Application Note

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Optical Sensors
Application Note
Designing the VEML6030 into an Application
By Reinhard Schaar
HIGH-ACCURACY AMBIENT LIGHT SENSOR: VEML6030
The VEML6030 is a very high-sensitivity, high-accuracy
ambient light sensor in a miniature transparent 2 mm by
2 mm package. It includes a highly sensitive photodiode,
low-noise amplifier, 16-bit A/D converter, and supports an
easy-to-use I2C bus communication interface and additional
interrupt feature.
The ambient light read-out is available as a digital value,
and the built-in photodiode response is near that of the
human eye. The 16-bit dynamic range for ambient light
detection is 0 lx to ~ 120 klx, with resolution down to
0.0036 lx/counts.
Beside100 Hz and 120 Hz flicker noise rejection and a low
temperature coefficient, the device consumes just 0.5 μA in
shutdown mode. In addition, another four power-saving
modes are available that allow operating current to be
reduced down to just 2 μA. The device operates within a
temperature range of -25 °C to +85 °C.
The VEML6030’s very high sensitivity of just 0.0036 lx allows
the sensor to be placed behind very dark cover glasses that
will dramatically reduce the total light reaching it. The
sensor will also work behind clear cover glass, because
even very high illumination - such as direct sunlight - will not
saturate the device and read-outs up to 120 klx are possible.
VEML6030
GND 1
Temperature
Sensor
VDD
5
SCL
4
ADDR
Low Pass
Filter
SDA 2
Timing
Controller
INT
Output Buffer
I2C Interface
ALS-PD
3
Oscillator
Fig. 1 - VEML6030 Block Diagram
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Designing the VEML6030 into an Application
APPLICATION CIRCUITRY FOR THE VEML6030
The VEML6030 can be connected to a power supply ranging from 2.5 V to 3.6 V. The pull-up resistors at the I2C bus lines, as
well as at the interrupt line, may also be connected to a power supply between 1.7 V to 3.6 V, allowing them to be at the same
level needed for the microcontroller.
Proposed values for the pull-up resistors should be > 1 kΩ, e.g.: 2.2 kΩ to 4.7 kΩ for the R1 and R2 resistors (at SDA and SCL)
and 10 kΩ to 100 kΩ for the R3 resistor (at interrupt). The interrupt pin is an open drain output for currents up to 12 mA.
2.5 V to 3.6 V
R1
R2
R3
GND (1)
2.5 V to 3.6 V
R4
10R
C1
C2
10 μF 100 nF
C1 and R4
are optional
for very
disturbed
supply
VDD (6)
Host
Microcontroller
VEML6030
ADDR (4)
SDA (2)
I2C bus data SDA
SCL (5)
I2C bus clock SCL
INT (3)
GPIO (interrupt)
Fig. 2 - VEML6030 Application Circuit
The VEML6030 is insensitive to any kind of disturbances, so a small ceramic capacitor at its supply pin will be enough. Only
if the power supply line could be very noisy and the voltage range close to the lower limit of 2.5 V should a R-C decoupler, as
shown in the above circuitry, be used.
The ADDR pin allows for two device addresses: pin 4 = high (VDD) = 0x48, pin 4 = low (GND) = 0x10.
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REGISTERS OF THE VEML6030
The VEML6030 has six user-accessible 16-bit command codes. The addresses are 00h to 06h (03h not defined / reserved).
COMMAND REGISTER FORMAT
COMMAND CODE
REGISTER NAME
BIT
00
ALS_CONF 0
15 : 0
ALS gain, integration time, interrupt, and shutdown
W
15 : 8
ALS high threshold window setting (MSB)
W
W
01
ALS_WH
02
ALS_WL
03
Power saving
04
ALS
05
WHITE
06
ALS_INT
FUNCTION / DESCRIPTION
R/W
7:0
ALS high threshold window setting (LSB)
15 : 8
ALS low threshold window setting (MSB)
W
7:0
ALS low threshold window setting (LSB)
W
15 : 0
Set (15 : 3) 0000 0000 0000 0b
15 : 8
MSB 8 bits data of whole ALS 16 bits
R
7:0
LSB 8 bits data of whole ALS 16 bits
R
15 : 8
MSB 8 bits data of whole WHITE 16 bits
R
7:0
LSB 8 bits data of whole WHITE 16 bits
R
15 : 0
ALS INT trigger event
R
Note
• Command code 0 default value is 01 = devices is shut down
WAKE-UP OF THE VEML6030
For random measurements, e.g. once per second, the sensor may be switched to shutdown mode, where power consumption
is lowest.
