# ACS709LLFTR-20BB-T

**Allegro MicroSystems, LLC** · Current Sensors · QSOP-24

ACS709LLFTR-20BB-T from Allegro MicroSystems, LLC, in a QSOP-24. 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 | IP+ | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP- pins; supports unidirectional or bidirectional current flow (pins 1 through 6). |
| 2 | IP+ | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP- pins; supports unidirectional or bidirectional current flow (pins 1 through 6). |
| 3 | IP+ | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP- pins; supports unidirectional or bidirectional current flow (pins 1 through 6). |
| 4 | IP+ | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP- pins; supports unidirectional or bidirectional current flow (pins 1 through 6). |
| 5 | IP+ | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP- pins; supports unidirectional or bidirectional current flow (pins 1 through 6). |
| 6 | IP+ | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP- pins; supports unidirectional or bidirectional current flow (pins 1 through 6). |
| 7 | IP- | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP+ pins; supports unidirectional or bidirectional current flow (pins 7 through 12). |
| 8 | IP- | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP+ pins; supports unidirectional or bidirectional current flow (pins 7 through 12). |
| 9 | IP- | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP+ pins; supports unidirectional or bidirectional current flow (pins 7 through 12). |
| 10 | IP- | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP+ pins; supports unidirectional or bidirectional current flow (pins 7 through 12). |
| 11 | IP- | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP+ pins; supports unidirectional or bidirectional current flow (pins 7 through 12). |
| 12 | IP- | passive | Sensed current copper conduction path terminal, fused internally and looped to the IP+ pins; supports unidirectional or bidirectional current flow (pins 7 through 12). |
| 13 | NC | unconnected | No connection. |
| 14 | NC | unconnected | No connection. |
| 15 | GND | power_in | Device ground connection. |
| 16 | VZCR | output | Voltage reference output giving the zero current (0 A) reference, equal to 0.5 × VCC and scaling with VCC; can source 3 mA minimum and sink 50 µA minimum. |
| 17 | FILTER | passive | Terminal for an external capacitor to GND that sets the device bandwidth; absolute maximum voltage is 8 V. |
| 18 | VIOUT | output | Analog output voltage proportional to the current flowing between the IP+ and IP- pins; load must be at least 10 kΩ and no more than 10 nF to GND. |
| 19 | FAULT | output | Active-low open-drain overcurrent fault output that goes low when the current between IP+ and IP- exceeds the fault threshold; VFAULT is 0.4 V maximum at 1 mA sink. |
| 20 | VCC | power_in | Supply voltage pin, operating range 3 to 5.5 V (absolute maximum 8 V). |
| 21 | VOC | input | Overcurrent input whose analog voltage sets the overcurrent fault threshold, valid from 0.25×VCC to 0.4×VCC (absolute maximum 8 V). |
| 22 | FAULT_EN | input | Enables overcurrent faulting when high and resets FAULT when low; VIH is 0.8×VCC minimum and VIL is 0.1×VCC maximum. |
| 23 | NC | unconnected | No connection. |
| 24 | NC | unconnected | No connection. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Allegro MicroSystems, LLC |
| Package | QSOP-24 |
| Category | Sensors |
| Pins | 24 |

