CT455

XtremeSense™ TMR Contactless Current Sensor with 1 MHz

Bandwidth and Programmable Gain

FEATURES AND BENEFITS DESCRIPTION

• User-programmable field range: The CT455 is a high-bandwidth and low-noise contactless
□ 6 to 8 mT □ 12 to 48 mT current sensor that uses Allegro patented XtremeSense tunnel
• Preset magnetic field ranges: magnetoresistance (TMR) technology to enable high-accuracy
□ ±6 mT □ ±48 mT current measurements for many consumer, enterprise, and
• AEC-Q100 Grade 1 [1] automotive qualified (A variants industrial applications. The device supports two standard field
only) ranges where the CT455 senses and translates the magnetic
• Optimized for high dV/dt applications field into a linear analog output voltage.
• Linear analog output voltage The CT455 is also available in a user-programmable variant,
• 1 MHz bandwidth which enables end-of-line calibration of gain and offset. While
• Response time: < 300 ns the sensor is preprogrammed to compensate for gain and offset
• Supply voltage: 3.3 or 5 V temperature drift, the ability to adjust offset and gain relaxes
• Low-noise performance mechanical tolerances during sensor mounting.
• Package options:
□ 8-lead SOIC The device has less than 300 ns output response time while
□ 8-lead TSSOP the current consumption is ~6 mA.
The CT455 is assembled in two package options—an eight-lead
small-outline integrated-circuit (SOIC) package and a low-
APPLICATIONS profile, industry-standard eight-lead thin-shrink small-outline
package (TSSOP). Both are green and RoHS compliant.
• Solar/power inverters
• Battery management systems
• Industrial equipment PACKAGES:
• Power utility meters
• Power conditioner
• DC-DC converters
8-lead SOIC 8-lead TSSOP
Not to scale

FUNCTIONAL BLOCK DIAGRAMS

TEST VCC GND TEST VCC GND
8 2 7 6 8 5

CSC BIAS UVLO POR CSC BIAS UVLO POR

XtremeSense Analog XtremeSense Analog

TMR Sensor Front-End 7 VOUT
TMR Sensor Front-End
1 VOUT

1 2 3 4

LDF LDF LDF LDF

Figure 1: CT455 Functional Block Diagram Figure 2: CT455 Functional Block Diagram
for TSSOP-8 for SOIC-8

[1] For more details, see the Testing and Quality Assurance section.

CT455-DS, Rev. 11 June 2, 2025

MCO-0001533
 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

Table of Contents
Features and Benefits............................................................ 1 Electrical Characteristics........................................................ 6
Description........................................................................... 1 Calibration Description......................................................... 13
Applications.......................................................................... 1 Device Programming........................................................... 13
Packages............................................................................. 1 Functional Description......................................................... 17
Functional Block Diagrams..................................................... 1 XtremeSense TMR Current Sensor Location.......................... 20
Selection Guide.................................................................... 2 Package Outline Drawings................................................... 21
Absolute Maximum Ratings.................................................... 3 Tape and Reel Pocket Drawings and Dimensions.................... 23
Recommended Operating Conditions...................................... 3 Device Markings................................................................. 24
Application Diagrams............................................................. 4 Part Ordering Number Legend.............................................. 25
Pinout Diagrams and Terminal Lists......................................... 5 Revision History.................................................................. 26

SELECTION GUIDE
Supply Operating Temperature
Part Number Qualification Polarity Range (mT) Package
Voltage (V) Range (°C)
FACTORY-CALIBRATED SENSORS
CT455-A06B5-TS08 AEC-Q100 Grade 1
Bipolar ±6
CT455-H06B5-TS08 – 8-lead TSSOP
5 –40 to 125
CT455-A48B5-TS08 AEC-Q100 Grade 1 3 mm × 6.4 mm × 1.1 mm
Bipolar ±48
CT455-H48B5-TS08 –
PROGRAMMABLE SENSORS
CT455-A00B3-TS08 AEC-Q100 Grade 1
Bipolar 3.3
CT455-H00B3-TS08 – ±6 to ±8 and
CT455-A00B5-TS08 AEC-Q100 Grade 1 ±12 to ±48
8-lead TSSOP
Bipolar –40 to 125
CT455-H00B5-TS08 – 3 mm × 6.4 mm × 1.1 mm
5
CT455-A00U5-TS08 AEC-Q100 Grade 1 6 to 8 and
Unipolar
CT455-H00U5-TS08 – 12 to 48
CT455-A00B5-SN08 AEC-Q100 Grade 1 ±6 to ±8 and 8-lead SOIC
Bipolar 5 –40 to 125
CT455-H00B5-SN08 – ±12 to ±48 4.89 mm × 6 mm × 1.62 mm

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

ABSOLUTE MAXIMUM RATINGS [1]

Characteristic Symbol Notes Rating Unit
Supply Voltage VCC –0.3 to 6 V
Analog Input/Output Pins, Maximum Voltage VI/O –0.3 to (VCC + 0.3) [2] V
Human Body Model (HBM) per JESD22-A114 ±2 (min) kV
Electrostatic Discharge Protection Level ESD
Charged Device Model (CDM) per JESD22-C101 ±0.5 (min) kV
Junction Temperature TJ –40 to 150 °C
Storage Temperature TSTG –65 to 155 °C
Lead Soldering Temperature TL 10 seconds 260 °C
Magnetic field above this value can cause a permanent
Magnetic Field B 100 mT
offset voltage drift

[1] Stresses exceeding the absolute maximum ratings may damage the CT455: The CT455 may not function or be operable at levels that exceed the
recommended operating conditions, and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses that
exceed the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only.
[2] The lower of (V
CC + 0.3 V) or 6 V.

