A1172ECGLT Datasheet, PDF(8/11 Page) Allegro MicroSystems – Micropower Ultra-Sensitive Hall-Ef fect Switch

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A1172ECGLT Datasheet, PDF (8/11 Pages) Allegro MicroSystems – Micropower Ultra-Sensitive Hall-Ef fect Switch

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A1172

Micropower Ultra-Sensitive Hall-Effect Switch

Functional Description

Low Average Power

Internal timing circuitry activates the IC for 50 Î¼s and deacti-

vates it for the remainder of the period (50 ms). A short awake

time allows stabilization prior to the sampling and data-latching

on the falling edge of the timing pulse. The output during the

sleep state is latched in the last sampled state. The supply current

is not affected by the output state.

IDD(EN)

Awake

tPeriod

Sleep

IDD(DIS)

Sample and Output Latched

Operation

The VOUTPS output switches low (turns on) when a magnetic

field perpendicular to the Hall element exceeds the operate point,

BOPS (or is less than BOPN). After turn-on, the output voltage

is VOUT(SAT). The output transistor is capable of sinking cur-

rent up to the short circuit current limit, IOM, which is a mini-

mum of 1 mA. When the magnetic field is reduced below the

release point, BRPS (or increased above BRPN), the device output

switches high (turns off). The pull-up transistor brings the output

voltage to VOUT(HIGH).

VOUTPN operates with the opposite output polarity. That is, the

output is low (on) in the absence of a magnetic field. The output

goes high (turns off) when sufficient field, of either north or

south polarity, is presented to the device.

The difference in the magnetic operate and release points is the

hysteresis, BHYS , of the device. This built-in hysteresis allows

clean switching of the output even in the presence of external

mechanical vibration and electrical noise.

The push-pull outputs are capable of sourcing or sinking a maxi-

mum of 1 mA.

Powering-on the device in a hysteresis region, between BOPX

and BRPX, allows an indeterminate output state. The correct state

is attained after the first excursion beyond BOPX or BRPX.

(A) VOUTPS

V+

VOUT(HIGH)

(B) VOUTPN

VOUT(HIGH)

Bâ

BHYS

VOUT(SAT)

B+

Bâ

BHYS

VOUT(SAT)

B+

Figure 1. Switching Behavior of Omnipolar Switches. On the horizontal axis, the B+ direction indicates increasing

south polarity magnetic field strength, and the Bâ direction indicates decreasing south polarity field strength

(including the case of increasing north polarity).

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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