AK8778B

[AK8778B]
AK8778B
Hall Effect IC for Pulse Encoders
Overview
The AK8778B is a Hall effect latch which detects both “vertical magnetic field” and “horizontal magnetic field”
(perpendicular and parallel to the marking side of the package) at the same time. The pulse output F and direction
output D are switched according to the vertical and horizontal magnetic fields applied to the device. The direction
is calculated internally and output D is switched at a rising or falling edge of output F. The AK8778B is for use in
the incremental pulse encoders or rotational detection systems.
Features
o
4.0 to 24V supply voltage operation
o
Sensitivity (Vertical, Horizontal) : ±1.7mT(Typ.)
o
Two outputs : F (Pulse), D (Direction)
o
Small package: SOP-6pin
o
Halogen free
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[AK8778B]
Block Diagram
VDD
0.1µF
REGULATOR
VSS
VREG
BIAS
OSC
HE_DRIVE
TIMING
LOGIC
COMP
CHOP_AMP
LATCH & LOGIC
CHOPPER_SW
F
D
HALL SENSORS
Figure 1. Block diagram
Circuit Configuration
Table 1. Circuit configuration
Block
REGULATOR
HALL SENSORS
CHOPPER_SW
CHOP_AMP
COMP
BIAS
HE_DRIVE
OSC
TIMING LOGIC
LATCH & LOGIC
Function
Generate internal operating voltage.
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 internal circuits.
Generates bias current for Hall sensors.
Generates operating clock.
Generates timing signal for internal circuits.
Logical circuits and open drain driver.
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[AK8778B]
Pin/Function
Table 2. Description of pin name and function
Pin No.
Pin name
I/O
Function
1
VDD
Power supply pin
2
TAB
(TAB pin)
3
F
O
Output F (Pulse) pin
4
D
O
Output D (Direction) pin
5
TAB
(TAB pin)
6
VSS
Ground pin
Note) TAB pins should be connected to VSS.
Note
Open drain
Open drain
Absolute Maximum Ratings
Table 3. Absolute maximum ratings
Parameter
Symbol
Min.
Max.
Unit
+32
Supply voltage
VDD
V
−0.3
+32
V
Output voltage
VOUT
−0.3
Output current
ISINK
20
mA
+150
Storage temperature
TSTG
−55
°C
Note) Stress beyond these listed values may cause permanent damage to the device.
Note
VSS=0V
F,D pin VSS=0V
F,D pin
Recommended Operating Conditions
Parameter
Supply voltage
Output current
Operating temperature
Table 4. Recommended operating conditions
Symbol
Min.
Typ.
VDD
4.0
12.0
ISINK
Ta
−40
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Max.
24.0
15
+125
Unit
V
mA
°C
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[AK8778B]
Electrical Characteristics
Table 5. Electrical characteristics at VDD=4.0 to 24.0V, Ta= −40 to +125°C
Parameter
Symbol
Min.
Typ.
Max.
Unit
Note
Current consumption
IDD
1.4
3.0
5.6
mA
Output saturation voltage
VSAT
0.4
V
F, D pin, ISINK= 15mA
Output leak current
ILEAK
10
F, D=VDD
µA
16.7
Output refresh period
TP
12.0
30.5
µs
Magnetic Characteristics
Table 6. Magnetic characteristics at VDD=4.0 to 24.0V, Ta= −40 to +125°C
Parameter
Symbol
Operating point of
BopV
vertical magnetic field
Releasing point of
BrpV
vertical magnetic field
Operating point of
BopH
horizontal magnetic field
Operating point of
BrpH
horizontal magnetic field
Hysteresis
BhV, BhH
(*1) Horizontal magnetic flux density is zero.
Min.
Typ.
Max.
Unit
Note
0.1
1.7
4.0
mT
(*1)
−4.0
−1.7
−0.1
mT
(*1)
0.1
1.7
4.0
mT
(*2)
−4.0
−1.7
−0.1
mT
(*2)
1.5
3.4
6.8
mT
(*1), (*2)
(*2) Vertical magnetic flux density is zero.
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[AK8778B]
Operational Characteristics
The internal signal A switches ‘Low’ state when the magnetic field perpendicular to the marking side of the package
exceeds BopV. When the magnetic field is reduced below BrpV, the internal signal A goes ‘High’ state. Otherwise;
that is, in case of the magnetic field strength is greater than BrpV and smaller than BopV; the internal signal A keeps
its status.
S
Internal signal A
Top(Marking)
BhV
BopV
BrpV
Bottom
0
N
N
S
Figure 2. Switching behavior of the internal signal A when vertical magnetic field is applied
The internal signal B switches ‘Low’ state when the magnetic field parallel to the marking side of the package
exceeds BopH. When the magnetic field is reduced below BrpH, the internal signal B goes ‘High’ state. Otherwise;
that is, in case of the magnetic field strength is greater than BrpH and smaller than BopH; the internal signal B keeps
its status.