RECOMMENDED OPERATING CONDITIONS [1]

Characteristic Symbol Notes Min. Typ. Max. Unit
5 VCC variant (-x5) 4.75 5 5.5 V
Supply Voltage Range VCC
3.3 VCC variant (-x3) 3 3.3 3.6 V
Output Voltage Range VOUT 0 – VCC V
Output Current IOUT – – ±1 mA
Operating Ambient Temperature TA Extended Industrial –40 25 125 °C

[1] TheRecommended Operating Conditions table defines the conditions for actual operation of the CT455. Recommended operating conditions are
specified to ensure optimal performance to the specifications. Allegro does not recommend exceeding them or designing to absolute maximum
ratings.

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

APPLICATION DIAGRAMS

Current
Flow
VOUT B+ B–
To calibration controller.
After calibration, connect to GND.
VCC
1 OUT TEST 8

2 VCC CT455 GND 7

CBYP
3 N/C N/C 6
1 µF
4 N/C N/C 5

Busbar
or
PCB Trace

Figure 3: CT455 Application Diagram for Measuring

Uniform Magnetic Field for TSSOP-8

VCC

1 LDF VCC 8
B+ CBYP
VOUT
2 LDF 7 1 µF
OUT Busbar or PCB Trace
CT455

3 LDF TEST 6 Current Flow

B–
4 LDF GND 5
To calibration controller.
After calibration, connect to GND.

Figure 4: CT455 Application Diagram for SOIC-8

4
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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

PINOUT DIAGRAMS AND TERMINAL LISTS

Pin 1 Indicator

1 8

2 CT455 7

3 6

4 5

Figure 5: CT455 Pinout Diagram for Eight-Lead TSSOP

(Top-Down View)
Terminal List
Number Name Function
1 OUT Analog output voltage that represents the measured current/field.
2 VCC Supply voltage.
3, 4, 5, 6 NC No connect (leave floating).
7 GND Ground.
8 TEST Pin used for calibration. Connect to ground if not used.

Pin 1 Indicator

1 8

2 CT455 7

3 6

4 5

Figure 6: CT455 Pinout Diagram for Eight-Lead SOIC

Package (Top-Down View)
Terminal List
Number Name Function
Leadframe pin—A single (1) LDF pin should be connected to GND. The other three (3) LDF pins should remain
1, 2, 3, 4 LDF
unconnected to avoid ground loops through the leadframe.
5 GND Ground.
6 TEST Pin used for calibration. Connect to ground if not used.
7 OUT Analog output voltage that represents the measured current/field.
8 VCC Supply voltage.

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

ELECTRICAL CHARACTERISTICS: VCC = 3 to 3.6 V or 4.75 to 5.5 V, TA = –40°C to 125°C, CBYP = 1 µF, unless otherwise
specified; typical values are VCC = 3.3 or 5 V and TA = 25°C
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
POWER SUPPLIES
Supply Current ICC fBW = 1 MHz, no load, BOP = 0 mT – 6 9 mA
OUT Maximum Drive Capability IOUT OUT covers 10% to 90% of VCC span –1 – 1 mA
OUT Capacitive Load CL – – 100 pF
OUT Resistive Load RL – 100 – kΩ
Sensitivity Power Supply Rejection
PSRRS – 35 – dB
Ratio [1]
Offset Power Supply Rejection Ratio [1] PSRRO – 40 – dB
Bandwidth [1] fBW Small signal = –3 dB – 1 – MHz
ANALOG OUTPUT (OUT)
5 VCC variant (-x5) 0.5 – 4.5 V
OUT Voltage Linear Range VOUT
3.3 VCC variant (-x3) 0.65 – 2.65 V
Output High Saturation Voltage VOUT_SAT TA = 25°C VCC – 0.3 VCC – 0.25 – V
TIMINGS
VCC ≥ 4 V variant (-x5),
Power-On Time tON – 100 200 µs
VCC ≥ 2.5 V variant (-x3)
Rise Time [1] tRISE BOP = BRNG(MAX), TA = 25°C, CL = 100 pF – 200 – ns
Response Time [1] tRESPONSE BOP = BRNG(MAX), TA = 25°C, CL = 100 pF – 300 – ns
Propagation Delay [1] tDELAY BOP = BRNG(MAX), TA = 25°C, CL = 100 pF – 250 – ns
PROTECTION
Rising VCC – 2.5 – V
Undervoltage Lockout VUVLO
Falling VCC – 2.45 – V
UVLO Hysteresis VUV_HYS – 50 – mV

[1] Guaranteed by design and characterization; not tested in production.

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

ELECTRICAL CHARACTERISTICS
VCC = 3.3 or 5 V, TA = 25°C, and CBYP = 1 µF (unless otherwise specified)

7.5 7.5

6.0 6.0

Supply Current (mA)

Supply Current (mA)

4.5 4.5

3.0 3.0

VCC = 4.75 V VCC = 3.0 V

1.5 VCC = 5.00 V 1.5 VCC = 3.3 V
VCC = 5.50 V VCC = 3.6 V

0.0 0.0
–50 –10 30 70 110 150 –50 –10 30 70 110 150
Temperature (°C) Temperature (°C)
Figure 7: 5 VCC Variant (-x5) Figure 8: 3.3 VCC Variant (-x3)
Supply Current vs. Temperature vs. Supply Voltage Supply Current vs. Temperature vs. Supply Voltage

1.00E+09

1.00E+08
Noise Density (nVRMS/√Hz)

