TSL27711 datasheet(18/51 Pages) OSRAM

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[v1-00] 2016-Mar-22

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TSL2771 − Principles Of Operation

Proximity Detection

Proximity sensing uses an external light source (generally an

infrared emitter) to emit light, which is then viewed by the

integrated light detector to measure the amount of reflected

light when an object is in the light path (Figure 19). The amount

of light detected from a reflected surface can then be used to

determine an object’s proximity to the sensor.

Figure 19:

Proximity Detection

The device has controls for the number of IR pulses (PPCOUNT ),

the integration time (PTIME), the LED drive current (PDRIVE),

and the photodiode configuration (PDIODE) (Figure 20). The

photodiode configuration can be set to CH1 diode

(recommended), CH0 diode, or a combination of both diodes.

At the end of the integration cycle, the results are latched into

the proximity data (PDATA) register.

Figure 20:

Proximity Detection Operation

IR LED

Prox

Sensor

Surface Reflectivity (SR)

Background Energy (BGE)

Optical Crosstalk (OC)

Glass Attenuation (GA)

Distance (D)

CH1

Prox

Integration

Prox Control

Prox

ADC

IR LED Constant

Current Sink

CH0

PDATAH(r 0x019), PDATAL(r 0x018)

PDRIVE(r 0x0F, b7:6)

Prox

Data

LED

PTIME(r 2)

PPCOUNT(r 0x0E)

VDD

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