Industry's Lowest-Power Ambient Light Sensor With ADC: General Description Features
Industry's Lowest-Power Ambient Light Sensor With ADC: General Description Features
Industry's Lowest-Power Ambient Light Sensor With ADC: General Description Features
AVAILAB
LE MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
General Description Features
The MAX44009 ambient light sensor features an I2C S Wide 0.045 Lux to 188,000 Lux Range
digital output that is ideal for a number of portable appli- S Small, 2mm x 2mm x 0.6mm UTDFN-Opto
cations such as smartphones, notebooks, and industrial
sensors. At less than 1µA operating current, it is the S VCC = 1.7V to 3.6V
lowest power ambient light sensor in the industry and S ICC = 0.65µA Operating Current
features an ultra-wide 22-bit dynamic range from 0.045 S -40NC to +85NC Temperature Range
lux to 188,000 lux.
S Device Address Options
Low-light operation allows easy operation in dark-glass 1001 010x and 1001 011x
applications.
The on-chip photodiode’s spectral response is optimized
to mimic the human eye’s perception of ambient light
and incorporates IR and UV blocking capability. The
adaptive gain block automatically selects the correct lux
range to optimize the counts/lux.
The IC is designed to operate from a 1.7V to 3.6V sup-
ply voltage range and consumes only 0.65µA in full
operation. It is available in a small, 2mm x 2mm x 0.6mm
UTDFN-Opto package.
SDA
16-BIT
VISIBLE +IR ADC SCL
I2C
PHOTODIODE AO
6-BIT RANGE DIGITAL
CDR, TIM SIGNAL
INT
CONTROL PROCESSING
MAX44009
16-BIT
N
ADC
IR
PHOTODIODE
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com. 19-5719; Rev 0; 1/11
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
ABSOLUTE MAXIMUM RATINGS
INT to GND................................................ -0.3V to (VCC + 0.3V) Continuous Input Current into Any Terminal.................... Q20mA
All Other Pins to GND..............................................-0.3V to +4V Continuous Power Dissipation
INT Short-Circuit Current Duration......................................... 10s 6 UTDFN-Opto (derate 11.9mW/NC above +70NC)......953mW
All Other Pins Short-Circuit Current Duration.............Continuous Operating Temperature Range........................... -40NC to +85NC
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation 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
(VCC = 1.8V, TMIN to TMAX = -40NC to +85NC, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OPTICAL CHARACTERISTICS
Maximum Lux Sensitivity Fluorescent light 0.045 Lux/LSB
Saturation Ambient Lux Level Sunlight 188,000 Lux
Green LED 538nm response,
Total Error TE 15 %
TA = +25NC (Note 2)
Light Source Matching Fluorescent/incandescent light 10 %
Ultraviolet Transmittance at
UVR TA = +25NC (Note 3) 1.2 %
363nm
Dark Level Count 0LUX 0 lux, TA = +25NC, 800ms range 0 0.045 Lux
Maximum Signal Integration
Has 50/60Hz rejection 800 ms
Time
Automatic mode, has 50/60Hz rejection 100
Minimum Signal Integration Time ms
Manual mode only 6.25
100ms range, TA = +25NC 99.6 100 100.4
ADC Conversion Time ACT ms
100ms range 97 103 107
POWER SUPPLY
Power-Supply Voltage VCC Guaranteed by TE test 1.7 3.6 V
TA = +25NC, 90 lux, I2C inputs inactive 0.65 1.2
Power-Supply Current ICC FA
TA = -40NC to +85NC 1.6
DIGITAL I/O CHARACTERISTICS
Output Low Voltage SDA, INT VOL ISINK = 6mA 0.06 0.4 V
INT Leakage Current TA = +25NC 0.01 20 nA
SCL, SDA, A0 Input Current IIH, IIL TA = +25NC 0.01 20 nA
0.3 x
I2C Input Low Voltage VIL_I2C SDA, SCL V
VCC
0.7 x
I2C Input High Voltage VIH_I2C SDA, SCL V
VCC
Address Input Low Voltage VIL_A0 A0 0.3 V
VCC -
Address Input High Voltage VIH_A0 A0 V
0.3V
Input Capacitance 3 pF
2 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 1.8V, TMIN to TMAX = -40NC to +85NC, unless otherwise noted.) (Note 1)
Note 1: All devices are 100% production tested at TA = +25NC. Temperature limits are guaranteed by design.