1.00E+07

1.00E+06

1.00E+05

1.00E+04

1.00E+03

1.00E+02
1.00E–01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06
Frequency (Hz)

Figure 9: Noise Density vs. Frequency

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

CT455-x06B5: ±6 mT – ELECTRICAL CHARACTERISTICS: [1][2] VCC = 4.75 to 5.5 V, TA = –40°C to 125°C, CBYP = 1 µF,
unless otherwise specified; typical values are VCC = 5 V and TA = 25°C
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Magnetic Field Range BRNG –6 – 6 mT
Voltage Output Quiescent VOQ 2.5 V
Sensitivity S – 333.3 – mV/mT
Bandwidth [3] fBW Small signal = –3 dB – 1 – MHz
Noise eN TA = 25°C, fBW = 100 kHz – 3 – µTRMS
OUT ACCURACY PERFORMANCE
Linearity Error ELIN BOP = BOP(MAX), TA = –40°C to 125°C – ±0.1 – % FS
BOP = BOP(MAX), TA = 25°C to 125°C – ±1.4 – %
Sensitivity Temperature Drift ESENS_Tdrift
BOP = BOP(MAX), TA = 25°C to –40°C – ±1.6 – %
Offset Voltage Error VOE BOP = 0 mT, TA = 25°C – ±4 – mV
BOP = 0 mT, TA = 25°C to 125°C – ±15 – mV
Offset Voltage Temperature Drift VOE_Tdrift
BOP = 0 mT, TA = 25°C to –40°C – ±26 – mV
LIFETIME DRIFT
Sensitivity Error Including Lifetime Drift ESENS(DRIFT) BOP = BOP(MAX), TA = –40°C to 125°C – ±3 – %
Offset Voltage Error Including Lifetime Drift VOE(DRIFT) BOP = 0 mT, TA = –40°C to 125°C – ±34 – mV

[1] Typical (typ) values are the mean ±3 sigma of a test sample population. These are formatted as mean ±3 sigma.
[2] Lifetime drift characteristics are based on a statistical combination of production distributions and the worst-case distribution of parametric drift of
individuals observed during AEC-Q100 qualification.
[3] Guaranteed by design and characterization. Not tested in production.

8
Allegro MicroSystems
955 Perimeter Road
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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

CT455-x48B5: ±48 mT – ELECTRICAL CHARACTERISTICS: [1][2]VCC = 4.75 to 5.5 V, TA = –40°C to 125°C, CBYP = 1 µF,
unless otherwise specified; typical values are VCC = 5 V and TA = 25°C
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Magnetic Field Range BRNG –48 – 48 mT
Voltage Output Quiescent VOQ 2.5 V
Sensitivity S – 41.7 – mV/mT
Bandwidth [3] fBW Small signal = –3 dB – 1 – MHz
Noise eN TA = 25°C, fBW = 100 kHz – 12 – µTRMS
OUT ACCURACY PERFORMANCE
Linearity Error ELIN BOP = BOP(MAX), TA = –40°C to 125°C – ±0.3 – % FS
BOP = BOP(MAX), TA = 25°C to 125°C – ±1.4 – %
Sensitivity Temperature Drift ESENS_Tdrift
BOP = BOP(MAX), TA = 25°C to –40°C – ±2.2 – %
Offset Voltage Error VOE BOP = 0 mT, TA = 25°C – ±4 – mV
BOP = 0 mT, TA = 25°C to 125°C – ±15 – mV
Offset Voltage Temperature Drift VOE_Tdrift
BOP = 0 mT, TA = 25°C to –40°C – ±26 – mV
LIFETIME DRIFT
Sensitivity Error Including Lifetime Drift ESENS(DRIFT) BOP = BOP(MAX), TA = –40°C to 125°C – ±3 – %
Offset Voltage Error Including Lifetime Drift VOE(DRIFT) BOP = 0 mT, TA = –40°C to 125°C – ±34 – mV

[1] Typical (typ) values are the mean ±3 sigma of a test sample population. These are formatted as mean ±3 sigma.
[2] Lifetime drift characteristics are based on a statistical combination of production distributions and the worst-case distribution of parametric drift of
individuals observed during AEC-Q100 qualification.
[3] Guaranteed by design and characterization. Not tested in production.

9
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

CT455-x00B5: Programmable Gain – ELECTRICAL CHARACTERISTICS: [1][2][3] VCC = 4.75 to 5.5 V, TA = –40°C to
125°C, CBYP = 1 µF, unless otherwise specified; typical values are VCC = 5 V and TA = 25°C
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
±6 – ±8 mT
Programmable Magnetic Field Range BPRNG
±12 – ±48 mT
Voltage Output Quiescent VOQ – 2.5 – V
Maximum Programmable Sensitivity SPMAX – 333.3 – mV/mT
Minimum Programmable Sensitivity SPMIN – 41.7 – mV/mT
Bandwidth [4] fBW Small signal = –3 dB – 1 – MHz
TA = 25°C, fBW = 100 kHz,
Noise eN – 6.44 – µTRMS
S = 41.7 mV/mT
OUT ACCURACY PERFORMANCE [5]
Linearity Error ELIN BOP = BOP(MAX), TA = –40°C to 125°C – ±0.3 – % FS
BOP = BOP(MAX), TA = 25°C to 125°C – ±1.4 – %
Sensitivity Temperature Drift ESENS_Tdrift
BOP = BOP(MAX), TA = 25°C to –40°C – ±2.2 – %
Offset Voltage Error VOE BOP = 0 mT, TA = 25°C – ±4 – mV
BOP = 0 mT, TA = 25°C to 125°C – ±15 – mV
Offset Voltage Temperature Drift VOE_Tdrift
BOP = 0 mT, TA = 25°C to –40°C – ±26 – mV
LIFETIME DRIFT [5]

Sensitivity Error Including Lifetime Drift ESENS(DRIFT) BOP = BOP(MAX), TA = –40°C to 125°C – ±3 – %
Offset Voltage Error Including Lifetime Drift VOE(DRIFT) BOP = 0 mT, TA = –40°C to 125°C – ±34 – mV

[1] Tested on TSSOP package.

