FEATURES
▪ Conversion of 4 sensor signals of
photodiodes (e.g. RGB/XYZ color plus one
blank channel for compensation of parasitic
currents or temperature conversion) or other
sensors with current signal output
▪ 12 bit signal resolution at an achievable
sensitivity of up to 2.8 pA/LSB
▪ Programmable full-scale range from 11.7 nA
to 12 μA
▪ Sampling rate up to 100 kS/s for all
channels
▪ Measurement of positive and negative
currents
▪ Up to 16 MHz fast SPI-interface
▪ High amplification linearity, no cross talk
▪ High absolute accuracy and reliability
without additional sources
▪ Supply and temperature independent
performance
▪ Supply voltage from 2.7 V to 3.6 V
▪ Temperature range from -25 °C to 85 °C
▪ Deliverable in standard SSOP20 package
APPLICATIONS
▪ Precise conversion of photo current for
optical sensors and arrays (e.g. UV, VIS, IR)
and other sensors with current output
▪ In combination with ams Sensors Germany’s
color sensors or other multi-channel pindiodes:
measurement of surfaces and
distances
▪ In combination with ams Sensors Germany’s
color sensors: measurement of light –
chromaticity coordinates (XYZ CIE1931,
DIN5033 and similar) or color temperatures
to control and process displays and
backlights (e.g. LED, CCFL)
▪ In combination with ams Sensors Germany’s
color and spectral sensors: measurement of
reflective and/or transmitted light –
chromaticity coordinates (XYZ CIE1931,
DIN5033 and similar) measurement of
objects and surfaces for analyses, quality
management, sorting, etc.
1 GENERAL DESCRIPTION
Transimpedance amplifiers (TIA) used as current-voltage converters ensure continuous signal processing
at high signal frequencies, thus meeting the demands of e.g. automated processes. They are best suited
to synchronous measuring procedures in the kilohertz range, where fast converters are required to scan
optical signals. Examples include sensors for quality testing in inline manufacturing processes or those in
touchless handheld devices. ams Sensors Germany offers several multichannel TIAs with digital and analog
interface.
The AS89020 is a 12 bit, 4 channel, current input analog-to-digital converter (ADC). It combines currentto-
voltage (TIA) and analog-to-digital (AD) conversion, so that 4 separate current output devices
(e.g. photodiodes) can be directly connected to its inputs and digitized.
For each of the 4 inputs the AS89020 provides an input amplifier with a track and hold circuit. The outputs
of the track and hold stages are serial converted to 12 bit digital words using an analog-to-digital converter
(ADC).
The 12 bit conversion results are available via SPI at a frequency up to 16 MHz and a conversion time as
low as 1 μs per channel.
The input amplifier is separately programmable for each channel in 17 stages. This results in a
programmable full-scale range for the ADC from 11.7 nA to 12 μA and a sensitivity up to 2.8 pA/LSB.
Input currents of both polarities can be fed to each of the input amplifiers. The adjustment is realized by
digital programming of each channel separately via standard SPI-interface.
All reference voltages are implemented internally; only some external passive devices are needed to
complete their operating mode.
The AS89020 supports Power Down functions for low power solutions.
Based on the high flexibility the AS89020 is suitable as a converter for a wide range of multi-channel
optoelectronic sensors (UV, VIS, NIR, IR) or other sensors with current output. The device achieves a high
dynamic range.
The combination of ams Sensors Germany’s color sensors with AS89020 is excellently suited especially for
fast color measurement and control in printing and automation, for mobile color measurement devices but
also for photometry applications (brightness, color coordinate and/or color temperature), for determining
current values for control of spectrally mixed LED light sources or as sensors for display and (back)light
calibration and mobile devices for light measurement.
The sensor compact signal IC is available in a SSOP20 package and or as bar die on request.