Note 2: Green 538nm LED chosen for production is such that the IC responds to 100 lux fluorescent light with 100 lux.
Note 3: With respect to green LED 538nm response.
Note 4: A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL of the SCL signal) to bridge
the undefined region of SCL’s falling edge.
Maxim Integrated 3
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Typical Operating Characteristics
(VCC = 1.8V, default power-up setting, unless otherwise noted.)
MAX44009 toc01
MAX44009 toc02
90
70
80
60
60 50
40
40
30
CIE 20 AUTO MODE,
20 INCANDESCENT LAMP
10
0 0
300 400 500 600 700 800 900 1000 -90 -60 -30 0 30 60 90
WAVELENGTH (nm) LUMINOSITY ANGLE (°)
MAX44009 toc04
160 0 LUX AND 100 LUX, CONT = 1
MAX44009 toc03
140 1.2
INCANDESCENT
SUPPLY CURRENT (µA)
80
0.6
100 LUX, CONT = 0
60
0.4
40
0.2 AUTO MODE,
20 FLUORESCENT LAMP
FLUORESCENT
0
0 1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6
300 400 500 600 700 800 900 1000
SUPPLY VOLTAGE (V)
WAVELENGTH (nm)
OUTPUT CODE ERROR vs. SUPPLY VOLTAGE SUPPLY CURRENT vs. TEMPERATURE
1.10 1.2
MAX44009 toc05
MAX44009 toc06
OUTPUT CODE ERROR (RATIO FROM 1.8V)
1.08
VCC = 3.3V
1.0
1.06
SUPPLY CURRENT (µA)
1.04
0.8
1.02
1.00 0.6 VCC = 1.8V
0.98 VCC = 2.5V
0.4
0.96
0.94 50 LUX AND 300 LUX 100 LUX
0.2
AUTO MODE, AUTO MODE,
0.92
FLUORESCENT LAMP FLUORESCENT LAMP
0.90 0
1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6 -40 -15 10 35 60 85
SUPPLY VOLTAGE (V) TEMPERATURE (°C)
4 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Typical Operating Characteristics (continued)
(VCC = 1.8V, default power-up setting; unless otherwise noted.)
MAX44009 toc07
MAX44009 toc08
120
MAX44009 toc09
FLUORESCENT 110
3.0 300
LAMP
100
OUTPUTS READING (LUX)
SUPPLY CURRENT (µA)
2.5 250 90
SDA
80
2.0 200 70
VOL (mV)
INCANDESCENT 60 INT
1.5 150
LAMP 50
1.0 100 40
30
0.5 50 20
SUNLIGHT 10
0 0
0
100 1k 10k 100k 0 50 100 150 200 250 300
0 1 2 3 4 5 6 7 8 9 10
LUX READING (LUX) REFERENCE METER READING (LUX)
ISINK (mA)
Pin Configuration
TOP VIEW
SDA SCL INT
6 5 4
MAX44009
EP
+
1 2 3
VCC GND A0
UTDFN-Opto
(2mm x 2mm)
Pin Description
PIN NAME PIN DESCRIPTION
1 VCC Power Supply
2 GND Ground
3 A0 Address Select. Pull high to select address 1001 011x or low to select address 1001 010x.
4 INT Interrupt Output. Use an external pullup resistor.
5 SCL I2C Clock Bus
6 SDA I2C Data Bus
— EP Exposed Pad. Connect EP to ground.
