MAX44004
Digital Ambient Light Sensor
1
Typical Application Circuit
19-5997; Rev 0; 5/12
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to www.maxim-ic.com/MAX44004.related.
EVALUATION KIT AVAILABLE
General Description
The MAX44004 is a wide dynamic range, low-
power ambient light sensor (ALS) ideal for many light
sensing applications: tablets, displays, accessories,
medical devices, and light management systems.
The on-chip ambient sensor has the power to measure
the exact visible light from 0.03 lux to 65,000 lux and com-
municate through an I2C digital communication bus. The
IC has patented sensors, filters, and circuitry to mimic the
human eye response. With on-chip calibration registers,
it performs the same in different light conditions (i.e., fluo-
rescent, incandescent). The interrupt pin minimizes the
need of constant polling of the device, freeing up micro-
controller resources for efficient communication and thus
reducing overall power consumption. The part-to-part
matching is optimized by proprietary Maxim process to
speed up end-product development time.
The IC can operate from a VDD of 1.7V to 3.6V, including
both supply and I2C times. It consumes just 5µA operat-
ing current.
Applications
Tablets and Netbooks
Displays, TVs, Projectors
Digital Lighting Management
Medical Devices
Industrial Automation
Benefits and Features
S Consumes Low Power
5µA Supply Current
Interrupt Pin Delivers Efficient Communication
S High Sensitivity
0.03 Lux Sensitivity
S Easy to Design
1.7V to 3.6V Supply Voltage
Tight Part-to-Part Variation
S Reliable Light Sensing
Perfect Rejection of 50Hz/60Hz Noise
Adjustable Visible and Infrared Sensor Gain
S Tiny, 2mm x 2mm x 0.6mm OTDFN Package
S -40°C to +105°C Temperature Range
VIS + IR
(ALS)
IR (ALS)
GND
14-BIT
14-BIT
I2CMICRO-
CONTROLLER
SCL
SDA
INT
MAX44004
GNDA0
VDD
VDD
ALS
PGA
ALS
PGA
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
2
MAX44004
Digital Ambient Light Sensor
All Pins to GND ....................................................-0.3V to +4.0V
Output Short-Circuit Current Duration .......................Continuous
Continuous Input Current into Any Terminal…… ............ Q20mA
Continuous Power Dissipation
OTDFN (derate 11.9mW/NC above +70NC) ................. 953mW
Operating Temperature Range ........................ -40NC to +105NC
Soldering Temperature (reflow) ......................................+260NC
ABSOLUTE MAXIMUM RATINGS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD = 1.8V, TA = -40NC to +105NC, TA = +25NC, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
AMBIENT LIGHT RECEIVER CHARACTERISTICS
Maximum Ambient Light Sensitivity Fluorescent light (Note 2) 0.03 Lux/
LSB
Ambient Light Saturation Level 65,535 Lux
Gain Error Green LED 538nm response, TA = +25NC
(Note 2) 15 %
Light Source Matching Fluorescent/incandescent light 10 %
Infrared Transmittance 850nm vs. 538nm, TA = +25NC0.5 %
Ultraviolet Transmittance 363nm vs. 538nm, TA = +25NC2 %
Dark Current Level 100ms conversion time, 0 lux, TA = +25NC0 Count
ADC Conversion Time
14-bit resolution, has 50Hz/60Hz rejection 100
ms
12-bit resolution 25
10-bit resolution 6.25
8-bit resolution 1.56
ADC Conversion Time Accuracy TA = +25NC 0.7 %
TA = -40NC to +105NC6
POWER SUPPLY
Power-Supply Voltage VDD 1.7 3.6 V
Quiescent Current Is 5 10 FA
Software Shutdown Current ISHDN
TA = +25NC0.1 0.3 FA
TA = -40NC to +105NC0.6
Power-Up Time tON 100 ms
3
MAX44004
Digital Ambient Light Sensor
Note 1: The device is 100% production tested at TA = +25NC. Temperature limits are guaranteed by design.
Note 2: Guaranteed by design, green 538nm LED chosen for production so that the IC responds to 100 lux fluorescent light with
100 lux.
