TSL27721 datasheet(4/56 Pages) AMSCO

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TSL2772 − Detailed Description

The TSL2772 light-to-digital device provides on-chip

photodiodes, integrating amplifiers, ADCs, accumulators,

clocks, buffers, comparators, a state machine, and an I²C

interface. Each device combines a Channel 0 photodiode (CH0),

which is responsive to both visible and infrared light, and a

channel 1 photodiode (CH1), which is responsive primarily to

infrared light. Two integrating ADCs simultaneously convert the

amplified photodiode currents into a digital value providing up

to 16 bits of resolution. Upon completion of the conversion

cycle, the conversion result is transferred to the data registers.

This digital output can be read by a microprocessor through

which 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 connection to

a microcontroller or embedded controller. The digital output of

the device is inherently more immune to noise when compared

to an analog interface.

The device 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. In addition, a

programmable 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 requires only a single external IR LED. An

internal LED driver can be configured to provide a constant

current sink of 15 mA, 30 mA, 60 mA, or 120 mA of current. No

external current limiting resistor is required. The power can also

be reduced by a factor of 8 with the PDL bit. The number of

proximity LED pulses can be programmed from 1 to 255 pulses.

Each pulse has a 16-

μs period. The programmable LED current,

coupled with the programmable number of pulses, provides a

16000:1 contiguous dynamic range.

Detailed Description

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