Maxim Integrated 5
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Detailed Description The default integration time of the ADC is 100ms, giving
it inherent rejection of 50Hz and 60Hz ripple common in
The MAX44009 is an ambient light sensor with integrated certain line-powered light sources.
photodiode and ADC with an I2C digital interface. To
measure ambient light, the die is placed inside an opti- Human Eye CIE Curve and
cally transparent (UTDFN-Opto) package. A photodi- Different Light Sources
ode inside the IC converts the light to a current that is The IC is designed to detect brightness in the same way
then processed by low-power circuitry into a digital bit as human eyes do. To achieve this, the sensor needs to
stream. This is digitally processed and stored in an out- have a spectral sensitivity that is similar to that of human
put register that is read by an I2C interface. An on-chip eyes. Figure 1 shows the spectral sensitivity of the IC
programmable interrupt function eliminates the need for and the human eye (CIE curve).
continually polling the device for data and results in sig- As can be seen, the human eye has its peak sensitivity
nificant power saving. at 555nm (green), while that of blue (~470nm) and red
A package-level optical filter prevents ultraviolet (~630nm) is much lower. The human eye also is blind to
and infrared from reaching the photodiode. Its opti- infrared (> 700nm) and ultraviolet (< 400nm) radiation.
cal response is also designed to match the spectral Light sources can have similar visible brightness (lux), but
response of the human eye. A second photodiode array, different IR radiation content (because the human eye is
sensitive primarily to the infrared spectrum, is then used blind to it). The differences in the light spectra affect bright-
to match flourescent and incandescent light response ness measurement because some of this infrared radiation
from the part. is picked up by silicon photodiodes. For example, light
sources with high IR content, such as an incandescent
Two key features of the IC analog design are its ultra-low bulb or sunlight, would suggest a much brighter environ-
current consumption (typically 0.65µA) and an extremely ment than our eyes would perceive them to be. Other light
wide dynamic light range that extends from 0.045 lux to sources, such as fluorescent and LED-based systems,
188,000 lux—more than a 4,000,000 to 1 range. The on- have very little infrared content. The IC exhibits good IR
chip autoranging scheme requires no user intervention rejection and internal IR compensation scheme to minimize
for the gain-range setting. these effects and give an accurate lux response.
The IC can be customized to operate at enhanced sen-
sitivity in applications where it needs to operate behind
a dark glass.
120
100
MAX44009 RESPONSE
NORMALIZED RESPONSE
80
60
40
CIE
20
0
300 400 500 600 700 800 900 1000
WAVELENGTH (nm)
6 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Register and Bit Descriptions
Table 1. Register Map
BIT POWER-ON
REGISTER
REGISTER RESET R/W
ADDRESS
7 6 5 4 3 2 1 0 STATE
STATUS
Interrupt Status — — — — — — — INTS 0x00 0x00 R
Interrupt Enable — — — — — — — INTE 0x01 0x00 R/W
CONFIGURATION
Configuration CONT MANUAL — — CDR TIM[2:0] 0x02 0x03 R/W
LUX READING
Lux High Byte E3 E2 E1 E0 M7 M6 M5 M4 0x03 0x00 R
Lux Low Byte — — — — M3 M2 M1 M0 0x04 0x00 R
THRESHOLD SET
Upper Threshold
UE3 UE2 UE1 UE0 UM7 UM6 UM5 UM4 0x05 0xFF R/W
High Byte
Lower Threshold
LE3 LE2 LE1 LE0 LM7 LM6 LM5 LM4 0x06 0x00 R/W
High Byte
Threshold Timer T7 T6 T5 T4 T3 T2 T1 T0 0x07 0xFF R/W
Maxim Integrated 7
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Interrupt events set the INTS bit (register 0x00, bit 0) and the INT pin only if the INTE bit is set to 1. If the INTE bit is set
(interrupt is enabled) and the interrupt condition is triggered, then the INT pin is pulled low (asserted) and the INTS bit
in the Interrupt Status register is set to 1. See Table 3.
