INTERSIL ISL29012IROZ

ISL29012
®
Data Sheet
December 10, 2008
Light-to-Digital Output Sensor with High
Sensitivity, Gain Selection, Interrupt
Function and I2C Bus™
The ISL29012 is an integrated light sensor with I2C (SMBus
Compatible) interface. It has an internal signed 15-bit
integrating type ADC designed based on the
charge-balancing A/D conversion technique. This ADC is
capable of rejecting 50Hz and 60Hz flicker caused by
artificial light sources. The lux range select feature allows
the user to program the lux range for optimized counts/lux.
FN6476.1
Features
• Range Select Via I2C
- Range 1 = 0.5 lux to 2,000 lux
- Range 2 = 0.5 lux to 8,000 lux
- Range 3 = 0.5 lux to 32,000 lux
- Range 4 = 0.5 lux to 128,000 lux
• Human Eye Response (540nm Peak Sensitivity)
• Temperature Compensated
• Signed 15-bit Resolution
In normal operation, power consumption is typically 250µA.
Furthermore, a power-down mode can be controlled by
software via the I2C interface, reducing power consumption
to less than 1µA.
• Adjustable Resolution: Up to 20 Counts per lux
The ISL29012 supports a hardware interrupt that remains
asserted low until the host clears it through I2C interface.
• IR + UV Rejection
Designed to operate on supplies from 2.5V to 3.3V, the
ISL29012 is specified for operation over the -40°C to +85°C
ambient temperature range.
TEMP.
RANGE (°C)
ISL29012IROZ-T7*
-40 to +85
ISL29012IROZ-EVALZ
• Simple Output Code, Directly Proportional to lux
• 50Hz/60Hz Rejection
• 2.5V to 3.3V Supply
• 6 Ld ODFN (2.1mmx2mm)
• Pb-Free (RoHS compliant)
Ordering Information
PART NUMBER
(Note)
• User-programmable Upper and Lower Threshold Interrupt
PACKAGE
(Pb-Free)
6 Ld ODFN
PKG.
DWG. #
L6.2x2.1
Evaluation Board
*Please refer to TB347 for details on reel specifications.
NOTE: These Intersil Pb-free plastic packaged products employ
special Pb-free material sets; molding compounds/die attach
materials and NiPdAu plate - e4 termination finish, which is RoHS
compliant and compatible with both SnPb and Pb-free soldering
operations. Intersil Pb-free products are MSL classified at Pb-free
peak reflow temperatures that meet or exceed the Pb-free
requirements of IPC/JEDEC J STD-020.
• Operating Temperature Range: -40°C to +85°C
• I2C and SMBus Compatible
Applications
• Display and Keypad Backlight Dimming
- Mobile Devices: Smart phone, PDA, and GPS
- Computing Devices: Notebook PC, UMPC Web Pod
- Consumer Devices: LCD-TV, Digital Picture Frame and
Digital Cameras
• Industrial and Medical Light Sensing
Pinout
ISL29012
(6 LD ODFN)
TOP VIEW
Block Diagram
LIGHT DATA
PROCESS
PHOTODIODE
ARRAY
IREF
SHDN
INT TIME
GAIN/RANGE
VDD
1
INTEGRATING
ADC
6 SDA
COMMAND
REGISTER
GND 2
5 SCL
DATA
REGISTER
REXT 3
4 INT
5 SCL
6 SDA
I2C
EXT
TIMING
FOSC
*EXPOSED PAD CAN BE CONNECTED TO GND OR
ELECTRICALLY ISOLATED
INT
216
COUNTER
3
REXT
VDD 1
INTERRUPT
4 INT
2
GND
ISL29012
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
I2C Bus is a registered trademark owned by NXP Semiconductors Netherlands, B.V
Copyright © Intersil Americas Inc. 2008. All Rights Reserved.
All other trademarks mentioned are the property of their respective owners.
ISL29012
Absolute Maximum Ratings (TA = +25°C)
Thermal Information
VDD Supply Voltage between VDD and GND . . . . . . . . . . . . . 3.6V
I2C Bus (SCL, SDA) and INT Pin Voltage . . . . . . . . . . -0.2V to 5.5V
I2C Bus (SCL, SDA) Pin Current . . . . . . . . . . . . . . . . . . . . . <10mA
REXT Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.2V to VDD
ESD Rating
Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV
Thermal Resistance (Typical, Note 1)
θJA (°C/W)
6 Lead ODFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
88
Maximum Die Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . +90°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +100°C
Operating Temperature . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
Pb-free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and
result in failures not covered by warranty.
NOTE:
1. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Electrical Specifications
PARAMETER
VDD = 3V, TA = +25°C, REXT = 100kΩ, unless otherwise specified. Internal Timing Mode operation (See
“Principles of Operation” on page 3).
