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Allegro MicroSystems A1381LLHLT-T
- Part No.:
- A1381LLHLT-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Linear, Compass (ICs)
- Package:
- SOT-23W
- Datasheet:
-
A1381LLHLT-T.pdf
- Description:
- SENSOR HALL EFFECT ANALOG SOT23W
- Quantity:
- Payment:
- Shipping:
Inventory:1,932
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Product details
Overview
A1381LLHLT-T from Allegro MicroSystems is a programmable linear Hall effect sensor IC with analog output, designed for high-accuracy magnetic field sensing in automotive and industrial systems. It delivers ratiometric voltage output (2.3–2.6 V quiescent), user-programmable sensitivity (6.00–9.00 mV/G), polarity, and temperature coefficient, operating across –40°C to 150°C in a 3-pin SOT-23W package.
For engineers reviewing the A1381LLHLT-T datasheet, A1381LLHLT-T pinout, A1381LLHLT-T application, or A1381LLHLT-T equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternatives, and supply guidance for legacy design support and obsolescence mitigation.
Technical Context
The A1381LLHLT-T integrates a BiCMOS monolithic circuit with a Hall element, dynamic offset cancellation, temperature-compensated gain amplifier, and clamped low-impedance output stage. Its chopper-stabilized architecture uses a 170 kHz clock and sample-and-hold demodulation at 340 kHz to suppress DC drift and enhance thermal stability.
It supports end-of-line programming via voltage pulses applied to the VOUT pin-enabling permanent fuse-based configuration of quiescent voltage (6-bit resolution), sensitivity (6-bit), sensitivity TC (3-bit), polarity (1-bit), and lock bit (1-bit). Output clamps (0.40–0.70 V low, 4.35–4.65 V high) provide short-circuit diagnostics and ratiometric scaling with VCC.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temp Range | –40°C to 150°C (L-grade): enables under-hood automotive and industrial motor control use without derating. |
| Sensitivity Range | 6.00–9.00 mV/G: supports precise current or angular position sensing with field-to-voltage linearity. |
| Quiescent Output | 2.3–2.6 V (at VCC = 5 V): ratiometric, programmable offset centered near mid-supply for ADC compatibility. |
| Internal Bandwidth | 12 kHz (–3 dB): sufficient for engine speed, throttle, and brake pedal position feedback in real-time control loops. |
| Supply Current | 6.9–8 mA: enables low-power operation in always-on vehicle subsystems with minimal thermal impact. |
| Noise (p-p) | 34 mV (no filter); 4.7 mV (with 2 kHz external LPF): defines minimum detectable field change in noisy environments. |
| Output Clamp Voltage | 0.40–0.70 V (low), 4.35–4.65 V (high): provides fault detection and rail-to-rail interface margin with 5 V microcontrollers. |
Pinout & Package
Package: 3-pin SOT-23W (LH suffix), thin-profile surface-mount, thermally optimized for 1- or 2-layer PCBs (RθJA = 228 °C/W or 110 °C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC | Power input | 4.5–5.5 V supply; requires 0.1 µF bypass capacitor to GND for stable operation and noise immunity. |
| GND | Ground reference | Common return path for supply and output; must be low-impedance to minimize offset error. |
| VOUT | Analog output & programming port | Delivers ratiometric voltage proportional to magnetic field; also accepts 14–28 V programming pulses for fuse-based configuration. |
Key Features
| Feature | Design Value |
|---|---|
| End-of-line programmability | Enables final-system calibration without dedicated programming hardware-reducing test cost and enabling field tuning. |
| Ratiometric output | Ensures consistent performance across supply variations (e.g., battery voltage sag), eliminating need for separate reference voltage. |
| Chopper-stabilized architecture | Reduces thermal drift and mechanical stress sensitivity-critical for repeatable accuracy after temperature cycling. |
| Output voltage clamps | Provide inherent short-circuit protection and diagnostic capability: low/high clamp violation signals system fault conditions. |
| Extended temperature range | Validated operation up to 150°C junction enables placement near engines, transmissions, and power inverters. |
Applications
| Automotive Throttle Position Sensing | Industrial Motor Current Monitoring |
|---|---|
Use Scenario: Detecting rotational angle of throttle body shaft in gasoline/diesel engines under hood temperatures up to 150°C. IC Role / Device Role / Timing Role: Linear Hall sensor converting magnetic flux from rotating magnet into analog voltage proportional to shaft angle. Use Value: Programmable quiescent voltage and sensitivity enable factory calibration to match magnet strength and mechanical tolerances-achieving ±1.5% linearity error. |
Use Scenario: Non-invasive current measurement in 3-phase inverter legs for HVAC compressors or industrial pumps. IC Role / Device Role / Timing Role: Closed-loop current sensor front-end, where magnetic field from conductor induces proportional analog output. Use Value: 12 kHz bandwidth and 34 mV peak-to-peak noise allow accurate RMS current estimation at 50/60 Hz and harmonics up to 1 kHz. |
| Electric Power Steering Torque Sensing | Heavy-Duty Brake Pedal Position Feedback |
Use Scenario: Measuring torsion bar twist in EPS column to determine driver steering torque input. IC Role / Device Role / Timing Role: Dual-sensor differential pair (A1381LLHLT-T + companion) rejecting common-mode mechanical stress and thermal gradients. Use Value: Immunity to mechanical stress and <±2% sensitivity hysteresis after thermal cycling ensure long-term zero-point stability over vehicle lifetime. |
