MAX44000 Maxim, MAX44000 Datasheet - Page 15

• Manufacturer Part Number: MAX44000
• Description: MAX44000 combines a wide-dynamic range ambient light sensor with an integrated infrared proximity sensor, making it a perfect solution for touch-screen portable devices
• Manufacturer: Maxim

The ALS upper threshold and ALS lower threshold (UPTHR[13:0] and LOTHR[13:0]) set the window limits that are used
to trigger an ALS interrupt. It is important to set these values according to the selected bit resolution/integration time
chosen for the ALS measurement based on the ALSTIM[1:0] and ALSPGA[1:0] settings. The upper 2 bits are always
ignored. If the INTE bit is set, and the lux level is greater or lower than the respective thresholds for a period greater
than that defined by the ALSPST persist time, the INTS bit in the Status register is set and the INT pin is pulled low.
The MAX44000 incorporates a persist function that allows the users to set the number of consecutive triggers before
interrupt. PRXPST[1:0] and ALSPST[1:0] set one of four persist values that control how readily the interrupt logic reacts
to a detected event. This feature is added to reduce false or nuisance interrupts.
When ALSPST[1:0] is set to 00, and the ALSINTE bit is set to 1, the first time an ALS interrupt event is detected, the
ALSINTE interrupt bit is set and the INT pin goes low. If ALSPST[1:0] is set to 01, then four consecutive interrupt events
must be detected on four consecutive measurement cycles. Similarly, if ALSPST[1:0] is set to 10, or 11, then 8 or 16
consecutive interrupts must be detected. If there is an intervening measurement cycle where no interrupt is detected,
then the count is reset to zero. The proximity interrupt function is managed in the same way with PRXPST[1:0].
ALS Upper Threshold
(High Byte)
ALS Upper Threshold
(Low Byte)
ALS Lower Threshold
(High Byte)
ALS Lower Threshold
(Low Byte)
Threshold Persist Timer
REGISTER
REGISTER
PRXPST[1:0] OR ALSPST[1:0]
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Ambient and Infrared Proximity Sensor
B7
B7
00
01
10
11
B6
B6
B5
B5
UPTHR[7:0]
LOTHR[7:0]
B4
B4
ALS/PROX Threshold Persist Timer Register (0x0A)
LOTHR[13:8]
UPTHR[13:8]
B3
PRXPST[1:0]
B3
ALS Interrupt Threshold Registers (0x06–0x09)
NO. OF CONSECUTIVE TRIGGERS BEFORE INTERRUPT
B2
B2
ALSPST[1:0]
B1
B1
B0
B0
REGISTER
REGISTER
16
ADDRESS
ADDRESS
1
2
4
0x0A
0x06
0x07
0x08
0x09
POWER-ON
POWER-ON
RESET
RESET
STATE
STATE
0x00
0x00
0x00
0x00
0x00
R/W
R/W
R/W
R/W
R/W
R/W
R/W
15