Configuration 0x02
REGISTER
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
ADDRESS
CONT MANUAL — — CDR TIM[2:0] 0x02
Continuous Mode
Table 4. Continuous Mode Register
BIT 7 OPERATION
Default mode. The IC measures lux intensity only once every 800ms regardless of integration time. This
0
mode allows the part to operate at its lowest possible supply current.
Continuous mode. The IC continuously measures lux intensity. That is, as soon as one reading is finished, a
new one begins. If integration time is 6.25ms, readings are taken every 6.25ms. If integration time is 800ms,
1
readings are taken every 800ms. In this mode, the part consumes slightly higher power than in the default
mode.
Note: Continuous mode is independent of the manual configuration mode setting.
Manual Configuration Mode
In automatic mode (MANUAL = 0), reading the contents of TIM[2:0] and CDR bits reflects the automatically generated
values from an internal timing register and are read-only. In manual mode (MANUAL = 1), the contents of TIM[2:0] and
CDR bits can be modified by the users through the I2C bus.
8 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Integration Timer Bits (TIM[2:0])
The TIM[2:0] bits can be used to program the signal integration time.
In automatic mode (MANUAL = 0), integration time is automatically selected by the on-chip algorithm to be either
100ms/200ms/400ms/800ms. In manual mode, integration time can be varied by the user all the way from 6.25ms to
800ms. See Table 7.
Bits in Lux High-Byte register 0x03 give the 4 bits of exponent E3:E0 and 4 most significant bits of the mantissa byte
M7:M4, and represent the lux reading of ambient light. The remaining 4 bits of the mantissa byte M3:M0 are in the Lux
Low-Byte register 0x04 and enhance resolution of the lux reading from the IC.
Exponent (E[3:0]): Exponent bits of the lux reading (0000 to 1110). Note: A reading of 1111 represents an overrange
condition.
Mantissa (M[7:4]): Four most significant bits of mantissa byte of the lux reading (0000 to 1111).
Lux = 2(exponent) x mantissa x 0.72
Exponent = 8xE3 + 4xE2 + 2xE1 + E0
Mantissa = 8xM7 + 4xM6 + 2xM5 + M4
A code of 0000 0001 calculates to be 0.72 lux.
A code of 1110 1111 calculates to be 176,947 lux.
A code of 1110 1110 calculates to be 165,151 lux.
Update of the contents of this register is internally disabled during I2C read operations to ensure proper data transfer
between internal ADC and I2C registers. Update of I2C registers is resumed when the master sends a STOP command.
If user wants to read both the Lux High-Byte register 0x03 and Lux Low-Byte register 0x04, then the master should not
send a STOP command between the reads of the two registers. Instead a Repeated START command should be used.
This ensures accurate data is obtained from the I2C registers (by disabling internal updates during the read process).
Maxim Integrated 9
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Lux Low-Byte Register 0x04
REGISTER
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
ADDRESS
— — — — M3 M2 M1 M0 0x04
Bits in Lux Low-Byte register 0x04 give the 4 least significant bits of the mantissa byte representing the lux reading
of ambient light. Combined with the Lux High-Byte register 0x03, it extends the resolution and dynamic range of lux
measurements of the IC.
E3–E0: Exponent bits of lux reading
M7–M0: Mantissa byte of lux reading
Lux = 2(exponent) x mantissa x 0.045
Exponent = 8xE3 + 4xE2 + 2xE1 + E0
Mantissa = 128xM7 + 64xM6 + 32xM5 + 16xM4 + 8xM3 + 4xM2 + 2xM1 + M0
Combining contents of register 0x03 and 0x04:
A code of 0000 0000 0001 calculates to be 0.045 lux.
