ACS723LLCTR-20AU-T

The ACS723LLCTR-20AU-T from Allegro MicroSystems is a high-accuracy, galvanically isolated Hall-effect current sensor IC in a compact 8-lead SOIC package with tape-and-reel packaging. The 20AU variant provides 20A unidirectional (0 to 20A) current measurement with 200 mV/A sensitivity.

The ACS723 uses Allegro’s patented digital temperature compensation circuitry to achieve near closed-loop accuracy in an open-loop sensor configuration. This eliminates the need for a magnetic concentrator while maintaining excellent accuracy across the -40C to +150C operating temperature range. The total accuracy is +/-2% (Farnell spec) to +/-3% (DigiKey spec) with +/-1% linearity.

The device features pin-selectable bandwidth: 80 kHz for high-speed applications or 20 kHz for lower noise operation. A dedicated BW pin selects the bandwidth. The integrated shield eliminates capacitive coupling from the current conductor to the chip, significantly suppressing output noise caused by high dv/dt transients, critical in motor drive and switching power supply applications.

The monolithic conductor path from pins 1-2 (IP+) to pins 3-4 (IP-) has a typical resistance of only 0.65 mOhm, resulting in minimal power loss and heat generation even at 20A continuous current. The conductor path is galvanically isolated from the sensor leads (pins 5-8) with 2.4 kVrms dielectric strength, UL60950-1 (ed. 2) certified. Basic isolation working voltage is 420 Vpk or 297 Vrms.

The ratiometric output voltage is proportional to the supply voltage, with sensitivity calibrated at 200 mV/A at VCC = 5V. The quiescent output voltage (zero current) is typically VCC/2 for bidirectional variants; for this unidirectional 20AU variant, the quiescent output is approximately 0.5V (100 mV typical offset from ground), and the output increases linearly to approximately 4.5V at 20A.

The chopper-stabilized BiCMOS Hall IC provides extremely stable quiescent output voltage with near-zero magnetic hysteresis. Factory calibration of sensitivity and quiescent output voltage ensures high initial accuracy without user calibration. Supply current is 9 mA typical, 14 mA maximum.

The ACS723LLCTR-20AU-T is the recommended replacement for the obsolete ACS713ELCTR-20A, offering improved accuracy and temperature performance in the same pinout.

**Hall-Effect Current Sensing:** The ACS723 integrates a low-offset linear Hall sensor circuit with a copper conduction path near the die surface. Current flowing through the copper path (pins 1-2 to pins 3-4) generates a magnetic field proportional to the current. The Hall sensor detects this magnetic field and produces a voltage proportional to both the magnetic field strength and thus the current.

**Digital Temperature Compensation:** Allegro’s patented digital temperature compensation circuitry corrects for the temperature-dependent drift of the Hall sensor sensitivity and offset. This is done in the digital domain during each clock cycle, achieving near closed-loop accuracy without the magnetic core and feedback coil used in closed-loop sensors. This provides the accuracy advantage of closed-loop sensors at the cost and size of open-loop sensors.

**Chopper Stabilization:** The BiCMOS Hall IC uses chopper stabilization to eliminate the offset drift that plagues conventional Hall sensors. The input is periodically switched (chopped) at a high frequency, and the DC offset is cancelled in the differential signal path. This results in extremely stable quiescent output voltage over time and temperature.

**Integrated Shield:** A conductive shield layer between the current conductor and the Hall element eliminates capacitive coupling. Without this shield, high dv/dt transients on the current conductor would couple into the Hall sensor through parasitic capacitance, creating noise spikes on the output. The shield diverts this capacitive current to ground, maintaining output noise performance even in noisy switching environments.

**Pin-Selectable Bandwidth:** The BW pin selects between 80 kHz bandwidth (for fast transient detection in motor control and overcurrent protection) and 20 kHz bandwidth (for lower output noise in precision measurement applications). Lower bandwidth reduces the integrated noise by approximately a factor of two.