DESCRIPTION
CONDITION
MIN
TYP
MAX
UNIT
Ee-max
Maximum Detectable Light Intensity
VDD
Power Supply Range
IDD
Supply Current
IDD1
Supply Current Disabled
Software disabled
fOSC1
Internal Oscillator Frequency
Gain/Range = 1 or 2
fOSC2
Internal Oscillator Frequency
Gain/Range = 3 or 4
fI2C
I2C Clock Rate
DATA0
Dark ADC Code
DATA1
Full Scale ADC Code
DATA2
Light Count Output
E = 300 lux, fluorescent light, Gain/Range = 1
(Note 2)
DATA3
Light Count Output
E = 300 lux, fluorescent light, Gain/Range = 2
(Note 2)
1100
Counts
DATA4
Light Count Output
E = 300 lux, fluorescent light, Gain/Range = 3
(Note 2)
275
Counts
DATA5
Light Count Output
E = 300 lux, fluorescent light, Gain/Range = 4
(Note 2)
69
Counts
VREF
Voltage of REXT Pin
VTL
SCL and SDA Threshold LO
(Note 3)
1.05
V
VTH
SCL and SDA Threshold HI
(Note 3)
1.95
V
ISDA
SDA Current Sinking Capability
3
5
mA
IINT
INT Current Sinking Capability
3
5
mA
@ Gain/Range = 4, and REXT = 25kΩ
128k
2.5
lux
3.30
V
0.25
0.33
mA
0.1
1
µA
308
342
377
kHz
616
684
754
kHz
1 to 400
E = 0 lux, Gain/Range = 1
0
kHz
6
Counts
32767
3300
0.490
4400
0.515
Counts
5500
0.540
Counts
V
NOTES:
2. Fluorescent light is substituted by a green LED during production.
3. The voltage threshold levels of the SDA and SCL pins are VDD dependent: VTL = 0.35*VDD. VTH = 0.65*VDD.
2
FN6476.1
December 10, 2008
ISL29012
Pin Descriptions
PIN NUMBER
PIN NAME
DESCRIPTION
1
VDD
Positive supply; connect this pin to a regulated 2.5V to 3.3V supply.
2
GND
Ground pin. The thermal pad is connected to the GND pin.
3
REXT
External resistor pin for ADC reference; connect this pin to ground through a (nominal) 100kΩ resistor with
1% tolerance.
4
INT
Interrupt pin; LO for interrupt/alarming, open drain output.
5
SCL
I2C serial clock
6
SDA
I2C serial data
Principles of Operation
Photodiodes
The ISL29012 contains two photodiode arrays which convert
light into current. One diode (D1) is sensitive to both visible
and infrared light, while the other one (D2) is only sensitive to
infrared light; see Figure 21. Using the infrared portion of the
light as a baseline, the visible light can be extracted. The
ambient light output is the difference between D1 and D2. The
resultant ALS spectral response vs wavelength is shown in
Figure 7 in the “Typical Performance Curves” on page 11.
After light is converted to current during the light data process,
the current output is converted to digital by a single built-in
integrating type signed 15-bit Analog-to-Digital Converter
(ADC). An I2C command reads the visible light intensity in
counts.
The converter is a charge-balancing integrating type signed
15-bit ADC. The chosen method for conversion is best for
converting small current signals in the presence of an AC
periodic noise. A 100ms integration time, for instance, highly
rejects 50Hz and 60Hz power line noise simultaneously. See
“Integration Time or Conversion Time” on page 7 and “Noise
Rejection” on page 8.
The built-in ADC offers user flexibility in integration time or
conversion time. There are two timing modes: Internal Timing
Mode and External Timing Mode. In Internal Timing Mode,
integration time is determined by an internal dual speed
oscillator (fOSC), and the n-bit (n = 4, 8, 12,16) counter inside
the ADC. In External Timing Mode, integration time is
determined by the time between two consecutive I2C External
Timing Mode commands. See “External Timing Mode” on
page 7. A good balancing act of integration time and resolution
depending on the application is required for optimal results.
The ADC has four I2C programmable range selects to
dynamically accommodate various lighting conditions. For
very dim conditions, the ADC can be configured at its lowest
range. For very bright conditions, the ADC can be configured
at its highest range.
The I2C bus lines can be pulled above VDD, 5.5V max.
Interrupt Function
The active low interrupt pin is an open drain pull-down
configuration. The interrupt pin serves as an alarm or
monitoring function to determine whether the ambient light
exceeds the upper threshold or goes below the lower
threshold. The user can also configure the persistency of the
interrupt pin. This helps to avoid false triggers, such as noise
or sudden spikes in ambient light conditions. An unexpected
camera flash, for example, can be ignored by setting the
persistency to 8 integration cycles.
I2C Interface
There are eight (8) 8-bit registers available inside the ISL29012.
The command and control registers define the operation of the
device. The command and control registers do not change until
the registers are overwritten. There are two 8-bit registers that
set the high and low interrupt thresholds. There are four 8-bit
data Read Only registers. Two bytes for the sensor reading and
another two bytes for the timer counts. The data registers
contain the ADC's latest digital output, and the number of clock
cycles in the previous integration period.
The ISL29012’s I2C interface slave address is hardwired
internally as 1000100. When 1000100x with x as R or W is
sent after a START condition, this device compares the first
7 bits of this byte to its address and matches.
Figure 1 shows a sample one-byte read. Figure 2 shows a
sample one-byte write. Figure 3 shows a sync_I2C timing
diagram sample for externally controlled integration time.
The I2C bus master always drives the SCL (clock) line, while
either the master or the slave can drive the SDA (data) line.
Figure 2 shows a sample write. Every I2C transaction begins
with the master asserting a start condition (SDA falling while
SCL remains high). The following byte is driven by the
master, and includes the slave address and read/write bit.
The receiving device is responsible for pulling SDA low
during the acknowledgement period.
Every I2C transaction ends with the master asserting a stop
condition (SDA rising while SCL remains high).