A code of 0000 0001 0000 calculates to be 0.72 lux.
A code of 0001 0001 0001 calculates to be 0.765 lux.
A code of 1110 1111 1111 calculates to be 188,006 lux.
A code of 1110 1111 1110 calculates to be 187,269 lux.
The Lux High-Byte 0x03 and Lux Low-Byte 0x04 register updates are internally disabled at the start of a valid address
transmission from the master. Updating reinitiates at the next valid STOP condition. This prevents erroneous readings
in the event an update occurs between readings of registers 0x03 and 0x04.
Update of the contents of this register is internally disabled during I2C read operations to ensure proper data transfer
between internal ADC and I2C registers. Update of I2C registers is resumed when the master sends a STOP command.
If the user wants to read both the Lux High-Byte register 0x03 and Lux Low-Byte register 0x04, then the master should
not send a STOP command between the reads of the two registers. Instead a Repeated START command should be
used. This ensures accurate data is obtained from the I2C registers (by disabling internal updates during the read
process).
Upper Threshold High-Byte Register 0x05
REGISTER
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
ADDRESS
UE3 UE2 UE1 UE0 UM7 UM6 UM5 UM4 0x05
The Upper Threshold High-Byte register exponent with the four most significant bits of the mantissa sets the upper trip
level for interrupt functionality. This upper limit is relevant only if the INTE bit in the interrupt enable register is set. If the
lux level is greater than this light level for a time greater than that specified in the Threshold Timer register, the INTS
bit in the Interrupt Status register is set and the INT pin is pulled low.
Mantissa (UM[7:4]): Four most significant bits of mantissa upper threshold
Exponent (UE[3:0]): Exponent bits upper threshold
Upper lux threshold = 2(exponent) x mantissa x 0.045
Exponent = 8xUE3 + 4xUE2 + 2xUE1 + UE0
Mantissa = 128xUM7+ 64xUM6+ 32xUM5 + 16xUM4 +15
10 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Lower Threshold High-Byte Register 0x06
REGISTER
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
ADDRESS
LE3 LE2 LE1 LE0 LM7 LM6 LM5 LM4 0x06
The Lower Threshold High-Byte register exponent with the four most significant bits of the mantissa sets the lower trip
level for interrupt functionality. This lower limit is relevant only if the INTE bit in the Interrupt Enable register is set. If the
lux level is below this light level for a time greater than that specified in the Threshold Timer register, the INTS bit in the
Interrupt Status register is set and the INT pin is pulled low.
Mantissa (LM[7:4]): Four most significant bits of mantissa lower threshold
Exponent (LE[3:0]): Exponent bits lower threshold
Lower lux threshold = 2(exponent) x mantissa x 0.045
Exponent = 8xLE3 + 4xLE2 + 2xLE1 + LE0
Mantissa = 128xLM7 + 64xLM6 + 32xLM5 + 16xLM4
Threshold Timer Register 0x07
REGISTER
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
ADDRESS
T7 T6 T5 T4 T3 T2 T1 T0 0x07
If the INTE bit = 1 and the ambient light level exceed either threshold limit for a time longer than that specified by the
Threshold Timer register, then the INTS bit is set to 1 and the INT pin is pulled low.
The value in this register sets the time used to control this delay. A value of 0x00 in this register (with INTE bit = 1 in the
Interrupt Enable register) configures the IC to assert the interrupt pin as soon as the light level exceeds either threshold.
Time delay = (128xT7 + 64xT6 + 32xT5 + 16xT4 + 8xT3 + 4xT2 + 2xT1 + T0) x 100ms.
Maxim Integrated 11
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
The count is multiplied by 0.045, which is the LSB. The mantissa is an 8-bit number ranging from 0000 0000
to 1111 0000 (zero to 240).
