Si1142-A10-GM Silicon Laboratories Inc, Si1142-A10-GM Datasheet - Page 11

• Manufacturer Part Number: Si1142-A10-GM
• Description: Proximity Sensors IC INTERFACE
• Manufacturer: Silicon Laboratories Inc

Specifications of Si1142-A10-GM

• Maximum Operating Temperature: + 85 C
• Supply Voltage: 3.3 V
• Supply Current: 5.6 mA to 360 mA
• Operating Supply Voltage: 1.8 V to 3.6 V
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Current Rating: 359 mA
• Voltage Rating: 4 V
• Sensing Distance: 1 m
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Si1141/42/43
2. Functional Description
2.1. Introduction
The Si1141/42/43 is an active optical reflectance proximity detector and ambient light sensor whose operational
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state is controlled through registers accessible through the I
C interface. The host can command the Si1141/42/43
to initiate on-demand proximity detection or ambient light sensing. The host can also place the Si1141/42/43 in an
autonomous operational state where it performs measurements at set intervals and interrupts the host either after
each measurement is completed or whenever a set threshold has been crossed. This results in an overall system
power saving allowing the host controller to operate longer in its sleep state instead of polling the Si1141/42/43. For
more details, refer to “AN498: Designer's Guide for the Si114x”.
2.2. Proximity Sensing (PS)
The Si1141/42/43 has been optimized for use as either a dual-port or single-port active reflection proximity
detector. Over distances of less than 50 cm, the dual-port active reflection proximity detector has significant
advantages over single-port, motion-based infrared systems, which are only good for triggered events. Motion-
based infrared detectors identify objects within proximity, but only if they are moving. Single-port motion-based
infrared systems are ambiguous about stationary objects even if they are within the proximity field. The Si1141/42/
43 can reliably detect an object entering or exiting a specified proximity field, even if the object is not moving or is
moving very slowly. However, beyond about 30–50 cm, even with good optical isolation, single-port signal
processing may be required due to static reflections from nearby objects, such as table tops, walls, etc. If motion
detection is acceptable, the Si1141/42/43 can achieve ranges of up to 50 cm, through a single product window.
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 sixteenfold change in an object's
reflectance means only a fifty-percent drop in detection range.
The Si1143 can drive three separate infrared LEDs. When the three infrared LEDs are placed in an L-shaped
configuration, it is possible to triangulate an object within the three-dimensional proximity field. Thus, a touchless
user interface can be implemented with the aid of host software.
The Si1141/42/43 can initiate proximity sense measurements when explicitly commanded by the host or
periodically through an autonomous process. Refer to "3. Operational Modes" on page 16 for additional details of
the Si1141/42/43's Operational Modes.
Whenever it is time to make a PS measurement, the Si1141/42/43 makes up to three measurements, depending
on what is enabled in the CHLIST parameter. Other ADC parameters for these measurements can also be
modified to allow proper operation under different ambient light conditions.
The LED choice is programmable for each of these three measurements. By default, each measurement turns on a
single LED driver. However, the order of measurements can be easily reversed or even have all LEDs turned on at
the same time. Optionally, each proximity measurement can be compared against a host-programmable threshold.
With threshold settings for each PS channel, it is also possible for the Si1141/42/43 to notify the host whenever the
threshold has been crossed. This reduces the number of interrupts to the host, aiding in efficient software
algorithms.
The Si1141/42/43 can also generate an interrupt after a complete set of proximity measurements, ignoring any
threshold settings.
To support different power usage cases dynamically, the infrared LED current of each output is independently
programmable. The current can be programmed anywhere from a few to several hundred milliamps. Therefore, the
host can optimize for proximity detection performance or for power saving dynamically. This feature can be useful
since it allows the host to reduce the LED current once an object has entered a proximity sphere, and the object
can still be tracked at a lower current setting. Finally, the flexible current settings make it possible to control the
infrared LED currents with a controlled current sink, resulting in higher precision.
The ADC properties are programmable. For indoor operation, the ADC should be configured for low signal range
for best reflectance sensitivity. When under high ambient conditions, the ADC should be configured for high signal
level range operation.
Rev. 1.1
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