[2] Typical (typ) values are the mean ±3 sigma of a test sample population. These are formatted as mean ±3 sigma.
[3] Lifetime drift characteristics are based on a statistical combination of production distributions and the worst-case distribution of parametric drift of
individuals observed during AEC-Q100 qualification.
[4] Guaranteed by design and characterization. Not tested in production.
[5] Linearity and sensitivity temperature drift performance vary as a function of the sensitivity programmed. Errors are smaller when sensitivity is
closer to the 6 mT version.

10
Allegro MicroSystems
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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

CT455-x00B3: Programmable Gain – ELECTRICAL CHARACTERISTICS: [1][2] VCC = 3 to 3.6 V, TA = –40°C to 125°C,
CBYP = 1 µF, unless otherwise specified; typical values are VCC = 3.3 V and TA = 25°C
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
±6 – ±8 mT
Programmable Magnetic Field Range BPRNG
±12 – ±48 mT
Voltage Output Quiescent VOQ – 1.65 – V
Maximum Programmable Sensitivity SPMAX – 166.7 – mV/mT
Minimum Programmable Sensitivity SPMIN – 20.8 – mV/mT
Bandwidth [3] fBW Small signal = –3 dB – 1 – MHz
TA = 25°C, fBW = 100 kHz,
Noise eN – 14 – µTRMS
S = 166 mV/mT
OUT ACCURACY PERFORMANCE [4]
Linearity Error ELIN BOP = BOP(MAX), TA = –40°C to 125°C – ±0.3 – % FS
BOP = BOP(MAX), TA = 25°C to 125°C – ±1.4 – %
Sensitivity Temperature Drift ESENS_Tdrift
BOP = BOP(MAX), TA = 25°C to –40°C – ±2.2 – %
Offset Voltage Error VOE BOP = 0 mT, TA = 25°C – ±4 – mV
BOP = 0 mT, TA = 25°C to 125°C – ±13 – mV
Offset Voltage Temperature Drift VOE_Tdrift
BOP = 0 mT, TA = 25°C to –40°C – ±15 – mV
LIFETIME DRIFT [4]

Sensitivity Error Including Lifetime Drift ESENS(DRIFT) BOP = BOP(MAX), TA = –40°C to 125°C – ±3 – %
Offset Voltage Error Including Lifetime Drift VOE(DRIFT) BOP = 0 mT, TA = –40°C to 125°C – ±20 – mV

[1] Typical values are the mean ±3 sigma of a test sample population. These are formatted as mean ±3 sigma.
[2] Lifetime drift characteristics are based on a statistical combination of production distributions and the worst-case distribution of parametric drift of
individuals observed during AEC-Q100 qualification.
[3] Guaranteed by design and characterization. Not tested in production.
[4] Linearity and sensitivity temperature drift performance vary as a function of the sensitivity programmed. Errors are smaller when sensitivity is closer
to the 6 mT version.

11
Allegro MicroSystems
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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

CT455-x00U5: Programmable Gain – ELECTRICAL CHARACTERISTICS: [1][2] VCC = 4.75 to 5.5 V, TA = –40°C to 125°C,
CBYP = 1 µF, unless otherwise specified; typical values are VCC = 5 V and TA = 25°C
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
0 to 6 – 0 to 8 mT
Programmable Magnetic Field Range BPRNG
0 to 12 – 0 to 48 mT
Voltage Output Quiescent VOQ – 0.5 – V
Maximum Programmable Sensitivity SPMAX – 666.7 – mV/mT
Minimum Programmable Sensitivity SPMIN – 83.3 – mV/mT
Bandwidth [3] fBW Small signal = –3 dB – 1 – MHz
TA = 25°C, fBW = 100 kHz,
Noise eN – 13 – µTRMS
S = 83.3 mV/mT
OUT ACCURACY PERFORMANCE [4]
Linearity Error ELIN BOP = BOP(MAX), TA = –40°C to 125°C – ±0.3 – % FS
BOP = BOP(MAX), TA = 25°C to 125°C – ±1.4 – %
Sensitivity Temperature Drift ESENS_Tdrift
BOP = BOP(MAX), TA = 25°C to –40°C – ±2.2 – %
Offset Voltage Error VOE BOP = 0 mT, TA = 25°C – ±7 – mV
BOP = 0 mT, TA = 25°C to 125°C – ±11 – mV
Offset Voltage Temperature Drift VOE_Tdrift
BOP = 0 mT, TA = 25°C to –40°C – ±25 – mV
LIFETIME DRIFT [4]

Sensitivity Error Including Lifetime Drift ESENS(DRIFT) BOP = BOP(MAX), TA = –40°C to 125°C – ±3 – %
Offset Voltage Error Including Lifetime Drift VOE(DRIFT) BOP = 0 mT, TA = –40°C to 125°C – ±32 – mV

[1] Typical (typ) values are the mean ±3 sigma of a test sample population. These are formatted as mean ±3 sigma.
[2] Lifetime drift characteristics are based on a statistical combination of production distributions and the worst-case distribution of parametric drift of
individuals observed during AEC-Q100 qualification.
[3] Guaranteed by design and characterization. Not tested in production.
[4] Linearity and sensitivity temperature drift performance vary as a function of the sensitivity programmed. Errors are smaller when sensitivity is
closer to the 6 mT version.

