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[AK8776]
AK8776
Hall IC for Pulse Encoder
Overview
AK8776 is a Hall effect latch which detects both “vertical” and “horizontal” (perpendicular and parallel to the
marking side of the package) magnetic field at the same time and outputs the pulse (F) and rotational direction (D).
AK8776 is for use in portable devices which uses rotational detection system or incremental pulse encoder such as
jog dial utilized for input devices.
Features
o 1.6 to 5.5V operation
o Bop, Brp(Vertical, Horizontal) ±1.5mT(Typ.), Highly sensitive
o Low power operation : Average 90μA(Typ.) @VDD=3V
o Two Output: F-Output (Pulse count), D-Output (Direction of rotation)
o Small package: SOP-4pin, Halogen free
MS1317-E-00
2011/July
1
Free Datasheet http://www.datasheet4u.com/

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Block Diagram
VDD
VSS
HALL SENSORS
BIAS
OSC
HE_DRIVE
TIMING LOGIC
CHOP_AMP
COMP
[AK8776]
F
D
Figure 1. Block diagram
Block
HALL SENSORS
CHOPPER_SW
CHOP_AMP
COMP
BIAS
HE_DRIVE
OSC
TIMING LOGIC
LATCH & LOGIC
Circuit Configuration
Table 1. Circuit configuration
Function
Two Hall elements fabricated by CMOS process.
Perform chopping in order to cancel the offset of Hall sensor.
Amplifies two Hall sensor output voltage with summation and subtraction
circuit.
Hysteresis comparator.
Generates bias current to other circuits.
Generates bias current for Hall sensors.
Generates operating clock.
Generates timing signal required for Chopper SW, AMP and COMP.
Logical circuits and CMOS output buffer.
MS1317-E-00
2011/July
2
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Pin/Function
Pin No.
1
2
3
4
Pin name
VDD
F
D
VSS
Table 2. Description of pin name and function
I/O Function
Power supply pin
O Output F (Pulse) pin
O Output D (Direction) pin
Ground pin
[AK8776]
Note
CMOS output
CMOS output
Absolute Maximum Ratings
Table 3. Absolute maximum ratings
Parameter
Symbol
Min.
Max.
Unit
Power supply voltage
Output current
Storage temperature
VDD 0.3 +6.5
V
IOUT 0.5 +0.5 mA
TSTG
40 +125
°C
Note) Stress beyond these listed values may cause permanent damage to the device.
Note
F,D pin
Recommended Operating Conditions
Parameter
Power supply voltage
Operating temperature
Table 4. Recommended operating conditions
Symbol
Min.
Typ.
VDD 1.6 3.0
Ta 30
Max.
5.5
+85
Unit
V
°C
Electrical Characteristics
Table 5. Electrical characteristics (Ta=25°C, VDD = 3.0V)
Parameter
Symbol Min. Typ. Max. Unit
Note
Current consumption
IDD
90 210 µA
Average
High level output Voltage VOH VDD-0.4
V F,D pin, IOUT= 0.5mA
Low level output Voltage VOL
0.4 V F,D pin, IOUT= +0.5mA
Pulse drive period
TPD1
0.5
1.0
2.0
ms
Pulse drive duration time TPD2 12.2 24.4 48.8
µs
Note) Internal data is determined just before the internal circuit turns off. And after 6.1μs (Typ.), the output
changes.
MS1317-E-00
2011/July
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[AK8776]
Magnetic Characteristics
The output F and D is processed signals from internal signal A and B which is determined by the applied magnetic
field and threshold level BopV, BrpV, BopH and BrpH as follows.
Table 6. Magnetic characteristics(Ta = 25°C, VDD = 3.0V)
Parameter
Symbol Min. Typ. Max. Unit
Vertical magnetic field
operating point
BopV
1.5 4.0 mT
Vertical magnetic field
releasing point
BrpV
4.0 1.5
mT
Horizontal magnetic field
operating point
BopH
1.5 4.0 mT
Horizontal magnetic field
releasing point
BrpH
4.0 1.5
mT
Hysteresis
BhV, BhH
3.0
mT
(*1) Horizontal magnetic flux density is zero.
(*2) Vertical magnetic flux density is zero.
Note
(*1)
(*1)
(*2)
(*2)
(*1), (*2)
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2011/July
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[AK8776]
Operational Characteristics
AK8776 detects the “vertical” (perpendicular to the marking side of the package) magnetic field, and the resulting
internal signal A changes state. When the magnetic field is more positive than BopV, the internal signal A changes to
‘Low’ state. And it is kept while the magnetic field remains more positive than BrpV. When the magnetic field drops
below BrpV, the internal signal A changes to ‘High’ state. Those threshold magnetic flux density levels are defined
in Table 6.
Top(Marking)
S
Bottom
N
Internal signal A
BhV
BrpV
N [T]
0
BopV
S [T]
Figure 2. Switching behavior of internal signal A when vertical
magnetic field is applied
AK8776 detects “horizontal “(parallel to the marking side of the package) magnetic field, and the resulting internal
signal B changes state. When the magnetic field is more positive than BopH, the internal signal B changes to ‘Low’
state. And it is kept while the magnetic field remains more positive than BrpH. When the magnetic field drops below
BrpH, the internal signal B changes to ‘High’ state. Those threshold magnetic flux density levels are defined in
Table 6.
Line Marking
Top(Marking)
N
VSS pin
S
Internal signal B
BhH
BrpH
BopH
Bottom
D pin
N [T]
0
S [T]
Figure 3. Switching behavior of internal signal B
when horizontal magnetic field is applied
MS1317-E-00
2011/July
5
Free Datasheet http://www.datasheet4u.com/