ALS31313 datasheet(18/25 Pages) ALLEGRO

18 / 25 page

Automotive Grade, 3-D Linear Hall-Effect Sensor

with I2C Output and Advanced Low Power Management

ALS31313

Allegro MicroSystems, LLC

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

THRESHOLD MODE

In Threshold Interrupt Mode, the most recent magnetic sample

data is compared to the user-selected threshold for each channel.

If the magnetic ADC value is greater than or equal to this thresh-

old, an interrupt event will occur.

DELTA MODE

Delta Interrupt Mode is used in combination with Low-Power

Duty Cycle Mode, where the ALS31313 toggles between an

Active and a Sleep state. In Delta Interrupt Mode, the ALS31313

will remember its last magnetic data sample when entering

LPDCM.

New magnetic data is compared to the original sample every time

the ALS31313 toggles into the active state. If the delta (change)

in magnetic data is larger than the user-selected delta, an interrupt

event will occur.

User-selectable values for threshold and delta share the registers

Z INT Threshold, Y INT Threshold, and X INT Threshold, address

0x03, bits 17:0.

In Threshold Mode, the value in these registers will be considered

a threshold, while in Delta Mode, the value in these registers will

be considered a delta. The ALS31313 may interpret these values

as signed or unsigned based on the Signed INT Enable bit.

SIGNED INTERRUPT THRESHOLD

By default, the value for Signed INT Enable is set to 0, and the

user-programmed value for threshold is unsigned. This will

trigger an interrupt event when applying a positive or negative

magnetic field, causing the absolute value of the magnetic data to

meet or exceed the user-selected threshold.

If Signed INT Enable is set to 1, the value for threshold becomes

signed. This may be used to trigger interrupts on only positive or

only negative magnetic fields that cause the value of the magnetic

data to meet or exceed the user-programmed threshold.

Interrupt threshold for each channel can be programmed indepen-

dently using registers Z INT Threshold, Y INT Threshold, and X

INT Threshold, address 0x03, bits 17:0. The following examples

set an interrupt threshold for the X axis, but the technique also

applies to Y and Z axes.

When Signed INT Enable = 0, the interrupt threshold will be

determined by the equation:

threshold = (INT Threshold + 1) × 25 – 1

When Signed INT Enable = 1, the interrupt threshold will be

determined by the equation:

if X INT Threshold ≥ 0

threshold = (INT Threshold + 1) × 26 – 1

if X INT Threshold < 0

threshold = (INT Threshold + 1) × 26

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