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Home > Products > Sensors, Transducers > Magnetic Sensors > Linear, Compass (ICs)

Allegro MicroSystems A1321LLHLT

Name: A1321LLHLT
Brand: Allegro MicroSystems
SKU: A1321LLHLT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: A1321LLHLT

Manufacturer:: Allegro MicroSystems

Category:: Linear, Compass (ICs)

Package:: SOT-23W

Datasheet:: A1321LLHLT.pdf

Description:: SENSOR HALL EFFECT ANALOG SOT23W

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Product details

Overview

A1321LLHLT from Allegro MicroSystems is a ratiometric linear Hall-effect sensor IC optimized for high-temperature operation in automotive and industrial position sensing. It delivers 5.000 mV/G sensitivity, operates from –40°C to +150°C, features rail-to-rail output with 50% V_CC quiescent voltage, and uses dynamic offset cancellation for stable performance under thermal stress.

For engineers reviewing the A1321LLHLT datasheet, A1321LLHLT pinout, A1321LLHLT application, or A1321LLHLT equivalent, this page provides verified technical context, package mapping, magnetic and electrical specifications, real-world use scenarios, and validated alternative options for legacy design support and obsolescence mitigation.

Technical Context

The A1321LLHLT integrates a BiCMOS monolithic circuit with Hall element, temperature-compensating circuitry, high-gain amplifier, and rail-to-rail output stage. Its proprietary dynamic offset cancellation uses a 150 kHz internal clock to suppress residual offset caused by overmolding and thermal stress.

It operates ratiometrically across 4.5–5.5 V supply, maintains ±1.5% ratiometry on both quiescent voltage and sensitivity, and achieves ±1.5% linearity over full temperature range. Output bandwidth is 30 kHz, enabling fast response in rotating or linear motion detection systems.

Key Specifications

Parameter	Value and Actual Design Meaning
Sensitivity	5.000 mV/G at 25°C - enables precise analog field measurement with minimal external gain
Operating Temperature	–40°C to +150°C - qualified for under-hood automotive and industrial motor control environments
Quiescent Output Voltage	2.5 V ±75 mV at 5 V supply - ratiometric 50% V_CC reference simplifies ADC interfacing and eliminates need for external voltage reference
Supply Voltage Range	4.5 V to 5.5 V - tight regulation requirement ensures stable magnetic transfer function across system rail variations
Output Bandwidth	30 kHz - supports real-time monitoring of fast-moving targets such as crankshaft or camshaft rotation
Dynamic Offset Cancellation Clock	150 kHz - high-frequency sampling reduces low-frequency drift and improves long-term DC stability
Noise (Peak-to-Peak)	40 mV (A1321) - defines minimum detectable field change in noisy EMI environments

Pinout & Package

Package: 3-pin SOT-23W (LH suffix), surface-mount, lead-free with 100% matte tin plating. Dimensions per Allegro DWG-802840: 2.98 × 1.49 × 1.00 mm, branded face orientation critical for magnetic field directionality.

Pin/Terminal	Circuit Role	Design Meaning
V_CC (Pin 1)	Power supply input	Must be bypassed with 0.1 μF capacitor near pin; Zener clamp activates above 6 V to protect against transients
V_OUT (Pin 2)	Analog output	Rail-to-rail, low-impedance (≤3 Ω); drives ≥4.7 kΩ load directly; polarity indicates magnetic pole orientation
GND (Pin 3)	Ground reference	Common return for supply and output; must be low-impedance path to minimize noise coupling into Hall element

Key Features

Feature	Design Value
Temperature-stable quiescent output	±10 G equivalent drift over –40°C to +150°C - ensures zero-point repeatability without recalibration after thermal cycling
Ratiometric rail-to-rail output	Output scales linearly with V_CC; eliminates error from supply variation in battery-powered or unregulated systems
Dynamic offset cancellation	150 kHz clock-driven technique - removes mechanical stress-induced offsets and enables robust mounting in vibration-prone assemblies
High-temperature qualification	150°C ambient rating with 165°C max junction temperature - supports placement near engines, transmissions, and power electronics
Robust EMC protection	Integrated filtering and layout-optimized die design - meets automotive-level immunity requirements without external shielding

