A1102LLHLT - Unipolar Hall Effect Switch, 180G Trip, SOT-23W
MPN: A1102LLHLT ✓ NakahandaA1102LLHLT Ulas
A Hall-effect switch is a magnetic sensor whose output changes state when the applied magnetic flux density crosses a programmed threshold. Compared with reed switches, Hall ICs offer solid-state reliability, sub-microsecond response, and integration of the sensing element, signal conditioning, and output driver in a single silicon die. The A1102 belongs to Allegro's continuous-time family: the on-chip oscillator drives a dynamic-cancellation chopper-stabilized Hall plate, eliminating the residual offset of DC-biased Hall elements and yielding a stable switch point over temperature and supply.
Key features include a south-pole-only unipolar transfer function (output turns on when |B| exceeds Bop and off when |B| falls below Brp), 20 kHz typical chopping frequency for clean output, low quiescent current, 30 V absolute-maximum supply tolerance, and reverse-battery protection on the supply pin. The open-drain output requires an external pull-up resistor, simplifying interface to 3.3 V, 5 V, or 12 V logic rails without level shifting.
Architecturally, the device combines a BiCMOS Hall sensing front-end, a precision comparator with trimmed thresholds, an open-drain DMOS output stage, and on-chip protection (reverse-supply, over-voltage, and output ESD). The BiCMOS process enables fast power-on (<10 µs) and low-noise operation without the offset drift seen in older bipolar Hall ICs, while the chopper-stabilized front end virtually eliminates the residual offset that would otherwise shift the switch point with mechanical stress.
Typical applications include automotive seat-belt buckle detection, gear-shift and transmission position sensing, BLDC motor commutation triggers, valve and solenoid position feedback, consumer appliance lid/door interlocks, and contactless limit switches. The wide 3.8 V-24 V supply range allows direct connection to 12 V automotive rails without an upstream regulator.
Designers should provide a bypass capacitor of at least 0.1 µF close to the supply pin and a pull-up resistor (typically 10 kΩ) on the output. Place the device so the brand-side marking aligns with the target magnet's pole direction; the sensitive axis is perpendicular to the package top.
This page synthesizes distributor pricing, drop-in SOT-23W alternatives, and practical design notes that the manufacturer datasheet alone does not aggregate.
Mga alternatibo na pwedeng ilagay na A1102LLHLT — parehas na package, pin-to-pin na katugmang. Hindi kasama ang mga bahagi ng iba't-ibang package na nangangailangan ng pagpapaayos ng PCB.
A1101LLHLT
✅ Drop-In📋 Alternatibo na Reference (hindi sa katalogo)
A1103LLHLT
✅ Drop-In📋 Alternatibo na Reference (hindi sa katalogo)
A1104LLHLT
✅ Drop-In📋 Alternatibo na Reference (hindi sa katalogo)
A1106LLHLT
✅ Drop-In📋 Alternatibo na Reference (hindi sa katalogo)
A1102EUA
✅ Drop-In📋 Alternatibo na Reference (hindi sa katalogo)
SS39ET
✅ Drop-In📋 Alternatibo na Reference (hindi sa katalogo)
A1102LLHLT Mga Pinakamataas na Rating at Electrical Characteristics
| Type ng Sensor | Hall Effect Digital Switch |
| Switch Type | Unipolar (South Pole) |
| Type ng Output | Open Drain |
| Magnetic Trip Point (Bop, typ.) | 180 G (24.5 mT) |
| Magnetic Release Point (Brp, typ.) | 125 G (6 mT) |
| Supply Voltage Range | 3.8 V to 24 V |
| Absolute Maximum Supply Voltage | 30 V |
| Hanay ng Temperature na Operasyon | -40 °C to +150 °C (TA) |
| Output Current (sink) | 30 mA (max) |
| Power-On Time | < 10 µs |
| Chopping Frequency | 20 kHz (typ.) |
| Packhaging | SOT-23W (3-pin) |
| Uri ng Pagpapasok | Surface Mount |
| Lead Finish | Matte Tin (Sn) |
| Level ng MSL | 1 |
| Tindminan RoHS | Compliant |
| ESD Protection | Output ESD protected (per datasheet) |
| Reverse Battery Protection | Yes |
Pin Configuration ng A1102LLHLT
| Pin 1 | VCC — Supply voltage input, 3.8 V to 24 V |
| Pin 2 | GND — Ground reference |
| Pin 3 | OUTPUT — Open-drain Hall switch output; external pull-up required |
Tipikal na mga Gamit
A1102LLHLT ay nararapat para sa 6 aplikasyons: Automotive Seat-Belt Buckle Detection, Gear-Shift and Transmission Position Sensing, BLDC Motor Commutation Trigger, Valve and Solenoid Position Feedback, Consumer Appliance Lid/Door Interlock, Contactless Limit Switch Replacement.