For more information about the I2C standard, please consult
the Phillips™ I2C specification documents.
3
FN6476.1
December 10, 2008
ISL29012
I2C DATA
Start
I2C SDA
In
DEVICE ADDRESS
A6
I2C SDA
Out
I2C CLK
A5
A4
A3
A2
A1
A0
W
A
W
A
2
3
4
5
6
R7
A
SDA DRIVEN BY MASTER
1
REGISTER ADDRESS
7
8
R6
R5
R4
R3
R2
A
R1
R0
SDA DRIVEN BY MASTER
9
1
2
3
4
5
6
7
8
STOP
DEVICE ADDRESS
START
A
A6
A5
A
SDA DRIVEN BY MASTER
9
1
2
A4
A3
3
A2
4
5
A1
6
A0
7
W
8
A
DATA BYTE0
A
A
SDA DRIVEN BY ISL29003
ISL29012
STOP
NAK
A
D7
D6
D5
D4
D3
D2
D1
D0
A
9
1
2
3
4
5
6
7
8
9
FIGURE 1. I2C READ TIMING DIAGRAM SAMPLE
I2C DATA
I2C SDA In
Start
DEVICE ADDRESS
W
A
A6 A5 A4 A3 A2 A1 A0
W
A
A
I2C SDA Out
SDA DRIVEN BY MASTER
1
I2C CLK In
2
3
4
5
6
7
8
9
REGISTER ADDRESS
A
FUNCTIONS
A
R7 R6 R5 R4 R3 R2 R1 R0
A
B7 B6 B5 B4 B3 B2 B1 B0
A
SDA DRIVEN BY MASTER
A
SDA DRIVEN BY MASTER
A
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
STOP
9
FIGURE 2. I2C WRITE TIMING DIAGRAM SAMPLE
I2 C D A T A
S t a rt
D E V IC E A D D R E S S
I2 C S D A In
A6
I2 C S D A O u t
A5
A4
A3
A2
A1
A0
W
A
W
A
S D A D R IV EN B Y M A S T ER
1
I2 C C L K In
2
3
4
5
6
R E G IS T E R A D D R E S S
R7
8
9
R5
R4
R3
R2
R1
R0
S D A D R IV EN B Y M A S T ER
A
7
R6
A S to p
1
2
3
4
5
6
7
A
A
8
9
FIGURE 3. I2C SYNC_I2C TIMING DIAGRAM SAMPLE
4
FN6476.1
December 10, 2008
ISL29012
Register Set
There are eight registers that are available in the ISL29012. Table 1 summarizes the available registers and their functions.
TABLE 1. REGISTER SET
BIT
ADDR
REG NAME
7
6
5
4
3
2
1
0
DEFAULT
00h
COMMAND
ADCE
ADCPD
TIMM
0
ADCM1
ADCM0
RES1
RES0
00h
01h
CONTROL
0
0
INT_FLAG
0
GAIN1
GAIN0
IC1
IC0
00h
02h
Interrupt
Threshold_HI
ITH_HI7
ITH_HI6
ITH_HI5
ITH_HI4
ITH_HI3
ITH_HI2
ITH_HI1
ITH_HI0
FFh
03h
Interrupt
ITH_LO7
Threshold_LO
ITH_LO6
ITH_LO5
ITH_LO4
ITH_LO3
ITH_LO2
ITH_LO1
ITH_LO0
00h
04h
LSB SENSOR
S7
S6
S5
S4
S3
S2
S1
S0
00h
05h
MSB
SENSOR
S15
S14
S13
S12
S11
S10
S9
S8
00h
06h
LSB TIMER
T7
T6
T5
T4
T3
T2
T1
T0
00h
07h
MSB TIMER
T15
T14
T13
T12
T11
T10
T9
T8
00h
TABLE 2. WRITE ONLY REGISTERS
REGISTER
ADDRESS
NAME
b1xxx_xxxx
bx1xx_xxxx
sync_I2C
TABLE 5. TIMING MODE
FUNCTIONS/
DESCRIPTION
Writing a logic 1 to this address bit ends the
current ADC-integration and starts another.
Used only with External Timing Mode.
clar_int
Writing a logic 1 to this address bit clears
the interrupt.
The Read/Write command register has five functions:
Enable ADC-core to normal operation
OPERATION
Normal operation (default)
1
Power Down
MODE
Disable ADC
0:1
Disable ADC
1:0
Light count DATA output in signed (n-1) bit *
1:1
No operation.
5. Width; Bits 1 and 0. This function determines the number
of clock cycles per conversion. Changing the number of
clock cycles does more than just change the resolution of
the device. It also changes the integration time, which is
the period the device’s analog-to-digital (A/D) converter
samples the photodiode current signal for a lux
measurement.
TABLE 4. ADCPD
0
External Timing Mode. Integration time is externally
timed by the I2C host.
* n = 4, 8, 12,16 depending on the number of clock cycles
function.
2. ADCPD; Bit 6. This function puts the device in a
power-down mode. A logic 0 puts the device in normal
operation. A logic 1 powers down the device.
BIT 6
1
0:0
OPERATION
1
Internal Timing Mode. Integration time is internally timed
determined by fOSC, REXT, and number of clock cycles.
