APDS-9901 datasheet(2/28 Pages) AVAGO

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Functional Block Diagram

Upper Threshold

Lower Threshold

Upper Threshold

Lower Threshold

Interrupt

LED Regulated

Constant Current

Sink

Control

Logic

ALS

ADC

Data

Prox

Detect

ADC

INT

SDA

SCL

VDD

GND

LDR

LED K

LED A

Prox IR

LED

Ch0

Ch1

Data

Detailed Description

The APDS-9900/9901 light-to-digital device provides

on-chip Ch0 and Ch1 diodes, integrating amplifiers,

ADCs, accumulators, clocks, buffers, comparators, a state

machine and an I2C interface. Each device combines one

Ch0 photodiode (visible plus infrared) and one Ch1 infra-

red-responding (IR) photodiode. Two integrating ADCs si-

multaneously convert the amplified photodiode currents

to a digital value providing up to 16-bits of resolution.

Upon completion of the conversion cycle, the conversion

result is transferred to the Ch0 and CH1 data registers. This

digital output can be read by a microprocessor where the

illuminance (ambient light level) in Lux is derived using an

empirical formula to approximate the human eye response.

Communication to the device is accomplished through a

fast (up to 400 kHz), two-wire I2C serial bus for easy con-

nection to a microcontroller or embedded controller. The

digital output of the APDS-9900/9901 device is inherent-

ly more immune to noise when compared to an analog

interface.

The APDS-9900/9901 provides a separate pin for level-style

interrupts. When interrupts are enabled and a pre-set

value is exceeded, the interrupt pin is asserted and

remains asserted until cleared by the controlling firmware.

The interrupt feature simplifies and improves system

efficiency by eliminating the need to poll a sensor for a

light intensity or proximity value. An interrupt is generated

when the value of an ALS or proximity conversion exceeds

either an upper or lower threshold. Additionally, a pro-

grammable interrupt persistence feature allows the user

to determine how many consecutive exceeded thresholds

are necessary to trigger an interrupt. Interrupt thresholds

and persistence settings are configured independently for

both ALS and proximity.

Proximity detection is fully provided with an 850 nm IR

LED. An internal LED driver (LDR) pin, is jumper connected

to the LED cathode (LED K) to provide a factory calibrated

proximity of 100 +/- 20 mm. This is accomplished with a

proprietary current calibration technique that accounts

for all variances in silicon, optics, package and most impor-

tantly IR LED output power. This will eliminate or greatly

reduce the need for factory calibration that is required for

most discrete proximity sensor solutions. While the APDS-

9900/9901 is factory calibrated at a given pulse count,

the number of proximity LED pulses can be programmed

from 1 to 255 pulses, which will allow greater proximity

distances to be achieved. Each pulse has a 16

µs period.

APDS-9901 Datasheet(PDF) 2 Page - AVAGO TECHNOLOGIES LIMITED

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