ISL29001IROZ Intersil, ISL29001IROZ Datasheet - Page 8

• Manufacturer Part Number: ISL29001IROZ
• Description: IC SENSOR LIGHT-DGTL I2C 6-ODFN
• Manufacturer: Intersil
• Series: -r

Specifications of ISL29001IROZ

• Wavelength: 540nm
• Output Type: I²C™
• Package / Case: 6-WDFN Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The internal oscillator,
internal and external timing modes, with the same
dependence on R
external timing modes, the number of clock cycles per
integration is no longer fixed at 32,768, but varies with the
chosen integration time, and is limited to 65,536. In order to
avoid erroneous lux readings the integration must be short
enough not to allow an overflow in the counter register.
where:
The number of clock cycles in the previous integration period
is provided in the third and fourth bytes of data read across
the I
counter value.
When using one of the three external timing modes, the
ISL29001’s resolution varies with the integration time. The
resolution is determined by the ratio of the max lux range to
the number of clock cycles per integration.
Equation 7 describes the light intensity as a function of
sensor reading, integration counter value, and integration
time:
where E is the measured light intensity, Data1 is the sensor
reading, Data2 is the integration counter value and R
external resistor value.
Noise Rejection and Integration Time
In general, integrating type ADC’s have an 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 n*16.66ms (n = 1,2...n
ISL29001’s integration time to an integer multiple of periodic
noise signal greatly improves the light sensor output signal
in the presence of noise. The integration time, t
ISL29001 is set by an external resistor R
Equation 2.
DESIGN EXAMPLE 1
Using the ISL29001, determine a suitable integration time,
t
noise. Specify the R
clock is at f
t
E Lux
int
int
t
F
oscillator (not to be confused with the I
R
100kΩ recommended.
(
int
, that will ignore the presence of both 60Hz and 50Hz
OSC
EXT
<
2
= user defined integration time
65,536
----------------- -
C bus. This two-byte value is called the integration
f
)
OSC
= user defined external resistor to adjust F
=
= 327.6kHz*100kΩ/R
------------------------------------------ -
(
R
I2C
10 000lux
EXT
,
= 10kHz.
⁄
100kΩ
EXT
EXT
. However, when using one of the three
F
OSC
)
value accordingly, given that the I
⋅
Data1
-----------------
Data2
, operates identically in both the
EXT
i
8
) is zero. Similarly, setting the
. ISL29001’s internal
2
EXT
C’s frequency).
. See
int
, of the
OSC
EXT
(EQ. 7)
(EQ. 6)
.
2
is
C
ISL29001
Solution 1 - Using Internal Timing
t
and 50Hz AC rejection, the integration time needs to be
adjusted to coincide with an integer multiple of the AC noise
cycle times.
n/m = 60Hz/50Hz = 6/5. The first instance of integer values
at which t
n = 6.
t
From Equation 2:
R
R
time and will reject the presence of both 60Hz and 50Hz
power line signals.
Solution 2 - Using External Timing
From Solution 1, the desired integration time is 100ms. Note
that the R
time when using external timing mode. Instead, the
integration and the 16-bit counter starts when an external
timing mode command is sent and end when another
external timing mode is sent. In other words, the time
between two external timing mode command is the
integration time. The programmer determines how many
clock cycles to wait between two external timing commands.
i
i
i
1,000 cycles after another external timing command rejects
both 60Hz and 50Hz AC noise signals.
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 diode 1, D
visible and IR, then reading from sensor diode 2, D
mostly sensitive from IR. The graph in Figure 9 shows the
effective spectral response after applying Equation 8 of the
ISL29001 from 400nm to 1000nm. Equation 8 describes the
method of cancelling IR in internal timing mode.
Where:
data = lux amount in number of counts less IR presence
D
D
n = 1.85. This is a fudge factor to scale back the sensitivity
up to ensure Equation 8 is valid.
int
int
I2C
I2C
I2C
D
EXT
EXT
1
2
3
= n(1/60Hz) = m(1/50Hz). In order to achieve both 60Hz
= 6(1/60Hz) = 5(1/50Hz) = 100ms
= data reading of Diode 1
= data reading of Diode 2
= f
= 10kHz
= 1,000 I
=
= t
= 100kΩ, the ISL29001 defaults to 100ms integration
n D
I2C *
(
int
int
EXT
1
* (100kΩ/100ms) = 100kΩ. By populating
–
t
rejects both 60Hz and 50Hz is when m = 5, and
int
2
kD
*
100ms
C clock cycles. An external timing command
resistor does not determine the integration
, where i
2
)
I2C
= number of I
1
, which is sensitive to
2
C cycles
December 10, 2008
2
which is
(EQ. 8)
FN6166.6