12
Allegro MicroSystems
955 Perimeter Road
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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

Calibration Description Once the test mode is activated, the device expects 106 clock
pulses on the TEST pin at the VCC voltage level or above, along
The CT455-x00 is factory-trimmed for sensitivity and offset with data on OUT. Those clock pulses should be separated by
temperature drift. The sensor provides the ability to adjust gain more than 1 µs and less than 100 µs. Data is read sequentially
to allow for all the mechanical tolerances during manufacturing. from the OUT pin upon each rising edge of TEST.
Gain calibration is recommended to be performed at room tem-
perature (25°C) using the LabView and NI PXI solution. A user The fields for the data transmitted are:
manual using this solution can be found on the Allegro software • Key code (8 bits): should be 0b11110010; this prevents
portal (https://registration.allegromicro.com/#/). incorrect access
Device Programming • OP code (2 bits):
OP OUT TEST
COMMUNICATION Description
Code Operation Operation
The programmable versions of the device allow customization of Analog
Open drain
the sensitivity and offset voltage. These devices use a one-time 0b00 Default operation digital
output
output
programming (OTP) method, and parameters can be adjusted
through test modes (volatile) before permanent programming. Program
(permanently Serial data
0b01 SCLK input
The test mode allows an external controller to read, write, and burns fuses; input
cannot be undone)
program the device. The device enters test mode when the TEST
pin is pulled to 1.4 V above the VCC level. VCC must be 3.3 V. Try (emulates
a configuration Serial data
0b10 SCLK input
without permanent input
change)
SDATA
Serial data SCLK
0b11 Read bits
output output
3.3 V OUT TEST SCLK • CTRL code (16 bits): controls the connections of multiplexers;
VCC GND leave at 0
GND • FBIT (80 bits): trimming bits for offset, sensitivity, and
temperature compensation
Device Controller

Figure 10: Programming Connections

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

TIMING AND ELECTRICAL CHARACTERISTICS READ

Table 1 After the device receives the correct KEY code and OP code =
Parameter Symbol Min. Typ. Max. Units
0b11, it starts to output FBIT from the 28th SCLK pulse start-
ing from FBIT[0]. The bits must be read on descending edge
SDATA Setup
Time to SCLK
TSETUP 15 – – ns of SCLK. After read, FBIT is set back to the fused values. Any
volatile write command set prior to the read should be sent again.
SDATA Hold
THOLD 50 – – ns
Time to SCLK
SCLK Rise SCLK
TR1 – – 50 ns 1 2 3 27 28

Time
(high voltage)
KEY OP
(8 bits) (2 bits)

SCLK Fall Controller to

TF1 – – 50 ns device
1 1 1 1 0 0 1 0 1 1
Time
CTRL FBIT

SCLK High (16 bits) (80 bits)

THIGH1 500 [1] – – ns

Time Device to
controller
- ... - 0/1 ... 0/1

SCLK Low
TLOW1 500 [1] – – ns READ
Time
SCLK High
WRITE (VOLATILE)
Voltage After the device receives the correct KEY code and OP
(typical pulse VHIGH1 0.7 × VDD – VDD + 1.5 V
level for a test
code = 0b10, if FBIT[76] is not set, update CTRL and FBIT with
sequence) the received data.
SCLK High KEY OP CTRL FBIT
(8 bits) (2 bits) (16 bits) (80 bits)
Voltage
(the first
VHIGH1 VDD + 1.4 VDD + 1.45 VDD + 1.5 V 1 1 1 1 0 0 1 0 1 0 0/1 ... 0/1 0/1 ... 0/1
pulse for
a test To update only a part of FBIT, all other bits must be written as
sequence)
well. It might be needed to first read FBIT, then write it back with
SCLK Low the relevant bits updated.
VLOW1 –0.3 – 0.3 × VDD V
Voltage
SDATA Rise
TR2 – – 50 ns WRITE (PERMANENT)
Time
After the device receives the correct KEY code and OP code =
SDATA Fall
Time
TF2 – – 50 ns 0b01, if FBIT[76] is not set, update CTRL and permanently fuse
FBIT with the previously volatile programmed data. The CTRL
SDATA High
TH2 500 – – ns and FBIT data sent along with the fuse command are discarded.
Time
SDATA Low
Cannot be undone. VCC should be equal to 4.0 V during perma-
TLOW2 500 – – ns nent write operation to ensure all fuses are correctly burnt.
Time
SDATA High KEY OP CTRL FBIT
VHIGH2 0.7 × VDD – VDD V (8 bits) (2 bits) (16 bits) (80 bits)
Voltage
SDATA Low 1 1 1 1 0 0 1 0 0 1 x ... x x ... x
VLOW2 –0.3 – 0.3 × VDD V
Voltage
Supply
TIME OUT
VDD 2.97 3.3 4 V
Voltage After a high-voltage pulse, the device returns to typical operation
Supply (timeout event) if:
Voltage VDD(FUSE) 4.0 – – V
During Fusing • An incorrect KEY code is received
[1] During fusing, it should be greater than 2500 ns. • OP code = 0b00
• Two SCLK rising edges are separated by more than 100 µs.
Additional SCLK pulses after the 106 needed are discarded, but
typical operation resumes only after timeout.

