BU52040HFV_10 Datasheet, PDF (5/13 Pages) Rohm – Bipolar Latch Hall IC

BU52040HFV
Technical Note
●Description of Operations
(Micro-power Operation)
The Hall Effect IC for wheel keys / trackballs adopts an intermittent operation method to save energy. At startup, the Hall
elements, amp, comparator and other detection circuits power ON and magnetic detection begins. During standby, the
detection circuits power OFF, thereby reducing current consumption. The detection results are held while standby is active,
and then output.
Reference period: 500 µs (MAX. 1200 µs)
Reference startup time: 24 µs
IDD
Period
Startup time
Standby
t
Fig.13
(Offset Cancellation)
The Hall elements form an equivalent Wheatstone (resistor) bridge circuit. Offset voltage may be generated by a
differential in this bridge resistance, or can arise from changes in resistance due to package or bonding stress.
A dynamic offset cancellation circuit is employed to cancel this offset voltage.
When Hall elements are connected as shown in Fig. 14 and a magnetic field is applied perpendicularly to the Hall
elements, voltage is generated at the mid-point terminal of the bridge. This is known as the Hall voltage.
Dynamic cancellation switches the wiring (shown in the figure) to redirect the current flow to a 90˚ angle from its original
path, and thereby cancels the Hall voltage.
The magnetic signal (only) is maintained in the sample/hold circuit during the offset cancellation process and then
released.
V_DD
I
B_×
GND
Fig.14
＋
Hall Voltage
－
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2010.01 - Rev.B