Applications

Automotive Crankshaft Position Sensing	Industrial Motor Commutation
Use Scenario: Detecting rotational position and speed of crankshaft in gasoline/diesel engines under hood temperatures up to 150°C. IC Role / Device Role / Timing Role: Analog magnetic field transducer converting gear tooth proximity into proportional voltage for ECU timing decisions. Use Value: Enables spark/fuel timing accuracy within ±1.5° CA due to 5 mV/G sensitivity and <40 mV peak-to-peak noise floor.	Use Scenario: Monitoring rotor position in brushless DC motors used in HVAC blowers, pumps, and compressors. IC Role / Device Role / Timing Role: Linear Hall sensor providing continuous analog angle feedback to motor controller for sinusoidal commutation. Use Value: Delivers ±1.5% linearity and ±1.5% symmetry over full temperature range, reducing torque ripple and acoustic noise.
Heavy-Duty Gear Tooth Detection	Hydraulic Valve Position Feedback
Use Scenario: Sensing large ferrous gear teeth in off-highway equipment transmissions operating at extreme ambient temperatures. IC Role / Device Role / Timing Role: High-temperature-stable analog sensor generating voltage swing proportional to air gap variation during gear rotation. Use Value: Maintains ±2% sensitivity drift after thermal cycling, ensuring consistent signal amplitude across seasonal temperature extremes.	Use Scenario: Closed-loop position monitoring of spool valves in electro-hydraulic actuators for construction and agricultural machinery. IC Role / Device Role / Timing Role: Ratiometric linear transducer translating valve core displacement into calibrated voltage for PLC or microcontroller input. Use Value: 50% V_CC quiescent point and ratiometric scaling eliminate calibration dependency on supply rail tolerance in 24 V industrial systems.

Automotive Crankshaft Position Sensing

Industrial Motor Commutation

Use Scenario: Detecting rotational position and speed of crankshaft in gasoline/diesel engines under hood temperatures up to 150°C.

IC Role / Device Role / Timing Role: Analog magnetic field transducer converting gear tooth proximity into proportional voltage for ECU timing decisions.

Use Value: Enables spark/fuel timing accuracy within ±1.5° CA due to 5 mV/G sensitivity and <40 mV peak-to-peak noise floor.

Use Scenario: Monitoring rotor position in brushless DC motors used in HVAC blowers, pumps, and compressors.

IC Role / Device Role / Timing Role: Linear Hall sensor providing continuous analog angle feedback to motor controller for sinusoidal commutation.

Use Value: Delivers ±1.5% linearity and ±1.5% symmetry over full temperature range, reducing torque ripple and acoustic noise.

Heavy-Duty Gear Tooth Detection

Hydraulic Valve Position Feedback

Use Scenario: Sensing large ferrous gear teeth in off-highway equipment transmissions operating at extreme ambient temperatures.

IC Role / Device Role / Timing Role: High-temperature-stable analog sensor generating voltage swing proportional to air gap variation during gear rotation.

Use Value: Maintains ±2% sensitivity drift after thermal cycling, ensuring consistent signal amplitude across seasonal temperature extremes.

Use Scenario: Closed-loop position monitoring of spool valves in electro-hydraulic actuators for construction and agricultural machinery.

IC Role / Device Role / Timing Role: Ratiometric linear transducer translating valve core displacement into calibrated voltage for PLC or microcontroller input.

Use Value: 50% V_CC quiescent point and ratiometric scaling eliminate calibration dependency on supply rail tolerance in 24 V industrial systems.

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear Hall-effect sensor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
A1324LLHLX-T	Successor device with identical LH package, same 5 mV/G sensitivity, but enhanced EMC performance and updated process node.	Qualified for new designs; supports same –40°C to +150°C range but with improved long-term stability metrics.	Recommended for production continuity where A1321LLHLT is obsolete; requires no PCB changes.
ACS724LLCTR-5AB-T	Current sensor IC with integrated conductor; not magnetic-field-based; outputs 400 mV/A with 1.5% total error.	Used for current sensing rather than position; unsuitable for rotary/linear field measurement but offers higher SNR in power monitoring.	Only viable if application shifts from position to current sensing; not a functional replacement for A1321LLHLT.

