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PDF A1642 Data sheet ( Hoja de datos )
| Número de pieza | A1642 | |
| Descripción | Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC | |
| Fabricantes | Allegro | |
| Logotipo |  |
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A1642
Two-Wire True Zero-Speed Miniature Differential
Peak-Detecting Sensor IC with Continuous Calibration
Features and Benefits
▪ Running mode calibration for continuous optimization
▪ Single chip IC for high reliability
▪ Internal current regulator for 2-wire operation
▪ Precise duty cycle signal over operating temperature range
▪ Large operating air gaps
▪ Automatic Gain Control (AGC) for air gap independent
switchpoints
▪ Automatic Offset Adjustment (AOA) for signal processing
optimization
▪ True zero-speed operation
▪ Undervoltage lockout
▪ Wide operating voltage range
▪ Wide-lead package suitable for welding external
components directly to the package leads or for welding
the device to a leadframe.
Package: 4-pin SIP (Suffix KN)
Not to scale
Description
The A1642 is an optimized Hall effect sensing integrated
circuit that provides a user-friendly solution for true zero-speed
digital ring-magnet sensing in two-wire applications.This small
package can be easily assembled and used in conjunction with
a wide variety of target shapes and sizes.
The integrated circuit incorporates dual Hall effect elements
and signal processing that switches in response to differential
magnetic signals created by ring magnet poles. The circuitry
contains a sophisticated digital circuit to reduce system offsets,
to calibrate the gain for air-gap–independent switchpoints,
and to achieve true zero-speed operation. Signal optimization
occurs at power-on through the combination of offset and
gain adjust and is maintained throughout the operating time
with the use of a running-mode calibration. The running-mode
calibration allows immunity to environmental effects such as
micro-oscillations of the target or sudden air gap changes.
The regulated current output is configured for two-wire
applications and the A1642 is ideally suited for obtaining
speed and duty cycle information in ABS (antilock braking
systems). The 1.5 mm spacing between the dual Hall elements
is optimized for fine pitch ring-magnet–based configurations.
For applications requiring sensing of rotating ferrous gears and
targets, refer to theAllegroATS series of products. The package
is lead (Pb) free, with 100% matte tin leadframe plating.
Hall
Amplifier
Functional Block Diagram
Gain
VCC
Automatic Offset
Control
AOA DAC
Tracking
DAC
Peak Hold
AGC DAC
Gain Control
A1642LKN-DS, Rev. 4
Internal Regulator
Test Signals
GND
Test
1 page  
A1642
Two-Wire True Zero-Speed Miniature Differential
Peak-Detecting Sensor IC with Continuous Calibration
Characteristic Data
Supply Current (High) versus Ambient Temperature
(I1 Trim)
16
15
Vcc (V)
14 24
12
4
13
12
-50
0 50 100 150
TA (°C)
Supply Current (Low) versus Ambient Temperature
(I1 Trim)
8
7
Vcc (V)
6 24
12
4
5
4
-50 0
50 100 150
TA (°C)
Supply Current (High) versus Supply Voltage
(I1 Trim)
16
15
14
13
12
0
TA (°C)
-40
25
85
150
5 10 15 20 25
VCC (V)
Supply Current (Low) versus Supply Voltage
(I1 Trim)
8
7
TA (°C)
6 -40
25
150
5
4
05
10 15 20 25
VCC (V)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
5 Page 
A1642
Two-Wire True Zero-Speed Miniature Differential
Peak-Detecting Sensor IC with Continuous Calibration
DEVICE OPERATION
Each operating mode is described in detail below.
Power-On
When power (VCC > VCC(Min)) is applied to the device, a short
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, ICC(High). After power-on, there are conditions that could
induce a change in the output state. Such an event could be
caused by thermal transients, but would require a static applied
magnetic field, 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 defined 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
AGC is active, and selects the optimal signal gain based on the
amplitude of the VPROC signal. Following each adjustment to
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
specification.
Running Mode
After the Initial Calibration period, CI, establishes a signal gain,
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 VPROC signal amplitude in instances where the
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 figure 9).
1
Internal Differential
Signal, VPROC
2 34
BOP
BRP
5
BOP
BRP
Device Electrical
Output, IOUT
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 VPROC is greater than the switching hysteresis (BOP and BRP), and the device output switches.
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.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet A1642.PDF ] | |
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