A1688
Two-Wire, True Zero-Speed, High Accuracy Sensor IC
FEATURES AND BENEFITS DESCRIPTION
Integrated capacitor reduces need for external EMI The A1688 is a Hall-effect-based integrated circuit (IC) that
protection components provides a user-friendly solution for true zero-speed digital
Wide leads facilitate ease of assembly ring magnet and gear tooth sensing in two-wire applications.
True zero-speed operation The A1688 is offered in the UB package, which integrates
Automatic Gain Control (AGC) for air gap independent the IC and a high temperature ceramic capacitor in a single
switchpoints overmolded SIP package. The integrated capacitor provides
Automatic Offset Adjustment (AOA) for signal enhanced EMC performance with reduced external components.
processing optimization
The integrated circuit incorporates a dual-element Hall-effect
Large operating air gap range
circuit and signal processing that switches in response to
Internal current regulator for two-wire operation
differential magnetic signals created by magnetic encoders, or,
Undervoltage lockout
when properly backbiased with a magnet, from ferromagnetic
Single chip sensing IC for high reliability
targets. The device contains a sophisticated digital circuit that
On-chip voltage regulator with wide operating voltage
reduces magnet and system offsets, calibrates the gain for air
range and stability in the presence of a variety of
gap independent switchpoints, and provides true zero-speed
complex load impedances
operation.
Fully synchronous digital logic with Scan and IDDQ
testing 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
Package: 2-pin SIP (suffix UB)
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.
Not to scale
VCC
Internal Regulator
Analog to
Digital
Offset Output
Amp AGC
Digital
Controller
Adjust Control
Converter
GND
Chopper
Stabilization
Functional Block Diagram
A1688-DS, Rev. 6A1688 Two-Wire, True Zero-Speed, High Accuracy Sensor IC
SPECIFICATIONS
SELECTION GUIDE
Part Number Packing* Power-On State
A1688LUBTNLT 4000 pieces per 13-in. reel I
CC(LOW)
A1688LUBTNHT 4000 pieces per 13-in. reel I
CC(HIGH)
*Contact Allegro for additional packing options.
ABSOLUTE MAXIMUM RATINGS
Characteristic Symbol Notes Rating Unit
Supply Voltage V 28 V
CC
Reverse Supply Voltage V 18 V
RCC
Operating Ambient Temperature T L temperature range 40 to 150 C
A
Maximum Junction Temperature T (max) 165 C
J
Storage Temperature T 65 to 170 C
stg
Internal Discrete Capacitor Ratings
Value
Characteristic Symbol Test Conditions* Unit
(Typ.)
Nominal Capacitance C Connected between VCC and GND 2200 pF
SUPPLY
Terminal List Table
Name Number Function
1 2
VCC 1 Supply Voltage
GND 2 Ground
UB Package, 2-Pin SIP Pinout Diagram
Allegro MicroSystems, LLC
2
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com