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

BITS DESCRIPTION
Table 2
Factory
Location Name Description Bits
Default
CTRL[0:16] Control bits Factory trimmed. Do not modify. 16 0x00
FBIT[2:0] – Factory trimmed. Do not modify. 3 Trimmed
FBIT [7:3] V_REF[0:4] Reference voltage added at the end of the signal processing path. 5 0
FBIT[19:8] – Factory trimmed. Do not modify. 12 Trimmed
FBIT[27:20] MAG_OFFSET_LEFT Magnetic offset of the Left TMR 8 0
FBIT[35:28] MAG_OFFSET _RIGHT Magnetic offset of the Right TMR 8 0
FBIT[43:36] ELEC_OFFSET_LEFT Electronic offset of the Left TMR 8 0
FBIT[51:44] ELEC_OFFSET _RIGHT Electronic offset of the Right TMR 8 0
FBIT [59:52] SENS_FINE_LEFT Fine sensitivity of the Left TMR 8 0
FBIT [67:60] SENS_FINE_RIGHT Fine sensitivity of the Right TMR 8 0
FBIT [69:68] – Factory trimmed. Do not modify. 2 Trimmed
FBIT [71:70] SENS_COARSE[0:1] Coarse sensitivity 2 0
FBIT [72] V_REF[5] Reference voltage added at the end of the signal processing path. 1 0
FBIT [73] – Factory trimmed. Do not modify. 1 Trimmed
FBIT [75:74] SENS_COARSE[2:3] Coarse sensitivity 2 0
FBIT [79:76] – Factory trimmed. Do not modify. 9 Trimmed

TRIMMING FLOW DESCRIPTION Table 4: Coarse Sensitivity To Gain Adjustment

For optimal trimming: Coarse
Sensitivity Fbit<75> Fbit<74> Fbit<71> Fbit<70> Gain
• SENS_FINE_LEFT and SENS_FINE_RIGHT should be set Code
to the same value. 0 0 0 0 0 5.01
• Trim order:
1 0 0 0 1 1
□ Vref
2 0 0 1 0 2.52
□ Magnetic offset
□ Sensitivity coarse 3 0 0 1 1 1.65
□ Sensitivity fine 4 0 1 0 0 4.26
□ Electrical offset 5 0 1 0 1 0.85
6 0 1 1 0 2.14
Table 3: Target Offset Voltage per VCC Level and Polarity
7 0 1 1 1 1.4
Bipolar Unipolar
8 1 0 0 0 5.76
5V 3.3 V 5V 3.3 V
9 1 0 0 1 1.15
Target Offset
2.5 1.65 0.5 0.65
Voltage (V) 10 1 0 1 0 2.89
11 1 0 1 1 1.9

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
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Vref

0 31 32 63
V_REF code

Figure 11: Vref behavior with V_REF code variations

Fine sensitivity

0 127 128 255

SENS_FINE_LEFT and SENS_FINE_RIGHT code

Figure 12: Sensitivity behavior with SENS_FINE_LEFT

and SENS_FINE_RIGHT code variations
Offset Voltage

0 127 128 255

ELEC_OFFSET _RIGHT code

or ELEC_OFFSET _LEFT code
or MAG_OFFSET _RIGHT code
or MAG_OFFSET_LEFT code

Figure 13: Offset voltage behavior with ...OFFSET... codes variations

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

FUNCTIONAL DESCRIPTION
Overview and bidirectional fields, respectively. The output voltage range of
the OUT pin as a function of the measured field is illustrated in
The CT455 is a very-high-accuracy, contactless current sensor Figure 15.
that can sense magnetic fields from 6 to 48 mT. The device has
high sensitivity and a wide dynamic range with excellent accuracy VOUT

across temperature.
4.50 V
The CT455 is also available in a user-programmable variant that
2.00 V
enables end-of-line calibration of gain. While the sensor is pre-
programmed to adjust sensitivity and offset temperature drift, the 4.00 V 2.50 V
ability to adjust gain relaxes mechanical tolerances during sensor
2.00 V
mounting.
0.50 V
When current is flowing through a busbar above or below the
Unidirectional Bidirectional
CT455, the XtremeSense TMR sensor inside the chip senses the
BRNG BRNG(MIN) + BRNG(MAX) BRNG
field and generates corresponding differential voltage signals that BOP
(MIN) 2 (MAX)
then pass through the analog front-end (AFE) to output a current
measurement. Figure 14: Linear Output Voltage Range (OUT) vs.
The chip is designed to enable a fast response time of 300 ns for Measured Magnetic Field (BOP)
the current measurement from the OUT pin, as the bandwidth V
OUT
for the CT455 is 1 MHz. Even with a high bandwidth, the chip
consumes a minimal amount of power. 2.65 V

Testing and Quality Assurance 1.00 V

Testing of the CT455 was conducted following AEC-Q100 2.00 V 1.65 V

standards to ensure reliability and performance in automotive 1.00 V

conditions. During qualification, only the offset voltage error
was tested at –40°C, 25°C, and 125°C. Sensitivity error was not 0.65 V

checked directly during qualification but is estimated from quali- Unidirectional Bidirectional
0 mT 50% +BOP
fication of the same ASIC in an SOIC8 package with a different –BOP BOP
0 mT
leadframe.
Figure 15: Linear Output Voltage Range (OUT) vs.
Linear Output Current Measurement Measured Magnetic Field (BOP)
The CT455 provides a continuous linear analog output voltage Power-On Time (tON)
that represents the magnetic field generated by the current flow-
ing through the busbar. Power-on time (tON) of 100 µs is the amount of time required
by CT455 to start up, fully power the chip, and become fully
For the 5 V variant, the output voltage range of OUT is from operational from the moment the supply voltage is greater than
0.5 to 4.5 V with a VOQ of 0.5 and 2.5 V for unidirectional and the UVLO voltage. This time includes the ramp-up time and the
bidirectional fields, respectively. The output voltage range of settling time (within 10% of steady-state voltage under an applied
the OUT pin as a function of the measured field is illustrated in magnetic field) after the power supply has reached the minimum
Figure 14. VCC.
For the 3.3 V variant, the output voltage range of OUT is from
0.65 to 2.65 V with a VOQ of 0.65 and 1.65 V for unidirectional

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

Response Time (tRESPONSE)

Response time (tRESPONSE) is the period of time between: B V
RNG OUT
1. When the primary current signal reaches 90% of its final value,
and 90%

2. When the chip reaches 90% of its output corresponding to the

applied current.
The CT455 has a response time of 300 ns.

