INTERSIL ISL76683AROZ-T7

Light-to-Digital Output Sensor with Gain Selection,
Interrupt Function and I2C Interface
ISL76683
Features
The ISL76683 is an integrated light sensor with an internal
integrating ADC intended for automotive applications. The ADC
provides 16-bit resolution and is capable of rejecting 50Hz and
60Hz flicker caused by artificial light sources. The I2C interface
provides four user programmable lux sensitivity ranges for
optimized counts/lux in a variety of lighting conditions. In
addition, the I2C interface provides multi-function control of the
sensor and remote monitoring capabilities.
• Range select via I2C
- Range 1 = 0 lux to 1000 lux
- Range 2 = 0 lux to 4000 lux
- Range 3 = 0 lux to 16,000 lux
- Range 4 = 0 lux to 64,000 lux
• Human Eye Response (540nm Peak Sensitivity)
• Temperature Compensated
In normal operation, power consumption is less than 300µA.
Furthermore, a software power-down mode controlled via the I2C
interface reduces power consumption to less than 1µA.
• 16-bit Resolution
• Adjustable Sensitivity: up to 65 Counts per Lux
The ISL76683 supports twin (upper & lower) user programmed
thresholds and provides a hardware interrupt that remains
asserted low until the host clears it via the I2C control interface.
• User-programmable Upper and Lower Threshold Interrupt
Designed to operate on supplies from 2.5V to 3.3V, the ISL76683 is
qualified to AECQ100 and specified for operation over the -40°C to
+105°C (grade 2) ambient temperature range. To achieve this, the
ISL76683 is packaged in a special extended temperature clear
package.
• 50Hz/60Hz Rejection
• Simple Output Code, Directly Proportional to Lux
• IR + UV Rejection
• 2.5V to 3.3V Supply
• 6 Ld ODFN (2.1mmx2mm)
• Pb-free (RoHS compliant)
Applications
• Automotive Ambient Light Sensing
• Backlight Control
• Lighting Controls
VDD
1
MUX
SHDN
INT TIME
GAIN/RANGE
MODE
PHOTODIODE 1
INTEGRATING
ADC
PHOTODIODE 2
FOSC
I2C
5
SCL
6
SDA
INT
216
COUNTER
3
DATA
REGISTER
EXT
TIMING
IREF
REXT
COMMAND
REGISTER
INTERRUPT
4 INT
2
GND
ISL76683
FIGURE 1. BLOCK DIAGRAM
March 17, 2011
FN7697.2
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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ISL76683
Pin Configuration
ISL76683
(6 LD ODFN)
TOP VIEW
VDD 1
GND 2
6 SDA
THERMAL
PAD
REXT 3
5 SCL
4 INT
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
4
INT
Interrupt pin; LO for interrupt/alarming. The INT pin is an open drain.
5
SCL
I2C serial clock
6
SDA
I2C serial data
The I2C bus lines can be pulled above VDD, 5.5V max.
Ordering Information
PART NUMBER
(Notes 1, 2, 3)
TEMP RANGE
(°C)
ISL76683AROZ-T7
-40 to +105
PACKAGE
(Pb-free)
6 Ld ODFN
PKG. DWG. #
L6.2x2.1
NOTES:
1. Please refer to TB347 for details on reel specifications.
2. 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.
3. For Moisture Sensitivity Level (MSL), please see device information page for ISL76683. For more information on MSL please see techbrief TB477.
2
FN7697.2
March 17, 2011
ISL76683
Absolute Maximum Ratings (TA = +25°C)
Thermal Information
VDD, Supply Voltage between VDD and GND. . . . . . . . . . . . . . . . . . . . . .3.6V
I2C Bus Pin Voltage (SCL, SDA). . . . . . . . . . . . . . . . . . . . . . . . . -0.2V to 5.5V
I2C Bus Pin Current (SCL, SDA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <10mA
INT, REXT Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.2V to VDD
ESD Rating
Human Body Model (Tested per JESD22-A114E) . . . . . . . . . . . . . . . . 2kV
Machine Model (Tested per JESD-A115-A) . . . . . . . . . . . . . . . . . . . 200V
Charge Device Model (Tested per JESD22-C101C). . . . . . . . . . . . . . . 1kV
Latch Up (Tested per JESD78B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100mA
Thermal Resistance (Typical)
θJA (°C/W) θJC (°C/W)
6 Ld ODFN Package (Notes 4, 5) . . . . . . . .
88
7.94
Maximum Die Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+105°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +105°C
Operating Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +105°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.