Automotive Seat-Belt Buckle Detection
The A1102LLHLT's 180 G unipolar trip point and -40 °C to +150 °C automotive temperature range make it ideal for seat-belt buckle latching sensors. A small permanent magnet embedded in the buckle slides into proximity with the SOT-23W sensor when latched; the open-drain output drives low and signals the airbag controller that the buckle is fastened. The 30 V absolute-maximum supply tolerance withstands 12 V automotive load-dump transients without external TVS protection, and the chopper-stabilized front-end prevents switch-point drift over the 15-year vehicle service life. Designers typically place the sensor on a flexible tail of the buckle PCB with a 0.1 µF VCC bypass capacitor.
Inirekomenda
Gear-Shift and Transmission Position Sensing
The A1102LLHLT delivers a clean digital edge for PRNDL position feedback in automatic transmissions. Mounted on a small PCB near each detent, the sensor triggers when a magnet embedded in the shift lever enters the trip window. The 20 kHz chopping frequency eliminates output chatter during slow lever movement, and the 55 G hysteresis prevents false release at the exact threshold. The 3.8 V to 24 V supply range allows direct connection to the 12 V body control module without an LDO, reducing BOM cost and quiescent draw. The SOT-23W footprint fits inside space-constrained gear-shift assemblies.
Inirekomenda
BLDC Motor Commutation Trigger
The A1102LLHLT functions as a low-cost Hall-sensor for trapezoidal commutation in small BLDC motors, fans, and water pumps. Three sensors spaced 120 electrical degrees apart provide six-step commutation signals directly to a driver IC. The sub-10 µs power-on time allows the controller to start the motor within one electrical cycle after release from standby, and the 30 mA sink current is sufficient to drive opto-isolated or gate-driver inputs directly. For sinusoidal (FOC) commutation requiring linear feedback, upgrade to the Allegro A1302 or A3214 instead.
Inirekomenda
Valve and Solenoid Position Feedback
The A1102LLHLT provides end-of-travel position confirmation for pneumatic and hydraulic solenoid valves used in industrial process control. A magnet mounted on the spool triggers the sensor when the valve reaches full open or full close, allowing the controller to verify actuation without a mechanical limit switch. The solid-state Hall IC survives millions more cycles than reed switches in high-vibration solenoid environments, and the chopper-stabilized front-end rejects the 50/60 Hz electromagnetic interference common in industrial cabinets.
Inirekomenda
Consumer Appliance Lid/Door Interlock
The A1102LLHLT's small SOT-23W footprint fits inside washing-machine door latches and microwave oven interlocks where PCB area is constrained. A magnet in the door triggers the sensor when the door closes, and the controller refuses to start the motor until the open-drain output confirms latching. The 3.8 V minimum supply allows operation directly from a 5 V logic rail, while the open-drain output interfaces cleanly to a 3.3 V MCU GPIO without level shifting. The -40 °C to +150 °C range covers unheated garage and laundry-room installations.
Inirekomenda
Contactless Limit Switch Replacement
The A1102LLHLT replaces mechanical limit switches in factory automation where dust, oil, or mechanical wear would otherwise shorten contact life. A permanent magnet on the moving part triggers the Hall switch when in position, eliminating contact bounce and providing sub-millimeter repeatability. The wide 3.8 V to 24 V supply range accommodates both 24 V PLC inputs and 5 V logic controller inputs. Reverse-battery protection prevents damage during installation rework, and the 30 V absolute-maximum rating tolerates the inductive kickback typical of long cable runs in industrial cabinets.
Inirekomenda
Buod ng mga Inirekomendang Produkto
Impormasyon ng Talumpati sa Engineering for A1102LLHLT — ikabit, gabay sa disenyo, at impormasyon ng pagsunod sa kautusan.
