A1688: Two-Wire, True Zero-Speed, High Accuracy Sensor IC

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. Runningmode 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.

• 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