Product Overview

The ACS720 is a high-accuracy, Hall-effect-based current sensor IC designed for industrial and consumer applications, particularly in motor control and power inverter stages. It offers high isolation with a reduced bill of materials due to its proprietary SOIC16W package. Operating from a single 5V supply, the ACS720 provides a 0-3V output swing with a stable 1.5V zero-current output, compatible with 3.3V ADCs. Its high PSRR effectively rejects noise in demanding environments. The device features dual, user-configurable fault functions (fast and slow) for short-circuit and overcurrent detection, with fault levels set via an external resistor divider. Integrated differential current sensing rejects external magnetic fields, simplifying board layout in 3-phase motor applications. The ACS720 boasts patented integrated digital temperature compensation for high accuracy over temperature and a low 1.0 m primary conductor resistance for minimal power loss.

Product Attributes

• Brand: Allegro MicroSystems
• Package: SOIC16 Wide-Body (LA)
• Certifications: 3600 Vrms Dielectric Strength certified under UL60950-1 (CB Certificate Number: US-23711-A2-UL)
• Material: Leadframe plated with 100% matte tin; internally Pb-free (except for flip-chip high-temperature Pb-based solder balls)

Technical Specifications

Fault Characteristics Overview:

The ACS720 features two user-settable overcurrent fault comparators (Fast Fault - FAULT_F, and Slow Fault - FAULT_S) that activate when the absolute input current (IP) exceeds a defined threshold. These are active-low, open-drain outputs. The Fast Fault offers ultrafast response with reduced accuracy, suitable for short-circuit detection. The Slow Fault provides higher accuracy for overload conditions. Fault thresholds are configured using external resistor dividers connected to the VOC_F and VOC_S pins, which are ratiometric to VCC. The VOC pins are sampled at 62.5 kHz, requiring filtering below 31 kHz to prevent aliasing.

Fault Threshold Equations:

Slow Fault Threshold:
IFAULT(S) = [(VOC(S) 0.3 VCC) / (0.4 VCC)] (0.75 IPR) + 0.5 IPR
VOC(S) = [(IFAULT(S) 0.5 IPR) 0.4 VCC] / (0.75 IPR) + (0.3 VCC)

Fast Fault Threshold:
IFAULT(F) = [(VOC(F) 0.3 VCC) / (0.4 VCC)] (1.25 IPR) + 1.0 IPR
VOC(F) = [(IFAULT(F) 1.0 IPR) 0.4 VCC] / (1.25 IPR) + (0.3 VCC)

Fault Response and Hysteresis:

Fault Response Time (tR(F)) is measured from IP exceeding the fault threshold until the fault pin asserts. Fault Clear Time (tC(F)) is from IP falling below the threshold minus hysteresis (IHYS) until the fault pin deasserts. Hysteresis values (IHYS(FF), IHYS(SF)) are typically 0.06 IPR and 0.05 IPR respectively.

Fault Masking:

Certain part numbers include a mask time (tMASK) to ignore nuisance current pulses. If the blank time (tB) between pulses is less than 4 s, repetitive pulses may be interpreted as a continuous overcurrent event.

Thermal Considerations:

Self-heating due to current flow must be considered. Plots are available for steady-state die temperature rise versus continuous current and maximum continuous current at various ambient temperatures. The maximum junction temperature (TJ(MAX) = 165C) must not be exceeded.

Definitions of Accuracy Characteristics:

• Sensitivity (Sens): Change in sensor IC output per 1A change through the primary conductor.
• Nonlinearity (ELIN): Measures the linearity of the output over the full current range.
• Zero-Current Output Voltage (VIOUT(Q)): Nominally 1.5V, the output when primary current is zero.
• Offset Voltage (VOE): Deviation from the ideal quiescent value due to non-magnetic causes.
• Total Output Error (ETOT): The difference between the sensor IC's measurement and the actual current, relative to the actual current.

Definitions of Dynamic Response Characteristics:

• Power-On Time (tPO): Time for the output voltage to settle within 10% of its steady-state value after VCC reaches its minimum operating voltage.
• Rise Time (tr): Time for the sensor IC output to go from 10% to 90% of its full-scale value.
• Response Time (tRESPONSE): Time from the primary current reaching 90% of its final value to the device output reaching 90% of its corresponding value.
• Propagation Delay (tpd): Time from the primary current reaching 20% of its final value to the device output reaching 20% of its corresponding value.
• Fault Response Time (tRFF, tRSF): Time from the primary current reaching the fault threshold until the device fault pin reacts.