NOTES:
4. θJA is measured with in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379.
5. For θJC, “case temperature” location is at the center of the exposed metal pad on the package underside. See Tech Brief TB379.
Electrical Specifications VDD = 3V, TA = +25°C, REXT = 100kΩ 1% tolerance, unless otherwise specified, Internal Timing Mode
Operation (see “Principles of Operation” on page 6).
PARAMETER
MAX
(Note 6)
UNIT
3.3
V
0.29
0.33
mA
Software disabled, -40°C to +85°C
0.1
1
µA
Software disabled, -40°C to +105°C, VDD = 3.3V
0.1
8
µA
DESCRIPTION
VDD
Power Supply Range
IDD
Supply Current
IDD1
Supply Current Disabled
CONDITION
MIN
(Note 6)
TYP
2.25
fOSC1
Internal Oscillator Frequency
Gain/Range = 1 or 2
290
327
360
kHz
fOSC2
Internal Oscillator Frequency
Gain/Range = 3 or 4
580
655
720
kHz
FI2C
I2C Clock Rate
400
kHz
5
Counts
65535
Counts
24440
Counts
1
DATA0
Diode1 Dark ADC Code
DATA1
Full Scale ADC Code
DATA2
Diode1 ADC Code Gain/Range = 1
Accuracy
Mode1
DATA3
Diode2 ADC Code Gain/Range = 1
Accuracy
Mode2
DATA4
Diode1 ADC Code Gain/Range = 2
Accuracy
Mode1
DATA5
Diode2 ADC Code Gain/Range = 2
Accuracy
Mode2
DATA6
Diode1 ADC Code Gain/Range = 3
Accuracy
Mode1
DATA5
Diode2 ADC Code Gain/Range = 3
Accuracy
Mode2
DATA6
Diode1 ADC Code Gain/Range = 4
Accuracy
Mode1
DATA6
Diode2 ADC Code Gain/Range = 4
Accuracy
Mode2
Voltage of REXT Pin
-40°C to +85°C
VREF
E = 0 lux, Mode1, Gain/Range = 1
E = 300 lux, fluorescent light,
Gain/Range = 1
(Note 7)
15760
20200
2020
Counts
E = 300 lux, fluorescent light,
Gain/Range = 2
(Note 7)
5050
Counts
505
Counts
E = 300 lux, fluorescent light,
Gain/Range = 3
(Note 7)
1262
Counts
126
Counts
E = 300 lux, fluorescent light,
Gain/Range = 4
(Note 7)
316
Counts
32
Counts
0.485
0.51
-40°C to +105°C
0.535
V
0.545
V
V TL
SCL and SDA Threshold LO
(Note 8)
1.05
V
V TH
SCL and SDA Threshold HI
(Note 8)
1.95
V
3
FN7697.2
March 17, 2011
ISL76683
Electrical Specifications VDD = 3V, TA = +25°C, REXT = 100kΩ 1% tolerance, unless otherwise specified, Internal Timing Mode
Operation (see “Principles of Operation” on page 6). (Continued)
PARAMETER
DESCRIPTION
CONDITION
MIN
(Note 6)
TYP
MAX
(Note 6)
UNIT
ISDA
SDA Current Sinking Capability
3
5
mA
IINT
INT Current Sinking Capability
3
5
mA
NOTES:
6. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design.
