OPT3001_15 Datasheet, PDF (24/43 Pages) Texas Instruments – Ambient Light Sensor (ALS)

OPT3001
SBOS681B – JULY 2014 – REVISED DECEMBER 2014
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7.6.1.1.3 Low-Limit Register (offset = 02h) [reset = C0000h]
This register sets the lower comparison limit for the interrupt reporting mechanisms: the INT pin, the flag high
field (FH), and flag low field (FL), as described in the Interrupt Reporting Mechanism Modes section.
Figure 25. Low-Limit Register
15
14
LE3
LE2
R/W
R/W
7
6
TL7
TL6
R/W
R/W
LEGEND: R/W = Read/Write
Bit
15:12
11:0
Field
LE[3:0]
TL[11:0]
13
12
11
10
9
8
LE1
LE0
TL11
TL10
TL9
TL8
R/W
R/W
R/W
R/W
R/W
R/W
5
4
3
2
1
0
TL5
TL4
TL3
TL2
TL1
TL0
R/W
R/W
R/W
R/W
R/W
R/W
Table 12. Low-Limit Register Field Descriptions
Type
R/W
R/W
Reset
0h
000h
Description
Exponent.
These bits are the exponent bits. Table 13 provides further details.
Result.
These bits are the result in straight binary coding (zero to full-scale).
The format of this register is nearly identical to the format of the result register described in the Result Register.
The low-limit register exponent (LE[3:0]) is similar to the result register exponent (E[3:0]). The low-limit register
result (TL[11:0]) is similar to result register result (R[11:0]).
The equation to translate this register into the lux threshold is given in Equation 4, which is similar to the
equation for the result register, Equation 3.
lux = 0.01 × (2^LE[3:0]) × TL[11:0]
(4)
Table 13 gives the full-scale range and LSB size as it applies to the low-limit register. The detailed discussion
and examples given in for the Result Register apply to the low-limit register as well.
Table 13. Full-Scale Range and LSB Size as a Function of Exponent Level
LE3
LE2
LE1
LE0
FULL-SCALE RANGE (lux)
LSB SIZE (lux per LSB)
0
0
0
0
40.95
0.01
0
0
0
1
81.90
0.02
0
0
1
0
163.80
0.04
0
0
1
1
327.60
0.08
0
1
0
0
655.20
0.16
0
1
0
1
1310.40
0.32
0
1
1
0
2620.80
0.64
0
1
1
1
5241.60
1.28
1
0
0
0
10483.20
2.56
1
0
0
1
20966.40
5.12
1
0
1
0
41932.80
10.24
1
0
1
1
83865.60
20.48
NOTE
The result and limit registers are all converted into lux values internally for comparison.
These registers can have different exponent fields. However, when using a manually-set
full-scale range (configuration register, RN < 0Ch, with mask enable (ME) active),
programming the manually-set full-scale range into the LE[3:0] and HE[3:0] fields can
simplify the choice of programming the register. This simplification results in the user only
having to think about the fractional result and not the exponent part of the result.
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