BASIC CHARACTERISTICS (Tamb = 25 °C, unless otherwise specified)
PARAMETER
TEST CONDITION
SYMBOL
MIN.
TYP.
MAX.
VDD
2.5
3.3
3.6
V
VDD is 3.3 V
Isd
-
0.5
-
μA
VDD is 3.3 V, PSM = 11, refresh time 4100 ms
IDD
-
2
-
μA
VDD is 3.3 V, PSM = 00, refresh time 600 ms
IDD
-
8
-
μA
VDD is 3.3 V, PSM_EN = 0, refresh time 100 ms
IDD
-
45
-
μA
Supply voltage
Shutdown current (rem_2)
Operation mode current (rem_2)
UNIT
Note
• rem_1: light source: white LED
rem_2: light conditions: dark
This shutdown mode is set with a “1” within bit 0 of the command register:
COMMAND CODE
00
REGISTER NAME
ALS_SD
BIT
0
FUNCTION / DESCRIPTION
ALS shutdown setting
0 = ALS power on
1 = ALS shut down
R/W
W
When activating the sensor, setting bit 0 of the command register to “0”; a wait time of 4 ms should be observed before the first
measurement is picked up, to allow for a correct start of the signal processor and oscillator.
Please also refer to the chapter “Power-Saving Modes.”
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COMMAND REGISTER FORMAT
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RESOLUTION AND GAIN SETTINGS OF THE VEML6030
The VEML6030 is specified with a resolution of 0.0036 lx/counts. This high resolution is only available for a smaller light range
of approximately 0 lx to 230 lx. For this range a high gain factor can be selected. For light levels up to about 120 000 lx, a reduced
gain factor of 1/8 would then lead to a possible resolution of 0.0576 lx/counts (with an integration time of 800 ms), respective
of 0.4608 lx/counts (with IT = 100 ms).
Command Code ALS_GAIN
Command code: 00, bits 12 and 11
COMMAND REGISTER FORMAT
COMMAND CODE
REGISTER NAME
BIT
00
Reserved
15 : 13
Set 000b
W
12 : 11
Gain selection
00 = ALS gain x 1
01 = ALS gain x 2
10 = ALS gain x (1/8)
11 = ALS gain x (1/4)
W
ALS_GAIN
FUNCTION / DESCRIPTION
R/W
Remark: to avoid possible saturation / overflow effects, application software should always start with low gain: ALS gain x 1/8
or gain 1/4. ALS gain x 2 shows the highest resolution and should only be used with very low illumination values,
e.g. if sensor is placed below a very “dark” cover allowing only low light levels reaching the photodiode.
Command Code ALS_IT
Command code: 00, bits 9 to 6
COMMAND REGISTER FORMAT
COMMAND CODE
REGISTER NAME
ALS_IT
BIT
9:6
FUNCTION / DESCRIPTION
ALS integration time setting
1100 = 25 ms
1000 = 50 ms
0000 = 100 ms
0001 = 200 ms
0010 = 400 ms
0011 = 800 ms
R/W
W
Remark: the standard integration time is 100 ms. If a very high resolution is needed, one may increase this integration time up
to 800 ms. If faster measurement results are needed, it can be decreased down to 25 ms.
READ-OUT OF ALS MEASUREMENT RESULTS
The VEML6030 stores the measurement results within the command code 04. The most significant bits are stored to bits
15 : 8 and the least significant bits to bits 7 : 0.
Command Code ALS
Command code: 04, bits 15 : 8 (MSB), bits 7 : 0 (LSB)
COMMAND REGISTER FORMAT
COMMAND CODE
04
Revision: 30-May-16
REGISTER NAME
ALS
BIT
FUNCTION / DESCRIPTION
R/W
15 : 8
MSB 8 bits data of whole ALS 16 bits
R
7:0
LSB 8 bits data of whole ALS 16 bits
R
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The VEML6030 can memorize the last ambient data before shutdown and keep this data before waking up. When the device
is in shutdown mode, the host can freely read this data directly via a read command. When the VEML6030 wakes up, the data
will be refreshed by new detection.
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TRANSFERRING ALS MEASUREMENT RESULTS INTO A DECIMAL VALUE
Command code 04 contains the results of the ALS measurement. This 16-bit code needs to be converted to a decimal value to
determine the corresponding lux value. The calculation of the corresponding lux level is dependent on the programmed gain
setting and the chosen integration time.
