VCNL4020
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Vishay Semiconductors
Rev. 1.2, 10-Oct-12
8
Document Number: 83476
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Register #4 Ambient Light Parameter Register
Register address = 84h.
Note
• If self_timed measurement is running, any new value written in this register will not be taken over until the mode is actualy cycled.
Register #5 and #6 Ambient Light Result Register
Register address = 85h and 86h. These registers are the result registers for ambient light measurement readings.
The result is a 16 bit value. The high byte is stored in register #5 and the low byte in register #6.
TABLE 5 - AMBIENT LIGHT PARAMETER REGISTER #4
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Cont. conv.
mode
als_rate
Auto offset
compensation
Averaging function
(number of measurements per run)
Description
Cont. conversion mode
R/W bit. Continuous conversion mode.
Enable = 1; Disable = 0 = DEFAULT
This function can be used for performing faster ambient light measurements. This mode should only be
used with ambient light on-demand measurements. Do not use with self-timed mode. Please refer to the
application information chapter 3.3 for details about this function.
Ambient light measurement rate
R/W bits. Ambient light measurement rate
000 - 1 samples/s
001 - 2 samples/s = DEFAULT
010 - 3 samples/s
011 - 4 samples/s
100 - 5 samples/s
101 - 6 samples/s
110 - 8 samples/s
111 - 10 samples/s
Auto offset compensation
R/W bit. Automatic offset compensation.
Enable = 1 = DEFAULT; Disable = 0
In order to compensate a technology, package or temperature related drift of the ambient light values
there is a built in automatic offset compensation function.
With active auto offset compensation the offset value is measured before each ambient light
measurement and subtracted automatically from actual reading.
Averaging function
R/W bits. Averaging function.
Bit values sets the number of single conversions done during one measurement cycle. Result is the
average value of all conversions.
Number of conversions = 2
decimal_value
e.g. 0 = 1 conv., 1 = 2 conv, 2 = 4 conv., ….7 = 128 conv.
DEFAULT = 32 conv. (bit 2 to bit 0: 101)
TABLE 6 - AMBIENT LIGHT RESULT REGISTER #5
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Description
Read only bits. High byte (15:8) of ambient light measurement result
TABLE 7 - AMBIENT LIGHT RESULT REGISTER #6
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Description
Read only bits. Low byte (7:0) of ambient light measurement result