Internal signal B
Line Marking
Top(Marking)
VSS pin
BhH
S
N
BopH
BrpH
0
N
D pin
S
Bottom
Figure 3. Switching behavior of the internal signal B when horizontal magnetic field is applied
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Behaviors of internal signal A,B and output signal F, D when a rotating magnetic field is applied on AK8778B
F signal (pulse) is correspond to the result of EX-OR operation of internal signal A and B. And signal D (direction)
is calculated by the state of internal signal A and B.
Direction changed
Direction changed
BopV
Vertical M.F.D.
BrpV
0
t
BopH
Horizontal M.F.D.
0
t
BrpH
Supply voltage VDD
0
t
Internal signal A
(Vertical)
t
Internal signal B
(Horizontal)
t
F (Pulse)
0
t
D (Direction)
0
t
Undefined (High or Low)
Signal F, D is determined.
Figure 4. Behaviors of internal signal A,B and signal F, D when a
rotating magnetic field is applied on AK8778B
*M.F.D. is Magnetic Flux Density.
Note) Signal D is determined after one signal F pulse is sent out. The indeterminate output state appears only in the
powering up of this device.
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[AK8778B]
Functional Timing
TP: 16.7μs(Typ.)
Sampling
Cycle
t
Vertical M.F.D.
BopV
0
BrpV
t
Horizontal M.F.D.
BopH
0
BrpH
t
Internal signal A
(Vertical)
t
Internal signal B
(Horizontal)
t
F (Pulse)
0
t
Figure 5. Timing diagram
*M.F.D. is Magnetic Flux Density.
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[AK8778B]
Direction
changed
Direction
changed
Sampling
Cycle
t
M.F.D.
Vertical M.F.D.
Horizontal M.F.D.
BopV,BopH
0
BrpV,BrpH
t
6μs(Typ.)
6μs(Typ.)
6μs(Typ.)
6μs(Typ.)
F (Pulse)
50%VDD
0
t
6μs(Typ.)
6μs(Typ.)
D (Direction)
50%VDD
0
t
Figure 6. Timing diagram (in detail)
*M.F.D. is Magnetic Flux Density.
Note ) VDD=12.0V ,RL=10kΩ, CL=20pF
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[AK8778B]
Typical Characteristic Data (for reference)
Figure 7. Temperature dependence of sensitivity
Figure 8. Temperature dependence of current consumption
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[AK8778B]
Package
6
5
4
1
2
3
1:VDD
2:TAB
3:F
4:D
5:TAB
6:VSS
Unit in mm
Figure 9. Package dimensions
Note 1) The center of the sensitive area is located within the φ0.3mm circle.
Note 2) Coplanarity: The differences between standoff of terminals are max. 0.1mm.
Note 3) The sensor part is located 0.71mm(Typ.) from marking surface.
Material of terminals： Cu alloy
Material of plating for terminals： Sn 100％
Thickness of plating for terminals：10μm (Typ.)
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[AK8778B]
Marking
Line Marking
6
5
4
Marking is performed by laser
6YWWL
Product name ：6 (AK8778B)
：YWWL
Date code
Y：Manufactured year
WW：Manufactured week
1
2
3
L：Lot
Figure 10. Marking
Recommended External Circuit
10kΩ
VDD
Output (D)
GND
5
4
Top View
1
2
3
VDD
10kΩ
VDD
0.1μF
6
Output (F)
Figure 11. Recommended external circuit
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[AK8778B]
IMPORTANT NOTICE
l These products and their specifications are subject to change without notice.
When you consider any use or application of these products, please make inquiries the sales office of Asahi Kasei
Microdevices Corporation (AKM) or authorized distributors as to current status of the products.
l Descriptions of external circuits, application circuits, software and other related information contained in this
document are provided only to illustrate the operation and application examples of the semiconductor products. You
are fully responsible for the incorporation of these external circuits, application circuits, software and other related
information in the design of your equipments. AKM assumes no responsibility for any losses incurred by you or third
parties arising from the use of these information herein. AKM assumes no liability for infringement of any patent,
intellectual property, or other rights in the application or use of such information contained herein.
l Any export of these products, or devices or systems containing them, may require an export license or other official
approval under the law and regulations of the country of export pertaining to customs and tariffs, currency exchange,
or strategic materials.
l AKM products are neither intended nor authorized for use as critical componentsNote1) in any safety, life support, or
other hazard related device or systemNote2), and AKM assumes no responsibility for such use, except for the use
approved with the express written consent by Representative Director of AKM. As used here:
Note1) A critical component is one whose failure to function or perform may reasonably be expected to result,
whether directly or indirectly, in the loss of the safety or effectiveness of the device or system containing it, and
which must therefore meet very high standards of performance and reliability.
Note2) A hazard related device or system is one designed or intended for life support or maintenance of safety or
for applications in medicine, aerospace, nuclear energy, or other fields, in which its failure to function or perform
may reasonably be expected to result in loss of life or in significant injury or damage to person or property.
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the product with a third party, to notify such third party in advance of the above content and conditions, and the buyer
or distributor agrees to assume any and all responsibility and liability for and hold AKM harmless from any and all
claims arising from the use of said product in the absence of such notification.
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