ISL29020IROZ-T7A Intersil, ISL29020IROZ-T7A Datasheet - Page 6

• Manufacturer Part Number: ISL29020IROZ-T7A
• Description: IC SENSOR LIGHT-DGTL I2C 6ODFN
• Manufacturer: Intersil

Specifications of ISL29020IROZ-T7A

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

.
Data Registers (01 hex and 02 hex)
The device has two 8-bit read-only registers to hold a 16-bit
data from ADC or Timer. The most significant byte is
accessed at 02 hex, and the least significant byte is
accessed at 01 hex. The registers are refreshed after every
conversion cycle.
Calculating Lux
The ISL29020’s ADC output codes, DATA, are directly
proportional to lux in the ambient light sensing, as shown in
Equation 1.
Here, E
determined by the Full Scale Range and the ADC’s
maximum output counts. The constant can also be viewed
as the sensitivity: the smallest lux measurement the device
can measure, as shown in Equation 2.
Here, Range(k) is defined in Table 8. Count
maximum output counts from the ADC.
The transfer function used for each timing mode becomes:
INTERNAL TIMING MODE
E
E
ADDRESS
5. Range: Bits 1 and 0. The Full Scale Range (FSR) can be
α
cal
BITS
=
1:0
0:0
0:1
1:0
1:1
(hex)
=
BITS 3:2
adjusted via I
possible values of FSR for the 500kΩ R
01
02
Range k ( )
---------------------------
=
----------------------------
Count
Range k ( )
0:0
0:1
1:0
1:1
α
cal
2
×
n
k
1
2
3
4
DATA
is the calculated lux reading. The constant α is
Least-significant byte of most recent ADC or Timer data.
Most-significant byte of most recent ADC or Timer data.
max
RANGE(k)
×
TABLE 7. RESOLUTION/WIDTH
2
2
2
2
Range1
Range2
Range3
Range4
DATA
TABLE 9. DATA REGISTERS
16
12
8
4
TABLE 8. RANGE/FSR LUX
2
= 256
= 16
C using Bits 1 and 0. Table 8 lists the
= 65,536
= 4,096
NUMBER OF CLOCK CYCLES
ALS SENSING
FSR (LUX) @
6
CONTENTS
16,000
64,000
1,000
4,000
max
EXT
FSR (LUX) @ IR
Refer to page 2
Refer to page 2
Refer to page 2
Refer to page 2
SENSING
is the
resistor.
(EQ. 2)
(EQ. 3)
(EQ. 1)
ISL29020
Here, n = 4, 8, 12 or 16. This is the number of ADC bits
programmed in the command register. 2
maximum number of counts possible from the ADC output in
Internal-Timing mode. Data is the ADC output stored in the
data registers (01 hex and 02 hex).
EXTERNAL TIMING MODE
Here, Timer sets up the ADC’s maximum count reading and
it is the number of clock cycles accrued in the integration
time (set by sync_I
stored in the data registers 01h and 02h when the command
is coded as 1xx101xx. Data is the ADC output. In this mode,
the command has to be sent out again with code 1xx100xx
to request the ADC output data from registers 01h and 02h.
External Scaling Resistor R
Range
The ISL29020 uses an external resistor R
internal oscillator frequency, f
range, Range. f
R
referenced to 500kΩ:
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 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 ISL29020 offers user flexibility in the integration time to
balance resolution, speed and noise rejection. Integration time
can be set internally or externally by programming the bit 4 of
the command register 00(hex).
INTEGRATION TIME IN INTERNAL-TIMING MODE
Most applications will use the Internal-Timing mode. In this
mode, f
integration time, t
where n is the number of bits of resolution and n = 4, 8, 12 or
16. 2
programmed at the command register 00(hex) bits 3 and 2.
E
Range
f
t
OSC
int
EXT
=
=
Range k ( )
---------------------------
n
. For user simplicity, the proportionality constant is
=
, therefore, is the number of clock cycles. n can be
Timer
2
OSC
=
n
500kΩ
----------------- -
R
×
500kΩ
----------------- -
EXT
R
------------- -
f
OSC
EXT
and ADC n-bits resolution determine the
1
×
×
OSC
DATA
725
×
=
int,
Range k ( )
2
2
C pulses) in External-Timing mode. It is
kHz
n
and Range are inversely proportional to
as shown in Equation 7.
×
--------------------------------------------- -
725kHz
R
OSC
EXT
×
500kΩ
EXT
and the light sensing
for f
n
EXT
represents the
OSC
to fix its
and
August 20, 2009
(EQ. 7)
FN6505.1
(EQ. 4)
(EQ. 5)
(EQ. 6)