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AS7331

General Description

Datasheet

• PUBLIC

DS001047

• v4-00 • 2023-Mar-24

71

│ 3

1

General Description

The AS7331 is a low-power, low noise integrated UV sensor. The three separated UVA, UVB and

UVC channels convert optical radiation signals via photodiodes to a digital result and realize a

continuous or triggered measurement. The irradiance responsivity can be adjusted via Gain,

conversion time and internal clock frequency to effect sensitivity, full scale range and LSB. The by the

AS7331 detected amount of radiation in the set Gain and conversion time configuration will be

provided as digital counts by the AS7331. The AS7331 offers a range of 12 Gain steps by a factor of

two for each step. The conversion time is internally controlled over a wide range of 15 steps by a

factor of two for each step. With the input pin (SYN), the conversion time can be externally controlled

to adapt the measurement to the given environment and time base.

With its irradiance responsivity factor and conversion time, the AS7331 supports an overall huge

dynamic range up to 3.43E+10 (resolution multiplied by gain range). It achieves an accuracy of up to

24-bit signal resolution (internal via I²C and shifter 16-bit), with an irradiance responsivity per count

down to 2.38 nW/cm² at 64 ms integration time. Via an integrated divider, the 16-bit I²C output can be

adjusted to the significant bits of interest.

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Automatic power down (sleep function) between subsequent measurements offers operation with very

low current consumption. Furthermore, a synchronized mode and other control modes adjustable by

user programming can be used. The supported operating modes of the AS7331 are:

●

CMD Mode

– Single measurement and conversion (controlled via I²C interface).

●

CONT Mode

– Continuous measurement and conversion (periodically recurring measuring

cycles) start and stop controlled via I²C interface.

●

SYN[x] Modes

– Synchronized measurement and conversion:

●

[SYNS Mode] synchronization of start via the control signal at pin SYN.

●

[SYND Mode] synchronization of start and stop of measuring cycles via control signal at

pin SYN.

The conversion data can be accessed by the I²C interface with programmable slave addresses via

16- bit / 400 kHz fast mode. The measurement of the current conversion time for an externally

triggered measurement can be performed. The measurement modes will not affect the settings of the

irradiance responsivity and conversion time. Furthermore, the converter supports functions like power

down and standby, which is suitable in mobile applications. Based on the high flexibility, the AS7331 is

suitable as an optical converter for three different wavelength ranges. The device achieves a high

dynamic range for fluorescence applications and for measurements of UV radiations. This makes the

UV sensors excellently suited for photometry applications (UV exposure, UV-index), for monitoring of

UVC disinfection treatments, fluorescence detection, and mobile devices for UV radiation

measurements. The AS7331 contains an integrated temperature sensor for rough compensation of

the thermic behavior. The device is available in a small SMD package.