CALCULATING THE LUX LEVEL
With the standard integration time of 100 ms, one has to just calculate the corresponding light level according to the
programmed gain and corresponding resolution. This resolution is most sensitive with gain = 2 and an integration time of
800 ms, specified to 0.0036 lx/step. For each shorter integration time by half, the resolution value is doubled.
The same principle is valid for the gain. For gain = 1 it is again doubled, and for gain = 1/4 it is four times higher, and for
gain = 1/8 it is again doubled.
The table below shows this factor of “2” for the four gain values:
RESOLUTION AND MAXIMUM DETECTION RANGE
GAIN 2
IT (ms)
GAIN 1
GAIN 1/4
GAIN 1/8
GAIN 2
TYPICAL RESOLUTION
GAIN 1
GAIN 1/4
GAIN 1/8
MAXIMUM POSSIBLE ILLUMINATION
800
0.0036
0.0072
0.0288
0.0576
236
472
1887
3775
400
0.0072
0.0144
0.0576
0.1152
472
944
3775
7550
200
0.0144
0.0288
0.1152
0.2304
944
1887
7550
15 099
100
0.0288
0.0576
0.2304
0.4608
1887
3775
15 099
30 199
50
0.0576
0.1152
0.4608
0.9216
3775
7550
30 199
60 398
25
0.1152
0.2304
0.9216
1.8432
7550
15 099
60 398
120 796
Example:
If the 16-bit word of the ALS data shows: 0000 0101 1100 1000 = 1480 (dec.), the programmed ALS gain is 1/4, and the
integration time is 100 ms. The corresponding lux level is:
light level [lx] = 1480 x 0.2304 = 341 lx
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Light level [lx] = 1480 x 0.2304 = 341 lx
Fig. 3
The screen shot below shows the linearity for the four gain factors.
Gain: x 2
3526
Gain: x 2
3526
Gain: x 1
1763
Gain: x 1/8
220
Fig. 4 - VEML6030 Counts vs. Gain
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Gain: x 1/4
440
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If the light level is very low, or if just a small percentage of outside light reaches the sensor, a higher integration time will need
to be chosen.
For just 1 lx, 35 counts are enough with the ALS gain mode: “gain x 2,” but for 0.1 lx just 3.5 counts will remain. With an
integration time of 200 ms, this will be doubled to 7 counts, and with 800 ms 28 counts are shown.
This also means that with this high integration time, together with the highest gain, even 0.007 lx will deliver 2 digital counts,
resulting in a high resolution of 0.0036 lx/counts.
Fig. 5 - VEML6030 Highest Sensitivity
The lowest possible detectable illuminance is 0.007 lx, because with a needed gain of “2” only 2 counts are shown as the lowest
result above “0.” Every next step (2, 3, 4, ...) is possible, so the resolution of 0.0036 lx/counts is valid.
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LUX LEVEL MATCHING FOR DIFFERENT LIGHT SOURCES
The VEML6030 shows very good matching for all kinds of light sources. LED light, fluorescent light, and normal daylight
show about the same results in a close tolerance range of just ± 10 %. Only a halogen lamp with strong infrared content may
show higher values.
Lux Error Referenced to Standard White LED Average Result Title
Transient Thermal Impedance
Lux Error (%)
ALS standard white LED
ALS halogen
ALS cold white LED
ALS warm white LED
20
15
1000
10
5
100
0
-5
-10
Transient Thermal Impedance
Transient Thermal Impedance
10000
25
10
1
2
3
4
5
6
7
8
9
10
Sample Number
2nd line
Fig. 6 - Tolerances for Different Light Sources
LINEARITY OF THE ALS RESULTS
For light levels from 0.0036 lx up to > 1000 lx, the output data is strictly linear for “gain 1/4” and “gain 1/8”.
Lux Result with White LED (Gain = 1)
10000
1000
1000
100
100
10
10
100
1000
Transient Thermal Impedance
Transient Thermal Impedance
Transient Thermal Impedance
VEML6030 (lx)
10 000
10
10 000
Fig. 7 - Linearity for Gain 1: VEML6030 Lux Value vs. Optometer Lux Value
“gain 1” and “gain 2” will show non-linearity for very high illuminations, so here only “gain 1/4” and “gain 1/8” should be used.
Comparison measurements with a calibrated optometer show the same results as the read-out from the VEML6030.
With a standard integration time of 100 ms, the actual ambient lux level exactly follows the digital counts multiplied by a
responsivity factor of 0.0576, so, 0.0036 x 2 x 2 x 2 x 2, factor 8 because of 100 ms instead of 800 ms and again factor 2 because
of “gain 1” instead of “gain 2”, so, factor 16 higher value = lower responsivity.
