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MAX44007/MAX44009 - Maxim's Digital Ambient-Light Sensors Cut Power Consumption by Over 100xAt Mobile World Congress 2011, Maxim Integrated Products (NASDAQ: MXIM) is introducing the MAX44007/MAX44009, digital ambient-light sensor (ALS) ICs with a unique adaptive-gain block. Designed using the Company's proprietary BiCMOS technology, these ICs integrate two optical sensors, an ADC, and digital functionality into a tiny 2mm x 2mm x 0.6mm package. This integration saves valuable board space while delivering the industry's highest performance.
The MAX44007/MAX44009 consume 100x less power than the nearest competitive
product, significantly extending battery life. They offer a unique interrupt
function that constantly measures the amount of light and reports to the
microcontroller when the measurement passes the threshold. This functionality
extends power savings by reducing the frequency of I2C communications.
The MAX44007/MAX44009 are well suited for applications such as tablet and
notebook PCs, smartphones, TVs, digital lighting-management systems, and
light-intensity monitoring applications.
Thinking beyond the
sensor
In light-sensing systems, any variance along the path that
the light travels results in different measurements. These variances are caused
by where the sensor is placed on the board, the distance tolerance between the
top of the sensor and the glass surface, the transmission characteristics of the
glass covering the sensor, and many others. If the part-to-part variation of the
sensor is also added to this equation, the reading error can be as much as 50%.
This causes false triggers and eventually poor yield at production.
With
the all-in-one integrated solution provided by the MAX44007/MAX44009, the
maximum total gain error is as little as 15%. In addition to this very precise
light measurement, the digital communication of Maxim's light sensors is immune
to parasitics on the communication interface. Both these features provide robust
and reliable light measurement to obtain good yield at production.
Seeing light as the human eye sees it
Replicating the
optical response of the human eye with electronic components is difficult.
Traditional light sensors measure the amount of light in an environment
regardless of wavelength. These designs are unduly influenced by ultraviolet and
infrared light, which are not perceptible by the human eye. This leads to
inaccurate ambient-light readings and, therefore, widely varying brightness
adjustments. This problem is exacerbated by the fact that light sources can have
different spectra; for instance, incandescent light has more infrared content
than fluorescent light.
Maxim's BiCMOS technology enables the integration of two photodiodes along
with an optical filter to reject ultraviolet and infrared light. This allows the
MAX44007/MAX44009 to replicate the optical response of the human eye and
accurately measure visible light in a variety of environmental settings.
Advanced algorithms correct for any spectra variations between light sources,
ensuring an extremely accurate lux response.
Moreover, the ADC
integration time of the sensors can be adjusted from 6.25ms to 800ms. A default
integration time of 100ms ensures excellent 50Hz/60Hz rejection.
Improving black-glass operation
Handheld devices frequently employ
tinted or black glass on top of the sensor. This causes many challenges for the
light sensor, since black glass shifts the response to various light sources,
all of which have different light emission spectra. Measurement errors typically
result when these different spectra are combined with the spectrum profile of
the glass.
The MAX44007 provides access to two different optical sensors: a
visible-plus-infrared photodiode and an infrared photodiode. Once the designer
knows the response of the black glass, it can be factored into the light
sensor's measurement for superior accuracy and sensitivity (down to 0.025 lux).
Increasing dynamic range and precision
Ambient-light
sensors require the widest dynamic range possible to support a broad spectrum of
light conditions, from direct sunlight to complete darkness with every variation
in between. Even in digital light sensors, the gain has to be set to a certain
value to address different modes of operation in multiple light scenarios. This
added configuration requirement increases both design complexity and time to
market.
The MAX44007/MAX44009 feature an integrated adaptive-gain block that
automatically selects the optimum gain range. This capability relieves designers
of the time-consuming process of manually programming the device, and it
offloads work from the application processor or microcontroller. Additionally,
it provides an extremely wide dynamic range. The MAX44009 can measure light
levels from 0.045 lux to 188,000 lux, yielding a dynamic range of more than
4,000,000 to 1. Simply stated, this technology provides the most precise lux
measurements over the widest range of ambient-light conditions.
Reducing power consumption and design complexity
The
MAX44007/MAX44009 are designed to meet the tightest of power budgets. The ICs
boast an operating current (0.65µA) that is lower than the power-down current of
many competitive products, and they operate from an industry-low 1.7V to 3.6V
supply voltage. Consuming as little as 1.1µW of operating power, Maxim's
solutions use 100x less power than the nearest competitor (124µW).
As an added benefit, the devices' low supply voltage
allows them to use the same 1.8V supply for both the supply voltage and the I2C
interface. This reduces power consumption and design complexity by only
requiring a single voltage rail for the part. An address pin allows the use of
two sensors on the same I2C bus.
Additional information
Designed for the tight space requirements of portable systems, the
MAX44007/MAX44009 are offered in a lead-free, 2mm x 2mm x 0.6mm, 6-pin
UTDFN-Opto-EP package. Prices start at $1.20 (1000-up, FOB USA).
Maxim Integrated Products
201102261525.2.2011LightingMAXIM
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