7. Fluorescent light is substituted by a white LED during production.
8. The voltage threshold levels of the SDA and SCL pins are VDD dependent: VTL = 0.35*VDD. V TH = 0.65*VDD.
NORMALIZED RESPONSE (%)
Typical Performance Curves
(REXT = 100kΩ)
100
90
RADIATION PATTERN
ISL76683 D1
80
70
LUMINOSITY 30º
ANGLE
40º
60
50
0º
10º
20º
30º
40º
50º
60º
ISL76683 D2
30
60º
70º
20
70º
80º
10
0
300
400
500
600
700
800
WAVELENGTH (nm)
900
1k
80º
90º
0.2
0.4
0.6
0.8
1.0
RELATIVE SENSITIVITY
FIGURE 2. SPECTRAL RESPONSE
90º
FIGURE 3. RADIATION PATTERN
320
10
OUTPUT CODE (COUNTS)
TA = +27°C
COMMAND = 00H
306
SUPPLY CURRENT (µA)
10º
50º
40
5000 lux
292
278
200 lux
264
250
20º
2.0
2.3
2.6
2.9
3.2
3.5
SUPPLY VOLTAGE (V)
FIGURE 4. SUPPLY CURRENT vs SUPPLY VOLTAGE
4
3.8
8
TA = +27°C
COMMAND = 00H
0 lux
6
4
RANGE 2
2
0
2.0
2.3
2.6
2.9
3.2
3.5
3.8
SUPPLY VOLTAGE (V)
FIGURE 5. OUTPUT CODE FOR 0 LUX vs SUPPLY VOLTAGE
FN7697.2
March 17, 2011
ISL76683
Typical Performance Curves
(REXT = 100kΩ) (Continued)
1.015
320.0
TA = +27°C
COMMAND = 00H
OSCILLATOR FREQUENCY (kHz)
OUTPUT CODE RATIO
(% FROM 3V)
1.010
TA = +27°C
5000 lux
1.005
1.000
200 lux
0.995
0.990
2.0
2.3
2.6
2.9
3.2
3.5
319.5
319.0
318.5
318.0
3.8
2.0
2.3
2.6
SUPPLY VOLTAGE (V)
FIGURE 6. OUTPUT CODE vs SUPPLY VOLTAGE
3.5
3.8
10
VDD = 3V
OUTPUT CODE (COUNTS)
320
SUPPLY CURRENT (µA)
3.2
FIGURE 7. OSCILLATOR FREQUENCY vs SUPPLY VOLTAGE
330
310
300
290
280
270
260
-60
-40
-20
0
20
40
60
TEMPERATURE (°C)
80
100
1.08
1.04
5000 LUX
200 LUX
RANGE 3
0.98
RANGE 1
0.96
0.94
0.92
-60
-40
-20
4
RANGE2
2
-40
-20
0
20
40
60
80
100
120
FIGURE 9. OUTPUT CODE FOR 0 LUX vs TEMPERATURE
VDD = 3V
1.06
1.00
6
330
VDD = 3V
COMMAND = 00H
1.02
VDD - 3V
COMMAND = 00H
0 LUX
TEMPERATURE (°C)
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 10. OUTPUT CODE vs TEMPERATURE
5
100 120
OSCILLATOR FREQUENCY (kHz)
1.10
8
0
-60
120
FIGURE 8. SUPPLY CURRENT vs TEMPERATURE
OUTPUT CODE RATIO
(% FROM +25°C)
2.9
SUPPLY VOLTAGE (V)
329
328
327
326
325
-60
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 11. OSCILLATOR FREQUENCY vs TEMPERATURE
FN7697.2
March 17, 2011
ISL76683
Principles of Operation
Interrupt Function
Photodiodes
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
eliminates any 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.
The ISL76683 contains two photodiodes. Diode1 is sensitive to
both visible and infrared light, while Diode2 is mostly sensitive to
infrared light. The spectral response of the two diodes are
independent from one another. See Figure 2 “Spectral Response” in
the “Typical Performance Curves” section. The photodiodes
convert light to current then the diodes’ current outputs are
converted to digital by a single built-in integrating type 16-bit
Analog-to-Digital Converter (ADC). An I2C command mode
determines which photodiode will be converted to a digital signal.
Mode1 is Diode1 only. Mode2 is Diode2 only. Mode3 is a
sequential Mode1 and Mode2 with an internal subtract function
(Diode1 - Diode2).
Analog-to-Digital Converter (ADC)
The converter is a charge-balancing integrating type 16-bit ADC.
The chosen method for conversion is best for converting small
current signals in the presence of 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 11 and “Noise Rejection” on page 12.
The built-in ADC offers the user flexibility in integration time or
conversion time. Two timing modes are available; 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 10. 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.
6
I2C Interface
There are eight (8) 8-bit registers available inside the ISL76683. 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 ISL76683’s I2C interface slave address is hardwired
internally as 1000100. When 1000100x with x as R or W is sent
after the Start condition, this device compares the first seven bits
of this byte to its address and matches.
