Allegro MicroSystems A1309LLHLT-RP9-T

Overview

A1309LLHLT-RP9-T from Allegro MicroSystems is a reverse-polarity, ratiometric linear Hall-effect sensor IC in a 3-pin SOT-23W package, delivering –9 mV/G sensitivity, ±1.5% linearity error, and quiescent output voltage of 2.5 V at 5 V supply. It operates from –40°C to 150°C with AEC-Q100 qualification, and features dynamic offset cancellation, high-speed chopping (400 kHz), and output clamps for automotive throttle position and brake pedal sensing.

For engineers reviewing the A1309LLHLT-RP9-T datasheet, A1309LLHLT-RP9-T pinout, A1309LLHLT-RP9-T application, or A1309LLHLT-RP9-T equivalent, this page delivers verified electrical specs, thermal performance data, real-world use cases in high-temp automotive subsystems, and two validated alternative parts with documented functional and packaging differences.

Technical Context

The A1309LLHLT-RP9-T integrates a BiCMOS monolithic circuit with a Hall element, temperature-compensating circuitry, high-gain amplifier, and proprietary dynamic offset cancellation. Its 400 kHz chopping frequency minimizes QVO drift across temperature, while end-of-line programming sets both sensitivity and QVO temperature coefficients for L-range (–40°C to 150°C) operation.

This device implements ratiometric analog output scaling with VCC, where VOUT(Q) = 50% × VCC, and output clamps (VCLPHIGH = 4.5 V, VCLPLOW = 0.55 V at 5 V) enable short-circuit diagnostics. Undervoltage lockout (UVLO) activates at 2.5 V (off) and 3 V (on), ensuring robust power sequencing in engine control units.

Key Specifications

Pinout & Package

Package: 3-pin SOT-23W (2 mm × 3 mm × 1 mm), surface-mount, lead-free with 100% matte-tin plating, thermal resistance RθJA = 110°C/W on 2-layer PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with A1309LLHLX-9-T, the A1309LLHLT-RP9-T eliminates need for external polarity inversion in north-pole sensing; compared with A1308LLHLX-9-T, it extends operational reliability to 150°C environments critical for modern powertrain systems.

Availability

A1309LLHLT-RP9-T is available at Aetrix Electronics and suitable for automotive throttle position sensing, brake pedal monitoring, transmission gear selection, and turbocharger vane control requiring stable component supply across extended temperature ranges and AEC-Q100-compliant sourcing.

Supply support for A1309LLHLT-RP9-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 designer and manufacturer of high-performance magnetic sensing and power ICs, specializing in automotive-grade semiconductor solutions since 1989.

The A1309 series belongs to Allegro's linear Hall-effect sensor product line, engineered specifically for high-accuracy, high-temperature position and displacement sensing in safety-critical automotive powertrain and chassis systems.

FAQ

What is the polarity configuration of the A1309LLHLT-RP9-T?

The A1309LLHLT-RP9-T features reverse polarity output with –9 mV/G sensitivity, meaning its output voltage decreases in response to increasing south-pole magnetic flux and increases for north-pole flux. This polarity is factory-programmed and fixed; the "RP9" suffix explicitly denotes reverse-polarity 9 mV/G calibration. The A1309LLHLT-RP9-T does not support polarity reconfiguration in-circuit.

Does the A1309LLHLT-RP9-T require an external bypass capacitor?

Yes, the A1309LLHLT-RP9-T requires a 0.1 µF ceramic bypass capacitor between VCC and GND, placed as close as possible to the device pins. This capacitor stabilizes the internal regulator, suppresses high-frequency noise from the 400 kHz chopper clock, and ensures proper undervoltage lockout (UVLO) behavior. Omitting it risks erratic output, increased noise, and failure to power up reliably - especially in electrically noisy automotive environments where the A1309LLHLT-RP9-T is commonly deployed.

How does the A1309LLHLT-RP9-T achieve ±1.5% linearity over temperature?

The A1309LLHLT-RP9-T achieves ±1.5% linearity through factory end-of-line optimization of sensitivity and quiescent voltage output (QVO), combined with programmed temperature coefficients for both parameters. Its BiCMOS architecture integrates dynamic offset cancellation and high-speed chopping (400 kHz) to suppress second-order thermal drift. These techniques are validated across –40°C to 150°C per the A1309LLHLT-RP9-T datasheet's LinERR specification, ensuring consistent performance without user calibration.

Can the A1309LLHLT-RP9-T be used in ASIL-B compliant systems?

Yes, the A1309LLHLT-RP9-T supports ASIL-B compliance when integrated into properly architected systems. It is AEC-Q100 Grade 0 qualified (–40°C to +150°C), features built-in diagnostics including output voltage clamps for short-circuit detection, undervoltage lockout with hysteresis, and precise recoverability after temperature cycling - all documented in the A1309LLHLT-RP9-T datasheet. System-level ASIL-B compliance requires additional design measures like redundant sensing paths or watchdog supervision, but the A1309LLHLT-RP9-T provides foundational hardware-level safety mechanisms.

What is the maximum allowable output load capacitance for the A1309LLHLT-RP9-T?

The A1309LLHLT-RP9-T specifies a maximum output load capacitance (CL) of 10 nF, as defined in its Electrical Characteristics table. Exceeding this value may cause instability, overshoot, or delayed settling - particularly during magnetic step transitions where the Delay to Clamp (tCLP) parameter (30 µs typical) assumes CL ≤ 10 nF. For longer cable runs or higher-capacitance PCB traces, a series resistor (e.g., 10–100 Ω) should be added near the A1309LLHLT-RP9-T output pin to isolate capacitive loading and preserve signal integrity.