Fast proximity sensor eliminates DACs to lower costs

23rd February 2016
Jordan Mulcare

Vishay Intertechnology has introduced an infrared (IR) sensor designed to provide fast, low-cost proximity sensing in a variety of systems. The Vishay Semiconductors TSSP4056 is the industry's first fixed-gain sensor containing a band-pass filter tuned to 56kHz to feature a monotonic sensitivity vs. frequency response curve from 30 to 54kHz.

The device detects modulated pulses from a separate IR emitter with a high sensitivity of 0.4mW/m², while fast readings in under 5ms are possible using successive approximation techniques, as demonstrated in Vishay's Fast Proximity Sensor software. Typically, proximity sensors determine an object's distance by varying the emitter's drive current to find the threshold emitter power at which the object is just detected, a technique that requires an expensive DAC to drive the emitter.

The TSSP4056, however, determines distance by varying the carrier frequency used to drive the emitter between 30 and 54kHz, thereby finding the threshold frequency at which the sensor just detects the object. This approach doesn't require the microcontroller to contain a DAC, thus lowering overall solution costs. More information on the operating principle behind the TSSP4056 can be found in the application note 'Vishay's TSSP4056 Sensor for Fast Proximity Sensing'.

The device released today offers proximity sensing from 10cm up to 2m and a > four times dynamic range from its lowest to highest sensitivity. Used as a proximity sensor, the TSSP4056 is ideal for sensing the distance to objects for toys, drones, autonomous robots and intelligent vicinity switches.

The device may also be used as a simple reflective sensor for hand dryers, towel or soap dispensers, water faucets, and toilets; vending machine fall detection; and security and pet gates. To simplify designs, the TSSP4056 features a PIN photodiode and sensor IC in a compact molded package measuring 6.0x6.95x5.6 mm. The IR sensor module operates at a supply voltage range from 2.5 to 5.5V and a typical supply current of 0.7mA. The sensor is designed to receive IR pulses from an emitter with a peak wavelength of 940nm.

The device is insensitive to supply voltage and ripple noise and provides shielding against EMI, while an IR filter suppresses visible light. The TSSP4056 is RoHS-compliant, halogen-free and Vishay Green.

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