Compared with A1321LLHLT, the A1324LLHLX-T provides direct drop-in compatibility and extended lifecycle support, while the ACS724LLCTR-5AB-T serves a fundamentally different measurement domain and requires redesign of signal conditioning and mechanical mounting.

Availability

A1321LLHLT is available at Aetrix Electronics and suitable for automotive crankshaft sensing, industrial BLDC motor commutation, and hydraulic valve position feedback requiring stable component supply despite end-of-life status.

Supply support for A1321LLHLT includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Allegro MicroSystems is a U.S.-based semiconductor company specializing in high-performance magnetic sensing and power ICs for automotive and industrial markets.

The A132X family was designed specifically for high-temperature linear and rotary position sensing in harsh environments, emphasizing ratiometric stability, mechanical stress immunity, and automotive-grade reliability.

FAQ

What is the operating temperature range of the A1321LLHLT?

The A1321LLHLT is rated for ambient operation from –40°C to +150°C, with a maximum junction temperature of 165°C. This specification is validated per Allegro's A1321-DS Rev. 23 and applies specifically to the LH package variant. The device maintains specified sensitivity and quiescent voltage accuracy across this full range, making it suitable for under-hood automotive and industrial motor applications.

Is the A1321LLHLT still in production?

No, the A1321LLHLT is a discontinued product. Allegro declared it obsolete effective October 31, 2011, and it is no longer manufactured or available for new design applications. Samples are unavailable. Aetrix Electronics maintains limited legacy stock for existing production continuity, subject to availability and lifecycle coordination support.

What is the pin configuration and package type of the A1321LLHLT?

The A1321LLHLT uses a 3-pin SOT-23W (LH) surface-mount package with pin 1 = V_CC, pin 2 = V_OUT, and pin 3 = GND. The branded face must face the magnetic source, and the active Hall element lies 0.28 mm below that surface. Mechanical dimensions conform to Allegro drawing DWG-802840.

What does "ratiometric" mean for the A1321LLHLT?

For the A1321LLHLT, ratiometric means both its quiescent output voltage (2.5 V at 5 V supply) and sensitivity (5.000 mV/G) scale linearly with supply voltage. If V_CC drops to 4.5 V, quiescent output becomes 2.25 V and sensitivity reduces to 4.5 mV/G - preserving measurement proportionality without external regulation or calibration.

What is the recommended bypass capacitor for the A1321LLHLT?

A 0.1 μF ceramic capacitor is required between V_CC and GND, placed as close as possible to the A1321LLHLT pins. This value is specified in the Functional Block Diagram and Electrical Characteristics section of the A1321-DS Rev. 23 datasheet to stabilize the internal amplifier and suppress high-frequency noise from the dynamic offset cancellation clock.

A1321LLHLT Specifications

Product attributes: Attribute value

Manufacturer:: Allegro MicroSystems

Series:: -

Package/Case:: SOT-23W

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Technology:: Hall Effect

Axis:: Single

Output Type:: Analog Voltage

Sensing Range:: -

Voltage - Supply:: 4.5V ~ 5.5V

Current - Supply (Max):: 8mA

Current - Output (Max):: 10mA

Resolution:: -

Bandwidth:: 30kHz

Operating Temperature:: -40°C ~ 150°C

Grade:: -

Qualification:: -

Features:: Temperature Compensated

Supplier Device Package:: SOT-23W

Mounting Type:: Surface Mount

A1321LLHLT FAQ

1.How can I place an order for A1321LLHLT through Aetrix?

Please submit a Request for Quotation (RFQ) for A1321LLHLT on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for A1321LLHLT reliable?

The price and inventory of A1321LLHLT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A1321LLHLT is usually 5 days.

3.What payment methods are accepted for A1321LLHLT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A1321LLHLT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A1321LLHLT?

A1321LLHLT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A1321LLHLT order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for A1321LLHLT?

For technical support, including A1321LLHLT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A1321LLHLT requirements.

6.How does Aetrix verify that A1321LLHLT is sourced from the original manufacturer or authorized distributors?

All A1321LLHLT products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that A1321LLHLT meets industry standards.

7.What is the process for return or replacement of A1321LLHLT?

All A1321LLHLT units undergo pre-shipment inspection (PSI). If there is an issue with A1321LLHLT, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The A1321LLHLT part is unused and in its original packaging.

Return procedure for A1321LLHLT:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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