low cost isolated current sensing IC - ACS710

For low cost isolated current sensing, Allegro hall effect current sensing IC has come into picture. Allegro has produces a series of low cost current sensing IC.

ACS710 has been in market for quite some time and it is suitable for renewable energy application as in described in “AN296110-Current Sensing for Renewable Energy”.

ACS710 has 1 mΩ sensing resistance for low power loss, user selectable overcurrent fault level, provided in surface mount SOIC16 package, operating temperature is from -40ºC to 125ºC.

Best part is no isolated voltage supply is needed. (Save the cost)

Maybe the only drawback is the low voltage isolation.

The voltage isolation characteristics that had been conducted by Allegro.

Test Characteristic	Rating (VAC)
Dielectric Strength Test Voltage (60s)	3000
Working Voltage for Basic Isolation	277

Neverthelss, for most applications, the continuous working voltage of 277VAC is more than enough.

ACS713 is provided in several sensing range such as follow:

Sensing Range (Ampere)	Sensitivity at Vcc=5V (mV/A)
±6	151
±10	85
±12.5	56
±25	28

Supply voltage – 3V to 5.5V.

Signal bandwidth – 120kHz

From the above picture, you can see that for the full operation of 120kHz, filter capacitor of 0.1nF or less is needed. 

Of course, you can increase the filter capacitance, the higher the filter capacitance, the lower the bandwidth. Good point is the RMS noise also significant reduced.

ACS713 has the over-current detection mechanism and the settings/calculation as follow

For the setting of overcurrent detection,

Version 6BB and 10BB, the formula is as follow:

VOC = 1.17 × Sens × | IOC |

Example,

For ACS710KLATR-6BB-T, if required overcurrent fault switchpoint is 10 A, and VCC = 5 V, then the required VOC can be calculated as follows:

VOC = 1.17 × Sens × IOC = 1.17 × 151 × 10 = 1767 (mV)

Version 12CB and 25CB, the formula is as follow:

VOC = Sens × | IOC |

Example,

For ACS710KLATR-25CB-T, if required overcurrent fault switchpoint is 50 A, and VCC = 5 V, then the required VOC can be calculated as follows:

VOC = Sens × IOC = 28 × 50 = 1400 (mV)

One more thing to consider when using this IC is the temperate effect toward the sensing accuracy.

The accuracy of the ACS710 against the temperature variation is as follow:

Although at constant 25 Celsius, the output voltage also has some variation.

However, for such low price, this temperature variation performance is acceptable. 

The brother ACS712 had been very popular among hobbyists, 

this not so new newbies (ACS713) can be worth trying, I am designing a breakout module for it.

Not sure when going to finish it. If I did finish it, I will test it even further.