# A1221LLHLT-T

**Allegro MicroSystems, LLC** · Hall Sensor · SOT-23

A1221LLHLT-T from Allegro MicroSystems, LLC, in a SOT-23. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VCC | power_in | Connects power supply to chip; operating range 3 to 24 V (26.5 V absolute maximum), with a 0.1 µF bypass capacitor recommended close to the device. |
| 2 | VOUT | output | Short-circuit protected open-drain output that sinks up to 25 mA continuous (current limit 30 to 60 mA) and goes low when B > BOP; off-state voltage up to 26 V. |
| 3 | GND | power_in | Ground connection for the device. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Allegro MicroSystems, LLC |
| Package | SOT-23 |
| Category | Sensors |
| Pins | 3 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Forward Supply Voltage | VCC |  |  | 26.5 | V |  | 3 |
| Reverse Supply Voltage | VRCC | -30 |  |  | V |  | 3 |
| Output Off Voltage | VOUT |  |  | 26 | V |  | 3 |
| Continuous Output Current | IOUT |  |  | 25 | mA |  | 3 |
| Reverse Output Current | IROUT | -50 |  |  | mA |  | 3 |
| Operating Ambient Temperature | TA | -40 |  | 150 | °C | Range L | 3 |
| Maximum Junction Temperature | TJ(max) |  |  | 165 | °C |  | 3 |
| Maximum Junction Temperature | TJ(max) |  |  | 175 | °C | For 500 hours | 3 |
| Storage Temperature | Tstg | -65 |  | 170 | °C |  | 3 |
| Forward Supply Voltage | VCC | 3 |  | 24 | V | Operating, TJ < 165°C | 4 |
| Output Leakage Current | IOUTOFF |  |  | 10 | µA | VOUT = 24 V, B < BRP | 4 |
| Output Saturation Voltage | VOUT(SAT) |  | 185 | 500 | mV | IOUT = 20 mA, B > BOP | 4 |
| Output Current Limit | IOM | 30 |  | 60 | mA | B > BOP | 4 |
| Power-On Time | tPO |  |  | 25 | µs | VCC > 3.0 V, B < BRP(min), 10 G, B > BOP(max) + 10 G | 4 |
| Output Rise Time | tr |  | 0.2 | 2 | µs | RL = 820 Ω, CL = 20 pF | 4 |
| Output Fall Time | tf |  | 0.1 | 2 | µs | RL = 820 Ω, CL = 20 pF | 4 |
| Supply Current (On) | ICC(ON) |  |  | 4 | mA | B > BOP, VCC = 12 V | 4 |
| Supply Current (Off) | ICC(OFF) |  |  | 4 | mA | B < BRP, VCC = 12 V | 4 |
| Reverse Supply Current | IRCC |  |  | -5 | mA | VRCC = -20 V | 4 |
| Supply Zener Clamp Voltage | VZ | 28 |  |  | V | ICC = 5 mA; TA = 25°C | 4 |
| Operate Point (A1221) | BOP | 15 | 50 | 90 | G | A1221 | 4 |
| Release Point (A1221) | BRP | -90 | -50 | -15 | G | A1221 | 4 |
| Hysteresis (A1221) | BHYS | 30 | 100 | 180 | G | A1221, BOP, BRP | 4 |
| Chopping Frequency | fC |  | 800 |  | kHz |  | 4 |
| Zener Impedance | IZ |  | 50 |  | Ω | ICC = 5 mA; TA = 25°C | 4 |
| Package Thermal Resistance | RθJA |  | 228 |  | °C/W | Package LH, 1-layer PCB with copper limited to solder pads | 5 |
| Package Thermal Resistance | RθJA |  | 110 |  | °C/W | Package LH, 2-layer PCB with 0.463 in.2 of copper area each side connected by thermal vias | 5 |

## Materials and finish

As the datasheet states them (page.json `metadata.appearance`; the 3D model's colours follow it).

| Part | Material | Colour / plating | Datasheet says | Page |
|---|---|---|---|---|
| contacts |  | tin | through-hole mounting. Both packages are lead (Pb) free, with 100% matte-tin-plated leadframes. | 2 |

## CAD (KiCad official)

- Symbol: `A1221LLHLT-T`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `a1221llhlt-t-etched.step` / `a1221llhlt-t-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `a1221llhlt-t.step` / `a1221llhlt-t.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [Allegro MicroSystems, LLC datasheet](docs/a1221llhlt-t-datasheet.pdf) (16 pp, sha256 `b9c5a500fa2b3a36`, retrieved 2026-10-31, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/a1221llhlt-t-datasheet.pdf)