Paunawang Hanapin
Ikabit sa Mga Alternatibo
| Parametro | Ito ang Producto | A1101LLHLT | A1103LLHLT | A1104LLHLT | A1106LLHLT | A1102EUA | SS39ET |
|---|---|---|---|---|---|---|---|
| Package | SOT-23W (3-pin) | SOT-23W (3-pin) - same | SOT-23W (3-pin) - same | SOT-23W (3-pin) - same | SOT-23W (3-pin) - same | SIP-3 (UA) - through-hole | SOT-23 (3-pin) - same footprint |
| Brand | Allegro MicroSystems | Allegro MicroSystems | Allegro MicroSystems | Allegro MicroSystems | Allegro MicroSystems | Allegro MicroSystems | Honeywell |
| Magnetic Trip (Bop, typ.) | 180 G (24.5 mT) | 230 G | 130 G | 175 G | 180 G (inverted polarity) | 180 G | 150 G |
| Supply Voltage | 3.8 V to 24 V | 3.8 V to 24 V | 3.8 V to 24 V | 3.8 V to 24 V | 3.8 V to 24 V | 3.8 V to 24 V | 2.7 V to 24 V |
| Output Type | Open Drain | Open Drain | Open Drain | Open Drain | Open Drain | Open Drain | Open Collector |
| Operating Temperature | -40 °C to +150 °C | -40 °C to +150 °C | -40 °C to +150 °C | -40 °C to +150 °C | -40 °C to +150 °C | -40 °C to +150 °C | -40 °C to +150 °C |
| Unit Price (qty-1, USD, as of 2026-10-06) | 2.45 | approx. 2.45 (Allegro family) | approx. 2.45 (Allegro family) | approx. 2.45 (Allegro family) | approx. 2.45 (Allegro family) | approx. 1.95 (through-hole, lower) | approx. 2.80 (Honeywell) |
Pangunahing mga Pagkakaiba
- Wide 3.8 V to 24 V supply supports direct 12 V automotive rails (kumpara saSS39ET (Honeywell))
- 180 G mid-range trip covers most magnet-air-gap combinations (kumpara saA1101LLHLT (230 G trip) and A1103LLHLT (130 G trip))
- Chopper-stabilized front-end eliminates switch-point drift over stress and temperature (kumpara saOlder Allegro 312x/314x bipolar Hall switches)
Talaan ng Disenyo
Place a 0.1 µF ceramic bypass capacitor within 5 mm of the VCC pin (Pin 1). For long VCC traces or noisy automotive environments, add a 10 µF bulk capacitor on the same node. Allegro's A110x application notes recommend keeping the bypass loop area under 25 mm² to minimize supply ringing at the 20 kHz chopping frequency.
The open-drain output (Pin 3) WILL NOT drive high without an external pull-up resistor. A 10 kΩ pull-up to VCC or to a 3.3 V/5 V logic rail is typical. Forgetting the pull-up is the single most common reason a Hall switch 'does not work' on the bench - the output simply floats at undefined voltage. If the pull-up is tied to a logic rail different from VCC, ensure the output's VOH does not exceed the sensor's absolute-maximum rating.
Estimated: at VCC = 24 V with open-drain output OFF (no current), quiescent dissipation is below 50 mW and the SOT-23W junction rises less than 5 °C above ambient. With output ON sinking 20 mA, dissipation adds 0.48 W at VCC = 24 V, but the SOT-23W theta_JA of ~250 °C/W on a small copper pour would push Tj above 150 °C. Derate sink current or increase copper pour for high-VCC continuous-on operation.
The Hall sensitive axis is perpendicular to the top face of the package. Position the SOT-23W so that the brand-side marking faces the incoming magnet's south pole - reversing the device 180° inverts the trip direction. For through-hole assemblies, the A1102EUA has the sensitive axis through the curved side of the SIP package per the Allegro datasheet.
Impormasyon ng Pagsunod sa Kautusan
RoHS compliant per Allegro product page. Matte-Tin lead finish confirmed from datasheet. AEC-Q100 qualification documentation should be requested from Allegro for the specific date code used in production builds. Halogen-free status not explicitly stated in the verified data.