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Optometer (lx)
2nd line
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APPLICATION-DEPENDENT LUX CALCULATION
If the application uses a darkened / tinted cover glass, just 10 % - or even just 1 % - of the ambient light will reach the sensor.
For a tinted cover glass where there is 1 lx up to 100 klx of light outside, just 0.01 lx to 1 klx is reaching the sensor, and the
application software may always stay with gain x 2.
If the application uses a clear cover glass, nearly all ambient light will reach the sensor. This means even 100 klx may be
possible. For this clear cover where < 1 lx to ≥ 100 klx is possible, the application software will need to adapt the gain steps
according to light conditions.
As explained before, with “gain 2” and IT = 100 ms, a maximum 1887 lx will be possible before saturation occurs; and with
“gain 1” 3775 lx is maximum, but as already explained these high gain modes should only be used for low illuminations < 100 lx.
For unknown brightness conditions, the application should always start with the lowest gain: 1/8 or 1/4. This avoids possible
overload / saturation if, for example, strong sunlight suddenly reaches the sensor. To show this high value, an even lower
integration time than 100 ms may be needed.
Only for lower illumination levels with too low digital counts should the gain be increased. One possible decision level could be
100 counts (= 368 lx with “gain x 1/8”). After a change to gain = 1/4, this would show then 400 counts. 400 counts x 4 x 0.2304
will result in the same lux value of 368 lx.
10000
100
1000
10
100
1
1
10
100
Transient Thermal Impedance
Transient Thermal Impedance
Transient Thermal Impedance
VEML6030 (lx)
Lux Result with White LED (Gain = 1/4)
1000
10
1000
Optometer (lx)
2nd line
Fig. 8 - Linearity for Gain 1/4: VEML6030 Lux Value vs. Optometer Lux Value
The VEML6030 shows good linear behavior for lux levels from 0.0036 lx to about 1 klx.
A software flow may look like the flow chart diagram at the end of this note:
• Starting with the lowest gain (gain x 1/8), check the ALS counts. If ≤ 100 counts, increase the gain to 1/4.
• Check the ALS counts again. If they are still ≤ 100 counts, increase the gain to 1.
• Check the ALS counts again. If they are still ≤ 100 counts, increase the gain to 2.
If the illumination value is > 100 counts (started with gain x 1/8), a correction formula may be applied to get rid of small
non-linearity for very high light levels.
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• Check the ALS counts again. If they are still ≤ 100 counts, increase the integration time from 100 ms to 200 ms, and continue
the procedure up to the longest integration time of 800 ms.
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Lux Result with White LED (Gain = 1/4)
10000
10 000
1000
1000
100
100
10
10
100
1000
10 000
Transient Thermal Impedance
Transient Thermal Impedance
Transient Thermal Impedance
VEML6030 (lx)
100 000
10
100 000
Optometer (lx)
2nd line
Fig. 9 - Linearity for Gain 1/4 and Gain 1/8 up to 100 klx
The VEML6030 shows good linear behavior for lux levels from 0.007 lx to about 1 klx.
Illumination values higher than 1000 lx show non-linearity. This non-linearity is the same for all sensors, so a compensation
formula can be applied if this light level is exceeded.
Lux Result with White LED (Gain = 1/4)
1 000 000
10000
VEML6030 (lx)
VEML6030 (lx)
100 000
1000
10 000
Average gain 1/4
Poly. (Average gain 1/4)
1000
100
100
10
10
100
1000
10 000
Transient Thermal Impedance
Transient Thermal Impedance
y = 6.0135E-13x4 - 9.3924E-09x3 + 8.1488E-05x2 + 1.0023E+00x
10
100 000
Optometer (lx)
2nd line
Fig. 10 - Correction Formula for Gain 1/4 and Gain 1/8 for Higher Light Levels than 100 lx
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With the help of this correction formula, the VEML6030 shows good linear results up to its maximum of 120 klx.
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Lux Calculation Result with Gain = 1/4
1 000 000
VEML6030 (lx)
100 000
10 000
1000
100
10
10
100
1000
10 000
100 000
Optometer (lx)
Fig. 11 - Linearity for Gain 1/4 and Gain 1/8 with Applied Correction Formula
For most single photodetectors / ambient light sensor devices, there is a certain discrepancy in the output value for the different
light sources. They either do not follow the exact v(λ) curve due to wider sensitivity within the blue area - being not that exact
within the red region - or they do not stay at zero for near infrared wavelengths.
