σ, 300 G, fPWM = 2 kHz, AVG = 0x4 or greater
0.095
–
%DC
3σ, 300 G, fPWM = 1 kHz, AVG = 0x5 or greater
0.03
–
%DC
3σ, 300 G, fPWM = 124 Hz, AVG = 0x7
0.027
–
%DC
–0.35
–
0.35
%DC
Tick time = 3 µs
–
–
1
ms
Tick time = 0.5 µs, 3 data nibbles, SCN, and CRC,
nibble length = 27 ticks
–
96
–
µs
5 kΩ ≤ Rpullup ≤ 50 kΩ
–
–
0.2
V
2 kΩ ≤ Rpullup < 5 kΩ
–
–
0.4
V
Minimum Rpullup = 2 kΩ
0.9 × VS
–
–
V
Maximum Rpullup = 50 kΩ
0.7 × VS
–
–
V
VSENTtrig(L)
–
–
1.4
V
VSENTtrig(H)
2.8
–
–
V
Tick time = 0.5 µs, 3 data nibbles, SCN, and CRC,
nibble length = 27 ticks
2
–
–
µs
PWM Frequency Jitter
PWM Duty Cycle Jitter
PWM Thermal Duty Cycle Drift [7]
fPWM(JITTER)
DPWM(JITTER)
DPWM(THDRIFT) Change in duty cycle from 25°C to 150°C; 300 G
SENT PROTOCOL SPECIFICATIONS (A1338LLETR-T variants only)
SENT Message Duration
Minimum Programmable SENT
Message Duration
tCVHST
tSENTMIN
VSENT(L)
SENT Output Signal [7]
VSENT(H)
SENT Output Trigger Signal
Minimum Time Frame for SENT
Trigger Signal
tSENTMIN
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
–
23
–
ms
–
10
–
ms
DIAGNOSTIC SPECIFICATIONS
CVH Self-Test Time
tUI_DIAG
Logic BIST Coverage vs. Time
tLBISTXX
70% Coverage
Continued on the next page…
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
8
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
OPERATING CHARACTERISTICS (continued): Valid over the full operating voltage and ambient temperature ranges,
unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ. [1]
Max.
Unit [2]
EEPROM PROGRAMMING PULSES
Pulse High Time
tPULSE(H)
Time above minimum pulse voltage
8
10
11
ms
Rise Time
tr
10% to 90% of minimum pulse level
300
–
–
µs
Fall Time
tf
10% to 90% of minimum pulse level
60
–
–
µs
Applied on VCC line
18
19
19.5
V
0.002
–
50
ms
–
–
1500
Gpp
–
12
–
bit
B = 300 G, TA = 25°C, ORATE = 0
–
11.59
–
bit
High RPM mode
–
25
–
µs
Low RPM mode, AVG = 011 (varies with AVG mode,
refer to the appendix Programming Reference)
–
200
–
µs
Low RPM mode (see Figure 4)
–
60
–
µs
TA = 25°C, ideal magnet alignment, B = 300 G,
target rpm = 0
–
0.5
–
degrees
TA = 150°C, ideal magnet alignment, B = 300 G,
target rpm = 0
–1.3
–
1.3
degrees
TA = 25°C, B = 300 G, 3 sigma noise,
no internal filtering
–
0.35
–
degrees
TA = 150°C, no internal filtering, B = 300 G,
3 sigma noise, target rpm = 0
–
0.55
–
degrees
TA = 150°C, B = 300 G
–1.4
–
1.4
degrees
TA = –40°C, B = 300 G
–
±1
–
degrees
B = 300 G, typical maximum drift observed after
AEC-Q100 qualification testing
–
±0.5
–
degrees
Pulse Voltage
VPULSE
Separation Time
tPULSE(f-r)
Timing between first pulse dropping below 6 V and
2nd pulse rising above 6 V
MAGNETIC CHARACTERISTICS
Magnetic Field
B
Range of input field
ANGLE CHARACTERISTICS
Digital Output Word Length [8]
Effective
RESANGLE
Resolution [9]
Angle Refresh Rate [10]
tANG
Response Time
tRESPONSE
Angle Error
ERRANG
Angle Noise
NANG
Temperature Drift
ANGLEDRIFT
ANGLEDRIFT-
Angle Drift Over Lifetime
LIFE
[1] Typical
data is at TA = 25°C and VCC = 5 V, and it is for design estimates only.
G (gauss) = 0.1 mT (millitesla).
[3] At power-on, the die will not respond to commands until V
CC rises above VUVLOHI.
After that, the die will perform and respond normally until VCC drops below
VUVLOLOW .
[4] VCC Low Threshold Flag will be sent via the SPI interface as part of the angle
measurement.
[5] During the power-on time period, the A1338 SPI transactions are not guaranteed.
[6] The output voltage and current specifications are to aid in PCB design. The pin
is not intended to drive any external circuitry. The specifications indicate the
peak capacitor charging and discharging currents to be expected during normal
operation.
[7] Parameter is not guaranteed at final test. Determined by design.
[8] RES
ANGLE represents the number of bits of data available for reading from the die
registers.
[9] Effective Resolution is calculated using the formula below:
[2] 1
log2(360) – log2
[10] The
( )
1
n
Magnet
Position
Position 1
Position 2
t
Response Time
Sensor
Output
Output 1
Output 2
n
i=1
i
rate at which a new angle reading will be ready.
Figure 5: Def inition of Response Time
Allegro MicroSystems
955 Perimeter Road
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t
9
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Overview
FUNCTIONAL DESCRIPTION
Table 1: Refresh Rate Based on Quantity of Samples Averaged
The A1338 is a rotary position Hall-sensor-based device. It
incorporates an electrically independent Hall-based sensor die to
provide solid-state consistency and reliability, and to support a
wide variety of automotive applications. The Hall-sensor-based
die measures the direction of the magnetic field vector through
360° in the x-y plane (parallel to the branded face of the device)
and computes an angle measurement based on the actual physical reading, as well as any internal configuration parameters that
have been set by the user. The output of the die is used by the
host microcontroller to provide a single channel of target data.