## Electrical characteristics

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

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Supply Voltage | VCC | 3 |  | 5.5 | V |  | 4 |
| Nominal Supply Voltage | VCCN |  | 5 |  | V |  | 4 |
| Supply Current | ICC |  | 11 | 14.5 | mA | VIOUT open, FAULT pin high | 4 |
| Output Capacitance Load | CLOAD |  |  | 10 | nF | VIOUT pin to GND | 4 |
| Output Resistive Load | RLOAD | 10 |  |  | kΩ | VIOUT pin to GND | 4 |
| Full Range Linearity | ELIN | -0.75 | 0.25 | 0.75 | % | IP = ±IP0A | 4 |
| Symmetry | ESYM | 99.1 | 100 | 100.9 | % | IP = ±IP0A | 4 |
| Setting Voltage for Overcurrent Switch Point | VOC | 0.25 |  | 0.4 | xVCC |  | 4 |
| Overcurrent FAULT Pin Output Voltage | VFAULT |  |  | 0.4 | V | 1 mA sink current at FAULT pin | 4 |
| FAULT_EN Input Low Voltage Threshold | VIL |  |  | 0.1 | xVCC |  | 4 |
| FAULT_EN Input High Voltage Threshold | VIH | 0.8 |  |  | xVCC |  | 4 |
| Overcurrent Input Pin Resistance | ROC | 2 |  |  | MΩ | TA = 25°C, VOC pin to GND | 5 |
| Voltage Reference Output Load Current (source) | IZCR | 3 |  |  | mA | Source current | 5 |
| Voltage Reference Output Load Current (sink) | IZCR | 50 |  |  | µA | Sink current | 5 |
| Voltage Reference Output | VZCR |  | 0.5 |  | xVCC | TA = 25 °C | 5 |
| Voltage Reference Output Drift | ΔVZCR |  | 10 |  | mV |  | 5 |
| Optimized Accuracy Range | IP(OA) | -20 |  | 20 | A |  | 6 |
| Linear Sensing Range | IP(LIN) | -37.5 |  | 37.5 | A |  | 6 |
| Sensitivity | Sens | 54.5 |  | 58 | mV/A | IP = 12.5 A, TA = 25°C to 150°C | 6 |
| Sensitivity | Sens | 54.5 |  | 58.5 | mV/A | IP = 12.5 A, TA =, 40°C to 25°C | 6 |
| Sensitivity | Sens |  | 56 |  | mV/A | IP = 12.5 A, TA = 25°C | 6 |
| Electrical Offset Voltage | VOE | -25 |  | 25 | mV | IP = 0 A, TA = 25°C to 150°C | 6 |
| Electrical Offset Voltage | VOE | -40 |  | 40 | mV | IP = 0 A, TA =, 40°C to 25°C | 6 |
| Electrical Offset Voltage | VOE |  | 5 |  | mV | IP = 0 A, TA = 25°C (±5) | 6 |
| Total Output Error | ETOT |  | 2 |  | % | Tested at IP =12.5 A, IP applied for 5 ms, TA = 25°C to 150°C (±2) | 6 |
| Total Output Error | ETOT |  | 3 |  | % | Tested at IP =12.5 A, IP applied for 5 ms, TA =, 40°C to 25°C (±3) | 6 |
| Noise | VNOISE(rms) |  | 1.5 |  | mV | TA = 25°C, Sens = 56 mV/A, Cf = 0, CLOAD = 4.7 nF, RLOAD open | 6 |
| Magnetic Coupling to Hall Element | MCHALL |  | 9.5 |  | G/A | Current flowing from IP+ to IP- pins | 4 |
| Internal Filter Resistance | RF(INT) |  | 1.7 |  | kΩ |  | 4 |
| Primary Conductor Resistance | RPRIMARY |  | 1.1 |  | mΩ | TA = 25°C | 4 |
| Bidirectional Quiescent Output | VOUT(QBI) |  | 0.5 |  | xVCC | IP = 0 A, TA = 25°C | 4 |
| VIOUT Signal Rise Time | tr |  | 3 |  | μs | TA = 25°C, no capacitor on FILTER pin, 100 pF from VIOUT to GND | 4 |
| VIOUT Signal Response Time | tRESPONSE |  | 4 |  | μs | TA = 25°C, no capacitor on FILTER pin, 100 pF from VIOUT to GND | 4 |
| Large Signal Bandwidth | f3dB |  | 120 |  | kHz | -3 dB, TA = 25°C, no capacitor on FILTER pin | 4 |
| Overcurrent Fault Switch Point Error | EOC |  | 5 |  | % | Switch point in VOC safe operating area; assumes INCOMP = 0 A (±5) | 4 |
| Overcurrent Fault Response Time | tOC |  | 1.9 |  | μs | VOC = 0.25 × VCC, without external COC capacitor | 5 |
| Supply Voltage | VCC |  |  | 8 | V |  | 2 |
| Analog Output Pin Voltage | VIOUT |  |  | 32 | V |  | 2 |
| DC Reverse Voltage | VRdcx | -0.5 |  |  | V | Supply, Filter, Analog Output, Overcurrent Input, Overcurrent Fault, Fault Enable, Voltage Reference Output pins | 2 |
| Output Current Source | IIOUT(Source) |  |  | 3 | mA |  | 2 |
| Output Current Sink | IIOUT(Sink) |  |  | 1 | mA |  | 2 |
| Operating Ambient Temperature | TA | -40 |  | 150 | °C | Range L | 2 |
| Junction Temperature | TJ(max) |  |  | 165 | °C |  | 2 |
| Storage Temperature | Tstg | -65 |  | 170 | °C |  | 2 |
| Steady State Package Thermal Resistance | RθJA |  | 21 |  | °C/W | Tested with 30 A DC current, ACS709 demo board in 1 cu. ft. of still air | 8 |

## 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 | [1] -S denotes the lead-free construction with tin-silver-based solder bumps. [2] -T denotes Pb-contained construction with Pb-based solder bumps. Operating performance of -T and -S devices are identi | 2 |

## CAD (KiCad official)

- Symbol: `ACS709LLFTR-20BB-T`
- Footprint: `Package_SO:QSOP-24_3.9x8.7mm_P0.635mm`
- 3D model: QSOP-24 (KiCad packages3D, STEP)
- 3D model files: `acs709llftr-20bb-t-etched.step` / `acs709llftr-20bb-t-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `acs709llftr-20bb-t.step` / `acs709llftr-20bb-t.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Allegro MicroSystems, LLC datasheet](docs/acs709llftr-20bb-t-datasheet.pdf) (20 pp, sha256 `01ee6a3818374c8e`, retrieved 2026-10-23, 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/acs709llftr-20bb-t-datasheet.pdf)