TSL2571
LIGHT-TO-DIGITAL CONVERTER
TAOS117A − FEBRUARY 2011
Detailed Description
The TSL2571 light-to-digital device includes on-chip photodiodes, integrating amplifiers, ADCs, accumulators,
clocks, buffers, comparators, a state machine, and an I
2
C interface. The device combines one photodiode
(CH0), which is responsive to both visible and infrared light, and one photodiode (CH1), which is responsive
primarily to infrared light. 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 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.
Communication to the device is accomplished through a fast (up to 400 kHz), two-wire I
2
C serial bus for easy
connection to a microcontroller or embedded controller. The digital output of the device is inherently more
immune to noise when compared to an analog interface.
The device 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 value. An interrupt is generated when the value of an ALS 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.
Copyright
E
2011, TAOS Inc.
r
r
The
LUMENOLOGY
r
Company
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www.taosinc.com
TAOS [ TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS ]