Figure 12 shows a sample one-byte read. Figure 13 shows a sample
one-byte write. Figure 14 shows a sync_iic 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 13 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
Philips® I2C specification documents.
FN7697.2
March 17, 2011
ISL76683
I2C DATA
Start
I2C SDA
In
DEVICE ADDRESS
A6
I2C SDA
Out
A5
A4
A3
A2
A1
A0
W
A
W
A
1
2
3
4
5
6
R7
7
8
9
R6
R5
R4
R3
R2
A
R1
R0
SDA DRIVEN BY MASTER
A
SDA DRIVEN BY MASTER
I2C CLK
REGISTER ADDRESS
1
2
3
4
5
6
7
8
STOP
DEVICE ADDRESS
START
A
A6
A5
A
SDA DRIVEN BY MASTER
9
1
2
A4
3
A3
4
A2
5
A1
A0
6
W
7
8
A
DATA BYTE0
A
A
ISL76683
SDA DRIVEN BY
ISL29003
STOP
NAK
A
D7
D6
D5
D4
D3
D2
D1
D0
A
9
1
2
3
4
5
6
7
8
9
FIGURE 12. I2C READ TIMING DIAGRAM SAMPLE
I2C DATA
Start
I2C SDA In
DEVICE ADDRESS
W
A
A6 A5 A4 A3 A2 A1 A0
W
A
I2C SDA Out
1
2
3
4
5
6
R7 R6
A
SDA DRIVEN BY MASTER
I2C CLK In
REGISTER ADDRESS
7
8
R5 R4 R3
A
R2 R1 R0
1
2
3
4
5
6
7
B7
A
SDA DRIVEN BY MASTER
9
A
FUNCTIONS
8
B6 B5 B4 B3 B2
A
B1 B0
1
2
3
4
5
6
7
A
A
SDA DRIVEN BY MASTER
9
STOP
8
9
FIGURE 13. I2C WRITE TIMING DIAGRAM SAMPLE
Start
I2 C DA TA
I2 C SDA In
DEVICE ADDRESS
A6
I2 C SDA Out
A5
A4
A3
A2
A1
A0
W
A
W
A
1
2
3
4
5
6
R7
A
SDA DRIV EN BY MA STER
I2 C CLK In
REGISTER ADDRESS
7
8
9
R6
R5
R4
R3
R2
A Stop
R1
R0
A
SDA DRIV EN BY MA STER
1
2
3
4
5
6
7
A
8
9
FIGURE 14. I2C sync_iic TIMING DIAGRAM SAMPLE
7
FN7697.2
March 17, 2011
ISL76683
Register Set
There are eight registers that are available in the ISL76683. Table 1 summarizes the available registers and their functions.
TABLE 1. REGISTER SET
ADDR
(HEX)
REGISTER
NAME
BIT(S)
FUNCTION NAME
00
Command
7
Enable
0: disable ADC-core
1: enable ADC-core
6
ADCPD
0: Normal operation
1: Power-down Mode
5
Timing_Mode
4
Reserved
3:2
Mode<1:0>
Selects ADC work mode
0: Diode1’s current to unsigned 16-bit data
1: Diode2’s current to unsigned 16-bit data
2: Difference between diodes (I1 - I2) to signed 15-bit data
3: reserved
1:0
Width<1:0>
Number of clock cycles; n-bit resolution
0: 216 cycles
1: 212 cycles
2: 28 cycles
3: 24 cycles
7
Ext_Mode
Always set to logic 0. Factory use only.
6
Test_Mode
Always set to logic 0
5
Int_Flag
0: Interrupt is cleared or not yet triggered
1: Interrupt is triggered
4
Reserved
Always set to logic 0. Factory use only.
3:2
Gain<1:0>
Selects the gain so range is
0: 0 to 1000 lux
1: 0 to 4000 lux
2: 0 to 16000 lux
3: 0 to 64000 lux
1:0
Int_Persist
<1:0>
Interrupt is triggered after
0: 1 integration cycle
1: 4 integration cycles
2: 8 integration cycles
3: 16 integration cycles
01
Control
FUNCTIONS/DESCRIPTION
0: Integration is internally timed
1: Integration is externally sync/controlled by I2C host
02
Interrupt Threshold
HI
7:0
Interrupt Threshold
HI
High byte of HI interrupt threshold. Default is 0xFF
03
Interrupt Threshold
LO
7:0
Interrupt Threshold
LO
High byte of the LO interrupt threshold. Default is 0x00
04
LSB_Sensor
7:0
LSB_Sensor
Read-Only data register that contains the least significant byte of the latest
sensor reading.