ELECTRICAL CHARACTERISTICS (continued)
(VDD = 1.8V, TA = -40NC to +105NC, TA = +25NC, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DIGITAL CHARACTERISTICS—SDA, SCL, INT, A0
Output Low Voltage SDA, INT VOL ISINK = 6mA 0.06 0.4 V
INT Leakage Current TA = +25NC0.01 1000 nA
SDA, SCL, A0 Input Current 0.01 1000 nA
I2C Input Low Voltage VIL_I2C SDA, SCL 0.4 V
I2C Input High Voltage VIH_I2C SDA, SCL 1.6 V
I2C Input Low Voltage VIL_I2C A0 0.3 V
I2C Input High Voltage VIH_I2C A0 VDD - 0.3 V
Input Capacitance SDA, SCL 3 pF
I2C TIMING CHARACTERISTICS
Serial Clock Frequency fSCL 400 kHz
Bus Free Time Between STOP and
START tBUF 1.3 Fs
Hold Time (Repeated) START
Condition tHD,STA 0.6 Fs
Low Period of the SCL Clock tLOW 1.3 Fs
High Period of the SCL Clock tHIGH 0.6 Fs
Setup Time for a Repeated START tSU.STA 0.6 Fs
Data Hold Time tHD,DAT 0 0.9 Fs
Data Setup Time tSU,DAT 100 ns
SDA Transmitting Fall Time tfISINK P 6mA; tR and tF between 0.3 x VDD
and 0.7 x VDD 100 ns
Setup Time for STOP Condition tSU,STO 0.6 Fs
Pulse Width of Suppressed Spike tSP 0 50 ns
4
MAX44004
Digital Ambient Light Sensor
Typical Operating Characteristics
(VDD = 1.8V, TA = -40NC to +85NC, unless otherwise noted. All devices are 100% production tested at TA = +25NC. Temperature limits
are guaranteed by design.)
SPECTRUM RESPONSE
MAX44004 toc01
WAVE LENGTH (nm)
NORMALIZED OUTPUT
970870770670570470370
20
40
60
80
100
120
0
270 1070
GREEN CHANNEL
RED CHANNEL
CIE CURVE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
vs. TEMPERATURE
MAX44004 toc04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
3.53.32.9 3.12.1 2.3 2.5 2.71.9
1
2
3
4
5
6
7
8
9
10
0
1.7 3.7
TA = -40°C
TA = +25°C
TA = +85°C
TA = +105°C
DARKROOM CONDITION
LUX
10k1k10010
1 100k
SUPPLY CURRENT vs. LUX
MAX44004 toc06
30
0
SUPPLY CURRENT (µA)
5
10
15
20
25
OUTPUT ERROR vs. TEMPERATURE
MAX44004 toc05
TEMPERATURE (°C)
COUNTS (UNITS)
85603510-15
1
2
3
4
5
6
7
8
9
10
11
0
-40 110
DARKROOM CONDITION
VDD = 1.7V TO 3.6V
OUTPUT LOW VOLTAGE
vs. SINK CURRENT
SINK CURRENT (mA)
OUTPUT LOW VOLTAGE (V)
2010515
20
40
60
80
100
120
140
160
180
0
MAX44004 toc07
THE DATA WAS TAKEN ON
THE INTERRUPT PIN
LIGHT SENSITIVITY vs. LUX LEVEL
MAX44004 toc02
REFERENCE METER READING (LUX)
ADC COUNT
900800600 700200 300 400 500100
200
400
600
800
1000
1200
1400
1600
FLUORESCENT
INCANDESCENT
1800
0
0 1000
ALSTIM[1:0] = 00
ALSPGA[1:0] = 10
RADIATION PATTERN
MAX44004 toc03
LUMINOSITY ANGLE (°)
RELATIVE SENSITIVITY (% FROM 0°)
40 60 80
3010
20-60
-50
-40
-30
-20
-10
0-80
-70
10
20
30
40
50
60
70
80
90
100
0
-90 50 70 90
ROTATED WITH AXIS BETWEEN
PIN 1/2/3 AND 4/5/6
5
MAX44004
Digital Ambient Light Sensor
Pin Description
Pin Configuration
PIN NAME FUNCTION
1 VDD Power Supply
2 GND Ground
3 A0 Address Select
4INT Active-Low Interrupt
5 SCL I2C Clock
6 SDA I2C Data
— EP Exposed Pad. EP is internally connected to GND. EP must be connected to GND.
VDD SDA
6
1
GND SCL
5
2
A0 EP 4
3
TOP VIEW
MAX44004
INT
+
6
MAX44004
Digital Ambient Light Sensor
Detailed Description
The MAX44004 is a wide-dynamic-range ALS. The die is
placed inside an optically transparent (ODFN) package. A
photodiode array inside the device converts the light to a
current, which is then processed by low-power circuitry into
a digital value stream. The data is then stored in an output
register that is read by an I2C interface.
