Allegro’s ACS723 Sensor Provides a Low Resistance of Just 0.65 Milliohms

Measuring currents is one of the oldest tasks of metrology

Measuring currents is one of the oldest tasks of metrology. The knee jerk reaction involves adding a resistor to the current path and then analysing the voltage drop. Hall effect sensors provide a variety of benefits ranging from simplicity to galvanic insulation.

Allegro’s ACS723 sensor comes in a handy SOIC8 package, and provides a low resistance of just 0.65 milliohms. System design is simple – simply look at figure 1, which shows how to get the Allegro chip into your design.

Instead of having to play around with a differential amplifier, simply supply between 4.5 and 5.5 V to the component. Then, change the current to be measured to the device using pins one, two, three and four. Allegro provides two pins each in order to simplify layout and reduce voltage drops on the PCB and the interconnect.

The actual current output is then dependent on the selected version of the component: as of this writing, Allegro provides a total of seven different versions handling current ranges from 5 to 40 Ampere. In all cases, however, an analog voltage is put out which can be used without further meddling.

A small trap

The only important consideration is the minimum input impendance of the attached amplifier, which is set to 4.7 Kiloohms. Most modern ADC parts do not have a problem meeting this – in the worst case, a simple operational amplifyer can be added to provide voltage buffering.

Whilst traditional resistor-based sensors need careful placement, a Hall effect sensor does not care about voltage potentials. You can set the sensing loop close to supply or close to ground – no special considerations need to be taken when designing the measuring loop.

Furthermore, resistors heat up significantly as currents raise. Our Allegro chip impresses with relatively constant thermic behaviour. Another very nice aspect of the product involves the presence of a bandwidth selection. Allegro provides you with a configurable filter, limiting the bandwidth of the filter to either 20 or 80 kHz. That way, unwanted noise and transients can be blocked out without having to perform additional filtering of the output signal.

Does it pay?

Feeding our price comparison engine yields a price range from £2.79 to £1.56 depending on the current range. Given the severe simplification and PCB space savings, going Hall effect definitely makes sense

Recent Articles
Reduced Web Prices from Future Electronics
For this week only, take advantage of reduced web prices on select parts  2213831-1  LUMAWISE 80 mm Base Assembly SR Module Accessory 1-776200-1  Header Assy, 23... Read Article
Types of electronic circuits discussed
There are many other interesting elements to electronic and circuits is top on my list. While this topic can quite complicated, it is nevertheless possible to... Read Article
New Renesas Industrial Ethernet Module R-IN32M3 Solution Kit
Register to win a solution kit! The R-IN32M3 Industrial Ethernet Module is a ready-to-use, certified hardware and software solution based on Renesas technology and quality standards.... Read Article
The Hitchhiker’s Guide to PCB Design
Want to create a solid, manufacturable PCB the first time? Get the only eBook you will ever need to upgrade your PCB knowledge and launch your... Read Article
Secure your supply with Future Electronics
Find what you need faster Hundreds of thousands of components. Three strategically-located Distribution Centers. ONE global IT infrastructure. Find what you need faster with access anywhere,... Read Article
Save 10% on Orders $500 or More
Promo code is valid for saving 10% on orders of $500 or more. Offer does not apply to products from Adafruit, DEEPWAVE DIGITAL, FTDI Chip, NVIDIA,... Read Article