# ACS712

**Allegro MicroSystems** · Hall-effect current sensor · SOIC-8

A fully integrated Hall-effect linear current sensor in a SOIC-8: current flows through an internal 1.2 milliohm copper path (pins IP+ to IP-) and the on-chip Hall sensor reports it as an analog voltage on VIOUT, with the sensing electronics galvanically isolated from the current path (up to 2.1 kV). The output sits at half-supply (2.5 V at 0 A) and swings proportionally, so it reads bidirectional AC or DC current. Factory-trimmed variants cover plus/minus 5 A (185 mV/A), plus/minus 20 A (100 mV/A), and plus/minus 30 A (66 mV/A). Runs from a single 5 V supply.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | IP+ | passive | Primary current input terminal (positive). Terminals for current being sampled; fused internally. Pins 1 and 2 are tied together to carry the sensed current into the on-die copper conduction path. |
| 2 | IP+ | passive | Primary current input terminal (positive). Terminals for current being sampled; fused internally. Pins 1 and 2 are tied together to carry the sensed current into the on-die copper conduction path. |
| 3 | IP- | passive | Primary current output terminal (negative/return). Terminals for current being sampled; fused internally. Pins 3 and 4 are tied together to carry the sensed current out of the on-die copper conduction path. |
| 4 | IP- | passive | Primary current output terminal (negative/return). Terminals for current being sampled; fused internally. Pins 3 and 4 are tied together to carry the sensed current out of the on-die copper conduction path. |
| 5 | GND | power_in | Signal ground terminal. Reference ground for VCC and VIOUT on the signal side of the isolation barrier. |
| 6 | FILTER | passive | Terminal for external capacitor (CF) that sets output bandwidth. Forms an RC filter with the internal RF(INT) ≈ 1.7 kΩ. Typical value is 1 nF for the default 80 kHz bandwidth. |
| 7 | VIOUT | output | Analog output signal. Voltage proportional to the sensed primary current IP, with a quiescent (zero-current) output of VCC × 0.5 (bidirectional variants). Sensitivity ranges from 66 to 185 mV/A depending on the current-range variant. |
| 8 | VCC | power_in | Device power supply terminal. 5.0 V nominal (4.5 V min / 5.5 V max). Typical supply current ICC ≈ 10 mA. Decouple with 0.1 µF to GND close to the pin. |

## Key specifications

| Parameter | Value |
|---|---|
| Type | Hall-effect linear current sensor |
| Sensing | galvanically isolated (2.1 kV) |
| Conductor resistance | 1.2 mΩ |
| Output | analog, 2.5 V at 0 A (ratiometric) |
| Ranges | ±5 A / ±20 A / ±30 A |
| Sensitivity | 185 / 100 / 66 mV/A |
| Supply voltage | 5 V |
| Package | SOIC-8 |

## Ordering variants

- `ACS712ELCTR-05B-T (±5 A)`
- `ACS712ELCTR-20A-T (±20 A)`
- `ACS712ELCTR-30A-T (±30 A)`

## CAD (KiCad official)

- Symbol: `Sensor_Current:ACS712xLCTR-20A`
- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`
- 3D model: SOIC-8 (KiCad packages3D)
- 3D model files: `acs712-etched.step` / `acs712-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `acs712.step` / `acs712.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Allegro MicroSystems datasheet](https://www.allegromicro.com/-/media/files/datasheets/acs712-datasheet.ashx) (16 pp, sha256 `21b345f7a98d3694`, retrieved 2026-08-17, tier: manufacturer)
- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/acs712-datasheet.pdf)