Two types of photodiodes are used in the device: a
green photodiode and an infrared photodiode. Ambient
light sensing is accomplished by subtracting the green
ALS photodiode signal and the infrared ALS photodiode
signals, after applying appropriate gains.
The photodiodes are connected to two ADCs. The user
can choose to view either just the green ALS signal, or
just the infrared ALS signal, or the difference of the green
and infrared ALS photodiodes.
Two key features of the device’s analog design are its
low-power design and interrupt pin operation.
The device can operate from a VDD of 1.7V to 3.6V and
consumes just 5FA current. An on-chip programmable
interrupt function eliminates the need to continually poll
the device for data, resulting in a significant power saving.
Ambient-Light Sensing
Ambient-light sensors are designed to detect bright-
ness in the same way as human eyes do. To achieve
this, the light sensor needs to have a spectral sensitivity
that is identical to the photopic curve of the human eye
(Figure 1). Small deviations from the photopic curve
can affect perceived brightness by ambient light
sensors to be wildly different. However, there are practical
difficulties in trying to reproduce the ideal photopic curve
in a small cost-efficient package. The devices instead
use two types of photodiodes (green and infrared) that
have different spectral sensitivities—each of which is
amplified and subtracted on-chip with suitable gain
coefficients so that the most extreme light sources (fluo-
rescent and incandescent) are well matched to a com-
mercial illuminance lux meter.
The photopic curve represents a typical human eye’s
sensitivity to different wavelengths of light. As can be
seen in Figures 1 and 2, its peak sensitivity is at 555nm
(green). The human eye is insensitive to infrared (>
700nm) and ultraviolet (< 400nm) radiation.
Variation between light sources can extend beyond the
visible spectral range—fluorescent and incandescent
light sources, for example—with similar visible brightness
(lux) and can have substantially different IR radiation con-
tent (since the human eye is blind to it). Since this infrared
radiation can be picked up by silicon photodiodes, differ-
ences in light spectra can affect brightness measurement
of light sensors. For example, light sources with high IR
content such as an incandescent bulb or sunlight could
suggest a much brighter environment than our eyes would
perceive them to be. Other light sources, such as fluo-
rescent and LED-based systems, have very little infrared
content. The devices incorporate on-chip compensation
techniques to minimize these effects and still output an
accurate lux response in a variety of lighting conditions.
On-chip, user-programmable green channel and IR
channel gain trim registers allow the light-sensor response
to be tailored to the application, such as when the light
sensor is placed under a dark or colored glass.
Figure 1. MAX44004 Spectral Response Compared to Ideal
Photopic Curve
Figure 2. Green Channel and IR Channel Response at
Identical Gains on a Typical MAX44004
WAVELENGTH (nm)
NORMALIZED RESPONSE
970870770670570470370
20
40
60
80
100
120
0
270 1070
STANDARD ALS
(GREEN-RED)
BLUE: IDEAL
PHOTOPIC CURVE
WAVELENGTH (nm)
NORMALIZED OUTPUT
970870770670570470370
20
40
60
80
100
120
0
270 1070
GREEN CHANNEL
RED CHANNEL
IDEAL PHOTOPIC
CURVE
7
MAX44004
Digital Ambient Light Sensor
Register Description
Table 1 is the register description.
The individual register bits are explained in Table 2.
Default power-up bit states are highlighted in bold.
Interrupt Status 0x00
The PWRON bit in the Status register 0x00, if set,
indicates that a power-on-reset (POR) condition has
occurred, and any user-programmed thresholds may not
be valid anymore. The ALSINTS bit in the Status register
0x00 indicates that an ambient-light-interrupt condition
has occurred. If any of these bits are set to 1, the INT pin
is pulled low and is asserted. See Table 2.
Reading the Interrupt Status register clears the PWRON
and ALSINTS bits if set, AND deasserts the INT pin
(i.e., INT is pulled high by the off-chip pullup resistor).
The ALSINTS bit is disabled and set to 0 if the ALSINTE
interrupt enable bit in Register 0x01 is set to 0.
