ALS31313 datasheet(16/25 Pages) ALLEGRO

16 / 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

The inactive time will be determined by the value set in Low-

Power Mode Count Max, Address 0x27, bits 6:4. The ALS31313

offers eight discrete time frames, explained in Table 10. Typical

ICC consumed in the inactive state is 12 µA.

Table 10: LPDCM Inactive Time (tINACTIVE)

Address

Bits

Value

tINACTIVE (typ) (ms)

0x27

6:4

0.5

100

500

1000

The active time will be determined by a combination of the

value in BW Select and the number of magnetic sensing chan-

nels enabled. For more information on LPDCM configuration,

refer to the Low-Power Management Application Note for the

ALS31313.

Bandwidth Selection

BW Select, address 0x02, bits 23:21, controls filtering modes on

the ALS31313 for the X, Y, and Z magnetic channels. This setting

will impact the resolution of sampled magnetic data, the device’s

update rate, and the overall bandwidth.

A lower value for BW Select offers increased measurement

resolution with a longer measurement duration. A higher value

for BW Select offers faster measurement time at the expense of

reduced resolution. This setting is valuable for controlling active

time during low-power duty cycle mode or increasing response

time. Typical noise versus BW Select are listed in Table 11.

Table 11: Bandwidth Select, Filtering Modes,

and Input Referred Noise

BW Select

Value

FIR Enabled

Z Channel

Noise (G)

X/Y Channel

Noise (G)

1.5

2.2

–

2.5

3.5

–

Update rate (typical) versus BW Select and active channels is

shown in Table 12. While the ALS31313 does update at high

bandwidths internally, throughput may be limited by the I2C

bus clocking frequency at the application level. This concept is

explained in the “Calculation Timing” section of the 3D Linear

and 2D Angle Sensing application note.

Table 12: Bandwidth Select and Update Rate

Select

Value

1 Channel

Update Rate

2 Channel

Update Rate

3 Channel

Update Rate

–3 dB

Bandwidth

µs

kHz

µs

kHz

µs

kHz

160

330

495

3.5

170

255

135

–

138

207

111

–

Magnetic sensing channels on the ALS31313 may be enabled

independently with channel x en, channel y en, and channel z en

bits, listed in Table 13.

Table 13: Channel Enable Control

Address

Bits

Value

Description

0x02

Enables Z sensing Channel

Enables Y Sensing Channel

Enables X Sensing Channel

Hall Modes

The ALS31313 offers multiple schemes to retrieve magnetic data

from the magnetic sensing elements. These settings are controlled

via Hall Mode, address 0x02, bits 20:19, described in Table 14.

Table 14: Hall Modes

Value

Mode

Description

Single Ended

Reports magnetic data from Xi, Yi, and Zi

sensing elements.

Differential Mode Reports magnetic data from XOE – XOW,

YON – YOS, and Zi sensing elements.

Common Mode Reports magnetic data from XOE + XOW,

YON +YOS, and Zi sensing elements.

Alternating Mode

Toggles between differential, and common

Hall modes. Use Hall status bits in register

0x29 to decipher origin of magnetic data

sample.

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