This device is an advanced, programmable system-on-chip (SoC).
The integrated circuit includes a circular vertical Hall (CVH)
analog frontend, a high-speed sampling A-to-D converter, digital
filtering, digital signal processing, and an SPI, SENT, or PWM
output of the processed angle data.
Angle Measurement
The A1338 can monitor the angular position of a rotating magnet at speeds ranging from 0 to more than 7600 rpm. At lower
rotational speeds, the A1338 is able to measure angle data with
minimal angular latency between the actual magnet and sensor
output. As the rpm increases, the angular latency between the
magnet and sensor output also increases. Above 7600 rpm, the
A1338 continues to provide angle data; however, the accuracy is
proportionally reduced.
The A1338 can be configured to operate in two angular measurement modes of operation: Low RPM mode, and High RPM
mode. Low RPM mode allows a programmable number of
internal angle samples to be accumulated and averaged, providing
greater resolution while reducing the update rate. This is suitable
for lower rpm applications (0 to ≈500 rpm). For high-speed applications, the averaging function may be bypassed by operating in
High RPM mode.
The actual update rate of Low RPM mode can be changed by
setting the AVERAGING bits in the EEPROM (see the appendix
Programming Reference for details). Table 1 describes the different levels of averaging available in Low RPM mode. A setting of
0002 is equivalent to High RPM mode.
AVG
[2:0]
Quantity of Samples
Averaged
Refresh Rate
(µs)
000
1
25
001
2
50
010
4
100
011
8
200
100
16
400
101
32
800
110
64
1600
111
128
3200
The A1338 has a typical output bandwidth of 40 kHz (25 µs
refresh rate) in High RPM mode. In High RPM mode, a new angle
measurement is available at the internal angle output register to be
transmitted over the SPI/SENT or PWM output ports every 25 µs.
There is a latency of 60 µs from when there is a change in the
position of the target magnet field to when the new representative
angle is updated in the internal angle output register. This latency
effectively represents the age of the angle measurement.
Impact of High-Speed Sensing
Due to signal path latency, the angle information is delayed by
tRESPONSE. This delay equates to a greater angle value as the
rotational velocity increases (i.e. a magnet rotating at 20,000 rpm
traverses twice as much angular distance in a fixed time period
as a magnet rotating at 10,000 rpm), and is referred to as angular
lag.
The lag is directly proportional to rpm, and may be compensated
for externally, if the velocity is known.
Angular lag can be expressed using the following equation:
Angle_Lag = (rpm × 6) / (16 × tRESPONSE)
(1)
where rpm represents the rotational velocity of the magnet,
Angle_lag is expressed in degrees, and tRESPONSE is in µs.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Angle Resolution and Representation
4
In addition to using the internal averaging of the sensor, angle
resolution is also dependent on the intensity (B, in gauss) of
the applied magnetic field from the target. At lower intensities,
a reduced signal-to-noise ratio will cause one or two LSBs to
change state randomly due to noise. These factors work together,
so when High RPM mode is selected, the effective range of resolution is 8 to 10 bits (from lower to higher field intensities), and
in Low RPM mode, the effective range is 11 to 12 bits, depending
on field strength and AVG selection.
Angle Lag (degrees)
3.5
3
2.5
2
1.5
1
0.5
0
0
2,000
4,000
6,000
RPM
8,000
10,000
12,000
Figure 6: Angle Lag versus RPM, 60 µs Response Time
Regardless of the field intensity and mode selection, the transmission protocol and number formatting remains the same. The MSB
is always transmitted first. The entire number should be read.
The Output Angle is always calculated at maximum resolution.
To be more explicit, when reading the digital angle value:
AngleOUT = 360 (°) × D[12:0] / (213)
(2)
This formula is always true, regardless of the applied field intensity. What changes with the field and speed setting is how “quiet”
the LSBs of the measurement data (D 12:x) will be.
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The A1338 wakes up in a default state that sets all SPI registers
to their default value. It is important to note that, regardless of the
state of the device before a power cycle, the device will re-power
with default values. For example, on every power-up, the device
will power up in the mode set in the EEPROM bit RPM. The
state of the EEPROM is unchanged.
PWM Output (“-P-” option)
The A1338LLETR-P-T option provides a pulse-width-modulated
output with duty cycle proportional to the measured angle. The
PWM duty cycle ranges between 5% (corresponding to 0° angle)
and 95% (corresponding to 360° angle). The 0% and 100%
(Pulled Low and Pulled High) states are reserved for error condi-
D0T
D1T
D2T
D3T
D4T
D5T
D6T
D7T
D8T
D9T
D10T
D(x) = tpulse(x) / Tperiod
tpulse(5)
Tperiod
0T
1T
2T
3T
4T
5T
6T
7T
8T
9T
10T
11T
Time
Figure 7: PWM mode outputs a duty-cycle-based waveform
that can be read by the external controller as a cumulatively
changing continuous voltage.
Within each cycle, the output is high for the first 5% of the period. The
middle 90% of the period is a linear interpolation of the angle as samples
at the beginning of the PWM period.
PWM Period
Power-Up
(0 Degrees)
PWM Period
PWM Period
5 % LOW
5 % HIGH
Upon applying power to the A1338, the device automatically runs
through an initialization routine. The purpose of this initialization is to ensure that the device comes up in the same predictable
operating condition every power cycle. This initialization routine
takes a finite amount of time to complete, which is referred to as
Power-On Time, tPO .