Table 1. Component List
Table 2. Interrupt Status
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
STATUS
Interrupt Status PWRON ALSINTS 0x00 0x04 R
CONFIGURATION
Main Configuration TRIM MODE[1:0] ALSINTE 0x01 0x24 R/W
Receiver
Configuration ALSTIM[1:0] ALSPGA[1:0] 0x02 0x00 R/W
ADC DATA
ADC High Byte—ALS OFL ALSDATA[13:8] 0x04 0x00 R
ADC Low Byte—ALS ALSDATA[7:0] 0x05 0x00 R
THRESHOLD SET
ALS Upper
Threshold—High Byte UPTHR [13:8] 0x06 0x00 R/W
ALS Upper
Threshold—Low Byte UPTHR[7:0] 0x07 0x00 R/W
ALS Lower
Threshold—High Byte LOTHR[13:8] 0x08 0x00 R/W
ALS Lower
Threshold—Low Byte LOTHR [7:0] 0x09 0x00 R/W
Threshold Persist
Timer ALSPST[1:0] 0x0A 0x00 R/W
Digital Gain Trim of
Green Channel TRIM _GAIN_GREEN [6:0] TRIM_GAIN_IR
[0] 0x0F 0x80 R/TW
Digital Gain Trim of
Infrared Channel TRIM _GAIN_IR [8:1] 0x10 0x80 R/TW
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
Interrupt Status PWRON ALSINTS 0x00 0x04 R
8
MAX44004
Digital Ambient Light Sensor
Ambient Interrupt Status (ALSINTS)
The individual ALSINTS register bits are explained in
Table 3.
Power-On Reset Status (PWRON)
The individual Power-On Reset Status (PWRON) register
bits are explained in Table 4.
Main Configuration 0x01
The individual Main Configuration register bits are
explained in Table 5.
This register is used to set the operating mode of the IC
and to enable interrupt operation of the device.
TRIM
The individual TRIM register bits are explained in Table 6.
The individual register bits are explained in Table 7.
Table 3. Ambient Interrupt Status (ALSINTS)
Table 4. Power-On Reset Status (PWRON)
Table 5. Main Configuration (0x01)
Table 6. TRIM
BIT0 OPERATION
0No interrupt trigger event has occurred.
1
The ambient light intensity has traversed outside the designated window limits defined by the Threshold
registers for greater than persist timer count ALSPST[1:0], or an overflow condition in the ambient-light readings
has occurred. This bit also causes the INT pin to be pulled low. Once set, the only way to clear this bit is to
read this register or to set the ALSINTE bit in register 0x01 to 0.
BIT2 OPERATION
0No interrupt trigger event has occurred.
1
The part went through a power-up event, either because the part was turned on, or because there was a
power-supply voltage glitch. All interrupt threshold settings in the registers have been reset to a default state,
and should be examined. A 1 on this bit also causes the INT pin to be pulled low. Once this bit is set, the only
way to clear this bit is to read this register.
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
Main Configuration TRIM MODE[1:0] ALSINTE 0x01 0x24 R/W
BIT 5 OPERATION
0Use bytes written to TRIM_GAIN_GREEN[6:0] and TRIM_GAIN_IR[8:0] registers to set the fine-trim gain of the
green and IR gain channels.
1Use factory-programmed gains for green and IR channels. Ignore bytes written to TRIM_GAIN_GREEN[6:0] and
TRIM_GAIN_IR[8:0] registers.
9
MAX44004
Digital Ambient Light Sensor
Ambient Interrupt Enable (ALSINTE)
The individual Ambient Interrupt Enable bits are explained
in Table 8.
Receive Configuration 0x02
Table 9 explains Receive Configuration 0x02.
This register sets the ADC integration time and front-end
photodiode circuitry sensitivity (gain). The ADC integra-
tion time also controls the bit resolution of measurements.
ADC conversions of MSB are made first (the device
needs longer conversion times for higher resolution mea-
surements, i.e., LSBs). Use of lower PGA gains helps
expand the full-scale range of the ADC at the expense of
per-LSB sensitivity.
Ambient ADC Conversion Time (ALSTIM)
The 2 bits ALSTIM [1:0] set the integration time for ALS
ADC conversion, as shown in Table 10.
Table 7. Individual Register Bits
Table 8. Ambient Interrupt Enable
Table 10. ALSTIM Integration Time for ADC Conversions
Table 9. Receive Configuration (0x02)
Note: 100–111 are reserved. Do not use.
MODE[1:0] OPERATING MODE OPERATION
00 Shutdown Analog circuits are shut down, but digital register retains values.
01 ALS G-IR Standard ALS mode—stores difference between green and infrared channel
readings.
10 ALS G ALS green channel only.
11 ALS IR Infrared channel only.
BIT0 OPERATION
0The ALSINTS bit remains unasserted; ALS channel readings are not compared with interrupt thresholds.