The VEML6030 follows a very exact v(λ) curve in all areas. This is the reason that it reproduces the exact same output values
under any kind of lighting condition, including fluorescent light, sunlight, halogen light, or LED light.
The maximum deviation to nominal value (as measured with an accurate optometer) is within ± 10 %.
Spectral Response
110
10000
90
80
1000
70
60
50
40
100
VEML6030
V(λ)
30
20
Transient Thermal Impedance
Transient Thermal Impedance
Transient Thermal Impedance
Relative Responsivity (%)
100
10
0
400
450
500
550
650
650
700
750
800
850
900
950
10
1000
Fig. 12 - Spectral Response ALS Channel
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Wavelength (nm)
2nd line
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WHITE CHANNEL
In addition to the ALS channel that follows the so-called human eye curve very well, there is also a second channel available
called the white channel, which offers a much higher responsivity for a much wider wavelength spectrum.
This white channel could be used to eliminate the last few tolerance percentages that light sources with strong infrared content
are showing at a bit higher values due to this small bump around 750 nm to 800 nm.
Average Gain 1/4 and Gain 1/8
10000
100
80
1000
60
40
100
20
0
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
Transient Thermal Impedance
Transient Thermal Impedance
Transient Thermal Impedance
Normalized Responsivity
120
10
1000 1050 1100
λ - Wavelength (nm)
2nd line
Fig. 13 - Spectral Response White Channel
COMMAND REGISTER FORMAT
COMMAND CODE
05
REGISTER NAME
WHITE
BIT
FUNCTION / DESCRIPTION
R/W
15 : 8
MSB 8 bits data of whole white 16 bits
R
7:0
LSB 8 bits data of whole white 16 bits
R
The data for this channel is available within the command code 05. Several measurements with many different light sources
show that the output data of this channel will lead to higher data, up to 2 times that read from the ALS channel.
All kind of LEDs, as well as fluorescent lights, will deliver output data within a small tolerance window of just ± 10 %.
Average Gain 1/4 and Gain 1/8
100 000
1000
80 000
60 000
nominal + 10 %
nominal
nominal - 10 %
40 000
100
20 000
0
10
0
20 000
40 000
60 000
80 000
100 000
120 000
140 000
Brightness According Calibrated Luxmeter (lx)
2nd line
Fig. 14 - ALS Measurement Deviation Between Different Light Sources: ≤ 10 %
Only strong light from incandescent or halogen lamps and strong sunlight may show higher tolerances within the ALS channel
(see Fig. 6).
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Reading of ALS (lx)
Optometer (lx)
120 000
Transient Thermal Impedance
Transient Thermal Impedance
10000
140 000
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White Channel Counts with Setup 100 ms Gain x 1, All Light Sourdes = 100 lx
ALS standard white LED
ALS halogen
6800
ALS cold white LED
ALS warm white LED
5800
10000
1000
4800
3800
100
2800
1800
800
Transient Thermal Impedance
Transient Thermal Impedance
Transient Thermal Impedance
White Channel Counts
7800
10
1
2
3
4
5
6
7
8
9
10
Sample Number
2nd line
Fig. 15 - White Channel Counts for Different Light Sources
Remark: standard white LED: 5600K, cold white LED: 7500K, warm white LED: 3500K
Nearly all light sources will show a factor of < 2
between ALS and white channel
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Fig. 16 - White Channel and ALS Channel for Fluorescent and Daylight Spectra
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Light sources containing strong infrared content
will show a factor of > 2
between ALS and white channel
Fig. 17 - White Channel and ALS Channel for Incandescent Lamp Spectra
Knowing that light sources with strong infrared content deliver about > 2 times higher output data at the white channel than all
other light sources, which show a maximum factor of about 2, one may use it to optimize the lux conversion now.
ALS Counts with Setup 100 ms Gain x 1, All Light Sourdes = 100 lx
White standard white LED
White halogen
6800
White cold white LED
White warm white LED
5800
10000
1000
4800
3800
100
2800
1800
10
1
2
3
4
5
6
7
8
9
10
Sample Number
2nd line
Fig. 18
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800
Transient Thermal Impedance
Transient Thermal Impedance
Transient Thermal Impedance
White Channel Counts
7800
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Designing the VEML6030 into an Application
POWER-SAVING MODES
The device stays in shutdown mode as long as no measurements need to be done. Once activated with ALS_SD = 0,
measurements are executed.