CLAMP_LOW
0
360 Degrees
5 % LOW
5 % HIGH
• Best case: 1.5 SPI cycles; 2 µs, assuming a 10 MHz SPI clock
D = 95%
120
Degrees
PWM Period
240 Degrees
5 % LOW
5 % HIGH
• Worst case: 2 CVH cycle + 2 SPI cycles
D = 50%
CLAMP_HIGH
5 % LOW
5 % HIGH
The A1338 outputs a new angle measurement every tANG µs. In
High RPM mode, the A1338 outputs a new angle measurement
every tANG µs, with an effective resolution of 10 bits. There
is, however, a latency of tLAT , from when the rotating magnet
is sampled by the CVH to when the sampled data has been
completely transmitted over the SPI interface. Because an SPI
interface Read command is not synchronous with the CVH timing, but instead is polled by the external host microcontroller, the
latency can vary. For single back-to-back SPI transactions (first
transaction is sending the Read register 0x0 command, second is
retrieving the angle data) the following scenarios are possible:
D = 5%
360
5 % LOW
5 % HIGH
SPI System-Level Timing
Magnetic Field Angle (°)
The EEPROM can be programmed through the dedicated SPI
interface pins or via Manchester encoding on the VCC pin, allowing 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). The EEPROM provides persistent storage at end of
line for final parameters.
tion notifications.
PWM Waveform (V)
Programing Modes
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
5 % LOW
5 % HIGH
A1338
Figure 8: Pulse-Width Modulation (PWM) Examples
The angle is represented in 12-bit resolution and can never reach exactly
360°. The maximum duty cycle high period is:
DutyCycleMax (%) = (4095 / 4096) × 90 + 5 .
Error Reporting in PWM
The PWM output will tristate when any unmasked error is present (see ERR and ERR2 register descriptions). Error flags are
masked via bits within EEPROM 0x1E.
By default, the BATD error mask is set in EEPROM for all PWM
output ICs. This prevents the PWM output from tristating on
power-on.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
MANCHESTER SERIAL INTERFACE
To facilitate addressable device programming when using the
unidirectional SENT output mode with no need for additional
wiring, the A1338 incorporates a serial interface on the VCC line.
(Note: The A1338 may be programmed via the SPI interface,
with additional wiring connections. For detailed information on
part programming, refer to the A1338 programming manual).
This interface allows an external controller to read and write registers in the A1338 EEPROM and volatile memory. The device
uses a point-to-point communication protocol, based on Manchester encoding per G.E. Thomas (a rising edge indicates a 0
and a falling edge indicates a 1), with address and data transmitted MSB first. The addressable Manchester code implementation
uses the logic states of the SA0 (SPI CS pin) / SA1 (SPI SCLK
pin) to set address values for the die. In this way, individual communication with up to four A1338 dies is possible.
To prevent any undesired programming of the A1338, the serial
interface can be disabled by setting the Disable Manchester bit
(0x19 bit 18) to a 1. With this bit set, the A1338 will ignore any
Manchester input on VCC.
Entering Manchester Communication Mode
Transaction Types
As shown in Figure 9, the A1338 receives all commands via the
VCC pin, and responds to Read commands via the SENT pin.
This implementation of Manchester encoding requires the communication pulses be within a high (VMAN(H)) and low (VMAN(L))
range of voltages on the VCC line. Writing to EEPROM is supported by two high-voltage pulses on the VCC line.
Each transaction is initiated by a command from the controller;
the A1338 does not initiate any transactions. Two commands are
recognized by the A1338: 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 A1338 to
boost the voltage on the EEPROM gates. Refer to the programming manual for specifics on sensor programming and protocol
details.
Provided the Disable Manchester bit is not set in EEPROM, the
A1338 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 Communication 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.
Write/Read Command Manchester Code
ECU
VCC
A1338
SENT
Read Manchester Code
GND
Figure 9: Top-Level Programming Interface
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Manchester Interface Reference
Table 2: Manchester Interface Protocol Characteristics [1]
Characteristics
Symbol
Note
Min.
Typ.
Max.
Unit
Defined by the input message bit rate sent from
the external controller
4
–
50
kbps
Data bit pulse width at 4 kbps
243
250
257
µs
Data bit pulse width at 100 kbps
9.5
10
10.5
µs
Deviation in tBIT during one command frame
–11
–
+11
%
VCC <
6.0 V
–
–
–
¼ × tbit
–
¾ × tbit
µs
INPUT/OUTPUT SIGNAL TIMING
Bit Rate
Bit Time
tBIT
Bit Time Error
Write Delay
errTBIT
tWRITE(E)
Required delay from the end of the second
EEPROM Program pulse to the leading edge of
a following command frame
Delay from the trailing edge of a Read
tSTART_READ command frame to the leading edge of the Read
Acknowledge frame
Read Delay
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
Pulse High Time
tPULSE(H)
Time above minimum pulse voltage
8
10
11
ms
tr
10% to 90% of minimum pulse level
300
–
–
µs
tf
10% to 90% of minimum pulse level
60
–
–
µs
Applied on VCC Line
18
19
19.5
V
0.002
–
50
ms
Rise Time
Fall Time
Pulse Voltage
VPULSE
tPULSE(f-r)
Timing between first pulse dropping below 6 V
and 2nd pulse rising above 6 V
Manchester Code High Voltage
VMAN(H)
Applied to VCC line
7.8
–
–
V
Manchester Code Low Voltage
VMAN(L)
Applied to VCC line
–
–
6.3
V
Minimum Rpullup = 5 kΩ
0.9 × VS
–
–
V
Maximum Rpullup = 50 kΩ
0.7 × VS
–
–
V
–
–
0.2
V
Separation Time
INPUT SIGNAL VOLTAGE
OUTPUT SIGNAL VOLTAGE (APPLIED ON SENT LINE)
Manchester Code High Voltage
VMAN(H)
Manchester Code Low Voltage
VMAN(L)
[1] Determined
5 kΩ ≤ Rpullup ≤ 50 kΩ
by design.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
SENT Output Mode
Angle (°)
The SENT frame may be configured via EEPROM. The A1338
may operate in one of three broadly defined SENT modes (see
the A1337/8 Programming Manual for details on SENT modes
and settings).
