Si1120-A-GM Silicon Laboratories Inc, Si1120-A-GM Datasheet - Page 6

• Manufacturer Part Number: Si1120-A-GM
• Description: Industrial Optical Sensors Proximity/Ambient Light Snsr w/PWM Out
• Manufacturer: Silicon Laboratories Inc
• Type: Ambient Light Sensor with Analog Outputr

Specifications of Si1120-A-GM

• Product: Integrated Ambient Light and Proximity Sensor
• Output Type: Analog - Voltage
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Si 1120
2. Application Information
2.1. Theory of Operation
The Si1120 is an active optical-reflectance proximity detector and ambient-light sensor with a pulse-width
modulated output. Depending on the mode selected, the duration of the PRX active (low) state is proportional to
the amount of reflected light, the amount of zero-reflectance offset, or the amount of ambient light. The detection
rate can be set by adjusting the frequency of the STX signal.
The dual-port, active reflection proximity detector has significant advantages over single-port, motion-based
infrared systems, which are good only for triggered events. Motion detection only identifies proximate moving
objects and is ambiguous about stationary objects. The Si1120 allows in- or out-of-proximity detection, reliably
determining if an object has left the proximity field or is still in the field even when it is not moving.
An example of a proximity detection application is controlling the display and speaker of a cellular telephone. In this
type of application, the cell phone turns off the power-consuming display and disables the loudspeaker when the
device is next to the ear, then reenables the display (and, optionally, the loudspeaker) when the phone moves more
than a few inches away from the ear.
For small objects, the drop in reflectance is as much as the fourth power of the distance; this means that there is
less range ambiguity than with passive motion-based devices. For example, a sixteen-fold change in an object's
reflectance means only a fifty-percent drop in detection range. The Si1120 periodically measures proximity at a rate
that can be set by an external controller.
The Si1120 modes are:
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PRX400
PRX50
PRX50H
OFC
VAMB
VIRL
VIRH
Proximity, 400 mA LED current
Proximity, 50 mA LED current
Proximity, 50 mA LED current, high reflectance range
Offset calibration (proximity mode, no LED current)
Visible ambient (10 klux sunlight)
Visible and infrared ambient light, low range (500 lux sunlight)
Visible and infrared ambient light, high range (128 klux sunlight)
Rev. 1.0