1
Detection of an ambient-light interrupt event triggers a hardware interrupt (INT pin is pulled low) and sets the
ALSINTS bit (register 0x00, B0). ALS channel readings are compared with ALS interrupt threshold settings and
ALS persist timer.
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
Receive Configuration ALSTIM[1:0] ALSINTE 0x02 0x00 R/W
ALSTIM[1:0] INTEGRATION TIME
(ms)
FULL-SCALE
ADC COUNTS BIT RESOLUTION RELATIVE LSB SIZE
00 100 16,384 14 1x
01 25 4096 12 4x
10 6.25 1024 10 16x
11 1.5625 256 8 64x
10
MAX44004
Digital Ambient Light Sensor
Ambient Light Measurement Gain (ALSPGA)
The 2 bits ALSPGA [1:0] set the gain of the ambient-light
sensing measurement according to Table 11.
ALS Data Register (0x04, 0x05)
The 2 bytes here (ALSDATA[13:0]) hold the results of
ALS signal conversion. The resolution and bit length of
the result is controlled by the value of the ALSTIM[1:0]
and ALSPGA[1:0] bits. The result is always right justified
in the two registers, and the unused high bits are zero.
See Table 12.
OFL indicates an overflow condition on the ALS chan-
nel. If this occurs, set the ALS range (ALSPGA[1:0]) to a
higher range (lower sensitivity). If the OFL bit is set to 1
(there is an overflow condition), and the ALSINTE bit is
set to 1 (enabled), then the ALSINTS bit is set to 1 and
the INT pin is pulled low.
The data in this register could be either the green chan-
nel, infrared channel, or ALS readings (green channel,
infrared channel readings), depending on the mode
selected by the user.
Internal update of these two registers is disabled dur-
ing I2C read operations to ensure proper data handoff
between the ADC and the I2C registers. Update of the
I2C registers is resumed once the master sends a STOP
command. Therefore, when reading the 2 bytes of this
register, the master should NOT send a STOP command
between the 2-byte reads. Instead, a Repeated START
command should be used. The exact read sequence
using the Repeated START command is shown in the I2C
Serial Interface section.
Table 12. ALS Data Register (0x04, 0x05)
Table 11. Ambient Light Measurement Gain (ALSPGA)
Table 13. ALS Interrupt Threshold Registers (0x06–0x09)
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
ADC High Byte—ALS OFL ALSDATA[13:8] 0x04 0x00 R
ADC Low Byte—ALS ALSDATA[7:0] 0x05 0x00 R
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
ALS Upper Threshold—
High Byte UPTHR [13:8] 0x06 0x00 R/W
ALS Upper Threshold—
Low Byte UPTHR [7:0] 0x07 0x00 R/W
ALS Lower Threshold—
High Byte LOTHR[13:8] 0x08 0x00 R/W
ALS Lower Threshold—
Low Byte LOTHR [7:0] 0x09 0x00 R/W
ALSPGA[1:0] LUX/LSB RELATIVE LSB SIZE
00 0.03125 1x
01 0.125 4x
10 0.5 16x
11 4 128x
11
MAX44004
Digital Ambient Light Sensor
ALS Interrupt Threshold Registers
(0x06-0x09)
ALS Interrupt Threshold registers (0x06-0x09) are
explained in Table 13.
The ALS upper threshold and ALS lower threshold
(UPTHR[13:0] and LOTHR[13:0]) set the window limits
that are used to trigger an ALS interrupt. It is important
to set these values according to the selected bit resolu-
tion/integration time chosen for the ALS measurement
based on the ALSTIM[1:0] and ALSPGA[1:0] settings.
The upper 2 bits are always ignored. If the INTE bit is set,
and the lux level is greater or lower than the respective
thresholds for a period greater than that defined by the
ALSPST persist time, the INTS bit in the Status register
are set and the INT pin is pulled low.
Threshold Persist Timer Register (0x0A)
The MAX44004 incorporates a persist function that allows
users to set the number of consecutive triggers before inter-
rupt. The Threshold Persist Timer register is explained in
Table 14.
ALSPST[1:0] sets one of four persist values that controls
how readily the interrupt logic reacts to a detected event.
This feature is useful in reducing false or nuisance interrupts
due to optical noise/minor disturbances. See Table 15.