• SAE J2716 SENT: Free-streaming SENT frame in accordance
with industry specification.
• 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).
4095
(1111 1111 1111)
2048
(1000 0000 0000)
0000
(0000 0000 0000)
SENT Data Value
(LSB)
(A1338LLETR-T option)
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 10. This data is inserted into a binary
pulse message, referred to as a frame, that conforms to the SENT
data transmission specification (SAEJ2716 JAN2010).
Figure 10: Angle is represented as a 12-bit digital value.
Vsupply
Sensor
ID = 0
Sensor
ID = 1
Sensor
ID = 2
Host
(ECU)
Sensor
ID = 3
R
C
Bus Capacitance
Figure 11: Allegro’s proprietary SENT protocol allows
multiple parts to share one common output bus.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
The duration of a nibble is denominated in ticks. The period of a
tick is set by the C_TICK_TIME parameter. The duration of the
nibble is the sum of the low-voltage interval plus the high-voltage
interval.
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 lowvoltage 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
C_SENT_DRIVE parameter.
0
5
12
0
Ticks
5
27
The parts of a SENT message are arranged in the following
required sequence (see Figure 13):
1. Synchronization and Calibration: Flags the start of the
SENT message.
2. Status and Communication Nibble: Provides A1338 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.
Table 3: Nibble Composition and Value
Ticks
Quantity of Ticks
Total
Binary
(4-bit)
Value
Decimal
Equivalent
Value
7
12
0000
0
5
8
13
0001
1
5
9
14
0002
2
Figure 12: General Value Formation for SENT
5
21
26
1110
14
0000 (left), 1111 (right)
5
22
27
1111
15
Message
Signal
Voltage
Message
Signal
Voltage
Low
High
Interval Interval
Low
Interval
Nibble Data Value = 0000
HighVoltage
Interval
5
High
Interval
Nibble Data Value = 1111
SENT_FIXED
SENT_FIXED
56 ticks
Nibble Name
LowVoltage
Interval
Synchronization
and Calibration
SENT_FIXED
12 to 27
ticks
Status and
Communication
12 to 27
ticks
Data 1
(MSB)
SENT_FIXED
SENT_FIXED
SENT_FIXED
12 to 27
ticks
12 to 27
ticks
Data 6
CRC
Pause
Pulse
(optional)
tSENT
Figure 13: General Format for SENT Message Frame
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Table 4: EEPROM Registers Map Table with Defaults (Factory-Reserved Registers Not Shown) [1]
EADR
State
0x17
SENT_CFG
0x18
CUST_CFG1
0x19
CUST_CFG2
0x1E
ERM
0x1F
CUST2
[1]
Bits
23
22
21
20
19
18
ZS
SS
SM
PO
IS
RES
LOCK
RES
RES
CIS
PWM_F
DA
RES
RES
17
16
MAXID
MAND
15
SCN_MODE
SCRC
NS
RPMD
14
13
12
11
DATA_MODE
FA
u_int_st
9
8
7
6
UV
4
3
2
1
0
SENT_DRIVE
MISSING_MAG_THRESHOLD
POL
MAN
5
TICK_TIME
pw_up_st
AVERAGE
MAN2
10
SENT_MODE
ANGLE_OFFSET
LBST CVHST GOVF
AH
AL
EU
ES
TR
TRNO
IE
MAGM BATD
CUST_EEP
For more details, see Programming Manual.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Diagnostics
The A1338 was designed with ISO 26262:2011 requirements in
mind and supports a number of on-chip self diagnostics to enable
the host microcontroller to assess the operational status of the
die. For example, the die can be user-configured for logic builtin self-test (LBIST) evaluation to ensure the digital circuits are
operational. Upon completion of an LBIST operation, the A1338
will set a pass/fail LBIST status flag in the device error (ERR)
register.
The A1338 die also supports several diagnostic features and status flags, accessible via an SPI read of the ERR register, to let the
user know if any issues are present with the A1338 or associated
magnetic system, as shown in Table 5.
USER-INITIATED DIAGNOSTICS
The die of the A1338 can be controlled by a microcontroller to
enter its CVH Self-Test mode via SPI or SENT.
When a CVH Self-Test mode operation is requested by the
microcontroller, the die initiates a test mode sequence whereby
it sequentially applies an internal constant bias current to every
contact element in the CVH ring. As each element in the CVH
ring is sequentially biased, an angle measurement is calculated.
The time to complete one revolution around the CVH ring and
calculate and store incremental angle measurements is tCVHST.
In addition, the die on the A1338 supports an on-chip userinitiated diagnostic (CVH Self-Test) mode that tests the entire
signal path, including the front end CVH sensing circuitry.
Table 5: Diagnostic Capabilities
Diagnostic/ Protection
Description
Output State
Loss of VCC
Determine if battery power was lost.
BATD Error flag is set; see ERR register table.
Reverse VCC Condition
Current Limiting (VCCx pin).
Output Below GND.
MISO/SENT/PWM Short to
VCC
Current Limiting (MISOx pin).
MISO/SENT/PWM Line: Pulled up to V-pullup.
Should not be tied to VCC if VCC > 5.5 V.
MISO/SENT/PWM Short to
Ground
Current Limiting (MISOx pin).
MISO/SENT/PWM Line: Pulled up to GND.
Logic Built-In Self-Test
(LBIST)
70% coverage for 10 ms BIST of all digital circuitry.