Because of the logarithmic nature of autoranging cir-
cuitry implemented on the IC, resolution of ambient lux Upper lux threshold = (2(exponent) x mantissa) x 0.045
readings scale with the absolute measurement. Table 8 The exponent is a 4-bit number ranging from 0000 to
lists the lux resolution and the lux ranges obtained from 1110 (zero to 14).
the IC. The mantissa is an 8-bit number ranging from 0000 1111
to 1111 1111 (15 to 255).
Interrupt Settings In the auto range mode (MANUAL = 0), the upper thresh-
Interrupt is enabled by setting bit 0 of register 0x01 to old and lower threshold bytes must be in a format that
1 (see Table 1). INT, an open-drain output, pulls low matches the format used in register 0x03, the lux high
when an interrupt condition occurs (lux readings that byte. There are only two rules to follow:
exceed threshold limits for a period greater than that set
by the Threshold Timer register). The interrupt status bit • For very low lux levels (light levels below 11.5 lux),
is cleared automatically if register 0x00 is read or if the set the exponent to zero, the code is merely: 0000
interrupt is disabled (INTE = 0). MMMM where the 4 zeroes are the exponent, and the
MMMM represent the 4 most significant bits of the
Threshold Register Data Format mantissa.
The IC’s interrupt circuit requires the upper and lower • For all other conditions (light levels above 11.5 lux)
limit thresholds to be in a specific format to be properly where the exponent is not zero, the format is: EEEE
interpreted. The upper and lower limits, from registers 1MMM. Notice that bit M7 (most significant bit) must
0x05 and 0x06 must match the lux high-byte format. This always be a 1. The other bits do not matter. EEEE is
consists of the 4 bits of the exponent and the 4 most sig- limited to a maximum value of 1110. The maximum
nificant bits of the mantissa (E3 E2 E1 E0 M7 M6 M5 M4). usable setting is a code of 1110 1111.
In this case, there is the following formula: In manual mode (MANUAL = 1), Table 9 gives the range
Lower lux threshold = (2(exponent) x mantissa) x 0.045 of exponent (E3 E2 E1 E0) that can be used for each
The exponent is a 4-bit number ranging from 0000 to TIM[2:0] and CDR bit setting.
1110 (zero to 14).
12 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Table 9. Recommended Manual Mode Settings for Configuration Register (0x02) and
Threshold Registers (0x05, 0x06)
RECOMMENDED SETTINGS RANGE OF EXPONENTS FOR
APPLICATION CONDITIONS FOR CONFIGURATION UPPER AND LOWER REGISTERS
REGISTER (0x03) (0x05 AND 0x06)
LUX LSB LUX LUX LSB INTEGRATION EXPONENT EXPONENT
TIM CDR
(MIN) (MAX) (MAX) TIME (ms) (MIN) (MAX)
0.045 2938 11.52 800 000 0 0000 1000
0.09 5875 23.04 400 001 0 0001 1001
0.18 11,750 46.08 200 010 0 0010 1010
100 011 0
0.36 23,501 92.16 0011 1011
800 000 1
50 100 0
0.72 47,002 184.32 0100 1100
400 001 1
25 101 0
1.44 94,003 368.64 0101 1101
200 010 1
12.5 110 0
2.88 188,006 737.28 0110 1110
100 011 1
6.25 111 0
5.76 188,006 737.28 0111 1110
50 100 1
11.52 188,006 737.28 25 101 1 1000 1110
23.04 188,006 737.28 12.5 110 1 1001 1110
46.08 188,006 737.28 6.25 111 1 1010 1110
Note: In manual mode, exceeding the lux (max) causes an overload error (exponent = 1111).
Typical Operating Sequence 2) Master sets the upper lux threshold and lower lux
To utilize the ultra-low power consumption of the IC in threshold in registers 0x05 and 0x06 so that a user-
end applications, an interrupt pin is provided to eliminate programmed window is defined around the current
the need for the system to poll the device continuously. lux readings.