BITS 3:2
TABLE 3. ENABLE
Disable ADC-core to reset-mode (default)
0
TABLE 6. PHOTODIODE SELECT MODE; BITS 2 AND 3
1. Enable; Bit 7. This function either resets the ADC or enables
the ADC in normal operation. A logic 0 disables ADC to
reset-mode. A logic 1 enables ADC to normal operation.
0
OPERATION
4. Photodiode Select Mode; Bits 3 and 2. Setting Bit 3 and
Bit 2 to 1 and 0 enables ADC to give light count DATA
output.
Command Register 00(hex)
BIT 7
BIT 5
.
3. Timing Mode; Bit 5. This function determines whether the
integration time is done internally or externally. In Internal
Timing Mode, integration time is determined by an
internal dual speed oscillator (fOSC), and the n-bit (n = 4,
8, 12,16) counter inside the ADC. In External Timing
Mode, integration time is determined by the time between
three consecutive external-sync sync_I2C pulses
commands.
5
TABLE 7. WIDTH
BITS 1:0
NUMBER OF CLOCK CYCLES
0:0
216 = 65,536
0:1
212 = 4,096
1:0
28 = 256
1:1
24 = 16
FN6476.1
December 10, 2008
ISL29012
Control Register 01(hex)
Sensor Data Register 04(hex) and 05(hex)
The Read/Write control register has three functions:
When the device is configured to output a signed 15-bit data,
the most significant byte is accessed at 04(hex), and the
least significant byte can be accessed at 05(hex). The
sensor data register is refreshed after very integration cycle.
1. Interrupt flag; Bit 5. This is the status bit of the interrupt.
The bit is set to logic high when the interrupt thresholds
have been triggered, and logic low when not yet
triggered. Writing a logic low clears/resets the status bit.
TABLE 8. INTERRUPT FLAG
BIT 5
OPERATION
0
Interrupt is cleared or not triggered yet
1
Interrupt is triggered
2. Range/Gain; Bits 3 and 2. The Full Scale Range can be
adjusted by an external resistor REXT and/or it can be
adjusted via I2C using the Gain/Range function.
Gain/Range has four possible values, Range(k) where k
is 1 through 4. Table 9 lists the possible values of
Range(k) and the resulting FSR for some typical value
REXT resistors.
Timer Data Register 06(hex) and 07(hex)
Note that the timer counter value is only available when
using the External Timing Mode. The 06(hex) and 07(hex)
are the LSB and MSB respectively of a 16-bit timer counter
value corresponding to the most recent sensor reading.
Each clock cycle increments the counter. At the end of each
integration period, the value of this counter is made available
over the I2C. This value can be used to eliminate noise
introduced by slight timing errors caused by imprecise
external timing. Microcontrollers, for example, often cannot
provide high-accuracy command-to-command timing, and
the timer counter value can be used to eliminate the
resulting noise.
TABLE 11. DATA REGISTERS
TABLE 9. RANGE/GAIN TYPICAL FSR LUX RANGES
BITS
3:2 k RANGE(k)
FSR LUX
RANGE@
REXT = 50k
FSR LUX
FSR LUX
RANGE@
RANGE@
REXT = 100k REXT = 500k
ADDRESS
(hex)
CONTENTS
04
Least-significant byte of most recent sensor reading.
Most-significant byte of most recent sensor reading.
0:0
1
2,000
2,000
1,000
200
05
0:1
2
8,000
8,000
4,000
800
06
Least-significant byte of timer counter value
corresponding to most recent sensor reading.
1:0
3
32,000
32,000
16,000
3200
07
1:1
4
128,000
128,000
64,000
12,800
Most-significant byte of timer counter value
corresponding to most recent sensor reading.
Interrupt persist; Bits 1 and 0. The interrupt pin and the
interrupt flag is triggered/set when the data sensor reading is
out of the interrupt threshold window after m consecutive
number of integration cycles. The interrupt persist bits
determine m.
TABLE 10. INTERRUPT PERSIST
BITS 1:0
NUMBER OF INTEGRATION CYCLES
0:0
1
0:1
4
1:0
8
1:1
16
Interrupt Threshold HI Register 02(hex)
This register sets the HI threshold for the interrupt pin and
the interrupt flag. By default the Interrupt threshold HI is
FF(hex). The 8-bit data written to the register represents the
upper MSB of a 16-bit value. The LSB is always 00(hex).
Calculating Lux
The ISL29012’s output codes, DATA, are directly
proportional to lux.
E = α × DATA
(EQ. 1)
The proportionality constant α is determined by the Full
Scale Range (FSR), and the n-bit ADC which is user defined
in the command register. The proportionality constant can
also be viewed as the resolution; The smallest lux
measurement the device can measure is α.
FSR
α = -----------n
2
(EQ. 2)
Full Scale Range (FSR), is determined by the software
programmable Range/Gain, Range(k), in the command
register and an external scaling resistor REXT which is
referenced to 100kΩ.
100kΩ
FSR = Range ( k ) × -----------------R EXT
(EQ. 3)
Interrupt Threshold LO Register 03(hex)
This register sets the LO threshold for the interrupt pin and
the interrupt flag. By default, the Interrupt threshold LO is
00(hex). The 8-bit data written to the register represents the
upper MSB of a 16-bit value. The LSB is always 00(hex).