Error Flags set in SPI message when errors are
detected; see ERR2 Register table.
Signal Path Diagnostics
User controlled advanced CVH and full signal path diagnostics.
Error Flags set in SPI message when errors are
detected; see ERR2 Register table.
Internal Error
Monitors digital logic for proper function.
IERR Error flag is set; see ERR Register table.
Missing Magnet
Monitors magnet field level in case of mechanical failure.
MAGM Error flag is set; see ERR Register table.
EEPROM Error Detection
and Correction
Detection of single and dual bit error, and correction of single
bit error.
Error flags set in SPI message when errors are
detected or corrected; see ERR Register table.
VCC Low Flag
Asserted when VCC < VUVLOTH.
Bit 2 of SPI Output on MISO is set high. See
Programming manual for more details.
Temperature Out of Range
Die temperature has exceeded acceptable range.
See ERR Register table for more details.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
SERIAL INTERFACE STRUCTURE
The serial interface contains the Primary Serial Interface (PSI)
registers and the restricted Extended Addressing registers. The
PSI fields are used by the host for routine communication with
the A1338, such as retrieving current angle and turns count, error,
and status data, and managing certain configuration settings. For
information on extended addressing and EEPROM access, see the
A1338 programming manual.
Table 6: Primary Serial Interface Registers (Reserved Registers Not Shown)
Address (Hex)
Name (Symbol)
0x00
Angle Output (ANG)
Usage
0x04
Error (ERR1)
Read out error flags
0x05
Error (ERR2)
Read out error flags
Read out current angle (Note: 12-bit Angle Output located MSB first, in bits12:1; Bit0 is always ‘0’)
0x08
Control (CTRL)
Read or write configuration commands
0x0F
Key Code (KEY)
Write the Key Code to enable access to Extended Addressing registers
Table 7: Primary Serial Interface Registers Bits Map (Reserved Registers Not Shown)
Serial
Address
Register
Symbol
0x00
ANG
0x04
Addressed Byte (MSB)
12
11
10
9
8
7
ERR
–
–
–
–
–
–
0X05
ERR2
–
–
–
–
–
0x08
CTRL
–
–
–
–
–
0x0F
KEY
–
–
–
–
–
6
5
4
3
2
1
0
EEP2
EEP1
TMP
RES
IERR
MAGM
BATD
–
MANER
RES3
LBIST
CVHST
RES2
RES1
RES0
–
–
–
STS
TRST
RPM
TEN
ERST
ANGLE OUTPUT (12:1)
0
KEY_CODE
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
ANG (Angle Output) Register
Address: 0x00
Address
Bit
0x00
12
11
10
9
8
Name
7
6
5
4
3
2
1
ANGLE_OUTPUT
0
–
R/W
R
R
R
R
R
R
R
R
R
R
R
R
R
Value
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
Stores data on current angle reading.
ANGLE_OUTPUT [12:1] Current Angle
Most recent angle reading. Value is unsigned, stored in bits 12:1 (bit 0
defaults to 0). As the target turns, the angle value increases or decreases
according to the rotational polarity setting in EEPROM (CUST_CFG2
register, POL bit).
Bit
Value
12:1
0/1
Description
Current angle reading.
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20
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
ERR (Error) Register
Address: 0x04
Address
0x04
Bit
12
11
10
9
8
7
6
5
4
3
2
1
0
Name
–
–
–
–
–
–
EEP2
EEP1
TMP
RES
IERR
MAGM
BATD
R/W
–
–
–
–
–
–
R
R
R
R
R
R
R
Value
X
X
X
X
X
X
0/1
0/1
0/1
0/1
0/1
0/1
0/1
Reset
0
0
0
0
0
0
0
0
0
0
0
0
1
Error register. Indicates various current error conditions. When set, can only be cleared via the CTRL register ERST field, hard reset, or power-on reset
(see BATD for exception). If any of the error bits are asserted, the error flag on the serial interface will be asserted. Masking an error bit will prevent the
bit from asserting the serial interface error flag, but the error bit may still be asserted in this register.
EEP2 [6] EEPROM Error Flag 2
IERR [2] Internal Error
Uncorrectable dual-bit EEPROM error flag.
Bit
6
Value
Description
0
Error condition not present.
1
Error condition present.
EEP1 [5] EEPROM Error Flag 1
5
Value
Description
0
Error condition not present.
1
Error condition present.
TMP [4] Temperature Out of Range
This bit indicates an error condition when the die temperature has
exceeded the acceptable range.
Bit
4
Value
2
Value
Description
0
No digital logic timer error has been detected.
1
Digital logic timer error has been detected.
Monitors target magnet field level to detect field loss due to mechanical
failure in the application. Missing Magnet Field Threshold can be
customer programmed by writing to EEPROM Address 0x18, Bits 10:0
(MISSING_MAG_THRESHOLD). Allegro programs this to a default value
of 100 G, but the customer can readjust this field if they prefer.
Bit
1
Description
0
Error condition not present.
1
Error condition present.
RES [3] Reserved
Bit
MAGM [1] Target Magnet Loss
Corrected single-bit EEPROM error flag.
Bit
This bit is set to 1 if an internal logic error condition has been detected.
When this bit is set to 1, a general reset is recommended.
Value
Description
0
Error condition not present.
1
Error condition present.
BATD [0] Power Supply Loss
Indicates if battery power (VCC supply) was lost. By default also indicates at expected low power events: start-up, power-on reset, and after
exiting Transport mode. Before commencing normal operation, must be
set to 0 by asserting the ERST bit of the CTRL register (unless field is
masked in EEPROM by ERM register BATD field).
Bit
0
Value
Description
0
Error condition not present.
