TSL2771 LIGHT-TO-DIGITAL CONVERTER with PROXIMITY SENSING TAOS100A FEBRUARY 2010 PACKAGE FN Features DUAL FLAT NO-LEAD Ambient Light Sensing and Proximity (TOP VIEW) Detection in Single Device Ambient Light Sensing (ALS) V 1 6 SDA DD Approximates Human Eye Response SCL 2 5 INT Programmable Analog Gain Programmable Integration Time GND 3 4 LDR Programmable Interrupt Function with Upper and Lower Threshold 2 Resolution Up to 16 Bits I C Interface Compatible 2 Very High Sensitivity Operates Well Up to 400 kHz (I C Fast Mode) Behind Darkened Glass Dedicated Interrupt Pin Up to 1,000,000:1 Dynamic Range Small 2 mm 2 mm ODFN Package Proximity Detection Sleep Mode 2.5 A Typical Current Programmable Number of IR Pulses Programmable Current Sink for the IR Applications LED No Limiting Resistor Needed Programmable Interrupt Function with Cell Phone Backlight Dimming Upper and Lower Threshold Cell Phone Touch Screen Disable Covers a 2000:1 Dynamic Range Notebook/Monitor Security Programmable Wait Timer Automatic Speakerphone Enable Programmable from 2.72 ms Automatic Menu Popup to > 8 Seconds Wait State 65 A Typical Current Description The TSL2771 family of devices provides both ambient light sensing (ALS) and proximity detection (when coupled with an external IR LED). The ALS approximates human eye response to light intensity under a variety of lighting conditions and through a variety of attenuation materials. The proximity detection feature allows a large dynamic range of operation for use in short distance detection behind dark glass such as in a cell phone or for longer distance measurements for applications such as presence detection for monitors or laptops. The programmable proximity detection enables continuous measurements across the entire range. In addition, an internal state machine provides the ability to put the device into a low power mode in between ALS and proximity measurements providing very low average power consumption. While useful for general purpose light sensing, the TSL2771 is particularly useful for display management with the purpose of extending battery life and providing optimum viewing in diverse lighting conditions. Display panel and keyboard backlighting can account for up to 30 to 40 percent of total platform power. The ALS features are ideal for use in notebook PCs, LCD monitors, flat-panel televisions, and cell phones. The proximity function is targeted specifically towards cell phone, LCD monitor, laptop, and flat-panel television applications. In cell phones, the proximity detection can detect when the user positions the phone close to their ear. The device is fast enough to provide proximity information at a high repetition rate needed when answering a phone call. It can also detect both close and far distances so the application can implement more complex algorithms to provide a more robust interface. In laptop or monitor applications, the product is sensitive enough to determine whether a user is in front of the laptop using the keyboard or away from the desk. This provides both improved green power saving capability and the added security to lock the computer when the user is not present. The LUMENOLOGY Company Copyright 2010, TAOS Inc. Texas Advanced Optoelectronic Solutions Inc. 1001 Klein Road Suite 300 Plano, TX 75074 (972) 673-0759 www.taosinc.com 1TSL2771 LIGHT-TO-DIGITAL CONVERTER with PROXIMITY SENSING TAOS100A FEBRUARY 2010 Functional Block Diagram Interrupt INT IR LED Constant LDR Current Sink Prox Control Upper Limit GND Prox Prox Prox Integration ADC Data Lower Limit V = 2.4 V SCL DD Wait Control to 3.6 V Upper Limit Clear Clear ADC Data Clear Lower Limit SDA ALS Control IR IR ADC Data IR Detailed Description The TSL2771 light-to-digital device provides on-chip clear and IR diodes, integrating amplifiers, ADCs, 2 accumulators, clocks, buffers, comparators, a state machine and an I C interface. Each device combines one clear photodiode (visible plus infrared) and one infrared-responding (IR) photodiode. Two integrating ADCs simultaneously convert the amplified photodiode currents into a digital value providing up to 16 bits of resolution. Upon completion of the conversion cycle, the conversion result is transferred to the clear and IR data registers. This digital output can be read by a microprocessor through which the illuminance (ambient light level) in Lux is derived using an empirical formula to approximate the human eye response. 2 Communication to the device is accomplished through a fast (up to 400 kHz), two-wire I C serial bus for easy connection to a microcontroller or embedded controller. The digital output of the TSL2771 device is inherently more immune to noise when compared to an analog interface. The TSL2771 provides a separate pin for level-style interrupts. When interrupts are enabled and a pre-set value is exceeded, the interrupt pin is asserted and remains asserted until cleared by the controlling firmware. The interrupt feature simplifies and improves system efficiency by eliminating the need to poll a sensor for a light intensity or proximity value. An interrupt is generated when the value of an ALS or proximity conversion exceeds either an upper or lower threshold. In addition, a programmable interrupt persistence feature allows the user to determine how many consecutive exceeded thresholds are necessary to trigger an interrupt. Interrupt thresholds and persistence settings are configured independently for both ALS and proximity. Proximity detection requires only a single external IR LED. An internal LED driver can be configured to provide a constant current sink of 12.5 mA, 25 mA, 50 mA, or 100 mA of current. No external current limiting resistor is required. The number of proximity LED pulses can be programmed from 1 to 255 pulses. Each pulse has a 16-s period. This LED current coupled with the programmable number of pulses provides a 2000:1 contiguous dynamic range. Copyright 2010, TAOS Inc. The LUMENOLOGY Company 2 www.taosinc.com 2 I C Interface