6
FN6476.1
December 10, 2008
ISL29012
The transfer function effectively for each timing mode
becomes:
TABLE 12. RESOLUTION AND INTEGRATION TIME
SELECTION
RANGE1
fOSC = 327kHz
INTERNAL TIMING MODE
100kΩ
Range ( k ) × -----------------R EXT
E = ---------------------------------------------------- × DATA
n
2
(EQ. 4)
EXTERNAL TIMING MODE
100kΩ
Range ( k ) × -----------------R EXT
E = ---------------------------------------------------- × DATA
COUNTER
(EQ. 5)
n = 3, 7, 11, or 15. This is the number of clock cycles
programmed in the command register.
Range(k) is the user defined range in the Gain/Range bit
in the command register.
REXT is an external scaling resistor hardwired to the REXT
pin.
DATA is the output sensor reading in number of counts
available at the data register.
2n represents the maximum number of counts possible in
Internal Timing Mode. For the External Timing Mode the
maximum number of counts is stored in the data register
named COUNTER.
COUNTER is the number increments accrued for between
integration time for External Timing Mode.
Gain/Range, Range(k)
The Gain/Range can be programmed in the control register
to give Range(k) determining the FSR. Note that Range(k) is
not the FSR (see Equation 3). Range(k) provides four
constants depending on programmed k that will be scaled by
REXT (see Table 9). Unlike REXT, Range(k) dynamically
adjusts the FSR. This function is especially useful when light
conditions are varying drastically while maintaining excellent
resolution.
Number of Clock Cycles, n-bit ADC
The number of clock cycles determines “n” in the n-bit ADC; 2n
clock cycles is a n-bit ADC. n is programmable in the command
register in the width function. Depending on the application, a
good balance of speed, and resolution has to be considered
when deciding for n. For fast and quick measurement, choose
the smallest n = 3. For maximum resolution without regard of
time, choose n = 15. Table 12 compares the trade-off between
integration time and resolution. See Equations 10 and 11 for the
relation between integration time and n. See Equation 3 for the
relation of n and resolution.
RANGE4
fOSC = 655kHz
n
tINT
(ms)
RESOLUTION
LUX/COUNT
tINT
(ms)
RESOLUTION
(LUX/COUNT)
15
200
0.06
100
2
11
12.8
1.0
6.4
62.5
7
0.8
15.6
0.4
1,000
3
0.05
250
0.025
16,000
REXT = 100kΩ
External Scaling Resistor REXT and fOSC
The ISL29012 uses an external resistor REXT to fix its
internal oscillator frequency, fOSC. Consequently, REXT
determines the fOSC, integration time and the FSR of the
device. fOSC, a dual speed mode oscillator, is inversely
proportional to REXT. For user simplicity, the proportionality
constant is referenced to fixed constants 100kΩ and 655kHz
in Equations 6 and 7:
1 100kΩ
f OSC 1 = --- × ------------------ × 684 kHz
2 R EXT
(EQ. 6)
100kΩ
f OSC 2 = ------------------ × 684 kHz
R EXT
(EQ. 7)
fOSC1 is oscillator frequency when Range1 or Range2 are
set. This is nominally 342kHz when REXT is 100kΩ.
fOSC2 is the oscillator frequency when Range3 or Range4
are set. This is nominally 684kHz when REXT is 100kΩ.
When the Range/Gain bits are set to Range1 or Range2,
fOSC runs at half speed compared to when Range/Gain bits
are set to Range3 and Range4 by using Equation 8:
1
f OSC 1 = --- ( f OSC 2 )
2
(EQ. 8)
The automatic fOSC adjustment feature allows significant
improvement of signal-to-noise ratio when detecting very low
lux signals.
Integration Time or Conversion Time
Integration time is the period during which the device’s
analog-to-digital ADC converter samples the photodiode
current signal for a lux measurement. Integration time, in
other words, is the time to complete the conversion of analog
photodiode current into a digital signal--number of counts.
Integration time affects the measurement resolution. For
better resolution, use a longer integration time. For short and
fast conversions, use a shorter integration time.
The ISL29012 offers user flexibility in the integration time to
balance resolution, speed and noise rejection. Integration time
can be set internally or externally and can be programmed in
the command register 00(hex) Bit 5.
7
FN6476.1
December 10, 2008
ISL29012
Integration time in Internal Timing Mode
This timing mode is programmed in the command register
00(hex) Bit 5. Most applications will be using this timing
mode. When using the Internal Timing Mode, fOSC and
n-bits resolution determine the integration time. tINT is a
function of the number of clock cycles and fOSC as shown in
Equation 9:
t INT = 2
m
1
× ---------f osc
(EQ. 9)
for Internal Timing Mode only
m = 4, 8, 12, and16. n is the number of bits of resolution.
2m therefore is the number of clock cycles. n can be
programmed at the command register 00(hex) Bits 1 and 0.
Since fOSC is dual speed depending on the Gain/Range bit,
tINT is dual time. The integration time as a function of REXT
is shown in Equation 10:
t INT 1 = 2
m
R EXT
× ---------------------------------------------342kHz × 100kΩ
(EQ. 10)
tINT1 is the integration time when the device is configured
for Internal Timing Mode and Gain/Range is set to Range1
or Range2.
t INT 2 = 2
m
R EXT
× ---------------------------------------------684kHz × 100kΩ
(EQ. 11)
tINT2 is the integration time when the device is configured
for Internal Timing Mode and Gain/Range is set to Range3
or Range4.
