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Data Sheet - D e t a i l e d D e s c r i p t i o n
7 Detailed Description
The AS5140H is manufactured in a CMOS standard process and uses a spinning current Hall technology for sensing the magnetic field
distribution across the surface of the chip. The integrated Hall elements are placed around the center of the device, and deliver a voltage
representation of the magnetic field at the surface of the IC. Through Sigma-Delta Analog / Digital Conversion and Digital Signal-Processing
(DSP) algorithms, the AS5140H provides accurate high-resolution absolute angular position information. For this purpose, a Coordinate Rotation
Digital Computer (CORDIC) calculates the angle and the magnitude of the Hall array signals. The DSP is also used to provide digital information
at the outputs MagINCn and MagDECn that indicate movements of the used magnet towards or away from the device’s surface. A small low cost
diametrically magnetized (two-pole) standard magnet provides the angular position information (see Figure 18).
The AS5140H senses the orientation of the magnetic field and calculates a 10-bit binary code. This code can be accessed via a Synchronous
Serial Interface (SSI). In addition, an absolute angular representation is given by a Pulse Width Modulated signal at pin 12 (PWM).
Simultaneously, the device also provides incremental output signals. The various incremental output modes can be selected by programming the
OTP mode register bits (see Table 20). As long as no programming voltage is applied to pin Prog, the new setting may be overwritten at any time
and will be reset to default when power is turned off. To make the setting permanent, the OTP register must be programmed. The default setting
is a quadrature A/B mode including the Index signal with a pulse width of 1 LSB. The Index signal is logic high at the user programmable zero
The AS5140H is tolerant to magnet misalignment and magnetic stray fields due to differential measurement technique and Hall sensor
Figure 4. Typical Arrangement of AS5140H and Magnet
7.1 10-bit Absolute Angular Position Output
7.1.1 Synchronous Serial Interface (SSI)
If CSn changes to logic low, Data Out (DO) will change from high impedance (tri-state) to logic high and the read-out will be initiated.
After a minimum time tCLK FE, data is latched into the output shift register with the first falling edge of CLK.
Each subsequent rising CLK edge shifts out one bit of data.
The serial word contains 16 bits; the first 10 bits are the angular information D[9:0], the subsequent 6 bits contain system information about
the validity of data such as OCF, COF, LIN, Parity and Magnetic Field status (increase/decrease).
A subsequent measurement is initiated by a log “high” pulse at CSn with a minimum duration of tCSn.