LX1977IDU MICROSEMI [Microsemi Corporation], LX1977IDU Datasheet - Page 14

• Manufacturer Part Number: LX1977IDU
• Description: SMBus Ambient Light Sensor
• Manufacturer: MICROSEMI [Microsemi Corporation]

Copyright © 2010
Rev. 1.0, 2010-03-25
Bit
4
0
0
1
1
T
INT_PERSIST_CTRL (bit 2, 1, 0, R / W): Set the time duration before generating interrupt. INT_ENA should be set to
Light input Lux and D
TM
Bit
INT
3
0
1
0
1
_SET (bit 4, 3, R / W): ADC integration (conversion) time control. The relationship between bit settings and
Integration Time
table for the values of 0 ~ 500 lux, 0 ~ 1000 lux, 0 ~ 5000 and 0 ~ 2500 lux light input. The equations for
calculating between D
determined by integration time as shown above. In the Electrical Characteristics table, D
accordance with the specified light input at ADC Clock = 40.96 kHz, integration time = 100ms and at 0 ~ 500 lux,
0 ~ 1000 lux, 0 ~ 5000 lux and 0 ~ 2500 lux range. D
measurement range selected. Below are the conversion methods between D
integration time.
D
COUNT
Register 00h, Bit 3 = 0, ADC Clock = 40.96kHz
1
6.25 ms
100 ms
When range is selected, the D
LX1977 output D
For example: 0 ~ 500 lux range, 100 lux input, integration time = 50ms
For example: 0 ~ 1000 lux range, 500 lux input, integration time = 100ms
25 ms
50 ms
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= (Input (lux) / Range) × (Nominal Full Range Reading)
1
COUNT
1 to enable the interrupt pin function. The actual time duration is determined by bit 3 of register
00h and bit 3 & 4 of this register. Please refer to T
integration times are shown in table below.
0 ~ 2500
Range Reading
Nominal Full
calculation:
COUNT
COUNT
D
D
1861
3723
233
931
COUNT
COUNT
Table 24: ALS ADC Integration Time
and lux are shown below.
= 001, generate interrupt if ADC result out of range
= 010, generate interrupt if ADC result out of range for 2 consecutive T
= 011, generate interrupt if ADC result out of range for 3 consecutive T
= 100, generate interrupt if ADC result out of range for 4 consecutive T
= 101, generate interrupt if ADC result out of range for 5 consecutive T
= 110, generate interrupt if ADC result out of range for 10 consecutive T
= 000, generate interrupt after ADC conversion
is in a linear relationship with the light input lux. D
= 100/500 × 1861 = 372
= 500/1000 × 3723 = 1862
Analog Mixed Signal Group
10.73
COUNT
®
Microsemi
Max Reading
Conversion Time / Reading
values with different input lux will also change. Please refer to the EC
1023
2047
4095
255
2.68
Integration Time
SMBus Ambient Light Sensor
Register 00h, Bit 3 = 1, ADC Clock = 10.24kHz
100 ms
200 ms
400 ms
COUNT
25 ms
P
RODUCTION
1.34
values are related to integration time and the
INT
Refer to Table 24
Refer to Table 24
_SET description.
Refer to Table 24
Range Reading
Nominal Full
COUNT
D
1861
3723
233
931
ATASHEET
0.67
and light input lux at different
COUNT
COUNT
full scale values are
Max Reading
values are listed in
1023
2047
4095
255
LX1977
INT
INT
INT
INT
INT
time
time
time
time
time
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