BU52040HFV_10 Datasheet, PDF (7/13 Pages) Rohm – Bipolar Latch Hall IC

BU52040HFV
●Intermittent Operation at Power ON
Technical Note
VDD
Supply current
(Intermittent operation)
Startup time
Standby time
Startup time
Standby time
OUT
(N magnetic field present)
(B<B_rp)
OUT
(S magnetic field present)
(B_op<B)
OUT
(No magnetic field present)
(B_rp<B< B_op)
Indefinite
Indefinite interval
High
Low
Indefinite interval
Fig.17
The Hall Effect IC for wheel keys / trackballs adopts an intermittent operation method in detecting the magnetic field during
startup, as shown in Fig. 17. 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, 1200μs. To accommodate the system design, the Hall IC output read should be
programmed within 1200μs of power ON, but after the time allowed for the period ambient temperature and supply voltage.
Additionally, if a magnetic flux density (B) of magnitude greater than Brp but less than Bop is applied at power ON, the output
from the IC remains undefined and will be either high or low until a flux density exceeding the B_op or B_rp threshold is applied.
●Application Example
Wheel Key
Two Hall ICs can enable detection of rotation direction of a magnetic zero-contact wheel key.
Circular magnet
SN
N
S
S
N
NS
Mounting Position of Hall IC Inside Wheel Key
BU52040HFV: 2pcs
The angular separation of the two Hall ICs within the footprint of the wheel key depends on N/S division angle of the internal
magnet (Φ), and can be set to either Φ/4 or ¾Φ. Mounting the two ICs in this position causes the magnetic phase
difference between the ICs to equal ±1/4, and the direction of rotation can be detected by measuring the change in this
difference. An example of the magnetic field characteristics for this application is shown in the figure below.
1) Mounting angle of Hall IC = Φ/4 2) Mounting angle of Hall IC = ¾Φ
Φ/4
3/4 Φ
N/S division angle of circular magnet = Φ
Φ
Hall IC A
Hall IC B
θ
Hall IC A
Center of magnet
Counterclockwise
Hall IC B
θ
rotation
SNS N
N
S
S
N
N
S
Center of magnet
S
N
NSNS
Clockwise
rotation
Mounting Angle of Hall IC
Circular Magnet
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2010.01 - Rev.B