COMMAND REGISTER FORMAT
COMMAND CODE
00
REGISTER NAME
ALS_SD
BIT
0
FUNCTION / DESCRIPTION
R/W
ALS shutdown setting
0 = ALS power on
1 = ALS shutdown
W
Without using the power-saving feature (PSM_EN = 0), the controller has to wait before reading out measurement results,
at least for the programmed integration time. For example, for ALS_IT = 100 ms a wait time of ≥ 100 ms is needed.
A more simple way of continuous measurements can be realized by activating the PSM feature, setting PSM_EN = 1.
COMMAND REGISTER FORMAT
COMMAND CODE
REGISTER NAME
BIT
FUNCTION / DESCRIPTION
Power-saving mode; see table “Refresh Time”
00 = mode 1
01 = mode 2
10 = mode 3
11 = mode 4
W
Power-saving mode enable setting
0 = disable
1 = enable
W
00
PSM
2:1
00
PSM_EN
0
R/W
The default this comes up with is mode 1 = 00 for the bits 2 and 1 within the command code. Depending on the chosen
integration time (ALS_IT), this leads to a certain measurement speed / repetition rate.
For ALS_IT = 100 ms (0000 for bits 9 : 6 within command register) this is about 600 ms. For 200 ms (0001) it will be 700 ms, for
400 ms (0010) 900 ms, and for 800 ms (0011) about 1300 ms.
PSM
ALS_IT
REFRESH TIME (ms)
00
0000
600
00
0001
700
00
0010
900
00
0011
1300
The higher the PSM value and the longer the integration time, the lower the current consumption will be. The possible sensitivity
also depends on integration time, where the longest (800 ms) will lead to 0.0036 lx/counts, together with the highest gain:
ALS_GAIN = 01 (ALS gain x 2).
All refresh times, corresponding current consumptions, and possible sensitivities are shown in the table on the next page.
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Other PSM modes will lead to even lower repetition rates. This will also lead to a lower power consumption (see the table on
the next page).
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Designing the VEML6030 into an Application
REFRESH TIME, IDD, AND RESOLUTION RELATION
ALS_GAIN
PSM
ALS_IT
01
00
0000
01
01
0000
01
10
0000
01
11
0000
01
00
01
01
REFRESH TIME (ms)
IDD (μA)
RESOLUTION (lx/bit)
600
8
0.0288
1100
5
0.0288
2100
3
0.0288
4100
2
0.0288
0001
700
13
0.0144
01
0001
1200
8
0.0144
10
0001
2200
5
0.0144
01
11
0001
4200
3
0.0144
01
00
0010
900
20
0.0072
01
01
0010
1400
13
0.0072
01
10
0010
2400
8
0.0072
01
11
0010
4400
5
0.0072
01
00
0011
1300
28
0.0036
01
01
0011
1800
20
0.0036
01
10
0011
2800
13
0.0036
01
11
0011
4800
8
0.0036
INTERRUPT HANDLING
To avoid too many interactions with the microcontroller, the interrupt feature may be used. This is activated with
ALS_INT_EN = 1.
Only when the programmed threshold is crossed (above / below) consecutively by the programmed number of measurements
(ALS_PERS) will the corresponding interrupt bit (ALS_IF_L or ALS_IF_H) be set and the interrupt pin pulled down.
COMMAND REGISTER FORMAT
COMMAND CODE
00
REGISTER NAME
ALS_INT_EN
BIT
1
ALS_PERS
01
ALS_WH
02
ALS_WL
ALS_IF_L
06
ALS_IF_H
reserved
13 : 0
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5:4
R/W
W
ALS persistence protect number setting
00 = 1
01 = 2
10 = 4
11 = 8
W
15 : 8
ALS high threshold window setting (MSB)
W
7:0
ALS high threshold window setting (LSB)
W
15 : 8
ALS low threshold window setting (MSB)
W
7:0
ALS low threshold window setting (LSB)
W
15
ALS crossing low threshold INT trigger event
R
14
ALS crossing high threshold INT trigger event
R
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00
FUNCTION / DESCRIPTION
ALS interrupt enable setting
0 = ALS INT disable
1 = ALS INT enable
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Designing the VEML6030 into an Application
MECHANICAL CONSIDERATIONS AND WINDOW CALCULATION FOR THE VEML6030
The ambient light sensor will be placed behind a window or cover. The window material should be completely transmissive to
visible light (400 nm to 700 nm). For optimal performance the window size should be large enough to maximize the light
irradiating the sensor. In calculating the window size, the only dimensions that the design engineer needs to consider are the
distance from the top surface of the sensor to the outside surface of the window and the size of the window. These dimensions
will determine the size of the detection zone.
