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MAX44005

RGB Color, Temperature,

and Infrared Proximity Sensor

Interrupt Operation

Ambient interrupt is enabled by setting bit 0 of Register

0x01 to 1 and proximity interrupt is enabled by setting bit

1 of Register 0x01 to 1 (see Tables 6 and 7). The interrupt

pin, INT, is an open-drain output and pulls low when an

interrupt condition occurs (e.g., when ambient lux read-

ings exceed threshold limits for a period greater than that

set by the persist timer register). The interrupt status bit

is cleared automatically if Register 0x00 is read or if the

interrupts are disabled.

A PWRON interrupt bit is set to alert the master of a chip

reset operation in case of a power-supply glitch, which

can happen on smartphones that place the light sensor

on a flex with a small connector.

It is recommended to utilize the interrupt pin on the IC to

alert the master to come and read measurements from

the IC. This eliminates the need for the microcontroller

substantially. In addition, this frees up the microcontroller

resources to service other background processes to

improve device performance. The wide variety of smarts

available on the chip, such as ability to set the threshold

levels and to count persist timer limits, allow the part to

operate in an autonomous mode most of the time.

Typical Operating Sequence

Here is the typical operating sequence for the master to

communicate to the IC:

A. Setup:

1) Read the Interrupt Status register (0x00) to confirm

only the PWRON bit is set (usually at power-up

only). This also clears a hardware interrupt.

2) Set the Threshold and Persist Timer registers for

ambient and proximity sensor measurements.

3) Write 0x01 to Proximity Configuration register

(Register 0x03) to set the proximity sensor in the

lowest gain setting, AMB sensor in the highest gain

setting, and the PROX and AMB ADCs are in 10-bit

and 14-bit modes separately.

4) Set IR LED current to suitable level by writing to the

Transmit Configuration register (0x03).

5) Write 0x43 to Main Configuration register (Register

0x01) to set the part in RGBC + IR + PROX

mode, and to enable AMB and proximity interrupts.

Ensure RGBC + IR + PROX mode is enabled.

6) Set new CLEAR, RGB, and infrared channel gains

if necessary to customize AMB operation for appli-

cation conditions. Ensure TRIM bit is set to 1 when

not using default factory-trim settings. Otherwise,

keep this bit set to 0 (power-on default state).

B. Wait for interrupt.

C. On interrupt:

1) Read the Interrupt Status register (0x00) to confirm

the IC to be source of interrupt and to check for

type of interrupt. This should clear the hardware

interrupt on the part, if set.

2) If an AMB interrupt has occurred, read AMB

registers (Register 0x04-0x0D) to confirm if data is

valid, and take appropriate action (e.g., sets

new backlight strength). Set new AMB thresholds if

necessary.

3) If a PROX interrupt has occurred, read the PROX

IR registers (Registers 0x10-0x11) and take

appropriate action (typically turn off or turn on

touch screen and backlight). Set new proximity

thresholds if necessary.

4) Return to step B.

serial interface consisting of a serial-data line (SDA) and

a serial-clock line (SCL). SDA and SCL facilitate com-

munication between the IC and the master at clock rates

up to 400kHz. Figure 3 shows the 2-wire interface timing

diagram. The master generates SCL and initiates data

Table 19. Slave Address

SMBus is a trademark of Intel Corp.

SLAVE ADDRESS FOR WRITING

SLAVE ADDRESS FOR READING

1000 1000

1000 1001