A1688 Datasheet, PDF (1/10 Pages) Allegro MicroSystems – Two-Wire, True Zero-Speed, High Accuracy Sensor IC

A1688
Two-Wire, True Zero-Speed, High Accuracy Sensor IC
FEATURES AND BENEFITS
• Integrated capacitor reduces need for external EMI
protection components
• Wide leads facilitate ease of assembly
• True zero-speed operation
• Automatic Gain Control (AGC) for air gap independent
switchpoints
• Automatic Offset Adjustment (AOA) for signal
processing optimization
• Large operating air gap range
• Internal current regulator for two-wire operation
• Undervoltage lockout
• Single chip sensing IC for high reliability
• On-chip voltage regulator with wide operating voltage
range and stability in the presence of a variety of
complex load impedances
• Fully synchronous digital logic with Scan and IDDQ
testing
Package: 2-pin SIP (suffix UB)
Not to scale
DESCRIPTION
The A1688 is a Hall-effect-based integrated circuit (IC) that
provides a user-friendly solution for true zero-speed digital
ring magnet and gear tooth sensing in two-wire applications.
The A1688 is offered in the UB package, which integrates
the IC and a high temperature ceramic capacitor in a single
overmolded SIP package. The integrated capacitor provides
enhanced EMC performance with reduced external components.
The integrated circuit incorporates a dual-element Hall-effect
circuit and signal processing that switches in response to
differential magnetic signals created by magnetic encoders, or,
when properly backbiased with a magnet, from ferromagnetic
targets. The device contains a sophisticated digital circuit that
reduces magnet and system offsets, calibrates the gain for air
gap independent switchpoints, and provides true zero-speed
operation.
Signal optimization occurs at power-up through the combination
of offset and gain-adjust and is maintained throughout operation
with the use of a running-mode calibration scheme. Running-
mode calibration provides immunity from environmental effects
such as micro-oscillations of the sensed target or sudden air
gap changes.
The regulated current output is configured for two-wire interface
circuitry and is ideally suited for obtaining speed information in
wheel speed applications. The Hall element spacing is optimized
for high resolution, small diameter targets. The package is lead
(Pb) free, with 100% matte-tin leadframe plating.
VCC
Internal Regulator
Amp
Offset
Adjust
AGC
Chopper
Stabilization
Analog to
Digital
Converter
Digital
Controller
Output
Control
A1688-DS, Rev. 6
Functional Block Diagram
GND