1
Error condition present.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
ERR2 (Error2) Register
Address: 0x05
Address
0x05
Bit
12
11
10
9
8
7
6
5
4
3
2
1
0
Name
–
–
–
–
–
–
MANER
RES3
LBIST
CVHST
RES2
RES1
RES0
R/W
–
–
–
–
–
–
R
–
R
R
–
R
R
Value
X
X
X
X
X
X
0/1
–
0/1
0/1
–
0/1
0/1
Reset
0
0
0
0
0
0
0
–
0
0
–
0
1
Error register. Indicates various current error conditions. When set, can only be cleared via the CTRL register ERST field, hard reset, or power-on reset
(see BATD for exception). If any of the error bits are asserted, the error flag on the serial interface will be asserted. Masking an error bit will prevent the
bit from asserting the serial interface error flag, but the error bit may still be asserted in this register.
MANER [6] Manchester/SENT Error Flag
Indicates Manchester/SENT Error.
Bit
6
Value
Description
0
Error condition not present.
1
Error condition present.
RES2 [2] Factory Reserved Bit
RES1 [1] Factory Reserved Bit
RES0 [0] Factory Reserved Bit
RES3 [5] Factory Reserved Bit
LBIST [4] LBIST Error Flag
This bit indicates that the Logic Built-In Self-Test (LBIST) failed.
Bit
4
Value
Description
0
Error condition not present.
1
Error condition present.
CVHST [3] Circular Vertical Hall Self-Test
This bit indicates that the CVH Built-In Self-Test (CVHST) failed.
Bit
3
Value
Description
0
Error condition not present.
1
Error condition present.
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
CTRL (Control) Register
Address: 0x08
Address
0x08
Bit
7
6
5
Name
–
–
R/W
–
–
Value
X
Reset
0
4
3
2
1
0
–
STST
RES1
RPM
RES0
ERST
–
RW1C
–
R/W
R/W
RW1C
X
X
X
X
0/1
0/1
0/1
0
0
0
0
0
0
0
Initialization and operation configuration control command settings.
RW1C: When a 1 is written to the field, the command is immediately executed, and the value returns to zero. When Reading the field, this type of field
will always read back 0.
STS [4] Self-Test Start
Commands the A1338 to begin Self-Test(s).
Which self-test is run, is determined by the U_INIT_ST field within
EEPROM. There are two self-tests:
1. Logic Built-In Self-Test (LBIST): Verifies digital gate integrity. This is a
modified version of digital scan testing. Requires approximately 10 ms to
run during which time no angle readings can take place
2. CVH Self-Test: Test of the front end transducer and signal path.
Requires approximately 40 ms to compete, during which time angle
readings are not available.
Bit
4
Value
RES0 [1] Reserved
ERST [0] Error Flags Reset
A feature to clear the values in the ERR register (0x04).
Bit
0
Value
Description
0
ERR register not cleared.
1
ERR register cleared.
Description
0
Does not trigger Self-Test.
1
Self-Test is triggered based on pre-selected
options in the “U_INIT_ST” field of EEPROM.
RES1 [3] Reserved
RPM [2] RPM Operating Mode (see Programming Manual)
This field is populated on power-up by the EEPROM field RPMD.
This field can be written during operation to temporarily override the
EEPROM. On the next power cycle, this field will reset to the value
determined by the EEPROM field RPMD. This bit must be a ‘1’ to enable
internal averaging.
Bit
2
Value
Description
0
Internal Averaging not allowed.
1
Internal Averaging allowed.
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23
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Normal
Operation
Diagnostic
Initiated Over
SPI or SENT
Bus?
Yes
No
Signal Path Test
Logic BIST
IC applies internal test
vectors to IC logic and
detects logic circuit
response.
(Angle output lost during
test for duration of
Logic BIST test.)
Bit asserted in register to
inform user of pass or fail
condition. User must read
register via SPI interface.
A1338 enters CVH Self-Test mode
and measures delta angle over
all 64 contacts of the CVH ring.
(Angle output lost for the duration of test)
Yes
All CVH
Delta Measurements =
Theta degrees?
Bit asserted in register to
inform user of pass condition.
User must read flag via
SPI interface, or SENT
interface, or PWM interfaces.
No
Bit asserted in register to
inform user of fail condition.
User must read flag via SPI
interface, or SENT interface, or
PWM interfaces.
Figure 14: User-Interface Diagnostic Diagram
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Serial Interface Description
APPLICATION INFORMATION
tion, and read the angle from the A1338 using the SPI interface
(AngleOUT). From this angle, the Reference Angle required to
program the A1338 can be computed as follows:
The A1338 features SPI, SENT, and PWM interfaces. The following figures show some typical application circuits for using
the A1338 with these interfaces.
Reference Angle = AngleOUT .
Bypass Pins Usage
Calculating Target Zero-Degree Angle
When shipped from the factory, the default angle value when oriented as shown in Figure 15, is approximately 21°. In some cases,
the end user may want to program an angle offset in the A1338 to
compensate for variation in magnetic assemblies, or for applications where absolute system level readings are required.
The internal algorithm for computing the output angle is as follows:
AngleOUT = AngleRAW – Reference Angle .
(4)
The bypass pins are required for proper operation of the device. A
0.1 µF capacitor should be placed in very close proximity to each
of the bypass pins.
When using the SPI communication protocol, the A1338 has
the ability to support host microcontroller inputs with Voltage
Input High (VIH) thresholds of 2 V (minimum). This option only
requires BYP1 to be populated with a 0.1 µF capacitor.
