AN522 Datasheet, PDF (1/8 Pages) Silicon Laboratories – TOUCHLESS LAVATORY APPLIANCES

AN522
USING THE Si1141 FOR TOUCHLESS LAVATORY APPLIANCES
1. Introduction
The Si1141 is a single-channel, reflectance-based proximity detector with an integrated ambient light sensor and
can be used as a touchless sensor IC in lavatory appliances. As a proximity detector, the Si1141 has two infrared
photodiodes, flexible ADC integration time, and multiple signal ranges. In addition to the configurable ADC
sensitivity configuration settings, the Si1141 can dynamically drive an irLED with anywhere from 6 to 400 mA. This
high level of flexibility in the ADC, photodiode choice, and irLED drive strength all contribute to allow the end
product to operate under various ambient light conditions.
In general, lavatory appliances operate indoors, typically under CFL lighting. However, it is common for these
appliances to be exposed to direct sunlight when the product is near a window. Therefore, having the flexibility to
allow operation under various light sources is key to making a robust product and helps provide end product
differentiation.
Another product feature that makes the Si1141 compelling in touchless lavatory appliances is the low system
power. Most touchless lavatory appliances, such as flushers and faucets, are battery operated since power mains
are typically unavailable in most lavatory stalls. A lavatory appliance spends much of its time waiting for the target
to enter its proximity. Minimizing the current draw from the battery benefits the end product by extending its lifetime
use.
The Si1141 achieves this low power by taking proximity measurements using a single 25.6 µs irLED pulse instead
of performing the multiple pulses commonly used in discrete photodiode approaches.
In addition to the Si1141 Proximity and Ambient Light Sensor, Silicon Labs offers an array of low-power MCU
devices (C8051F9xx series). When combined, these devices offer best-in-class, low-power operation.
In general, lavatory appliances are subdivided into the following categories:
 Lavatory Flushers
 Lavatory Faucets
 Soap Dispenser
Toilet flushers, faucets, and soap dispenser assemblies are typically battery powered since a power plug is
generally not available nearby. Toilet flushers generally aim to detect the presence of a human body, while faucets
and soap dispensers are designed to detect the presence of hands. All of these application uses are similar in that
the proximity detector generates an action, typically the driving of a motor.
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