05
MSB_Sensor
7:0
MSB_Sensor
Read-Only data register that contains the most significant byte of the latest
sensor reading.
06
LSB_Timer
7:0
LSB_Timer
Read-Only data register that contains the least significant byte of the timer
counter value corresponding to the latest sensor reading.
07
MSB_Timer
7:0
MSB_Timer
Read-Only data register that contains the most significant byte of the timer
counter value corresponding to the latest sensor reading.
8
FN7697.2
March 17, 2011
ISL76683
TABLE 2. WRITE ONLY REGISTERS
ADDRESS
REGISTER
NAME
FUNCTIONS/
DESCRIPTION
b1xxx_xxxx
sync_iic
Writing a logic 1 to this address bit ends
the current ADC-integration and starts
another. Used only with External Timing
Mode.
bx1xx_xxxx
clar_int
Writing a logic 1 to this address bit clears
the interrupt.
Command Register 00(hex)
4. Photodiode Select Mode; Bits 3 and 2. This function controls
the mux attached to the two photodiodes. At Mode1, the mux
directs the current of Diode1 to the ADC. At Mode2, the mux
directs the current of Diode2 only to the ADC. Mode3 is a
sequential Mode1 and Mode2 with an internal subtract
function (Diode1 - Diode2).
TABLE 6. PHOTODIODE SELECT MODE; BITS 2 AND 3
BITS 3:2
MODE
0:0
MODE1. ADC integrates or converts Diode1 only. Current
is converted to an n-bit unsigned data.*
0:1
MODE2. ADC integrates or coverts Diode2 only. Current is
converted to an n-bit unsigned data.*
1:0
MODE3. A sequential MODE1 then MODE2 operation.
The difference current is an (n-1) signed data.*
1:1
No Operation.
The Read/Write command register has five functions:
1. Enable; Bit 7. This function either resets the ADC or enables
the ADC in normal operation. A logic 0 disables ADC to resetmode. A logic 1 enables ADC to normal operation.
TABLE 3. ENABLE
BIT 7
OPERATION
0
Disable ADC-Core to Reset-Mode (default)
1
Enable ADC-Core to Normal Operation
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.
TABLE 4. ADCPD
BIT 6
OPERATION
*n = 4, 8, 12,16 depending on the number of clock cycles
function.
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 7. WIDTH
BITS 1:0
NUMBER OF CLOCK CYCLES
0:0
216 = 65,536
0
Normal Operation (default)
0:1
212 = 4,096
1
Power-Down
1:0
28 = 256
1:1
24 = 16
For proper shut down operation, it is recommended to disable
ADC first then disable the chip. Specifically, the user should first
send I2C command with Bit 7 = 0 and then send I2C command
with Bit 6 = 1.
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 two consecutive external-sync
sync_iic pulse commands.
TABLE 5. TIMING MODE
BIT 5
OPERATION
0
Internal Timing Mode. Integration time is internally
timed determined by fOSC, REXT, and number of clock
cycles.
1
External Timing Mode. Integration time is externally
timed by the I2C host.
9
Control Register 01(hex)
The Read/Write control register has three functions:
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
FN7697.2
March 17, 2011
ISL76683
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.
TABLE 9. RANGE/GAIN TYPICAL FSR LUX RANGES
BITS
3:2
k
RANGE
(k)
FSR LUX
RANGE@
REXT = 100k
0:0
1
973
973
1946
195
0:1
2
3892
3892
7784
778
1:0
3
15,568
15,568
31,136
3114
1:1
4
62,272
62,272
124,544
12,454
FSR LUX
RANGE@
REXT = 50k
FSR LUX
RANGE@
REXT = 500k
3. 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).
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).
Sensor Data Register 04(hex) and 05(hex)
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
ADDRESS
(hex)
CONTENTS
04
Least-significant byte of most recent sensor reading.
05
Most-significant byte of most recent sensor reading.
06
Least-significant byte of timer counter value corresponding to
most recent sensor reading.