B V
RNG OUT 20%

90% 10%

t t
DELAY
t
RISE

Figure 17: CT455 Propagation Delay and Rise Time Curve

Undervoltage Lockout (UVLO)

The undervoltage lockout protection circuitry of the CT455 is
activated when the supply voltage (VCC) reduces to less than
t 2.45 V. The CT455 remains in a low quiescent state until VCC
RESP t
increases to greater than the UVLO threshold (2.5 V). In the
Figure 16: CT455 Response Time Curve condition where VCC is less than 2.45 V and UVLO is triggered,
Rise Time (tRISE) the output from the CT455 is not valid. Once VCC increases to
greater than 2.5 V, the UVLO is cleared.
Rise time (tRISE) is the period of time between when 10% and 90% of
the full-scale output voltage is reached. Current Sensing
The CT455 has a rise time of 200 ns. The CT455 can sense and, therefore, measure the current by
either placing a current-carrying busbar above or under the
Propagation Delay (tDELAY) device. The chip is also sensitive enough to measure the current
Propagation delay (tDELAY) is the period of time between: from a PCB trace that is routed beneath it.

1. When the primary current reaches 20% of its final value, and Bypass Capacitor
2. When the chip reaches 20% of its output corresponding to the A single 1 µF capacitor is needed for the VCC pin to reduce the
applied current. noise from the power supply and other circuits. This capacitor
The CT455 has a propagation delay of 250 ns. should be placed as close as practical to the CT455 to minimize
inductance and resistance between the two devices.

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 SenseI2±
ELIN(±) = �1 −V � × 100%
SensI1± − VREF
IOUT(IX−)
SensIX− =
IX−

VIOUT(IX+) − VREF
SensIX+I = = 2 × I XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 2+ I1+
X+
Bandwidth and Programmable Gain
I2− V=IOUT(IX−)
2 × I1− − VREF
SensIX− =
IX−
Offset Power Supply Rejection
V
Ratio (PSRRO)
IOUT_Actual
E = �1 − � × 100%
The offset power supply
TOT
rejection 2ratio,
× I1+ PSRRO, is defined
I2+ V=IOUT_Ideal
as 20 × log of the ratio of the change of QVO in volts over a
±100 mV variable AC VCC centered at 5 V, reported as dB in a
specified frequency range.=This
VIOUT_Ideal II2−
P×=is2an
Sens IAC version of the VOE(PS)
1− + VRef_Ideal
× Ideal
parameter.
Equation 1:
VIOUT_ActualΔQVO
ETOTPSRR = 20
= �1O − × log � � × 100%
�
VIOUT_Ideal ΔVCC

Sensitivity Power Supply Rejection Ratio (PSRRS)

Δ%Sens
VIOUT_Ideal = IP × SensIdeal + VRef_Ideal
The sensitivity powerPSRR S = 20
supply × log � ratio, PSRR
rejection �
ΔVCC S, is defined
as 20 × log of the ratio of the percentage of change in sensitivity
over the percentage of change in VCC (±100 mV variable AC VCC
ΔQVO
centered at 5 V), reported
PSRRasO =dB20in×alog
specified
� �frequency range.
ΔVCC
This is the AC version of the ESens(PS) parameter.

Equation 2:
Δ%Sens
PSRRS = 20 × log � �
ΔVCC

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

XtremeSense TMR Current Sensor Location

The XtremeSense TMR current sensor location of the CT455 is shown in the figures that follow. All dimensions in the figures are
nominal.
4.890 mm
8

1.950 mm

0.500 mm
6.000 mm
1.620 mm
1

2.445 mm

Figure 18: XtremeSense TMR Current Sensor Location Figure 19: XtremeSense TMR Current Sensor Location
in x-y Plane for CT455 in SOIC-8 Package in z Dimension for CT455 in SOIC-8 Package

2.200 mm

1 8
2.207 mm
2 7
3.050 mm
0.310 mm
3 6
1.000 mm
4 5

6.400 mm

Figure 20: XtremeSense TMR Current Sensor Location Figure 21: XtremeSense TMR Current Sensor Location
in x-y Plane for CT455 in TSSOP-8 Package in z Dimension for CT455 in TSSOP-8 Package

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

PACKAGE OUTLINE DRAWINGS

For Reference Only – Not for Tooling Use
Dimensions in millimeters – ­NOT TO SCALE
Dimensions exclusive of mold flash, gate burs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown

Figure 22: SOIC-8 Package Drawing and Dimensions

Table 5: CT455 SOIC-8 Package Dimensions
Dimensions in Millimeters (mm)
Symbol
Min. Typ. Max.
A1 0.10 0.18 0.25
b 0.36 0.41 0.46
C 0.19 0.22 0.25
D 4.80 4.89 4.98
E 3.81 3.90 3.99
e 1.27 BSC
H 5.80 6.00 6.20
h 0.25 0.37 0.50
L 0.41 – 1.27
A 1.52 1.62 1.72
α 0° – 8°
ZD 0.53 REF
A2 1.37 1.47 1.57