Since every clock and data bit transmitted on I2C can 3) Master sets suitable threshold timer data in register
consume up to 1mA (assuming 1.8kI pullup resistor to 0x07.
a 1.8V rail), minimizing the number of I2C transactions
on the data bus can save a lot of power. In addition, 4) Master works on other tasks until alerted by the INT
eliminating the need to poll the device frees up process- pin going low. This is where the master spends much
ing resources for the master, improving overall system of its time.
performance. 5) When alerted by the INT pin going low, the master
The typical sequence of communication with the IC is reads the Interrupt Status register 0x00 to confirm
as follows: the source of interrupt was the IC. The master takes
appropriate action.
1) Master reads lux reading from registers 0x03 and
6) Repeat from Step 1.
0x04.
Maxim Integrated 13
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
START
N
WOKEN BY
INTERRUPT?
Y N
MAX44009 CAUSED
INTERRUPT?
14 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
I2C Serial Interface IC from high-voltage spikes on the bus lines, and mini-
mize crosstalk and undershoot of the bus signals.
The IC features an I2C/SMBus™-compatible, 2-wire
serial interface consisting of a serial-data line (SDA) and Bit Transfer
a serial-clock line (SCL). SDA and SCL facilitate com- One data bit is transferred during each SCL cycle. The
munication between the IC and the master at clock rates data on SDA must remain stable during the high period
up to 400kHz. Figure 3 shows the 2-wire interface timing of the SCL pulse. Changes in SDA while SCL is high are
diagram. The master generates SCL and initiates data control signals (see the START and STOP Conditions
transfer on the bus. A master device writes data to the section). SDA and SCL idle high when the I2C bus is not
IC by transmitting the proper slave address followed by busy.
the register address and then the data word. Each trans-
START and STOP Conditions
mit sequence is framed by a START (S) or Repeated
SDA and SCL idle high when the bus is not in use. A
START (Sr) condition and a STOP (P) condition. Each
master initiates communication by issuing a START con-
word transmitted to the IC is 8 bits long and is followed
dition. A START condition is a high-to-low transition on
by an acknowledge clock pulse. A master reading data
SDA with SCL high. A STOP condition is a low-to-high
from the IC transmits the proper slave address followed
transition on SDA while SCL is high (Figure 4). A START
by a series of nine SCL pulses. The IC transmits data
condition from the master signals the beginning of a
on SDA in sync with the master-generated SCL pulses.
transmission to the IC. The master terminates transmis-
The master acknowledges receipt of each byte of data.
sion, and frees the bus by issuing a STOP condition. The
Each read sequence is framed by a START or Repeated
bus remains active if a REPEATED START condition is
START condition, a not acknowledge, and a STOP condi-
generated instead of a STOP condition.
tion. SDA operates as both an input and an open-drain
output. A pullup resistor, typically greater than 500I, is Early STOP Conditions
required on the SDA bus. SCL operates as only an input. The IC recognizes a STOP condition at any point during
A pullup resistor, typically greater than 500I, is required data transmission except if the STOP condition occurs in
on SCL if there are multiple masters on the bus, or if the the same high pulse as a START condition. For proper
master in a single-master system has an open-drain SCL operation, do not send a STOP condition during the
output. Series resistors in line with SDA and SCL are same SCL high pulse as the START condition.
optional. Series resistors protect the digital inputs of the
SDA
tBUF
tSU,DAT tSU,STA
tHD,STA tSP
tLOW tHD,DAT tSU,STO
SCL
tHIGH
tHD,STA
tR tF
START REPEATED STOP START
CONDITION START CONDITION CONDITION CONDITION
Maxim Integrated 15
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
S SR P
CLOCK PULSE FOR
ACKNOWLEDGMENT
START
SCL CONDITION
SCL 1 2 8 9
NOT ACKNOWLEDGE
SDA
SDA
ACKNOWLEDGE
Slave Address The slave address with the R/W bit set to 0 indicates
The slave address is controlled by the A0 pin. Connect that the master intends to write data to the IC. The IC
A0 to either ground or VCC to set the address. Table 10 acknowledges receipt of the address byte during the
shows the two possible addresses for the IC. master-generated ninth SCL pulse.
