Data Sheet

ams Datasheet Page 19
[v1-04] 2018-Jul-09 Document Feedback
AS7265x − Detailed Description
AS7265x 18-Channel Spectral_ID Detector
Overview
Each of the three AS7265x Spectral_ID devices are next-gener-
ation digital 6-channel spectral sensor devices. Each of the 6
channels has a Gaussian filter characteristic with a full width
half maximum (FWHM) bandwidth of 20nm. The filters use an
interference topology design providing high stability in terms
of drift in time and temperature. The drifts are so small that it
is undetectable in the measurement. The temperature drift of
the device is largely determined by the drift of the sensor and
the electronics. To compensate for the temperature drift in the
application, every device of the AS7265x chipset includes an
integrated temperature sensor.
Filter accuracy will be affected by the angle of incidence which
itself is limited by integrated aperture and internal micro-lens
structure. The aperture-limited average field of view is ±20.5°
to deliver specified accuracy. All optical characteristics are
optimized for using diffused light.
Each device contains an analog-to-digital converter (16-bit res-
olution ADC) which integrates the current from each channel’s
photodiode. Upon completion of the conversion cycle, the in-
tegrated result is transferred to the corresponding data regis-
ters. The transfers are double-buffered to ensure data integrity
is maintained.
The external MCU interface control via I²C registers or AT com-
mands, transparently controls the AS72652 and/or AS72653.
A serial flash is a required operating companion for this device
and enables factory calibration/normalization of the filters.
Supported device types are noted in
Ordering & Contact Information at the end of this document.
Required operating code can be downloaded at
download.ams.com.
Channel Data Conversion of the AS7265x
Devices
All three of these 6 channel devices use conversion implement-
ed via two photodiode banks in each device. Refer to
Figure 21and Figure 22. Bank 1 consists of register data from 4
of the 6 photodiodes, with 2 registers zeroed and Bank 2 con-
sists of data from a different set of 4 of the 6 photodiodes, with
2 different registers zeroed. Spectral conversion requires the
integration time (IT in ms) set to complete. If both photodiode
banks are required to complete the conversion, the 2
nd
bank
requires an additional IT ms. Minimum IT for a single bank con-
version is 2.8 ms. If data is required from all 6 photodiodes then
the device must perform 2 full conversions (2 x Integration
Time).
Detailed Description