When ALSPST[1:0] is set to 00, and the ALSINTE bit is set
to 1, the first time an ALS interrupt event is detected, the
ALSINTE interrupt bit is set and the INT pin goes low. If
ALSPST[1:0] is set to 01, then four consecutive interrupt
events must be detected on four consecutive measure-
ment cycles. Similarly, if ALSPST[1:0] is set to 10 or 11,
then 8 or 16 consecutive interrupts must be detected
before the INT pin is pulled low. If there is an intervening
measurement cycle where no interrupt is detected, then
the count is reset to zero.
Digital Gain Trim Registers (0x0F, 0x10)
Digital gain trim registers are described in Table 16.
TRIM_GAIN_GREEN [6:0] is used to modify the gain of
the green channel.
TRIM_GAIN_IR [8:0] is used to modify the gain of the IR
channel.
To tell the part to use the values written to this register,
set the TRIMB bit to 0 in the Main Configuration register
after writing new values to these registers.
Table 14. Threshold Persist Timer Register (0x0A)
Table 15. APSPT [1:0]
Table 16. Digital Gain Trim Registers (0x0F, 0x10)
Note 1: Values read from the Trim_Gain registers are the complement of the written value. This is true for reading both the factory-
programmed values and the customer-programmed values.
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
Threshold Persist Timer ALSPST[1:0] 0x0A 0x00 R/W
ALSPST[1:0] NO. OF CONSECUTIVE TRIGGERS BEFORE AN INTERRUPT
00 1
01 2
10 4
11 16
REGISTER BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 REGISTER
ADDRESS
POWER-
ON RESET
STATE
R/W
Digital Gain Trim of
Green Channel TRIM _GAIN_GREEN [6:0] TRIM_GAIN_IR 0x0F 0x80 R/TW
Digital Gain Trim of
Infrared Channel TRIM _GAIN_IR [8:1] 0x10 0x80 R/TW
12
MAX44004
Digital Ambient Light Sensor
Applications Information
Ambient-Sensing Applications
Typical applications involve placing the device behind a
glass with a small semitransparent window above it. Use
the photodiode-sensitive area as shown in Figure 3 to
properly position the window above the part.
The part comes equipped with internal gain trim regis-
ters for the green and IR ALS photodiodes. By suitably
choosing the gains for these channels, accurate ambient
light readings can be generated in all lighting conditions
regardless of the type of glass/ink under which the part
is used. This is especially useful for black glass applica-
tions where, for cosmetic reasons, the part is placed
behind a black film to hide its presence, and this film has
the peculiar property of attenuating most ambient light,
but passing through IR radiation.
In standard ALS mode, the green channel and infrared
channel readings are internally subtracted. Since one is
observing only the difference is observed in two separate
ADC measurements, wrong readings can be obtained if
one of the channels becomes saturated, while the other
channel continues to rise. Since the green photodiode
also picks up a lot of the infrared signal, this saturation
can occur earlier than before the maximum expected
full-scale lux, depending on lighting conditions. For exam-
ple, under incandescent light, there is a lot more infrared
optical power than in the visible spectral range. In these
situations, the green channel can saturate much earlier
than 511 lux in the most sensitive range. To assist the
user in detecting these conditions, an OFL bit is provided
that alerts the user of an overrange condition. This bit
also triggers an ALS interrupt if it has been enabled.
Typical Operating Sequence
The typical operating sequence for the master to com-
municate to the device on first power-up is shown below:
1) Setup:
a) Read the Interrupt Status register (0x00) to
confirm only the PWRON bit is set. This also clears
a hardware interrupt.
b) Set Threshold and Persist Timer registers (regis-
ters 0x06–0x0C).
c) Write 0x00 to the Receiver Configuration register
(register 0x02) to set the ALS sensor in the highest
gain setting, and in 14-bit modes of operation.
d) Write 0x05 to the Main Configuration register
(register 0x01) to set the part in ALS mode and to
enable ALS interrupt.
e) Set new green channel gains and IR channel
gains, if necessary, to customize ALS operation for
application conditions. Ensure the TRIM bit is set to
0 when not using default factory-trim settings.
2) Wait for interrupt.
3) On interrupt:
a) Read the Interrupt Status register (0x00) to confirm
the device to be the source of interrupt, and to
check for type of interrupt. This should clear the
hardware interrupt on the part, if set.
b) If an ALS interrupt has occurred, read ALS ADC
registers (register 0x04–0x05) to confirm if data is
valid (i.e., OFL = 0), and take appropriate action
(e.g., set new backlight strength). Set new ALS
thresholds, if necessary.
c) Return to Step 2.
