BU52012NVX-TR Datasheet, PDF (15/20 Pages) Rohm – Unipolar Detection Hall ICs

BU52002GUL,BU52003GUL,BU52012NVX,BU52012HFV,BU52013HFV
●Intermittent Operation at Power ON
Power ON
Technical Note
VDD
Supply current
(Intermittentaction)
OUT
(No magnetic
field present)
OUT
(Magnetic
field present)
Startup time
Indefinite
interval
Indefinite
interval
Standby time
Startup time
High
Low
Standby time
Fig.44
The unipolar detection Hall IC adopts an intermittent operation method in detecting the magnetic field during startup, as
shown in Fig.44. It outputs to the appropriate terminal based on the detection result and maintains the output condition
during the standby period. The time from power ON until the end of the initial startup period is an indefinite interval, but it
cannot exceed the maximum period, 100ms. To accommodate the system design, the Hall IC output read should be
programmed within 100ms of power ON, but after the time allowed for the period ambient temperature and supply voltage.
●Magnet Selection
Of the two representative varieties of permanent magnet, neodymium generally offers greater magnetic power per volume
than ferrite, thereby enabling the highest degree of miniaturization, thus, neodymium is best suited for small equipment
applications. Fig.45 shows the relation between the size (volume) of a neodymium magnet and magnetic flux density. The
graph plots the correlation between the distance (L) from three versions of a 4mm X 4mm cross-section neodymium magnet
(1mm, 2mm, and 3mm thick) and magnetic flux density. Fig.46 shows Hall IC detection distance – a good guide for
determining the proper size and detection distance of the magnet. Based on the BU52012HFV, BU52013HFV operating
point max 5.0 mT, the minimum detection distance for the 1mm, 2mm and 3mm magnets would be 7.6mm, 9.22mm, and
10.4mm, respectively. To increase the magnet’s detection distance, either increase its thickness or sectional area.
10
9
t=3mm
8
7
t=1mm
6
t=2mm
5
4
3
2
1
7.6mm 9.2mm _10.4mm
0
0
2
4
6
8
10
12
14
16
18
20
Distance between magnet and Hall IC [mm]
Fig.45
X
Y
Magnet size
t
X=Y=4mm
t=1mm,2mm,3mm
Magnet
Magnet material: NEOMAX-44H (material)
Maker: NEOMAX CO.,LTD.
t
L: Variable
…Flux density measuring point
Fig.46 Magnet Dimensions and Flux Density Measuring Point
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2010.08 - Rev.C