ISL29011_14 Datasheet, PDF (11/19 Pages) Intersil Corporation – Digital Ambient Light Sensor and Proximity Sensor with Interrupt Function

ISL29011
3. Amplitude of IR driver current; Bits 5 and 4: This device
provides current source to drive an external IR LED. The drive
capability can be programmed through Bits 5 and 4. For
example, the device sources 12.5mA out of the IRDR pin if
Bits 5 and 4 are 0.
TABLE 7. CURRENT SOURCE CAPABILITY AT IRDR PIN
BITS 5 TO 4
IRDR PIN SOURCE CURRENT
00
12.5mA IR LED driver
01
25mA IR LED driver
10
50mA IR LED driver
11
100mA IR LED driver
4. Resolution; Bits 3 and 2: determine the ADC’s resolution and
the number of clock cycles per conversion in Internal Timing
Mode. 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 measurement. The ONLY 16-bit ADC resolution is capable
of rejecting 50Hz and 60Hz flicker caused by artificial light
sources. Table 8 lists possible ADC resolution.
.
TABLE 8. RESOLUTION/WIDTH
BITS 3 TO 2
00
01
10
11
NUMBER OF CLOCK CYCLES
2¹⁶ = 65,536
2¹² = 4,096
2⁸ = 256
2⁴ = 16
n-BIT ADC
16
12
8
4
5. Range; Bits 1 and 0; The Full Scale Range (FSR) can be
adjusted via I²C using Bits 1 and 0. Table 9 lists the possible
values of FSR for the 499kΩ R_EXT resistor.
TABLE 9. RANGE/FSR LUX
BITS 1:0 k
RANGE
(k)
FSR (LUX) @ ALS
SENSING
FSR @ IR SENSING
00 1
Range1
1,000
Refer to page 4
01 2
Range2
4,000
Refer to page 4
10 3
Range3
16,000
Refer to page 4
11 4
Range4
64,000
Refer to page 4
Data Registers (02 hex and 03 hex)
The device has two 8-bit read-only registers to hold the data from
LSB to MSB for ADC. The most significant bit (MSB) is accessed
at 03 hex, and the least significant bit (LSB) is accessed at 02
hex. For 16-bit resolution, the data is from D0 to D15; for 12-bit
resolution, the data is from D0 to D11; for 8-bit resolution, the
data is from D0 to D7. The registers are refreshed after every
conversion cycle.
TABLE 10. DATA REGISTERS
ADDRESS
(hex)
CONTENTS
02
D0 is LSB for 4, 8, 12 or 16-bit resolution, D3 is MSB for
4-bit resolution, D7 is MSB for 8-bit resolution.
03
D15 is MSB for 16-bit resolution, D11 is MSB for 12-bit
resolution.
Interrupt Registers (04, 05, 06 and 07 hex)
Registers 04 and 05 hex set the low (LO) threshold for the
interrupt pin and the interrupt flag. 04 hex is the LSB and 05 hex
is the MSB. By default, the Interrupt threshold LO is 00 hex for
both LSB and MSB.
Registers 06 and 07 hex set the high (HI) threshold for the
interrupt pin and the interrupt flag. 06 hex is the LSB and 07 hex
is the MSB. By default, the Interrupt threshold HI is FF hex for
both LSB and MSB.
Test Register (08 hex)
Register 8 is a reserved register that holds 00h during normal
operation.
Calculating Lux
The ISL29011’s ADC output codes, DATA, are directly
proportional to lux in the ambient light sensing.
E_cal =   DATA
(EQ. 1)
Here, E_cal is the calculated lux reading. The constant  is
determined by the Full Scale Range and the ADC’s maximum output
counts. The constant is independent on the light sources
(fluorescent, incandescent and sunlight) because of the light
sources IR component is removed during the light signal process.
The constant can also be viewed as the sensitivity: The smallest lux
measurement the device can measure as shown in Equation 2.

=
-^R-----^a----ⁿ---^g----^e----^--^k----^-
Count_max
(EQ. 2)
Here, Range(k) is defined in Table 9. Count_max is the maximum
output counts from the ADC.
The transfer function used for n-bit ADC becomes Equation 3:
E_cal
=
R_-----a_----n_----g_----e_----_--k_----
2ⁿ

D
A
T
A
(EQ. 3)
Here, n = 4, 8, 12 or 16. This is the number of ADC bits programmed
in the command register. The 2ⁿ represents the maximum number
of counts possible from the ADC output. Data is the ADC output
stored in the data registers (02 hex and 03 hex).
Integration and Conversion Time
The ADC resolution and f_OSC determines the integration time, t_int
as shown in Equation 4.
t_int
=
2ⁿ

------¹-------
f_OSC
=
2ⁿ

----------------^R-----^E----^X---^T------------------
725kHz  499k
(EQ. 4)
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FN6467.6
May 1, 2014