TABLE 13. INTEGRATION TIMES FOR TYPICAL REXT VALUES
RANGE1
RANGE2
RANGE3
RANGE4
REXT
(kΩ)
n = 15-BIT
n = 11-BIT
n = 11-BIT
n=3
50
100
6.4
3.2
0.013
100**
200
13
6.5
0.025
200
400
26
13
0.050
500
1000
64
32
0.125
*Integration time in milliseconds
**Recommended REXT resistor value
Integration time in External Timing Mode
This timing mode is programmed in the command register
00(hex) Bit 5. External Timing Mode is recommended when
integration time can be synchronized to an external signal
such as a PWM to eliminate noise.
To read the light count DATA output, the device needs three
sync_I2C commands to complete one measurement. The 1st
sync_I2C command starts the conversion of the diode array 1.
The 2nd sync_I2C completes the conversion of diode array 1
and starts the conversion of diode array 2. The 3rd sync_I2C
pules ends the conversion of diode array 2, outputs the light
8
count DATA, and starts over again to commence conversion
of diode array 1.
The integration time, tINT, is the sum of two identical time
intervals between the three sync pulses. tINT is determined
by Equation 12:
k OSC
t INT = --------------f OSC
(EQ. 12)
where KOSC is the number of internal clock cycles obtained
from Timer data register and fOSC is the internal I2C
operating frequency
The internal oscillator, fOSC, operates identically in both the
internal and external timing modes, with the same
dependence on REXT. However, in External Timing Mode,
the number of clock cycles per integration is no longer fixed
at 2n. The number of clock cycles varies with the chosen
integration time, and is limited to 216 = 65,536. In order to
avoid erroneous lux readings, the integration time must be
short enough not to allow an overflow in the counter register.
65,535
t INT < -----------------f OSC
(EQ. 13)
fOSC = 342kHz*100kΩ/REXT. When Range/Gain is set to
Range1 or Range2.
fosc = 684kHz*100kΩ/REXT. When Range/Gain is set to
Range3 or Range4.
Noise Rejection
In general, integrating type ADC’s have excellent
noise-rejection characteristics for periodic noise sources
whose frequency is an integer multiple of the integration
time. For instance, a 60Hz AC unwanted signal’s sum from
0ms to k*16.66ms (k = 1,2...ki) is zero. Similarly, setting the
device’s integration time to be an integer multiple of the
periodic noise signal, greatly improves the light sensor
output signal in the presence of noise.
Ambient Light Sensing Operation
The operation of ambient light sensing (ALS) within the
ISL29012 utilizes two diodes; D1 and D2. The D1 diode is
sensitive to both visible and IR light spectrum. The D2 diode
is sensitive to IR spectrum. D1 and D2 spectrum response is
shown in Figure 21. The diodes are measured sequentially
and their outputs are converted with an ADC. The output of
the ALS is the difference between these two measurements.
Maximum Ambient Intensity Condition
In typical applications, the ISL29012 is installed behind a
dark cover window. In this low-light condition, both D1 and
D2 operate linearly and the ALS output is linear as well
(Figures 19 and 20). In brighter environments and with
transparent glass, however, D1 and D2 can be subject to
saturation. As the ambient light grows bright enough to
subject one or both diodes to saturation, the ALS count
(output) decreases and eventually reaches zero in deep
FN6476.1
December 10, 2008
ISL29012
saturation (Figure 18). When using the ISL29012 in high lux
applications, one can reduce the REXT value and select
Range4, the lowest gain to avoid saturation. For example,
REXT = 25kΩ is recommended with ambient light near
100,000 lux. If you are operating the ISL29012 at a lower
range/higher gain and detect a zero output, the firmware
should change the range and recheck the ALS count. One of
two situations will be identified. If the output is non-zero, the
ISL29012 is saturated. If the output remains zero, the
ISL29012 is in a totally dark environment.
.
WINDOW LENS
t
ISL29012
Unstable Ambient Light Condition
The ISL29012 sequentially measures the difference in the
output of two diodes. That's suitable since most changes in
ambient light are gradual and any difference between the
ambient light conditions for D1 and D2 are negligible.
However, it is possible to cause an abrupt change in
brightness with a fast-moving hand over the sensor or
passing a tree shadow in a fast moving car. To handle these
anomalies, we suggest comparing several sequential
readings and discarding any data with sudden changes.
Flat Window Lens Design
A window lens will surely limit the viewing angle of the
ISL29012. The window lens should be placed directly on top
of the device. The thickness of the lens should be kept at
minimum to minimize loss of power due to reflection and
also to minimize loss of loss due to absorption of energy in
the plastic material. A thickness of t = 1mm is recommended
for a window lens design. The bigger the diameter of the
window lens the wider the viewing angle is of the ISL29012.
Table 14 shows the recommended dimensions of the optical
window to ensure both 35° and 45° viewing angle. These
dimensions are based on a window lens thickness of 1.0mm
and a refractive index of 1.59.
9
E=
DATA
215
D1
DLENS
ALS Range For Various Light Sources
Figure 9 shows spectrum response of various light sources.
Fluorescent has little IR content while sunlight, halogen and
incandescent light have large IR content. Since both the
internal photo diodes D1 and D2 are sensitive to IR
spectrum, they saturate at a higher level for the fluorescent
light source in comparison to the other 3 light sources. This
effect is shown in Figure 22.
