ISL76683AROZ-T7 Intersil, ISL76683AROZ-T7 Datasheet - Page 11

• Manufacturer Part Number: ISL76683AROZ-T7
• Description: DIGITAL LIGHT SENSOR ADC 6ODFN
• Manufacturer: Intersil

Specifications of ISL76683AROZ-T7

• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 R
Table 9). Unlike R
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; 2
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.
External Scaling Resistor R
The ISL76683 uses an external resistor R
oscillator frequency, f
f
speed mode oscillator, is inversely proportional to R
simplicity, the proportionality constant is referenced to fixed
constants 100kΩ and 655kHz:
f
This is nominally 327kHz when R
f
set. This is nominally 655kHz when R
When the Range/Gain bits are set to Range1 or Range2, f
runs at half speed compared to when Range/Gain bits are set to
Range3 and Range4.
fosc1
fosc2
f
R
OSC
OSC
OSC
12
16
OSC
8
4
n
EXT
TABLE 12. RESOLUTION AND INTEGRATION TIME SELECTION
, integration time and the FSR of the device. f
1 is oscillator frequency when Range1 or Range2 are set.
2 is the oscillator frequency when Range3 or Range4 are
1
=
t
INT
100k
=
=
=
12.8
0.05
200
0.8
1
-- -
2
100kΩ
------------------ -
1
-- - f
2
(ms)
R
(
×
EXT
Ω
OSC
100kΩ
------------------ -
f
OSC
R
EXT
RANGE1
2
×
EXT
= 327kHz
)
655
RESOLUTION
LUX/COUNT
×
, Range(k) dynamically adjusts the FSR. This
OSC
655
kHz
0.01
0.24
3.90
62.5
. Consequently, R
kHz
11
EXT
t
INT
is 100kΩ.
0.025
EXT
100
6.4
0.4
EXT
(ms)
EXT
is 100kΩ.
EXT
f
OSC
and f
to fix its internal
RANGE4
determines the
= 655kHz
(LUX/COUNT)
RESOLUTION
OSC
EXT
osc
4000
EXT
250
16
, a dual
1
. For user
(see
n
ISL76683
OSC
(EQ. 6)
(EQ. 7)
(EQ. 8)
clock
The automatic f
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 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, f
determine the integration time. t
clock cycles and f
n = 4, 8, 12, and 16. n is the number of bits of resolution.
Therefore, 2
at the command register 00(hex) bits 1 and 0.
Since f
dual time. The integration time as a function of R
t
Internal Timing Mode and Gain/Range is set to Range1 or
Range2.
t
Internal Timing Mode and Gain/Range is set to Range3 or
Range4.
t
t
t
*Integration time in milliseconds
**Recommended R
int1
int2
int
int
int
TABLE 13. INTEGRATION TIMES FOR TYPICAL R
100**
1
2
R
(kΩ)
200
500
=
50
is the integration time when the device is configured for
is the integration time when the device is configured for
EXT
=
=
2
OSC
n
2
2
n
n
×
×
×
--------- -
f
is dual speed depending on the Gain/Range bit, t
n
osc
1
---------------------------------------------- -
327kHz
---------------------------------------------- -
655kHz
is the number of clock cycles. n can be programmed
n = 16-BIT
OSC
1000
100
200
400
OSC
R
R
EXT
EXT
EXT
adjustment feature allows significant
for Internal Timing Mode only
×
×
RANGE1
RANGE2
.
resistor value
100kΩ
100kΩ
n = 12-BIT
6.4
13
26
64
int
is a function of the number of
OSC
n = 12-BIT
3.2
6.5
13
32
and n-bits resolution
EXT
RANGE3
RANGE4
VALUES
EXT
March 17, 2011
and n is:
0.013
0.025
0.050
0.125
n = 4
FN7697.2
(EQ. 10)
(EQ. 11)
(EQ. 9)
int
is