Onechip Encoders

The Onechip Encoder is a 2-in-1 type Hall IC which is specially designed for magnetic type rotary/linear incremental pulse encoders. It's unique detection principle - operating both on the vertical and horizontal magnetic fields - enables not only a single chip solution but 'pitch free' and 'lay-out free' encoder design.

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AK8775/AK8776
Low current consumption type one chip encoder

AK8775 and AK8776 are low current consumption type products for mobile and consumer applications.

Product Name AK8775
Low current consumption type one chip encoder
AK8776
Low current consumption type one chip encoder
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AK8777B/AK8778B/AK8779A/AK8779B
High response speed type one chip encoder

AK8777B, AK8778B, AK8779A and AK8779B are high response speed type products for consumer, industrial and automotive applications.

Product Name AK8777B
High response speed type one chip encoder
AK8778B
High response speed type one chip encoder
AK8779A
High response speed type one chip encoder
AK8779B
High response speed type one chip encoder
Sales Start Available Now Available Now
Available Now
Available Now
Samples
Distributors / Representatives
Global WEB Distributor
Digi-Key
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Part# Data
Sheet
Auto-
motive
qualified
Power
Supply
Current
Comsumption
Oper.
Temp.
Output
refresh
period
Sensitivity
(Bop,Brp)
Output
signal
Output
Stage
Package



V mA us mT
 
   
AK87751.6 to 5.50.09-30 to 8510001.5A/B phaseCMOS4-SOP
AK87761.6 to 5.50.09-30 to 8510001.5Speed & DirCMOS4-SOP
AK8777BYes4.0 to 243-40 to 12516.61.7A/B phaseOpen DrainSOT23-6W
AK8778BYes4.0 to 243-40 to 12516.61.7Speed & DirOpen DrainSOT23-6W
AK8779A
Yes3.8 to 243.5-40 to 1508.32.0Speed & DirOpen DrainSOT23-6W
AK8779B
Yes3.8 to 243.5-40 to 1508.32.0A/B phaseOpen DrainSOT23-6W

Technical Resources

Operating Principle

NOTE) Please see application note for detailed technical information.

Onechip Encoders is the Hall effect latch which detect both “(1) vertical” and “(2) horizontal” (perpendicular and parallel to the marking side of the package) magnetic field.

*This figure shows the direction for AK8779A/B. For other parts, please refer the datasheets.

As the multipole magnetic ring rotates, the vector of the magnetic flux around the magnetic ring also rotates. The vertical component and horizontal component forms 90 degree of phase difference which depend on the direction of the rotation, regardless to the magnetic pole pitch.



'Pitch-Free'
Fits with any pitches of magnets

AK877x series can output the correct signal regardless of the magnetic pitch.
This feature can reduce the time and cost to re-design the board layout due to the change of encoder specification.



'Lay-out Free'
Enables mounting position flexibility

Compared with conventional Hall ICs, there are less restrictions for mounting position. This feature enables the various mounting strategy.
The figure below shows the examples of magnet and sensor position with AK8779A/B.

Application

Body components for Automotive

Magnetic encoders using our onechip encoder products are most applicable for rotation detection of actuator motors in automotive body components, because these encoders have good reliability and long lifetime.

- Anti-Pinch Detection of Window Lifters/Sunroofs/Power Slide Doors/etc.
- Power Seat Motors
- Car Navigation Displays, etc.

Input devices

Onechip encoder products can realize downsized, dust-proof input devices. Their contactless detecting pronciple can also make it easy to design a water-proof structure.

- Control Knobs for Audio Products, Air Conditioners, etc.
- Steering Switches
- Jog Dials/Crowns for Portable Devices, etc

Others

Onechip Encoders can be used in many other applications which require speed/rotation detection.

- Electric Garage Doors
- Motorized Window Blinds/Curtain
- Flow Meters

FAQs

Is any specially magnetized magnet needed with One-chip encoder ICs?

No. Any of the magnetic ring or magnet which is commonly used in the magnetic type rotary encoder is capable.

How is the output during 'OFF (sleep)' in the pulse drive? (AK8775/8776)

During the 'OFF (sleep)' state, no sampling operation is performed and the output keeps its previous state. The output is refreshed 6.1μs after the sampling operation is finished.

What is the difference with 'F' signal of the F/D output, and OUTA/OUTB signal of the A/B phase output?

The 'F' signal of AK8776/AK8778B/AK8779A is correspond to the result of EX-OR operation of internal signal A and B. Consequently, the 'F' changes twice than OUTA / OUTB on AK8775/AK8777B/AK8779B ,or the output of normal Hall effect latches. It means 'F' has twice resolution than the output of Hall effect latches.

The system needs only 'F' pin output. How should an unused 'D' pin be handled?

Unused pin should be pull-up, pull-down or leave it open. DO NOT be connected to VDD, VSS or other voltage level. Or it causes permanent damage to the device

How the output signal change if the magnetic field is in the hysteresis range (less than Bop and larger than Brp)?

The output is latched. i.e. keeps its previous status until the magnetic flux density crossed either of Bop and Brp.

Is there any method for improving the resolution or accuracy of detection?

Use much smaller pole pitch (distance between the consecutive poles). However, the smaller the pole pitch, the lower the magnetic flux density from the magnet is given. In case of the sufficient magnetic flux density is not given, it is needed to re-consider following items -- a) change the material of the magnet b) use much thicker magnet c) shorten the air gap between the magnet and the sensor.

What are necessary conditions for magnetic field simulation?

Conditions to calculate the receiving magnetic flux density are shown below.

(1) Characteristics of the Magnet

(Size, Residual Magnetic Flux Density (Br), Coercive force (Hcb), Thermal Coefficient of Br and Hcb)

(2) Position of the Magnet and Sensor

(3) Information of if there is any magnetized substance around the magnet and sensor

What is the maximum the rotation speed the One-chip encoder IC have track it accurately?

The maximum tracking frequency of One-chip encoder ICs are depends on number of magnetic poles. On Table 1, the maximum tracking rotation speed which is taking account of the number of pole (M should be even number i.e. 2, 4, 6, ….).

Table1:Maximum Supported Rotation Speed (rpm) of One-chip Encoder


AK8775/AK8776AK8777B/AK8778BAK8779A/AK8779B
Maximum Supported
Rotation Speed
7500 / M490000 / M890000/ M

*in case of sufficient large magnetic flux density is applied

Can the large magnetic field damage the device?

No. The operation is not affected with the range of the magnetic flux density from the permanent magnet which is actually used.

What is the recommended layout for the One-chip Pulse Encoder IC?

Axially magnetized magnet: The device may be located at the middle point between the inner and outer circumference of magnet. The magnetic flux density Bz and Bθ at this point is maximum as shown in Figure 1.

Figure 1: The magnetic flux density Br and Bθ with axially magnetized magnet



Radially magnetized magnet: The device may be located underneath of the magnet. The magnetic flux density Br and Bθ at this point (Z=0) is maximum as shown in Figure 2.

Figure 2: The magnetic flux density Br and Bθ with radially magnetized magnet



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