Figure 3. MAX44004 Photodiode Location
MAX44004
TOP VIEW
2mm
2mm
0.753mm
1.226mm
0.39mm
0.492mm
A0 3
1
VCC
25SCL
6 SDA
GND
PHOTO-
DIODE
4INT
13
MAX44004
Digital Ambient Light Sensor
I2C Serial Interface
The device features an I2C/SMBusK-compatible, 2-wire
serial interface consisting of a serial data line (SDA) and
a serial clock line (SCL). SDA and SCL facilitate com-
munication between the device and the master at clock
rates up to 400kHz. Figure 4 shows the 2-wire interface
timing diagram. The master generates SCL and initiates
data transfer on the bus. A master device writes data to
the device by transmitting the proper slave address fol-
lowed by the register address and then the data word.
Each transmit sequence is framed by a START (S) or
Repeated START (Sr) condition and a STOP (P) condi-
tion. Each word transmitted to the device is 8 bits long
and is followed by an acknowledge clock pulse. A master
reading data from the device transmits the proper slave
address followed by a series of nine SCL pulses. The IC
transmits data on SDA in sync with the master-generated
SCL pulses. The master acknowledges receipt of each
byte of data. Each read sequence is framed by a START
or Repeated START condition, a not acknowledge, and a
STOP condition. SDA operates as both an input and an
open-drain output. A pullup resistor, typically greater than
500I, is required on the SDA bus. SCL operates as only
an input. A pullup resistor, typically greater than 500I, is
required on SCL if there are multiple masters on the bus,
or if the master in a single-master system has an open-
drain SCL output. Series resistors in line with SDA and
SCL are optional. Series resistors protect the digital inputs
of the device from high-voltage spikes on the bus lines,
and minimize crosstalk and undershoot of the bus signal.
Bit Transfer
One data bit is transferred during each SCL cycle. The
data on SDA must remain stable during the high period
of the SCL pulse. Changes in SDA while SCL is high are
control signals. See the START and STOP Conditions
section. SDA and SCL idle high when the I2C bus is not
busy.
Table 17. Slave Address
Figure 4. 2-Wire Interface Timing Diagram
SMBus is a trademark of Motorola Corp.
A0 SLAVE ADDRESS
GND 0x94
VDD 0x96
SCL
SDA
START
CONDITION
STOP
CONDITION
REPEATED
START CONDITION
START
CONDITION
tHD, STA
tSU, STA tHD, STA tSP
tBUF
tSU, STO
tLOW
tSU, DAT
tHD, DAT
tHIGH
tRtF
14
MAX44004
Digital Ambient Light Sensor
START and STOP Conditions
SDA and SCL idle high when the bus is not in use. A mas-
ter initiates communication by issuing a START condition.
A START condition is a high-to-low transition on SDA with
SCL high. A STOP condition is a low-to-high transition on
SDA while SCL is high (Figure 5). A START condition from
the master signals the beginning of a transmission to the
device. The master terminates transmission, and frees
the bus by issuing a STOP condition. The bus remains
active if a Repeated START condition is generated
instead of a STOP condition.
Early STOP Conditions
The device recognizes a STOP condition at any point
during data transmission, except if the STOP condition
occurs in the same high pulse as a START condition. For
proper operation, do not send a STOP condition during
the same SCL high pulse as the START condition.
Acknowledge
The acknowledge bit (ACK) is a clocked 9th bit that the
device uses to handshake receipt of each byte of data
when in write mode (Figure 6). The device pulls down
SDA during the entire master-generated 9th clock pulse
if the previous byte is successfully received. Monitoring
ACK allows for detection of unsuccessful data transfers.
An unsuccessful data transfer occurs if a receiving
device is busy or if a system fault has occurred. In the
event of an unsuccessful data transfer, the bus master
may retry communication. The master pulls down SDA
during the 9th clock cycle to acknowledge receipt of data
when the device is in read mode. An acknowledge is sent
by the master after each read byte to allow data transfer
to continue. A not acknowledge is sent when the master
reads the final byte of data from the device, followed by
a STOP condition.
Write Data Format
A write to the device includes transmission of a START
condition, the slave address with the R/W bit set to 0, 1
byte of data to configure the internal register address
pointer, 1 or more bytes of data, and a STOP condition.
Figure 7 illustrates the proper frame format for writing 1
byte of data to the device. Figure 8 illustrates the frame
format for writing n bytes of data to the device.
The slave address with the R/W bit set to 0 indicates that
the master intends to write data to the device. The device
acknowledges receipt of the address byte during the
master-generated 9th SCL pulse.
