 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ACS780XLR Datasheet(PDF) 21 Page - Allegro MicroSystems |
|
||||||||||||||||||||||||||||||
ACS780XLR Datasheet(HTML) 21 Page - Allegro MicroSystems |
|
|
21 / 24 page 
High-Precision Linear Hall-Effect-Based Current Sensor IC With 200 µΩ Current Conductor ACS780xLR 21 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com APPLICATION-SPECIFIC INFORMATION Field from Nearby Current Path TobestusetheCMRcapabilitiesofthesedevices,thecircuit board containing the ICs should be designed to make the external magnetic fields on both Hall plates equal. This helps to minimize error due to external fields generated by the current-carrying PCBtracesthemselves.Therearethreemainparametersforeach current-carrying trace that determine the error that it will induce onanIC:distance from the IC, width of the current-carrying conductor, and the anglebetweenitandtheIC.Figure3shows an example of a current-carrying conductor routed near an IC. The distance between the device and the conductor, d, is the distance from the device center to the center of the conductor. The width of the current path is w. The angle between the device and the current path, θ, is defined as the angle between a straight line connecting the two Hall plates and a line perpendicular to the current path. d H1 H2 θ I w Figure 3: ACS780 with nearby current path, viewed from the bottom of the sensor Whenitisnotpossibletokeepθcloseto90°,thenextbest option is to keep the distance from the current path to the current sensor IC, d, as large as possible. Assuming that the current path isattheworst-caseangleinrelationtotheIC,θ=0°or180°,the equation: Error = 2 × I Cf × 1 d – 2 Hspace × cosθ ┌ │ │ │ └ – 1 d + 2 Hspace × cosθ ┐ │ │ │ ┘ where Hspace is the distance between the two Hall plates and Cf is the coupling factor of the IC. This coupling factor varies between the different ICs. The ACS780 has a coupling factor of 5 to 5.5 G/A,whereasotherAllegroICscanrangefrom10to15G/A. Other Layout Practices to Consider When laying out a board that contains an Allegro current sensor ICwithCMR,thedirectionandproximityofallcurrent-carrying paths are important, but they are not the only factors to consider whenoptimizingICperformance.Othersourcesofstrayfields that can contribute to system error include traces that connect to theIC’sintegratedcurrentconductor,aswellasthepositionof nearby permanent magnets. The way that the circuit board connects to a current sensor IC must be planned with care. Common mistakes that can impact performanceare: • The angle of approach of the current path to the IP pins • ExtendingthecurrenttracetoofarbeneaththeIC THE ANGLE OF APPROACH OnecommonmistakewhenusinganAllegrocurrentsensorICis tobringthecurrentinfromanundesirableangle.Figure4shows an example of the approach of the current traces to the IC (in this case, the ACS780). In this figure, traces are shown for IP+ and IP–. The light green region is the desired area of approach for the current trace going to IP+. This region is from 0° to 85°. This rule applies likewise for the IP– trace. The limitation of this region is to prevent the current-carrying trace from contributing any stray field that can cause error on the IC output. When the current traces connected to IP are outside thisregion,theymustbetreatedasdiscussedabove(Fieldfroma Nearby Current Path). |
|
English ▼
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
