TMD2771 Datasheet, PDF (3/33 Pages) ams AG – DIGITAL ALS and PROXIMITY MODULE

TMD2771
DIGITAL ALS
and PROXIMITY MODULE
TAOS143B − SEPTEMBER 2012
Functional Block Diagram
LDR
V_DD
IR LED Constant
Current Sink
Interrupt
INT
lid ^LEDA
till ^{va LEDK}
Prox
Integration
Prox Control
Prox
ADC
Prox
Data
Channel 0
Wait Control
CH0
ADC
CH0
Data
ALS Control
CH1
ADC
CH1
Data
Channel 1
Upper Limit
Lower Limit
Upper Limit
Lower Limit
SCL
SDA
GND
G _{s Detailed Description}
A ^t _{The light-to-digital device provides on-chip photodiodes, integrating amplifiers, ADCs, accumulators, clocks,}
buffers, comparators, a state machine, and an I²C interface. Each device combines one photodiode (CH0),
s ^{n which is responsive to both visible and infrared light, and a second photodiode (CH1), which is responsive}
e ^{primarily to infrared light. Two integrating ADCs simultaneously convert the amplified photodiode currents to}
m ^{t a digital value providing up to 16-bits of resolution. Upon completion of the conversion cycle, the conversion}
result is transferred to the Ch0 and Ch1 data registers. This digital output can be read by a microprocessor
a ^{n where the luminance (ambient light level in lux) is derived using an empirical formula to approximate the human}
eye response.
o _{A fully integrated proximity detection solution is provided with an 850-nm IR LED, LED driver circuit, and}
proximity detection engine. An internal LED driver (LDR) pin, is connected to the LED cathode (LEDK) to provide
c _{a factory calibrated proximity of 100 mm, ± 20 mm. This is accomplished with a proprietary current calibration}
technique that accounts for all variances in silicon, optics, package, and most important, IR LED output power.
l _{This eliminates or greatly reduces the need for factory calibration that is required for most discrete proximity}
a ^{sensor solutions. While the device is factory calibrated at a given pulse count, the number of proximity LED}
pulses can be programmed from 1 to 255 pulses, which allows different proximity distances to be achieved.
ic ^{Each pulse has a 16 μs period with a 7.2 μs on time.}
Communication with the device is accomplished through a fast (up to 400 kHz), two-wire I²C serial bus for easy
connection to a microcontroller or embedded controller. The digital output of the device is inherently more
n _{immune to noise when compared to an analog photodiode interface.}
h _{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
c _{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
e _{either an upper or lower threshold. In addition, a programmable interrupt persistence feature allows the user}
T^{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.
Copyright E 2012, TAOS Inc.
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www.taosinc.com
The LUMENOLOGY r Company
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