First, the center of the sensor and center of the window should be aligned. The VEML6030 has an angle of half sensitivity of
about ± 55°, as shown in the figure below.
20°
1.0
0.9
40°
0.8
0.7
60°
0.6
ϕ - Angular Displacement
Srel - Relative Sensitivity
0°
80°
0.5 0.4 0.3 0.2 0.1 0
22308
Fig. 19 - Relative Radiant Sensitivity vs. Angular Displacement
Fig. 20 - Angle of Half Sensitivity: Cone
Remark:
This wide angle and the placement of the sensor as close
as possible to the cover is needed if it should show
comparable results to an optometer, which also detects
light reflections from the complete surroundings.
Fig. 21 - Windows Above Sensitive Area
The size of the window is simply calculated according to triangular rules. The dimensions of the device are shown within the
datasheet, and with the known distance below the window’s upper surface and the specified angle below the given window
diameter (w), the best results are achieved.
VEML6030
0.3362
Dimensions (L x W x H in mm): 2 x 2 x 0.85
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4
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w
x
0.5
.
D
d
tan 55° = 1.43 = x / d
x = 1.43 x d
α
0.85
here in drawing α = 55°
dimensions in mm
Fig. 22 - Window Area for an Opening Angle of ± 55°
The calculation is then: tan α = x / d → with α = 55° and tan 55° 1.43 = x / d → x = 1.43 x d
Then the total width is w = 0.5 mm + 2 x x.
d = 0.5 mm → x = 0.72 mm → w = 0.5 mm + 1.44 mm = 1.94 mm
d = 1.0 mm → x = 1.43 mm → w = 0.5 mm + 2.86 mm = 3.36 mm
d = 1.5 mm → x = 2.15 mm → w = 0.5 mm + 4.30 mm = 4.80 mm
d = 2.0 mm → x = 2.86 mm → w = 0.5 mm + 5.72 mm = 6.22 mm
d = 2.5 mm → x = 3.58 mm → w = 0.5 mm + 7.16 mm = 7.66 mm
d = 3.0 mm → x = 4.29 mm → w = 0.5 mm + 8.58 mm = 9.08 mm
A smaller window is also sufficient if reference measurements can be done and / or if the output result does not need to be as
exact as an optometer.
VEML6030
0.332
Dimensions (L x W x H in mm): 2 x 2 x 0.85
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Designing the VEML6030 into an Application
w
x
0.5
.
D
d
tan 40° = 0.84 = x / d
x = 0.84 x d
α
0.85
here in drawing α = 40°
dimensions in mm
Fig. 23 - Window Area for an Opening Angle of ± 40°
The calculation is then: tan α = x / d → with α = 40° and tan 40° 0.84 = x / d → x = 0.84 x d
Then the total width is w = 0.5 mm + 2 x x.
d = 0.5 mm → x = 0.42 mm → w = 0.5 mm + 0.84 mm = 1.34 mm
d = 1.0 mm → x = 0.84 mm → w = 0.5 mm + 1.68 mm = 2.18 mm
d = 1.5 mm → x = 1.28 mm → w = 0.5 mm + 2.56 mm = 3.06 mm
d = 2.0 mm → x = 1.68 mm → w = 0.5 mm + 3.36 mm = 3.86 mm
d = 2.5 mm → x = 2.10 mm → w = 0.5 mm + 4.20 mm = 4.70 mm
d = 3.0 mm → x = 2.52 mm → w = 0.5 mm + 5.04 mm = 5.54 mm
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Designing the VEML6030 into an Application
TYPICAL SOFTWARE FLOW CHART
For a wide light detection range of more than seven decades (from 0.007 lx to 120 klx), it is necessary to adjust the sensor. This
is done with the help of four gain steps and seven steps for the integration time. To deal with these steps, they are numbered
as needed for the application software.
The ALS gain modes are called G1 to G4 and the integration times are called IT:
Sensitivity Mode Selection
G
ALS Integration Time Setting
00 = ALS gain x 1
→3
IT
1100 = 25 ms
→ -2
01 = ALS gain x 2
→4
1000 = 50 ms
→ -1
10 = ALS gain x (1/8)
→1
0000 = 100 ms
→0
11 = ALS gain x (1/4)
→2
0001 = 200 ms
→1
0010 = 400 ms
→2
0011 = 800 ms
→3
Whereas the programmed gain begins with the lowest possible value, in order to avoid any saturation effect the integration time
starts with 100 ms: IT = 0.