Use Scenario: Redundant pedal travel sensing in commercial vehicles requiring functional safety compliance (ASIL-B). IC Role / Device Role / Timing Role: Primary analog position transducer delivering fail-safe voltage output with diagnostic clamps. Use Value: Output voltage clamps (0.40–0.70 V / 4.35–4.65 V) enable immediate detection of open-load, short-to-VCC, or short-to-GND faults per ISO 26262 requirements. |
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 |
|---|---|---|---|
| A1389ELHLT-T | Successor device with enhanced ESD rating (±8 kV HBM), lower noise (2.5 mV p-p with filter), and extended sensitivity range (5.0–10.0 mV/G). | Designed for new designs requiring higher robustness and tighter accuracy; not drop-in due to different programming protocol and pin-compatible but non-identical timing. | Select A1389ELHLT-T for new automotive programs; verify layout compatibility and revalidate programming firmware. |
| ACS724LLCTR-10AU-T | Integrated current sensor IC (10 A range), not programmable, with fixed 400 mV/A output and built-in conductor-no external magnet required. | Replaces discrete Hall + magnet assemblies in current sensing; eliminates mechanical alignment but lacks field-programmable offset/sensitivity. | Choose ACS724LLCTR-10AU-T when measuring conductor current directly; avoid if angular/displacement sensing or field-level calibration is needed. |
Compared with A1381LLHLT-T, the A1389ELHLT-T offers improved noise floor and ESD tolerance for next-gen designs, while the ACS724LLCTR-10AU-T trades programmability for integrated current sensing-making it suitable only where conductor proximity and fixed gain are acceptable.
Availability
A1381LLHLT-T is available at Aetrix Electronics and suitable for automotive throttle control, industrial motor current monitoring, electric power steering, and heavy-duty brake pedal position sensing requiring stable component supply despite end-of-life status.
Supply support for A1381LLHLT-T 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 magnetic sensing, power ICs, and precision motion control solutions for automotive and industrial markets.
The A138x family was engineered to deliver programmable, temperature-stable linear Hall sensing in miniature packages-targeting high-accuracy displacement, angular position, and current measurement where calibration flexibility and extended temperature operation are critical.
FAQ
Is A1381LLHLT-T still in production?
No, A1381LLHLT-T is a discontinued product. Allegro ceased production as of December 1, 2015. Aetrix Electronics maintains limited legacy inventory for existing design support and repair programs, but no new manufacturing runs are planned. Customers are advised to transition to A1389ELHLT-T for new designs.
What does the 'LL' in A1381LLHLT-T signify?
The 'LL' suffix in A1381LLHLT-T indicates the L-grade temperature rating (–40°C to 150°C ambient), distinguishing it from E-grade variants (–40°C to 85°C). This grade is qualified for under-hood automotive applications and high-temperature industrial environments where sustained thermal stress is expected.
Can A1381LLHLT-T be programmed without the Allegro evaluation kit?
Yes-A1381LLHLT-T supports voltage-pulse programming via its VOUT pin using externally generated 14–28 V pulses meeting defined timing (e.g., tBLOW ≥ 30 µs, tPr ≤ 100 µs). However, Allegro strongly recommends the official Sensor IC Evaluation Kit to ensure reliable fuse blowing and avoid accidental misprogramming due to noise or timing violations.
What is the maximum allowable supply voltage for A1381LLHLT-T?
The absolute maximum forward supply voltage for A1381LLHLT-T is 8 V. Operation above 5.5 V (recommended max) risks exceeding internal Zener clamp limits and may cause irreversible damage. The supply Zener clamp activates at ~6–8.3 V, but sustained overvoltage is not supported.
Does A1381LLHLT-T require an external bypass capacitor?
Yes, A1381LLHLT-T requires a 0.1 µF ceramic bypass capacitor between VCC and GND, placed as close as possible to the pins. This capacitor stabilizes the internal regulator, suppresses supply noise, and ensures proper power-on timing (tPO ≤ 32 µs) and clamp response (tCLP ≤ 30 µs).
A1381LLHLT-T 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:
- 12kHz
- Operating Temperature:
- -40°C ~ 150°C
- Grade:
- -
- Qualification:
- -
- Features:
- Programmable, Temperature Compensated
- Supplier Device Package:
- SOT-23W
- Mounting Type:
- Surface Mount
A1381LLHLT-T FAQ
1.How can I place an order for A1381LLHLT-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A1381LLHLT-T 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 A1381LLHLT-T reliable?
The price and inventory of A1381LLHLT-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A1381LLHLT-T is usually 5 days.
3.What payment methods are accepted for A1381LLHLT-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A1381LLHLT-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A1381LLHLT-T?
A1381LLHLT-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A1381LLHLT-T 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 A1381LLHLT-T?
For technical support, including A1381LLHLT-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A1381LLHLT-T requirements.
6.How does Aetrix verify that A1381LLHLT-T is sourced from the original manufacturer or authorized distributors?
All A1381LLHLT-T 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 A1381LLHLT-T meets industry standards.
7.What is the process for return or replacement of A1381LLHLT-T?
All A1381LLHLT-T units undergo pre-shipment inspection (PSI). If there is an issue with A1381LLHLT-T, 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 A1381LLHLT-T part is unused and in its original packaging.
Return procedure for A1381LLHLT-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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