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AS5311

Datasheet - D e t a il e d D es c r i pt io n

If CLK is low at the falling edge of CSn, the first 12 bits represent the magnitude information, which is proportional to the magnetic field strength.

This information can be used to detect the presence and proper distance of the magnetic strip by comparing it to a known good value (depends

on the magnet material and distance).

The automatic gain control (AGC) maintains a constant MAGnitude value of 3F hex (=“green” range). If the MAG value is <>3F hex, the AGC is

out of the regulating range (“yellow” or “red” range). See Table 13 for more details. For AGC algorithm only M11: M4 of the magnitude are used.

A value of zero or close to zero indicates a missing magnet.

Figure 7. Synchronous Serial Interface with Magnetic Field Strength Data

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.

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Each subsequent rising CLK edge shifts out one bit of data.

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The serial word contains 18 bits, if CLK is high at the falling edge of CSn (see Figure 6), the first 12 bits are the absolute distance informa-

tion D[11:0], the subsequent 6 bits contain system information, about the validity of data such as OCF, COF, LIN, Parity and Magnetic Field

status (increase/decrease).

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If CLK is low at the falling edge of CSn, the first 12 bits contain the magnitude information and the subsequent bits contain the status bits

(see Figure 7).

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Data Contents:

D11:D0 absolute linear position data (MSB is clocked out first)

M11:M0 magnitude / magnetic field strength information (MSB is clocked out first)

OCF (Offset Compensation Finished), logic high indicates the finished Offset Compensation Algorithm. If this bit is not set, the data at D11:D0

(likewise M11:M0) may be invalid.

COF (Cordic Overflow), logic high indicates an out of range error in the CORDIC part. When this bit is set, the data at D11:D0 (likewise M11:M0)

is invalid.

This alarm may be resolved by bringing the magnet within the X-Y-Z tolerance limits.

LIN (Linearity Alarm), logic high indicates that the input field generates a critical output linearity.

When this bit is set, the data at D11:D0 may still be used, but can contain invalid data. This warning can be resolved by increasing the magnetic

field strength.

Even Parity bit for transmission error detection of bits 1…17 (D11…D0, OCF, COF, LIN, MagINC, MagDEC)

M11

1

M10

M9

M8

M7

M6

M5

M4

M3

M2

M1

M0

OCF COF

LIN

Mag

INC

Mag

DEC

Even

PAR

D11

1

18

8

Status Bits

Magnetic field strength data

CSn

DO

CLK