07
Most-significant byte of timer counter value corresponding to
most recent sensor reading.
Calculating Lux
The ISL76683’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.
(EQ. 3)
100kΩ
FSR = Range ( k ) × ------------------R EXT
The transfer function effectively for each timing mode becomes:
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 = 4, 8, 12, or 16. This is the number of clock cycles
programmed in the command register.
When the device is configured to output a 16-bit data, the least
significant byte is accessed at 04(hex), and the most significant
byte can be accessed at 05(hex). The sensor data register is
refreshed after every integration cycle.
Range(k) is the user defined range in the Gain/Range bit in the
command register.
Timer Data Register 06(hex) and 07(hex)
DATA is the output sensor reading in number of counts available
at the data register.
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
10
REXT is an external scaling resistor hardwired to the REXT pin.
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.
FN7697.2
March 17, 2011
ISL76683
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 = 4. For
maximum resolution without regard of time, choose n = 16.
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.
TABLE 12. RESOLUTION AND INTEGRATION TIME SELECTION
RANGE1
fOSC = 327kHz
RANGE4
fOSC = 655kHz
Integration Time or Conversion Time
Integration time is the period during which the device’s analogto-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 ISL76683 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.
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.
tINT (ms)
RESOLUTION
LUX/COUNT
tINT (ms)
16
200
0.01
100
1
12
12.8
0.24
6.4
16
n = 4, 8, 12, and 16. n is the number of bits of resolution.
Therefore, 2n is the number of clock cycles. n can be programmed
at the command register 00(hex) bits 1 and 0.
n
RESOLUTION
(LUX/COUNT)
The automatic fOSC adjustment feature allows significant
improvement of signal-to-noise ratio when detecting very low lux
signals.
8
0.8
3.90
0.4
250
4
0.05
62.5
0.025
4000
REXT = 100kΩ
(EQ. 9)
for Internal Timing Mode only
Since fOSC is dual speed depending on the Gain/Range bit, tint is
dual time. The integration time as a function of REXT and n is:
External Scaling Resistor REXT and fosc
The ISL76683 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:
1 100kΩ
fosc1 = --- × ------------------- × 655 kHz
2
R EXT
(EQ. 6)
100kΩ
fosc2 = ------------------- × 655 kHz
R EXT
(EQ. 7)
fOSC1 is oscillator frequency when Range1 or Range2 are set.
This is nominally 327kHz when REXT is 100kΩ.
fOSC2 is the oscillator frequency when Range3 or Range4 are
set. This is nominally 655kHz 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.
(EQ. 8)
1
f OSC 1 = --- ( f OSC 2 )
2
n
1
t int = 2 × ---------f osc
R EXT
n
t int 1 = 2 × ----------------------------------------------327kHz × 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.
R EXT
n
t int 2 = 2 × ----------------------------------------------655kHz × 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 = 16-BIT
n = 12-BIT
n = 12-BIT
n=4
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
11
FN7697.2
March 17, 2011
ISL76683
INTEGRATION TIME IN EXTERNAL TIMING MODE
Solution 1
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.
Using Internal Timing Mode
For Mode1 or Mode2 operation, the integration starts when the
sync_iic command is sent over the I2C lines. The device needs
two sync_iic commands to complete a photodiode conversion.
The integration then stops when another sync_iic command is
received. Writing a logic 1 to the sync_iic bit ends the current
ADC integration and starts another one.
t int = i ( 1 ⁄ 60Hz ) = j ( 1 ⁄ 50Hz )
For Mode3, the operation is a sequential Mode1 and Mode2. The
device needs three sync_iic commands to complete two
photodiode measurements. The 1st sync_iic command starts the
conversion of the Diode1. The 2nd sync_iic completes the
conversion of Diode1 and starts the conversion of Diode2. The 3rd
sync_iic pulse ends the conversion of Diode2 and starts over again
to commence conversion of Diode1.