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

Figure 23: TSSOP-8 Package Drawing and Dimensions

Table 6: CT455 TSSOP-8 Package Dimensions

Dimensions in Millimeters (mm)
Symbol
Min. Typ. Max.
A 1.05 1.10 1.20
A1 0.05 0.10 0.15
A2 – 1.00 1.05
b 0.25 – 0.30
C – 0.127 –
D 2.90 3.05 3.10
E 6.20 6.40 6.60
E1 4.30 4.40 4.50
e – 0.65 –
L 0.50 0.60 0.70
y – – 0.076
θ 0° 4° 8°

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

TAPE AND REEL POCKET DRAWINGS AND DIMENSIONS

For Reference Only – Not for Tooling Use
Dimensions in millimeters – ­NOT TO SCALE
Dimensions exclusive of mold flash, gate burs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown

Figure 24: Tape-and-Pocket Drawing for SOIC-8 Package

Figure 25: Tape-and-Pocket Drawing for TSSOP-8 Package

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

DEVICE MARKINGS

Table 7: CT455 Device Marking Definition for Eight-Lead TSSOP

Package
Row No. Code Definition
1 8 1 • Pin 1 Indicator
2 CT455 Allegro Part Number
2 7
3 XX Maximum Magnetic Field Rating
CT455 3 B Sensing Polarity
3 1
XXBV 6 8
3 V Supply Voltage
4 2 YYWWLL 5 7 4 YY Calendar Year

CT455 4 WW Work Week

3
XXBV 6 4 LL Lot Code

4 YYWWLL
Figure 26: CT455 Device Marking
for Eight-Lead TSSOP Package
5
8

CT455 Table 8: CT455 Device Marking Definition for Eight-Lead SOIC Pack-
8

XXBV age

YYWWLL Row No. Code Definition

4 • Pin 1 Indicator
CT455
1 CT455 Allegro Part Number
XXBV 2 XX Maximum Field Rating
YYWWLL
1

2 B Sensing Polarity
2 V Supply Voltage
3 YY Calendar Year
1

3 WW Work Week
3 LL Lot Code
Figure 27: CT455 Device Marking
for Eight-Lead SOIC Package

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

PART ORDERING NUMBER LEGEND

CT 4 5 5 - T FR X V - PKG

Package Type
SN08 = 8-lead SOIC
TS08 = 8-lead TSSOP

Voltage
5 = VCC is 5 V
3 = VCC is 3.3 V

Polarity
U = Unipolar Magnetic Field
B = Bipolar Magnetic Field
Field Range
00 = User Programmable
06 = 6 mT
48 = 48 mT

Temperature Range
A = AEC-Q100 Grade 1
Current Sensor Variant
5 = dV/dt Optimized Sensor
Current Sensor Type
5 = Contactless Current Sensor
Product Family
4 = Current Sensor
CT = Product Identifier

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 XtremeSense™ TMR Contactless Current Sensor with 1 MHz
CT455 Bandwidth and Programmable Gain

Revision History
Number Date Description
2 November 2, 2023 Document rebranded and minor editorial updates
3 January 25, 2024 Corrected packaging column in Selection Guide table (page 3)
Removed AEC-Q100 (pages 1, 2, 19-20) Updated Offset Voltage (pages 8-11); removed Out
4 March 6, 2024
Accuracy Performance (pages 8-11); updated Sensitivity and removed Noise (page 11)
Updated Features and Benefits (page 1), Figure 3 and 4 (page 4), Terminal Lists (page 5), and
5 March 20, 2024
Device Markings (page 19)
Major overhaul to reflect automotive-qualified part per details provided in the new Testing and
Quality Assurance section: changed preset magnetic field ranges (page 1) and all part numbers in
the selection guide (page 2); removed evaluation board selection guide (page 3) and recommended
external components tables (page 4); changed application diagrams (page 4) and electrical
characteristics symbols for OUT capacitive load and OUT resistive load (page 6); removed voltage
output quiescent and lifetime drift characteristics (page 6) and bandwidth performance plot (page
7); replaced device-specific electrical characteristic tables (pages 8 through 12); added Device
6 July 29, 2024
Programming section (pages 13 through 15), Testing and Quality Assurance section (page 16),
and 3.3 variant information in the Linear Output Current Measurement section (page 16); replaced
current sensor position images (page 18); added PCB outlines to package drawings (pages 19-
20); updated Device Markings section (page 22) and Part Ordering Number Legend section (page
23); and made minor editorial changes throughout (all pages), including removal of trailing zeros,
reformatting of some images for readability (larger text), removal of archaic language (normal
changed to typical), and minimization of the use of title case.
Updated Selection Guide (page 2); updated Device Programming Communication Table (page 13);
7 August 9, 2024
updated Device Markings section (page 22)
Editorial updates throughout; updated Description (page 1); updated Electrical Characteristics table
8 September 10, 2024 Noise typical values (pages 8-12); updated Device Programming Read section (page 14); updated
Functional Description (page 16)
9 September 26, 2024 Updated Selection Guide (page 2); updated Functional Description (page 16)
10 October 10, 2024 Updated Absolute Maximum Ratings table (page 3)
Updated Figures 3 and 4 (page 4); removed PSRR and updated PSRRS and PSRRO symbols (page
6); updated Calibration Description (page 13) and Read and Write sections (page 14); updated Bits
11 June 2, 2025
Description table (page 15); added Trimming Flow description, tables, and diagrams (pages 15-16);
added PSRRS and PSRRO sections (page 19)

Copyright 2025, 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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