TSL2550 Просмотр технического описания (PDF) - austriamicrosystems AG
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TSL2550 Datasheet PDF : 21 Pages
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TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029L − OCTOBER 2007
The specific ADC value register read depends on the last read command written to the command register, as
described above and in the Operation section, below.
The MSB of the ADC register (VALID bit B7) is used to indicate that data has been written to the ADC register
after the device is powered up as described in Command Register section.
Bits 6 through 0 contain the 7-bit code representing the ADC count value, which is proportional to a
photodetector current. In this code, the ADC count value is represented by a piece-wise linear approximation
to a log function. The transfer function is broken into 8 chords of 16 steps each. (This code is very similar to μ-law
code used in audio compression — it differs in that it does not have a sign bit and it is not inverted.) Table 3 shows
the relationship between the CHORD and STEP bits and the CHORD and STEP numbers and values. These
lid are used to calculate the ADC count value.
Table 3. CHORD and STEP Numbers and Values vs Register Bits
a CHORD
BITS
v B6, B5, B4
000
ill 001
010
t 011
100
G s 101
A t 110
111
C, CHORD
NUMBER
0
1
2
3
4
5
6
7
CHORD
VALUE
(Note A)
0
16
49
115
247
511
1039
2095
STEP
VALUE
(Note B)
1
2
4
8
16
32
64
128
amsconten NOTES: A. CHORD VALUE = INT (16.5 × ((2C) − 1))
l B. STEP VALUE = 2C
STEP
BITS
B3, B2, B1, B0
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
S, STEP
NUMBER
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
a The ADC count value is obtained by adding the CHORD VALUE and the product of the STEP NUMBER and
ic STEP VALUE (which depends on CHORD NUMBER).
ADC Count Value + ((Chord Value) ) (Step Value) (Step Number))
n The ADC count value can also be expressed as a formula:
hADC Count Value + (INT (16.5 ((2C * 1))) ) (S (2C))
Tec where:
C
is the CHORD NUMBER (0 to 7)
S
is the STEP NUMBER (0 to 15)
as defined in Table 3.
The LUMENOLOGY r Company
r
r
www.taosinc.com
Copyright E 2007, TAOS Inc.
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