ACS712
Economical Hall-effect current sensor with 2.1kV isolation, 5A/20A/30A ranges, and 80kHz bandwidth for AC/DC current...
Product Overview
Description
The ACS712 is a fully integrated Hall-effect current sensor that provides economical and precise AC or DC current sensing. The device consists of a precise, low-offset linear Hall circuit with a copper conduction path located near the surface of the die.
When current flows through the copper conduction path, the resulting magnetic field is sensed by the integrated Hall IC and converted to a proportional voltage. The device is packaged in a SOIC-8 package with internal isolation providing 2.1kV RMS dielectric strength.
The ACS712 is available in three current ranges: ±5A (185mV/A), ±20A (100mV/A), and ±30A (66mV/A). The output is ratiometric to the supply voltage and has a zero-current output of Vcc/2, allowing bidirectional current measurement.
Product Series
ACS
Primary Application
Motor control load monitoring
Key Features
- Fully integrated Hall-effect current sensing
- 2.1kV RMS isolation voltage
- Low resistance current conductor (1.2mΩ)
- Ratiometric analog output
- Bidirectional current measurement
- 80kHz bandwidth for AC applications
- Factory-trimmed for accuracy
- Small SOIC-8 surface mount package
Specifications
| Current Range | ±5A, ±20A, ±30A |
|---|---|
| Sensitivity | 185, 100, 66 mV/A |
| Bandwidth | 80kHz typical |
| Isolation Voltage | 2.1kV RMS |
| Total Error | ±1.5% at 25°C |
| Response Time | 5μs typical |
| Supply Voltage | 5V |
| Output | Analog, ratiometric |
| Package | SOIC-8 |
| Temperature Range | -40°C to +85°C (E), -40°C to +150°C (K) |
Applications
Motor control load monitoring
Motor drive and control systems
Switch mode power supplies
Electronic system design
Overcurrent fault detection
Electronic system design
Battery management systems
Battery and charging management
Solar inverter monitoring
Renewable energy systems
Industrial automation
Industrial automation and control
FAE Expert Insights
"The ACS712 is my go-to recommendation for cost-sensitive current sensing applications. At around $1-2 in volume, it offers excellent value for basic current monitoring. The 2.1kV isolation is adequate for most low-to-medium voltage applications up to 400V working voltage. I've used it successfully in motor drives, power supplies, and battery management systems. The ratiometric output simplifies interface to 5V ADCs. Key limitations: 80kHz bandwidth limits it to lower-frequency applications - don't use for high-frequency inverter monitoring. The ±1.5% accuracy is good for monitoring but not precise enough for energy metering. Temperature drift is noticeable - expect ±3-4% over the full automotive range. For higher accuracy, step up to the ACS720. Overall, an excellent entry-level current sensor for non-critical applications."
Excellent value at $1-2; 2.1kV isolation adequate for most apps; ratiometric output simplifies ADC interface
— Michael Chen, BeiLuo
Frequently Asked Questions
What is the maximum working voltage for ACS712?
The ACS712 provides 2.1kV RMS isolation voltage between the current path and sensor circuitry. The maximum working voltage (continuous) is determined by safety agency standards and is typically 400-600V depending on pollution degree and overvoltage category. The basic insulation rating is 2.1kV RMS for 60 seconds. For reinforced insulation (touch-safe applications), derate to 600V working voltage. The isolation barrier is tested to 4.2kV peak for 60 seconds during production. For higher working voltages, consider the ACS720 with 4.8kV isolation. Always check the specific safety certifications (UL, CSA, IEC) for your application requirements and ensure compliance with local electrical safety regulations.
2.1kV isolation supports 400-600V working voltage; use ACS720 for higher voltages; check safety certifications.
How do I calculate the output voltage for a given current?
The ACS712 output voltage is calculated as: Vout = Vcc/2 + (I × Sensitivity). For bidirectional sensing, Vcc/2 is the zero-current output (2.5V with 5V supply). For example, ACS712-05B (±5A, 185mV/A): At +5A: Vout = 2.5V + (5 × 0.185) = 3.425V; At -5A: Vout = 2.5V + (-5 × 0.185) = 1.575V; At 0A: Vout = 2.5V. The sensitivity is ratiometric to Vcc, so at 3.3V supply, sensitivity scales to 122mV/A (185 × 3.3/5). For ADC interface: Current = (Vadc - Vcc/2) / Sensitivity. Include offset calibration for best accuracy by measuring output at 0A and subtracting from readings.
Use Vout = Vcc/2 + (I × Sensitivity); sensitivity is ratiometric to Vcc; calibrate offset at 0A.
What is the noise level of ACS712 and how do I filter it?
The ACS712 has output noise of approximately 7mV RMS (21mV peak-to-peak) with 80kHz bandwidth. This corresponds to current noise of: ACS712-05B: 7mV / 185mV/A = 38mA RMS; ACS712-30A: 7mV / 66mV/A = 106mA RMS. To reduce noise, add an RC low-pass filter at the output: Cutoff frequency fc = 1 / (2πRC). For 1kHz cutoff with 1kΩ resistor: C = 1 / (2π × 1000 × 1000) = 159nF, use 150nF standard value. Trade-off: lower bandwidth means slower response. For DC measurements, use 10-100Hz cutoff. For AC line monitoring, use > 100Hz cutoff. The internal bandwidth can also be limited by adding capacitor between FILTER pin and ground (if available on variant). For lowest noise, average multiple ADC samples in software.
7mV RMS noise; add RC filter for noise reduction; trade-off between noise and bandwidth.
Can ACS712 measure AC current?
Yes, the ACS712 can measure AC current with its 80kHz bandwidth. The output is a sine wave centered at Vcc/2 (2.5V for 5V supply). For AC measurements: Peak current = (Vpeak - 2.5V) / Sensitivity; RMS current = Peak / √2. Example: ACS712-05B measuring 3A RMS: Peak = 3 × √2 = 4.24A; Vpeak = 2.5V + (4.24 × 0.185) = 3.28V; Vmin = 2.5V - (4.24 × 0.185) = 1.72V. The output swings between 1.72V and 3.28V at the AC frequency. For microcontroller interface: Sample at > 2× AC frequency (e.g., > 100Hz for 50Hz line); Calculate RMS by averaging squared samples; Or use peak detection circuit. The 80kHz bandwidth supports AC measurements up to several kHz, making it suitable for inverter output monitoring and motor current sensing.
Yes, 80kHz bandwidth supports AC; output centered at Vcc/2; sample at > 2× frequency for RMS calculation.
What is the temperature drift of ACS712?
The ACS712 has temperature drift specifications: Sensitivity drift: ±0.5% to ±1.5% over -40°C to 150°C depending on grade; Offset drift: ±5mV to ±15mV over temperature; Total error: ±2% to ±4% over temperature range. The ECO grade (E suffix, -40°C to +85°C) has better drift characteristics than the automotive grade (K suffix, -40°C to +150°C). For highest accuracy over temperature: Use ECO grade for industrial applications; Implement temperature compensation in software using external temp sensor; Perform calibration at multiple temperatures; Use ACS720 for better temperature performance (±1% over temp). Example impact: At 100°C with 2% drift, a 10A measurement could read 9.8-10.2A. For applications requiring < 2% accuracy over temperature, consider the ACS720 or implement calibration.
±2-4% drift over temperature; use ECO grade for better specs; implement calibration for highest accuracy.