A1645LK-I2 Allegro Microsystems Inc, A1645LK-I2 Datasheet - Page 11

• Manufacturer Part Number: A1645LK-I2
• Description: IC SENSOR HALL EFFECT AC 4-SIP
• Manufacturer: Allegro Microsystems Inc
• Type: Special Purposer

Specifications of A1645LK-I2

• Sensing Range: 120mV Trip, 120mV Release
• Voltage - Supply: 4 V ~ 24 V
• Current - Supply: 8.4mA
• Output Type: Digital, Open Collector
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 4-SIP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output (max): -
• Features: -

A1642
DEVICE OPERATION
Each operating mode is described in detail below.
Power-On
When power (V
period of time is required to power the various portions of the
IC. During this period, the A1642 powers-on in the high current
state, I
induce a change in the output state. Such an event could be
caused by thermal transients, but would require a static applied
magnetic fi eld, proper signal polarity, and particular direction
and magnitude of internal signal drift.
Initial Offset Adjust
The device initially cancels the effects of chip, magnet, and
installation offsets. Once offsets have been cancelled, the digital
tracking DAC is ready to track the signal and provide output
switching. The period of time required for both Power-On and
Initial Offset Adjust is defi ned as the Power-On Time.
Calibration Mode
The calibration mode allows the device to automatically select
the proper signal gain and continue to adjust for offsets. The
CC(High)
Figure 9: Operation of Running Mode Gain Adjust.
Position 1. The device is initially powered-on. Self-calibration occurs.
Position 2. Small amplitude oscillation of the target sends an erroneously small differential signal to the device. The ampli-
tude of V
Position 3. The calibration period completes on the third rising output edge, and the device enters Running mode.
Position 4. True target rotation occurs and the correct magnetic signal is generated for the installation air gap. The estab-
lished signal gain is too large for the target’s rotational magnetic signal at the given air gap.
Position 5. Running Mode Calibration corrects the signal gain to an optimal level for the installation air gap.
Internal Differential
Signal, V
Device Electrical
Output, I
. After power-on, there are conditions that could
CC
> V
PROC
OUT
PROC
CC(Min)
is greater than the switching hysteresis (B
) is applied to the device, a short
1
Peak-Detecting Sensor IC with Continuous Calibration
Two-Wire True Zero-Speed Miniature Differential
2
B
OP
B
RP
OP
and B
3
AGC is active, and selects the optimal signal gain based on the
amplitude of the V
the AGC DAC, the Offset DAC is also adjusted to ensure the
internal analog signal is properly centered.
During this mode, the tracking DAC is active and output switch-
ing occurs, but the duty cycle is not guaranteed to be within
specifi cation.
Running Mode
After the Initial Calibration period, C
the device moves to Running mode. During Running mode, the
device tracks the input signal and gives an output edge for every
peak of the signal. AOA remains active to compensate for any
offset drift over time.
The A1642 incorporates a novel algorithm for adjusting the
signal gain during Running mode. This algorithm is designed
to optimize the V
magnetic signal “seen” during the calibration period is not repre-
sentative of the amplitude of the magnetic signal for the installed
device air gap (see fi gure 9).
RP
), and the device output switches.
4
PROC
PROC
signal amplitude in instances where the
signal. Following each adjustment to
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Worcester, Massachusetts 01615-0036 U.S.A.
5
B
OP
B
RP
I
, establishes a signal gain,
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