The integration time, tint, is determined by Equation 12:
iI 2 C
t int = ---------fI 2 C
(EQ. 12)
(EQ. 14)
The first instance of integer values at which tint rejects both 60Hz
and 50Hz is when i = 6, and j = 5.
t int = 6 ( 1 ⁄ 60Hz ) = 5 ( 1 ⁄ 50Hz )
(EQ. 15)
t int = 100ms
Next, the Gain/Range needs to be determined. Based on the
application condition given, lux(max) = 500 lux, a range of 1000
lux is desirable. This corresponds to a Gain/Range Range1
mode. Also impose a resolution of n = 16-bit. Hence, we choose
Equation 10 to determine REXT.
t int × 327kHz × 100 kΩ
R EXT = -------------------------------------------------------------n
2
(EQ. 16)
R EXT = 50kΩ
iI2C is the number of I2C clock cycles to obtain the tint.
fI2C is the I2C operating frequency.
for Internal Timing Mode and Gain/Range is set to Range3 or Range4 only
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
In order to achieve both 60Hz and 50Hz AC noise rejection, the
integration time needs to be adjusted to coincide with an integer
multiple of the AC noise cycle times.
(EQ. 13)
fOSC = 327kHz*100kΩ/REXT. When Range/Gain is set to
Range1 or Range2.
fOSC = 655kHz*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.
The Full Scale Range, FSR, needs to be determined from
Equation 3:
100kΩ
FSR = 1000 lux ------------------50kΩ
(EQ. 17)
FSR = 2000 lux
The effective transfer function becomes:
data
E = ------------- × 2000 lux
16
2
(EQ. 18)
TABLE 14. SOLUTION1 SUMMARY TO EXAMPLE DESIGN PROBLEM
DESIGN PARAMETER
VALUE
tint
100ms
REXT
50kΩ
Gain/Range Mode
Range1 = 1000 lux
FSR
2000 lux
# of clock cycles
216
Transfer Function
DATA
E = --------------- × 2000 lux
16
2
Solution 2
Using External Timing Mode
DESIGN EXAMPLE 1
The ISL76683 will be designed in a portable system. The
ambient light conditions that the device will be exposed to is at
most 500 lux, which is a good office lighting. The light source has
a 50/60Hz power line noise, which is not visible by the human
eye. The I2C clock is 10kHz.
From Solution 1, the desired integration time is 100ms. Note
that the REXT resistor only determines the inter oscillator
frequency when using external timing mode. Instead, the
integration time is the time between two sync_iic commands
sent through the I2C. The programmer determines how many I2C
clock cycles to wait between two external timing commands.
iI2C = fI2C*tint = number of I2C clock cycles
12
FN7697.2
March 17, 2011
ISL76683
iI2C = 10kHz *100ms
Flat Window Lens Design
iI2C = 1,000 I2C clock cycles. An external sync_iic command sent
A window lens will surely limit the viewing angle of the ISL76683.
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 ISL76683. Table 16 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.
1,000 cycles after another sync_iic command rejects both 60Hz
and 50Hz AC noise signals.
Next, is to pick an arbitrary REXT = 100kΩ and to choose the
Gain/Range Mode. For a maximum 500 lux, Range1 is
adequate. From Equation 3:
100kΩ
FSR = 1000 lux ------------------100kΩ
FSR = 1000 lux
The effective transfer function becomes:
WINDOW LENS
DATA
E = --------------------------- × 1000 lux
COUNTER
DATA is the sensor reading data located in data registers 04(hex)
and 05(hex)
t
DTOTAL
∅
COUNTER is the timer counter value data located in data registers
06(hex) and 07(hex). In this sample problem, COUNTER = 1000.
D1
TABLE 15. SOLUTION 2 SUMMARY TO EXAMPLE DESIGN PROBLEM
DESIGN PARAMETER
VALUE
tint
100ms
REXT
100kΩ
Gain/Range Mode
Range1 = 1000 lux
FSR
1000 lux
# of clock cycles
COUNTER = 1000
Transfer Function
ISL76683
∅ = VIEWING ANGLE
FIGURE 15. FLAT WINDOW LENS
Window with Light Guide Design
DATA
E = --------------------------- × 1000 lux
COUNTER
IR Rejection
Any filament type light source has a high presence of infrared
component invisible to the human eye. A white fluorescent lamp,
on the other hand has a low IR content. As a result, output
sensitivity may vary depending on the light source. Maximum
attenuation of IR can be achieved by properly scaling the readings
of Diode1 and Diode2. The user obtains data reading from sensor
Diode1 (D1), which is sensitive to visible and IR, then reading from
sensor Diode2 (D2), which is mostly sensitive from IR. The graph in
Figure 2 shows the effective spectral response after applying
Equation 19 of the ISL76683 from 400nm to 1000nm.
