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Rev. 0.1 1/15 Copyright © 2015 by Silicon Laboratories AN522 AN522 USING THE Si1141 FOR TOUCHLESS L AVATORY A PPLIANCES 1. Introduction The Si1141 is a single-channel, reflectance-based proxim ity 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 in tegration 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, ph otodiode choice, and irLED drive streng th all contribute to allow the end product to operate under various ambient light conditions. In general, lavatory appliances operate indoors, typica lly under CFL lighting. Howeve r, it is common for these appliances to be expo sed to direct sunlight when t he product is near a win dow. 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 featur e that makes the Si1141 compelling in touc hless lavatory appli ances is the low system power. Most touchless lavatory appliances, such as flus hers and faucets, are battery operated since power mains are typically unavailable in most lavato ry stalls. A lavatory appliance spends mu ch 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 Proximit y 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 assemblie s 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.

additional proximity sensor on the sides of the faucet for selection of hot and cold water. piping to bring the light to and from the PCB hosting the optical components and main host controller. illustrates the block diagram of a similar system making use of the C8051F9xx and the Si1141. mechanical and optical system has been designed. Figure 3. Faucet with Temperature Control (Left) and Proximity-Only Faucet

still the dominating factor that differentiates the various lavatory systems. Figure 4. Forward-Facing Soap Dispenser (Left), Downward-Facing Soap Dispenser (Right)

6 Rev. 0.1 5. Power Consumption A lavatory appliance generally spends much of its time waiting for an object to enter its proximity. In Table 1, the Proximity Polling Period is measured by examining the period of the irLED current pulses when no object is in range. The irLED current and on-time is also measured. In most systems, the irLED on-time consists of multiple pulses. For these systems, the reported on-time is the accumulation of th e irLED on-time within one Proximity Polling Period. The System Current is defined as the amount of current drawn through the System Power Source. The F9xx and Si114x combination offers the best-in-class system current draw under the no-proximity condition. To best show this, an irLED current is estimated based on the detection distance and the size of the object. The estimated irLED current is then run through a calculator to achieve an estimated current consumption for the Si114x plus the irLED. Next, 1.2 µA is added to this to simulate the expected current drawn by the F9xx. It is important to note that the Si114x supports “interrupt on threshold”. This means that the Si114x can be set up so that the F9xx only wakes up from its sleep state if the reflectance reaches a certain level. The F9xx can then be woken up only when there is a proxim ity event. The 1.2 µA sleep current F9xx assumes that the Si114x interrupt pin is connected to a Port Match interrupt, allowing the F9xx to stay in its sleep state and only wake up when the Port Match interrupt is triggered.

The C8051F9xx and Si114x combination can provide significant power reduction in lavatory appliances. C8051F9xx require an external crystal to operate. The C8051F9xx and Si114x are well-suited for use in lavatory appliances. Table 1. Typical Lavatory Power Consumption

Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific written consent of Silicon Laboratories. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected to result in significant personal injury or death. Silicon Laboratories products are generally not intended for military applications. Silicon Laboratories products shall under no circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons. Trademark Information Silicon Laboratories Inc., Silicon Laboratories, Silicon Labs, SiLabs and the Silicon Labs logo, CMEMS®, EFM, EFM32, EFR, Energy Micro, Energy Micro logo and combinations thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZMac®, EZRadio®, EZRadioPRO®, DSPLL®, ISOmodem ®, Precision32®, ProSLIC®, SiPHY®, USBXpress® and others are trademarks or registered trademarks of Silicon Laboratories Inc. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of ARM Holdings. Keil is a registered trademark of ARM Limited. All other products or brand names mentioned herein are trademarks of their respective holders. http://www.silabs.com Silicon Laboratories Inc.

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