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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 o o o o 1.6 to 5.5V operation Bop, Brp(Vertical, Horizontal) ±1.5mT(Typ.), Highly sensitive Low power operation : Average 90μA(Typ.) @VDD=3V Two Output: F-Output (Pulse count), D-Output (Direction of rotation) Small package: SOP-4pin, Halogen free
MS1317-E-00
1
2011/July
Free Datasheet http://www.datasheet4u.com/
[AK8776]
Block Diagram
VDD
BIAS
OSC
VSS
HE_DRIVE HALL SENSORS TIMING LOGIC
LATCH&LOGIC
CHOPPER_SW
F
CHOP_AMP
COMP
D
Figure 1. Block diagram
Circuit Configuration
Table 1. Circuit configuration Block HALL SENSORS CHOPPER_SW CHOP_AMP COMP BIAS HE_DRIVE OSC TIMING LOGIC LATCH & LOGIC 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
2
2011/July
Free Datasheet http://www.datasheet4u.com/
[AK8776]
Pin/Function
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 −
Pin No. 1 2 3 4
Pin name VDD F D VSS
Note CMOS output CMOS output
Absolute Maximum Ratings
Table 3. Absolute maximum ratings Parameter Symbol Min. Max. Unit +6.5 Power supply voltage VDD V −0.3 +0.5 Output current IOUT mA −0.5 +125 Storage temperature TSTG −40 °C Note) Stress beyond these listed values may cause permanent damage to the device.
Note F,D pin
Recommended Operating Conditions
Table 4. Recommended operating conditions Symbol Min. Typ. VDD 1.6 3.0 Ta −30
Parameter Power supply voltage Operating temperature
Max. 5.5 +85
Unit V °C
Electrical Characteristics
Table 5. Electrical characteristics (Ta=25°C, VDD = 3.0V) Min. Typ. Max. Unit Note Parameter Symbol 90 Current consumption IDD 210 Average µA V High level output Voltage VOH VDD-0.4 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 24.4 Pulse drive duration time TPD2 12.2 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
3
2011/July
Free Datasheet http://www.datasheet4u.com/
[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. Vertical magnetic field BopV operating point Vertical magnetic field BrpV −4.0 releasing point Horizontal magnetic field BopH operating point Horizontal magnetic field BrpH −4.0 releasing point Hysteresis BhV, BhH (*1) Horizontal magnetic flux density is zero. (*2) Vertical magnetic flux density is zero. Typ. 1.5 −1.5 1.5 −1.5 3.0 4.0 Max. 4.0 Unit mT mT mT mT mT Note (*1) (*1) (*2) (*2) (*1), (*2)
MS1317-E-00
4
2011/July
Free Datasheet http://www.datasheet4u.com/
[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.
S
Top(Marking)
Internal signal A
BrpV
Bottom
BhV
BopV
N
0 N [mT] S [mT]
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) VSS pin
Internal signal B
BhH
N S
BrpH
BopH
0
D pin Bottom
N [mT]
S [mT]
Figure 3. Switching behavior of internal signal B when horizontal magnetic field is applied
MS1317-E-00
5
2011/.