Equation 19 describes the method of cancelling IR in internal
timing mode.
D3 = n ( D1 – kD2 )
DLENS
(EQ. 19)
Where:
data = lux amount in number of counts less IR presence
D1 = data reading of Diode1
D2 = data reading of Diode2
n = 1.85. This is a fudge factor to scale back the sensitivity up to
ensure Equation 4 is valid.
If a smaller window is desired while maintaining a wide effective
viewing angle of the ISL76683, 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 minimum of 1.5mm in
diameter to ensure that whole area of the sensor will be exposed.
See Figure 16.
TABLE 16. 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 ISL76683 and inner edge of lens
Diameter of lens
Distance constraint between the ISL76683 and lens
outer edge
*All dimensions are in mm.
k = 7.5. This is a scaling factor for the IR sensitive Diode2.
13
FN7697.2
March 17, 2011
ISL76683
DLENS
D2 >1.5mm
LIGHT PIPE
t
D2
DLENS
L
ISL76683
FIGURE 16. WINDOW WITH LIGHT GUIDE/PIPE
2.00mm
SENSOR OFFSET
2.10mm
1
6
2
5
0.29mm
0.56mm
3
4
0.46mm
FIGURE 17. SENSOR LOCATION DRAWING
Suggested PCB Footprint
Typical Circuit
Footprint pads should be a nominal 1-to-1 correspondence with
package pads. Since ambient light sensor devices do not
dissipate high power, heat dissipation through the exposed pad is
not important; instead, similar to DFN or QFN, the exposed pad
provides robustness in board mount process. Intersil
recommends mounting the exposed pad to the PCB, but this is
not mandatory.
A typical application for the ISL76683 is shown in Figure 18. The
ISL76683’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.
Layout Considerations
The ISL76683 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.
Soldering 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.
Route the supply and I2C traces as far as possible from all
sources of noise. Use two power-supply decoupling capacitors,
4.7µF and 0.1µF, placed close to the device.
14
FN7697.2
March 17, 2011
ISL76683
1.8V TO 5.5V
R1
10k
R2
10k
I2C MASTER
R3
RES1
MICROCONTROLLER
SDA
SCL
2.5V TO 3.3V
I2C SLAVE_1
I2C SLAVE_0
1
2
C1
4.7µF
C2
0.1µF
3
VDD
SDA
GND
SCL
REXT
INT
REXT
100k
6
5
I2C SLAVE_n
SDA
SDA
SCL
SCL
4
ISL76683
FIGURE 18. ISL76683 TYPICAL CIRCUIT
15
FN7697.2
March 17, 2011
ISL76683
Revision History
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to web to make
sure you have the latest revision.
DATE
REVISION
CHANGE
3/8/11
FN7697.2
Changed TechBrief reference in ordering information for MSL info from TB363 to TB477.
1/24/11
FN7697.1
Initial Release to web.
Products
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16
FN7697.2
March 17, 2011
ISL76683
Package Outline Drawing
L6.2x2.1
6 LEAD OPTICAL DUAL FLAT NO-LEAD PLASTIC PACKAGE (ODFN)
Rev 2, 6/10
2.10
A
6
PIN #1
INDEX AREA
B
6
PIN 1
INDEX AREA
1
0.65
1.35
2.00
1.30 REF
4 6X 0.30±0.05
(4X)
0.10
0.10 M C A B
0.65
TOP VIEW
6x0.35 ± 0.05
BOTTOM VIEW
2.50
PACKAGE
OUTLINE
2.10
SEE DETAIL "X"
0.65
0.10 C
(4x0.65)
C
BASE PLANE
SEATING PLANE
0.08 C
SIDE VIEW
(1.35)
(6x0.30)
C
(6x0.20)
0 . 2 REF
5
0 . 00 MIN.
0 . 05 MAX.
(6x0.55)
TYPICAL RECOMMENDED LAND PATTERN
DETAIL "X"
NOTES:
1.
Dimensions are in millimeters.
Dimensions in ( ) for Reference Only.
2.
Dimensioning and tolerancing conform to ASME Y14.5m-1994.
3.
Unless otherwise specified, tolerance : Decimal ± 0.05
4.
Dimension 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.
17
FN7697.2
March 17, 2011