DTOTAL
∅
∅ = VIEWING ANGLE
x 2000
FIGURE 4. FLAT WINDOW LENS
TABLE 14. RECOMMENDED DIMENSIONS FOR A FLAT
WINDOW DESIGN
DTOTAL
D1
DLENS @ 35°
VIEWING ANGLE
DLENS @ 45°
VIEWING ANGLE
1.5
0.50
2.25
3.75
2.0
1.00
3.00
4.75
2.5
1.50
3.75
5.75
3.0
2.00
4.30
6.75
3.5
2.50
5.00
7.75
t=1
d1
DLENS
dTOTAL
Thickness of lens
Distance between ISL29012 and inner edge of lens
Diameter of lens
Distance constraint between the ISL29012 and lens
outer edge
* All dimensions are in mm.
Window with Light Guide Design
If a smaller window is desired while maintaining a wide
effective viewing angle of the ISL29012, a cylindrical piece of
transparent plastic is needed to trap the light and then focus
and guide the light on to the device. Hence, the name light
guide or also known as light pipe. The pipe should be placed
directly on top of the device with a distance of d1 = 0.5mm to
achieve peak performance. The light pipe should have a
minimum of 1.5mm in diameter to ensure that whole area of
the sensor will be exposed. See Figure 5.
FN6476.1
December 10, 2008
ISL29012
DLENS
D2 > 1.5mm
LIGHT PIPE
t
D2
DLENS
L
ISL29012
FIGURE 5. WINDOW WITH LIGHT GUIDE/PIPE
Suggested PCB Footprint
Typical Circuit
It is important that the users check the “Surface Mount
Assembly Guidelines for Optical Dual FlatPack No Lead
(ODFN) Package” before starting ODFN product board
mounting.
A typical application for the ISL29012 is shown in Figure 6.
The ISL29012’s I2C address is internally hardwired as
1000100. The device can be tied onto a system’s I2C bus
together with other I2C compliant devices.
http://www.intersil.com/data/tb/TB477.pdf
Soldering Considerations
Layout Considerations
Convection heating is recommended for reflow soldering;
direct-infrared heating is not recommended. The plastic
ODFN package does not require a custom reflow soldering
profile, and is qualified to +260°C. A standard reflow
soldering profile with a +260°C maximum is recommended.
The ISL29012 is relatively insensitive to layout. Like other
I2C devices, it is intended to provide excellent performance
even in significantly noisy environments. There are only a
few considerations that will ensure best performance.
Route the supply and I2C traces as far as possible from all
sources of noise. Use one 0.01µF power-supply decoupling
capacitor, placed close to the device.
10
FN6476.1
December 10, 2008
ISL29012
2.5V TO 5.5V
R1
10k
R2
10k
I2C MASTER
R3
RES1
MICROCONTROLLER
SDA
SCL
INT
2.5V TO 3.3V
I2C SLAVE_0
1
2
C1
3
0.01µF
I2C SLAVE_1
VDD
SDA
GND
SCL
REXT
INT
REXT
100k
I2C SLAVE_n
6
SDA
SDA
5
SCL
SCL
4
ISL29012
FIGURE 6. ISL29012 TYPICAL CIRCUIT
Typical Performance Curves (REXT = 100kΩ)
1.2
NORMALIZED RESPONSE
HUMAN EYE RESPONSE
RADIATION PATTERN
1.0
20°
10°
0°
10°
LUMINOSITY
30°
ANGLE 40°
0.8
0.6
20°
30°
40°
50°
50°
ISL29012 RESPONSE
60°
60°
0.4
70°
70°
0.2
80°
0.0
80°
90°
-0.2
300
400
600
800
WAVELENGTH (nm)
1.0k
0.2 0.4
0.6 0.8
RELATIVE SENSITIVITY
1.1k
FIGURE 8. RADIATION PATTERN
FIGURE 7. SPECTRAL RESPONSE
1.2
320
TA = +27°C
1.0
SUN
0.8
HALOGEN
0.6
INCANDESCENT
FLUORESCENT
0.4
0.2
0
300
400
500
600
700
800
900
1000
WAVELENGTH (nm)
FIGURE 9. SPECTRUM OF LIGHT SOURCES FOR
MEASUREMENT
11
1100
SUPPLY CURRENT (µA)
NORMALIZED LIGHT INTENSITY
90°
1.0
306
5000 lux
292
278
200 lux
264
250
2.0
2.3
2.6
2.9
3.2
3.5
3.8
SUPPLY VOLTAGE (V)
FIGURE 10. SUPPLY CURRENT vs SUPPLY VOLTAGE
FN6476.1
December 10, 2008
ISL29012
Typical Performance Curves (REXT = 100kΩ)
(Continued)
1.015
TA = +27°C
0 lux
TA = +27°C
8
OUTPUT CODE RATIO
(% FROM 3V)