With this just about 30 klx is possible. If this is not enough due to a wide and clear cover, and the sensor is being exposed to
direct bright sunlight, one may also begin with the shortest integration time.
Read-out
ALS data
Counts too low?
Y
Increase
gain
Still too low?
Y
Fig. 24 - Simple Flow Chart View
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Decrease
integration time
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Designing the VEML6030 into an Application
TYPICAL SOFTWARE FLOW CHART WITH CORRECTION FORMULA (1)
Initialize μC
ALS_SD = 0
wait
ALS_IT
Set gain: G = 1
(ALS_GAIN: 1/8)
Read-out
ALS data
ALS power on,
wait ≥ 2.5 ms
Integration time (ALS_IT = 0):
100 ms
ALS gain setting
ALS integration time setting
1100 = 25 ms
1000 = 50 ms
0000 = 100 ms
0001 = 200 ms
0010 = 400 ms
0011 = 800 ms
→
→
→
→
→
→
IT:
-2
-1
0
1
2
3
Gain selection
00 = ALS gain x 1
01 = ALS gain x 2
10 = ALS gain x (1/8)
11 = ALS gain x (1/4)
→
→
→
→
G:
3
4
1
2
ALS command code #4
Correction formula:
Lux calc. = 6.0135E-13x4 - 9.3924E-09x3 + 8.1488E-05x2 + 1.0023E+00x
ALS
≤ 100 cts?
Y
ALS_SD = 1
G=G+1
ALS_SD = 0
N
ALS between 100 and 65 535 counts →
G = 1 = ALS gain 1/8
(with x = Lux_VEML)
If ALS counts ≤ 100 cts
set higher gain
ALS >
10 000 cts?
N
ALS between
100 and 10 000 counts →
G = 1 = ALS gain 1/8
Calculation of
Lux_calc
set ALS_SD to 1 = stand_by!
Y
IT = IT - 1
N
Decrease of integration time
G = 4?
Y
N
ALS_SD = 0
IT = IT + 1
Increase of integration time
IT = -2?
Y
N
Ambient light really ≥ 200 klx?
IT = 4?
ALS_IT = 3 (800 ms)
Y
Output =
LUX_VEML
Lux_VEML = output data (dec.)/(ALS gain x responsivity)
Fig. 25 - Flow Chart with Correction Formula from ≥ 100 lx
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Calculation of
Lux_calc
ALS_IT = -2 (25 ms)
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Designing the VEML6030 into an Application
TYPICAL LUMINANCE VALUES
Luminance
10-5 lx
10-4 lx
0.002 lx
0.01 lx
1 lx
3.4 lx
50 lx
80 lx
100 lx
320 lx to 500 lx
400 lx
1000 lx
10 000 lx to 25 000 lx
32 000 lx to 130 000 lx
Example
Light from Sirius, the brightest star in the night sky
Total starlight, overcast sky
Moonless clear night sky with airglow
Quarter moon, 0.27 lx; full moon on a clear night
Full moon overhead at tropical latitudes
Dark limit of civil twilight under a clear sky
Family living room
Hallway / bathroom
Very dark overcast day
Office lighting
Sunrise or sunset on a clear day
Overcast day; typical TV studio lighting
Full daylight (not direct sun)
Direct sunlight
VEML6030 SENSOR BOARD AND DEMO SOFTWARE
The small blue VEML6030 sensor board is compatible with the SensorStarterKit.
Please also see www.vishay.com/moreinfo/vcnldemokit/
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Designing the VEML6030 into an Application
After plugging in the VEML6030 sensor board to the USB dongle (both up or down are possible) and activating with the
“VEML6030.exe” file, the “Ambient Light” menu appears.
Halogen lamp as light source contains strong
infrared content and
shows a factor of > 3
between ALS and white channel
The ALS sensitivity mode is preprogrammed to “gain x 1/8” and integration time to “100 ms.” Self-timed measurements are
started by clicking the measure button.
Both, the ALS and the white channel are shown. A channel can be deactivated by clicking within the small white box on top of
the graph and clicked again to make visible. In addition, decimal, binary, or hex formats can be selected in the small white boxes
on the right side, where the small letters “d” and “b” are shown.
The lux level is calculated according to the rules mentioned above, and the chosen gain and integration time are displayed in
the lowest white box “Lux.”
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The screen shots below appear when programming the upper and lower thresholds within the “Settings” menu.
Selecting “ALS INT Enable” and “Show” within the
measurement menu will then show the high and low
thresholds as blue and green lines, respectively. If the light
source changes to that higher or lower value, the below
appears.
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