Acknowledge The second byte transmitted from the master configures
The acknowledge bit (ACK) is a clocked 9th bit that the the IC’s internal register address pointer. The pointer
IC uses to handshake receipt each byte of data when in tells the IC where to write the next byte of data. An
write mode (see Figure 5). The IC pulls down SDA dur- acknowledge pulse is sent by the IC upon receipt of the
ing the entire master-generated ninth clock pulse if the address pointer data.
previous byte is successfully received. Monitoring ACK The third byte sent to the IC contains the data that is writ-
allows for detection of unsuccessful data transfers. An ten to the chosen register. The master signals the end of
unsuccessful data transfer occurs if a receiving device transmission by issuing a STOP condition.
is busy or if a system fault has occurred. In the event of
Read Data Format
an unsuccessful data transfer, the bus master can retry
To read a byte of data, the register pointer must first be
communication. The master pulls down SDA during the
set through a write operation (Figure 7). Send the slave
ninth clock cycle to acknowledge receipt of data when
address with the R/W set to 0, followed by the address
the IC is in read mode. An acknowledge is sent by the
of the register that needs to be read. After a Repeated
master after each read byte to allow data transfer to
START condition, send the slave address with the R/W
continue. A not acknowledge is sent when the master
bit set to 1 to initiate a read operation. The IC then sends
reads the final byte of data from the IC, followed by a
an acknowledge pulse followed by the contents of the
STOP condition.
register to be read. Transmitted data is valid on the rising
Write Data Format edge of the master-generated serial clock (SCL).
A write to the IC includes transmission of a START condi- Figure 8 illustrates the frame format for reading two reg-
tion, the slave address with the R/W bit set to 0, 1 byte isters consecutively without a STOP condition in between
of data to configure the internal register address pointer, reads. This applies to reading the Lux Data registers
1 or more bytes of data, and a STOP condition. Figure 0x03 and 0x04 consecutively only.
6 illustrates the proper frame format for writing 1 byte of
data to the IC. Sensor Position
The photo sensitive area of the IC is 0.37mm x 0.37mm
Table 10. Slave Address and much smaller than the device itself. When placing
SLAVE ADDRESS SLAVE ADDRESS the part behind a light guide, only this sensitive area has
A0 to be taken into account. Figure 9 shows the position and
FOR WRITING FOR READING
size of the photo-sensitive area within the package.
GND 1001 0100 1001 0101
VCC 1001 0110 1001 0111
16 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
B7 B6 B5 B4 B3 B2 B1 B0
ACKNOWLEDGE FROM MAX44009 ACKNOWLEDGE FROM MAX44009
R/W 1 BYTE
Figure 8. Reading Two Registers Consecutively Without a STOP Condition in Between Reads
Maxim Integrated 17
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
2mm
0.76mm
VCC 1 MAX44009 6 SDA
TOP VIEW
0.75mm
CENTER OF 0.24mm
2mm
GND 2 MAX44009 5 SCL
0.13mm
0.88mm
0.12mm
0.25mm
0.87mm
AD 3 4 INT
1µF
10kI 10kI 10kI
µC
SDA (I2C MASTER)
MAX44009 SDA
Chip Information
PROCESS: BiCMOS
18 Maxim Integrated
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Package Information
For the latest package outline information and land patterns, 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.
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
6 UTDFN-Opto D622+1 21-0490 90-0344
Maxim Integrated 19
MAX44009
Industry’s Lowest-Power
Ambient Light Sensor with ADC
Revision History
REVISION REVISION PAGES
DESCRIPTION
NUMBER DATE CHANGED
0 1/11 Initial release —
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. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
20 Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.