By using an optional second bypass capacitor on the BYP2 pins,
the A1338 can also support host microcontroller inputs with Voltage Input High (VIH) thresholds of 2.5 V (minimum). This option
requires that both BYP1 and BYP2 pins be populated with 0.1 µF
capacitors, and that the appropriate EEPROM configuration bit
(3)
The procedure to “zero out” the A1338 is quite simple. During final application calibration and programming, position
the magnet above the A1338 in the required zero-degree posi-
Target rotation axis
Target poles aligned with
A1338 elements
Target alignment for default angle setting
• Target rotation axis intersects the die
• Sets die 21° default point
(Example shows the die as element E1)
S
S
N
N
E1
E1
Pin 1
Figure 15: Orientation of Magnet Relative to Die
24
14
Hall element
location
Hall element
E1 location
1
Hall element
E2 location
1
Figure 16: Hall Element Located Off-Center within the Device Body
(refer to the Package Outline Drawing for reference dimensions)
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
be enabled. Contact Allegro for availability of parts with elevated
SPI output levels.
Changing Sampling Modes
The A1338 features a High RPM sampling mode and a Low
RPM sampling mode. The default power-on state of the A1338
is loaded from EEPROM. To configure the A1338 to Low RPM
mode, set the Operating mode to Low RPM mode by writing a
logic 1 to bit 2 (RPM) of the configuration commands (CTRL)
register, via the SPI interface.
Magnetic Target Requirements
The A1338 is designed to operate with magnets constructed with
a variety of magnetic materials, cylindrical geometries, and field
strengths, as shown in Table 8. Contact Allegro for more detailed
information on magnet selection and theoretical error.
1400
Magnetic Field (G)
The bypass pins are not intended to be used to source external
components. To assist with PCB layout, see the Operating Characteristics table for output voltage and current requirements.
1600
1000
800
NdFe30
600
SmCo24
400
200
0
Ceramic
(Ferrite)
0.5
2.5
4.5
6.5
8.5
Air Gap (mm)
Figure 17: Magnetic Field versus Air Gap for a magnet 6 mm
in diameter and 2.5 mm thick.
Allegro can provide similar curves for customer application magnets
upon request. Larger magnets are recommended for applications
that require optimized accuracy performance.
Table 8: Target Magnet Parameters
14
Diameter
(mm)
13
Thickness
(mm)
Neodymium (bonded)
15
4
Neodymium (sintered)*
10
2.5
Neodymium (sintered)
8
3
Neodymium / SmCo
6
2.5
12
11
10
Angle Error (±°)
Magnetic Material
1200
9
8
7
6
5
4
Thickness
S
N
3
2
1
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Eccentricity of SOC Chip Relative to Magnet Rotation Axis (mm)
Diameter
Figure 18: Angle Error versus Eccentricity
*A sintered Neodymium magnet with 10 mm (or greater) diameter and 2.5 mm
thickness is the recommended magnet for redundant applications.
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26
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Redundant Applications and Alignment Error
System Timing and Error
The A1338 is designed to be used in redundant, on-axis applications with a single magnet spinning over the die mounted in the
package. One challenge with this configuration is correctly lining
up the magnet with the device package, so it is important to be
aware of the physical location of the die.
The A1338 is a digital system, and therefore takes angle samples
at a fixed sampling rate. When using a sensing device with a
fixed sampling rate to sample a continuously moving target, there
will be error introduced that can be simply calculated with the
sampling rate of the device and the speed at which the magnetic
signal is changing. In the case of the A1338, the input signal is
rotating at various speeds, and the sampling rate of the A1338 is
fixed at ANG . The calculation would be:
Figure 18 illustrates the behavior of alignment error when using
a Ø10 mm × 2.5 mm Neodymium magnet that is located 2.7 mm
above the branded face of the package. The curve shows the
relationship between absolute angle error present on the output of
the die versus eccentricity of the die relative to the rotation axis
of the magnet.
The curve provides guidance to determine what the optimal magnet placement should be for a given application. For example, if
the center of the magnet rotation is placed at the midpoint of the
package, the die will have a maximum eccentricity of 0.88 mm.
ANG (µs) × angular velocity ( ° / µs) .
(5)
So the faster the magnetic object is spinning, the further behind in
angle the output signal will seem for a fixed sampling rate.
The magnet axis of rotation can be positioned directly above the
die, yielding zero alignment error.
dAXIAL1
Target rotation axis
Example of eccentricity:
Target rotation axis
centered on the package
Target counterclockwise
rotation (Minus counts)
Target clockwise rotation
(Plus counts)
dAXIAL1 = 0
Example of eccentricity:
Target rotation axis
centered on the die
Figure 19: Demonstration of Magnet to Sensing Element Eccentricity
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
CHARACTERISTIC PERFORMANCE DATA
2
1.8
1.6
1.6
1.4
1.4
1.2
1
0.8
0.6
1.2
1
0.8
0.6
0.4
0.4
0.2
0.2
0
-40
-20
0
20
40
60
80
Temperature (°C)
100
120
0
-40
140
Figure 20: Angle Error over Temperature (300 G)
1.5
-20
0
20
40
60
80
Temperature (°C)
100
120
140
Figure 21: Angle Drift Relative to 25°C (300 G)
25°C
150°C
1
-40°C
25°C
150°C
0.8
1
Noise (degrees)
Peak Angle Error (degrees)
Mean
±3 Sigma
1.8
Drift in Degrees
Angle Error in Degrees
2
Mean
±3 Sigma
0.5
0.6
0.4
0.2
0
300
400
500
600
700
800
Field Strength in Gauss
900
Figure 22: Angle Error over Field Strength
1000
0
300
400
500
600
700
Field Strength in Gauss
800
900
Figure 23: Typical Three Sigma Angle Noise
Over Field Strength
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
25
1.0
-40°C
25°C
150°C
0.8
15
Noise in degrees
Frequency (%)
20
Mean
±3 Sigma
10
5
0
0.4
0.2
0
0.3
0.6
0.9
1.2
0
-50
1.5
0
50
100
150
Noise in degrees
Ambient Temperature in °C
Figure 24: Noise Distribution over Temperature
(3 σ, 300 G)
Figure 25: Noise Performance over Temperature
(3 σ, 300 G)
15
14
-40°C
25°C
150°C
-40°C
25°C
150°C
12
10
Count (%)
10
Count (%)
0.6
5
8
6
4
2
0
6
7
8
ICC in mA
9
Figure 26: ICC Distribution over Temperature
(ICC, VCC = 3.7 V)
10
0
6
7
8
ICC in mA
9
10
Figure 27: ICC Distribution over Temperature
(ICC, VCC = 16 V)
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29
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
EMC Reduction
For applications with stringent EMC requirements, a 100 Ω
resistance should be added to the supply for the device in order to
suppress noise. A recommended circuit is shown in Figure 28.