Figure 7. Writing 1 Byte of Data to the MAX44004
Figure 5. START, STOP, and Repeated START Conditions Figure 6. Acknowledge
SCL
SDA
SS
rP
1
SCL
START
CONDITION
SDA
289
CLOCK PULSE FOR
ACKNOWLEDGMENT
ACKNOWLEDGE
NOT ACKNOWLEDGE
A
0SLAVE ADDRESS REGISTER ADDRESS DATA BYTE
ACKNOWLEDGE FROM MAX44004
R/W 1 BYTE
ACKNOWLEDGE FROM MAX44004
ACKNOWLEDGE FROM MAX44004
B1 B0B3 B2B5 B4B7 B6
S AA P
15
MAX44004
Digital Ambient Light Sensor
The second byte transmitted from the master configures
the device’s internal register address pointer. The pointer
tells the device where to write the next byte of data. An
acknowledge pulse is sent by the device upon receipt of
the address pointer data.
The third byte sent to the device contains the data that
is written to the chosen register. An acknowledge pulse
from the device signals receipt of the data byte.
Read Data Format
Send the slave address with the R/W bit set to 1 to initi-
ate a read operation. The device acknowledges receipt
of its slave address by pulling SDA low during the 9th
SCL clock pulse. A start command followed by a read
command resets the address pointer to register 0x00.
The first byte transmitted from the device is the contents of
register 0x00. Transmitted data is valid on the rising edge
of the master-generated serial clock (SCL). The address
pointer does not autoincrement after each read data
byte. A STOP condition can be issued after any number
of read data bytes. If a STOP condition is issued followed
by another read operation, the first data byte to be read is
from register 0x00 and subsequent reads autoincrement
the address pointer until the next STOP condition.
The address pointer can be preset to a specific register
before a read command is issued. The master presets
the address pointer by first sending the device’s slave
address with the R/W bit set to 0 followed by the register
address. A Repeated START condition is then sent, fol-
lowed by the slave address with the R//W bit set to 1. The
device transmits the contents of the specified register.
Attempting to read from register addresses higher than
0xFF results in repeated reads of 0xFF. Note that 0xF6 to
0xFF are reserved registers.
The master acknowledges receipt of each read byte during
the acknowledge clock pulse. The master must acknowl-
edge all correctly received bytes except the last byte. The
final byte must be followed by a not acknowledge from the
master and then a STOP condition. Figure 8 illustrates the
frame format for reading 1 byte from the device. Figure 9
illustrates the frame format for reading two registers con-
secutively without a STOP condition in between reads.
Figure 9. Reading Two Registers Consecutively Without a STOP Condition in Between Reads
Figure 8. Reading 1 Byte of Data from the MAX44004
ACKNOWLEDGE FROM MAX44004
1 BYTE
ACKNOWLEDGE FROM MAX44004
NOT ACKNOWLEDGE FROM MASTER
AA Sr
NOT ACKNOWLEDGE FROM MASTER
A
0
ACKNOWLEDGE FROM MAX44004
R/W
SA
R/WREPEATED START
Sr 1SLAVE ADDRESS REGISTER ADDRESS 1 SLAVE ADDRESS DATA BYTE 1
ACKNOWLEDGE FROM MAX44004
1 BYTE
ACKNOWLEDGE FROM MAX44004
AA AP
0
ACKNOWLEDGE FROM MAX44004
R/W
AS
R/WREPEATED START
Sr 1SLAVE ADDRESS REGISTER ADDRESS 2 SLAVE ADDRESS DATA BYTE 2
ACKNOWLEDGE FROM MAX44004
1 BYTE
ACKNOWLEDGE FROM MAX44004
NOT ACKNOWLEDGE FROM MASTER
AA P
A
0
ACKNOWLEDGE FROM MAX44004
R/W
SA
R/WREPEATED START
Sr 1SLAVE ADDRESS REGISTER ADDRESS SLAVE ADDRESS DATA BYTE
16
MAX44004
Digital Ambient Light Sensor
Ordering Information Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PART TEMP RANGE PIN-PACKAGE
MAX44004GDT+ -40NC to +105NC6 OTDFN
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
6 OTDFN D622N+2 21-0490 90-0344
+Denotes a lead(Pb)-free/RoHS-compliant package.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 160 Rio Robles Drive, San Jose, CA 95134 408-601-1000 17
© 2012 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX44004
Digital Ambient Light Sensor
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 5/12 Initial release —