OUTPUT CODE (COUNTS)
10
6
4
RANGE 2
2
0
2.0
2.3
2.6
2.9
3.2
3.5
1.010
5000 lux
1.005
1.000
0.990
2.0
3.8
200 lux
0.995
2.3
2.6
SUPPLY VOLTAGE (V)
FIGURE 11. OUTPUT CODE FOR 0 LUX vs SUPPLY VOLTAGE
SUPPLY CURRENT (mA)
OSCILLATOR FREQUENCY (kHz)
319.0
318.5
318.0
2.0
2.3
2.6
2.9
3.2
3.5
305
5000 lux
RANGE 3
295
285
200 lux
RANGE 1
275
265
-60
3.8
-20
SUPPLY VOLTAGE (V)
20
60
100
TEMPERATURE (°C)
FIGURE 13. OSCILLATOR FREQUENCY vs SUPPLY VOLTAGE
FIGURE 14. SUPPLY CURRENT vs TEMPERATURE
10
1.080
VDD = 3V
VDD = 3V
0 lux
OUTPUT CODE RATIO
(% FROM +25°C)
OUTPUT CODE (COUNTS)
3.8
VDD = 3V
319.5
6
4
0
-60
3.5
315
TA = +27°C
2
3.2
FIGURE 12. OUTPUT CODE vs SUPPLY VOLTAGE
320.0
8
2.9
SUPPLY VOLTAGE (V)
RANGE 2
-20
20
60
TEMPERATURE (°C)
FIGURE 15. OUTPUT CODE FOR 0 LUX vs TEMPERATURE
12
1.048
5000 lux
RANGE3
1.016
200 lux
RANGE1
0.984
0.952
0.920
-60
-20
20
60
100
TEMPERATURE (°C)
FIGURE 16. OUTPUT CODE vs TEMPERATURE
FN6476.1
December 10, 2008
ISL29012
Typical Performance Curves (REXT = 100kΩ)
(Continued)
12k
ALS RANGE 3
VDD = 3V
ADC READING (COUNTS)
OSCILLATOR FREQUENCY (kHz)
330
329
328
327
326
325
-60
-20
20
10k
ALS RANGE 4
8k
6k
4k
2k
0
60
100
0
20k
TEMPERATURE (°C)
FIGURE 17. OSCILLATOR FREQUENCY vs TEMPERATURE
HALOGEN
800
INCANDESCENT
600
FLUORESCENT
500
400
300
200
100
0
0
100
200
300
400
500
600
700
800
900
VDD = 3V
90
100k
120k
HALOGEN
80
70
FLUORESCENT
60
50
40
INCANDESCENT
30
20
10
0
1k
0
10
20
30
40
50
60
70
80
90
100
LUX METER READING (LUX)
LUX METER READING (LUX)
FIGURE 19. LIGHT SENSITIVITY vs LUX LEVEL
FIGURE 20. LIGHT SENSITIVITY vs LUX LEVEL
18000
1.2
HUMAN EYE RESPONSE
16000
INTERNAL
D1
1.0
0.8
INTERNAL
D2
0.6
0.4
0.2
0
ALS OUTPUT (D1 - D2)
NORMALIZED RESPONSE
80k
100
VDD = 3V
900
700
60k
FIGURE 18. SATURATION CHARACTERISTICS
CALCULATED ALS READING (LUX)
CALCULATED ALS READING (LUX)
1000
40k
LUX METER READING (LUX), SUN LIGHT
FLUORESCENT
14000
12000
10000
SUNLIGHT
8000
6000 HALOGEN
INCANDESCENT
4000
2000
0
-0.2
400
500
600
700
800
900
1000
WAVELENGTH (nm)
FIGURE 21. SPECTRAL RESPONSE INTERNAL DIODES
13
1100
00
30
00
28
00
26
00
24
00
22
00
20
00
18
00
16
00
14
00
12
00
10
0
80
0
60
0
40
0
20
0
300
LUX METER READING (LUX)
FIGURE 22. ALS OUTPUT vs LUX LEVEL @ RANGE = 1,
REXT = 50kΩ
FN6476.1
December 10, 2008
ISL29012
2.10mm
2.00mm
VDD
1
6
SDA
GND
2
5
SCK
0.29mm
0.56mm
REXT
3
4
INT
0.43mm
FIGURE 23. 6 LD ODFN SENSOR LOCATION OUTLINE
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
14
FN6476.1
December 10, 2008
ISL29012
Package Outline Drawing
L6.2x2.1
6 LEAD OPTICAL DUAL FLAT NO-LEAD PLASTIC PACKAGE (ODFN)
Rev 0, 9/06
2.10
A
6
PIN 1
INDEX AREA
B
1
6
PIN 1
INDEX AREA
0.65
2.00
(4X)
1 . 30 REF
1 . 35
0.10
6X 0 . 30 ± 0 . 05
0 . 65
TOP VIEW
0.10 M C A B
6X 0 . 35 ± 0 . 05
BOTTOM VIEW
(0 . 65)
MAX 0.75
SEE DETAIL "X"
0.10 C
(0 . 65)
(1 . 35)
C
BASE PLANE
( 6X 0 . 30 )
SEATING PLANE
0.08 C
SIDE VIEW
( 6X 0 . 55 )
C
0 . 2 REF
5
(1 . 95)
0 . 00 MIN.
0 . 05 MAX.
DETAIL "X"
TYPICAL RECOMMENDED LAND PATTERN
NOTES:
1. Dimensions are in millimeters.
Dimensions in ( ) for Reference Only.
2. Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
3. Unless otherwise specified, tolerance : Decimal ± 0.05
4. Dimension b applies to the metallized terminal and is measured
between 0.15mm and 0.30mm from the terminal tip.
5. Tiebar shown (if present) is a non-functional feature.
6. The configuration of the pin #1 identifier is optional, but must be
located within the zone indicated. The pin #1 identifier may be
either a mold or mark feature.
15
FN6476.1
December 10, 2008