ADP5588ACPZ-R7 datasheet(12/28 Pages) AD

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ADP5588

Data Sheet

Rev. D | Page 12 of 28

Light Sensor Inputs

Each light sensor input has two built-in comparators (the L2

comparator and the L3 comparator) with two programmable

trip points, L2 and L3. The trip points are used to select among

three operation modes based on ambient lighting conditions:

outdoor, office, and dark modes.

BRIGHTNESS

DARK

OFFICE

OUTDOOR

0 LUX

1 kLUX

0µA

1000µA

L2 = 1

L3 = 1

L2 = 1

L3 = 0

L2 = 0

L3 = 0

Figure 11. Light Sensor Comparator Modes and Trip Points

L2 Comparator

The L2 comparator is used to detect when the photosensor

output drops below the programmable L2_TRIP point. When

this event occurs, the L2_OUT status signal is set. L2_CMPR

contains programmable hysteresis, meaning that the photo-

sensor output must rise above L2_TRIP + L2_HYS before

L2_OUT is cleared.

L2_CMPR is enabled via the L2_EN bit (Bit 0, Register 0x31 for

Sensor 1 and Bit 0, Register 0x32 for Sensor 2). The L2_TRIP

and L2_HYS values of L2_CMPR can be set between 0 μA and

1000 μA in steps of 4 μA.

L3 Comparator

The L3 comparator is used to detect when the photosensor

output drops below the programmable L3_TRIP point. When

this event occurs, the L3_OUT status signal is set. L3_CMPR

contains programmable hysteresis, meaning that the photo-

sensor output must rise above L3_TRIP + L3_HYS before

L3_OUT is cleared. L3_CMPR is enabled via the L3_EN bit.

The L3_TRIP and L3_HYS values of L3_CMPR can be set

between 0 μA and 127.5 μA in steps of 0.5 μA.

L3_TRIP

L2_TRIP

L3_HYST

L2_HYST

100

1000

ADC RANGE (µA)

Figure 12. Comparator Ranges

The L2_CMPR and L3_CMPR comparators can be enabled

independently of each other, and the ADC and comparator(s)

run continuously when L2_EN and/or L3_EN is set.

Photosensor Operation

The comparator inputs remain idle until enabled, at which

point they detect lighting conditions from the photosensor

output. Depending on lighting conditions, and where the L2

and L3 trip points are set in the comparator level trip registers

(Register 0x33 through Register 0x3A), the comparators set a

value of 1 or 0 to L2_OUT and L3_OUT. The values of L2 and

L3 determine what mode or setting adjustment is required for a

particular lighting condition. Figure 11, Figure 12, and Table 15

summarize the mode settings and logical values of L2 and L3.

Table 15. L2_OUT and L3_OUT Comparator Mode

Combination

Mode

Outdoor

Office

Dark

It is also possible to use the light sensor comparators in single-

shot mode. A single-shot measurement is done when the

FORCE_RD bit in Register 0x31 is set. After the single-shot

measurement is completed, the internal state machine clears the

FORCE_RD bit. It takes 80 ms for a complete conversion. To

reduce the potential for flickering, the sensors can be programmed

for a number of sequential readings. The filter settings in

sequential readings needed by the user; these settings range

from 80 ms to 10.24 sec.

L2_TRIP

L2_HYST

FILTER

SETTING

L2_EN

L2_OUT

L3_OUT

COMP

INPUT

ADC

PHOTO-

SENSOR

L3_EN

VCC

L2_CMP

L3_CMP

L3_TRIP

L3_HYST

Figure 13. Light Sensor and Trip Points Block Diagram

ADP5588ACPZ-R7 数据表(PDF) 12 Page - Analog Devices

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