AS5040 datasheet(4/28 Pages) AMSCO

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AS5040 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER

Revision 1.6, 03-Oct-06

www.austriamicrosystems.com

Page 4 of 28

10-bit Absolute Angular Position Output

4.1

Synchronous Serial Interface (SSI)

Even

PAR

CSn

CLK

COF

LIN

OCF

Mag

INC

Mag

DEC

t DO active

t DO Tristate

t CLK FE

t DO valid

t CLK FE

t CSn

T CLK / 2

Angular Position Data

Status Bits

Figure 4: Synchronous serial interface with absolute angular position 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.

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.

Data Content:

D9:D0 absolute angular position data (MSB is

clocked out first)

OCF (Offset Compensation Finished), logic high

indicates the finished Offset Compensation Algorithm.

For fast startup, this bit may be polled by the external

microcontroller. As soon as this bit is set, the AS5040

has completed the startup and the data is valid (see

Table 4)

COF (Cordic Overflow), logic high indicates an out of

range error in the CORDIC part. When this bit is set,

the data at D9:D0 is invalid. The absolute output

maintains the last valid angular value.

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 D9:D0 may still be

used, but can contain invalid data. This warning may

be resolved by bringing the magnet within the X-Y-Z

tolerance limits.

MagINCn, (Magnitude Increase) becomes HIGH, when

the magnet is pushed towards the IC, thus the magnetic

field strength is increasing.

MagDECn, (Magnitude Decrease) becomes HIGH, when

the magnet is pulled away from the IC, thus the magnetic

field strength is decreasing.

Both signals HIGH indicate a magnetic field that is out of

the allowed range (see Table 3).

Mag

INCn

Mag

DECn

Description

No distance change

Magnetic Input Field OK (in range)

Distance increase: Pull-function. This state

is dynamic, it is only active while the magnet

is moving away from the chip in Z-axis

Distance decrease: Push- function. This

state is dynamic, it is only active while the

magnet is moving towards the chip in Z.-

axis.

Magnetic Input Field invalid – out of range:

too large, too small (missing magnet)

Table 3: Magnetic magnitude variation indicator

Note: Pins 1 and 2 (MagINCn, MagDECn) are open drain

outputs and require external pull-up resistors. If the

magnetic field is in range, both outputs are turned off.

The two pins may also be combined with a single pull-up

resistor. In this case, the signal is high when the

magnetic field is in range. It is low in all other cases (see

Table 3).

Even Parity bit for transmission error detection of bits

1…15 (D9…D0, OCF, COF, LIN, MagINCn, MagDECn)

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