VCC
RSPLY
0.1 µF
0.1 µF
0.1 µF
BYP1_1
Host
Microprocessor
(Optional)
BYP2_1* VCC_1
CS_1
SCLK_1
MOSI_1
MISO_1
BIAS_1
Tachometer
GNDA_1
PWM_1/SENT_1
A1338
Target
Magnet
GNDD_1
Figure 28: Typical application diagram with EMC suppression resistor, RSPLY , on supply line.
*Secondary bypass capacitors only required when using Elevated SPI Output Voltage. Contact Allegro for availability.
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30
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
PACKAGE OUTLINE DRAWINGS
For Reference Only – Not for Tooling Use
(Reference Allegro DWG-0000381, Rev. 1)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
E
5.00 ±0.10
0.45
8º
0º
14
14
0.20
0.09
0.65
1.70
D
4.40 ±0.10 6.40 BSC
2.20
A
1
2
1.00 REF
1.62
16×
SEATING
PLANE
0.10 C
1 2
0.25 BSC
Branded Face
0.30
0.19
6.00
0.60 +0.15
–0.10
C
SEATING PLANE
B
GAUGE PLANE
PCB Layout Reference View
1.10 MAX
0.65 BSC
0.15
0.00
A
Terminal #1 mark area
B
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)
C
Branding scale and appearance at supplier discretion
D
Hall element, not to scale
E
Active Area Depth 0.36 mm REF
NNNNNNNNNNNN
YYWW
LLLLLLLLLLLL
C
Standard Branding Reference View
N = Device part number
= Supplier emblem
Y = Last two digits of year of manufacture
W = Week of manufacture
L = Lot number
Figure 29: Package LE, 14-Pin TSSOP
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31
Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Revision History
Number
Date
Description
–
November 18, 2016
Initial release
1
July 13, 2017
2
January 25, 2018
Updated MOSI_1/SCLK_1/ID1_1 and MOSI_2/SCLK_2/ID1_2 pinouts, WAKEx Input Specifications,
PWM Output Signal, SENT Output Signal, Figure 12, 13, and 16.
Updated Typical Application Diagram (page 4);
Bypass2 Pin Output Voltage characteristic and test conditions (page 7);
PWM Carrier Frequency test conditions, Sent Output Signal maximum value, Logical BIST
Coverage versus Time (page 8);
Effective Resolution typical value, footnotes 8-15 (page 9);
Overview, Angle Measurement sections (page 10-11);
Manchester Code Low Voltage maximum value (page 14);
Table 4 (page 17);
Table 5 (page 18);
ERR Register Address table and bit 3 detail (page 19);
CTRL Register, STS Self-Test Start (page 21);
Calculating Target Zero-Degree Angle (page 23); and
Figure 22 (page 28).
Updated PWM Interface Specifications (page 8);
PWM Output section (page 12);
EEPROM Registers Map Table (page 17);
Serial Interface Structure (pages 19-23);
Figures 18 and 20 (pages 28-29).
3
April 4, 2018
4
January 25, 2019
Minor editorial updates
5
March 6, 2020
Minor editorial updates
6
January 15, 2021
Updated Typical Applications (page 4), MOSI Hold Time value (page 7), Figure 11 (page 15),
Table 4 (page 17), and Package Outline Drawing reference numbers (pages 31-32).
Continued on the next page…
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Precision, Hall-Effect Angle Sensor IC
with SPI, and SENT or PWM Outputs
A1338
Revision History
Number
7
Date
Description
October 19, 2021
Removes dual-die part numbers and refers customer to Allegro for dual-die availability:
Removed 24-pin image (page 1);
Edited “Description” and “Selection Guide” table (page 2);
Removed thermal characteristics for LE-24 package (page 3);
Replaced Figure 2 with 14-pin product and edited caption (page 4);
Removed all 24-pin data from “Terminal List” table (page 5);
Replaced Figure 4 with 14-pin product (page 6);
Pemoved “per die” from Supply Current charactersitic (page 7).
Removed 24-pin data from “Operating Characteristics” table (page 8);
Edited/Removed text from: “Overview” (page 10); “Angle Resolution and Representation” (page 11);
“Functional Description,” “PWM Output” (page 12); “Manchester Serial Interface” (page 13 and page
15); “User-Intiated Diagnostics” (page 18); “Calculating Target Zero-Degree Angle” (page 25);
Replaced Figues 15 and 16 (page 25);
Edited/Removed text and replaced Figure 19 with 14-pin product image (page 27);
Removed “per die” from captions in Figure 26 and Figure 27 (page 29);
Replaced Figure 28 with 14-pin image and removed Figure 29, which was redundant with Figure 16
(page 30); and
Deleted package outline drawing and deleted page (formerly Figure 31, formerly page 32).
Copyright 2021, Allegro MicroSystems.
Allegro MicroSystems 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 assumes no responsibility for its use; nor
for any infringement of patents or other rights of third parties which may result from its use.
Copies of this document are considered uncontrolled documents.
For the latest version of this document, visit our website:
www.allegromicro.com
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