The Hall device converts into an electrical signal output by detecting changes in the magnetic field, which can be used to monitor changes in operating parameters such as position, displacement, angle, angular velocity, and rotational speed in applications such as automobiles. As the requirements for energy efficiency become higher and higher, these parameters need to be measured more accurately. Allegro's A1262 2D dual-channel Hall-effect sensor ICs are available in a 5-lead SOT23W surface mount package or a 4-pin SIP via package that operates in both a normal planar magnetic field and a vertical magnetic field (see Figure 1). The dual operation of planar and vertical Hall elements has the following advantages:
Orthogonal
The inherent 90° phase difference between outputs reduces the package size of the orthogonal pole pitch and air gap independently. PCB size and effective total air gap (TEAG). The XZ option provides a smaller effective total air gap (TEAG). Spherical magnets can be freely selected based on availability and/or cost. In-plane sensing can be achieved by using SMT devices, and via devices may be replaced.
Figure 5: The A1262LLH-X sensing works in conjunction with the Z-plane Hall element using an X-direction vertical Hall element.
The Z-axis plane Hall (red display) can be used on the front side (Figure A). The front of the X-axis vertical Hall (green display) can be used (B).
In the YZ configuration (Figure 6), the Hall element is placed to detect the magnetic field parallel to the cross-lead side (Y-axis) package surface and the magnetic field perpendicular to the package surface (Z-axis). Configure the vertical Hall to sense the magnetic pole (front). Conventional two-channel devices, such as the A1230 and A3425, do not sense ring magnets in any of the configurations (A or B) in Figure 6.
Figure 7: Effective total air gap advantage for XZ (A) and YZ (B) configurations.
Dual output
The A1262 is a dual output sensor that uses a vertical Hall element (X or Y) and a planar Hall element (Z) at two independent output pins (OUTPUTA and OUTPUTB, respectively). This is achieved by time division multiplexing of the channels. See Figure 8 for a block diagram. Each channel is sampled at approximately 16 μs (typical) for the channel to stabilize, so the two channels can be updated approximately every 32 μs. See Figure 9.
The A1262 sample rate uses a relatively fast time-division multiplex that can withstand high magnetic input frequencies and is suitable for most applications. Please contact your Allegro agent for more information on the suitability of high frequency applications.
Figure 9: Time consuming of time division multiplexing.
Each channel is updated before the channel is stabilized.
Intrinsic orthogonal
The planar and vertical components are essentially identical in position, and this sensing technique reduces the need for ring magnets to achieve quadrature (90° phase difference between output channels).
The two-plane sensor IC contains only two orthogonal channels, and the ring magnet pole pair spacing is four times the Hall element pitch.
Figure 11: Orthogonality of large pitch ring magnets
Figure 13: Phase difference as a function of tangential offset
in conclusion
The A1262 includes a new vertical Hall sensing technology that provides an ideal solution for rotating ring magnets and motors. Compared to existing dual-channel Hall latch ICs, designing with the A1262 is much easier, with fewer overall system configurations and mechanical packaging options. The 2D dual-channel magnetic sensor IC offers unparalleled flexibility, reduces the need for quadrature magnet target output quadrature optimization, and offers two different vertical sensing axes for more options for IC and PCB mounting.
Designers can choose between four sensing directions or between surface mount (LH) or through-hole packages (K). Regardless of the design of the ring magnet, 2D sensing provides inherent output signal quadrature, with the choice of existing ring magnets in other applications, or the choice of off-the-shelf ring magnets. The XZ option provides an improved version of TEAG compared to older dual channel devices, including those in SOT packages. The use of in-plane sensing of surface mount devices results in a smaller design, a lighter system, and a more streamlined assembly step than older devices that use through-hole (SIP) packaged sensors.
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