Multi-Channel Amplifier IC for Fast Digital Power Conversion

Transimpedance amplifiers are preferred in industrial measurement technology for their rapid and cyclic conversion and amplification of the very small currents used in optoelectronic sensors. The ASIC MDDC is suitable for fast applications in conjunction with detectors and arrays, such as In-Line (Color) Measurement and control in automated processes, such as printing and analysis.

The transimpedance (gain) is independently programmable digitally for each channel above 5 bits in 16 stages via the SPI interface. The gradation between the transimpedance per channel is implemented in binary with additional intermediate stages in the range of about 1.6 MOhm to 100MOhm. At the maximum transimpedance, even currents in the nA range can be quickly measured and a dynamic range of 30dB (from 11.7 nA to 2µA; LSB down to 2.8pA) covered. The amplifier stages are characterized by low noise levels and operate with high linearity and synchronism of the channels. Beyond the external programming of the amplifier stages, dynamic in-line amplification on all channels is also available separately in the operation.

The ASIC MDDC includes internally a 12-bit A/D conversion on-chip. The A/D converter basically works as a successive approximation A/D converter. Also implemented in the A/D converter is a procedure for temperature modulation, which compensates as far as possible for the large temperature variation in the transimpedance of the current-voltage converter.

The reference programming for the conversion (equivalent to a reference voltage for a conventional A/D voltage converter) can be regulated through the programming of the transimpedance. This is done independently for each channel. Thus, each channel can have its own reference current or current range (Full Scale Range - FSR). All necessary references are implemented internally.

A kind of Track & Hold circuit with a four-to-one multiplexer is emplaced before the A/D converter. This implementation allows simultaneous parallel sampling and subsequent serial conversion of the analog values of the channels.


The communication to and from the ASIC is realized through a bi-directional 12-bit SPI interface with a clock up to 16MHz. The SPI clock is used simultaneously for the A/D converter. A conversion time of 1?s per channel and thus a sampling rate of up to 100kS/s for all four channels can be achieved this way.

The MDDC 4-channel current-to-digital converter is very suitable for multi-sensor applications with minimal sensor current. They are typically color sensors and other optical arrays and lines (UV, VIS, NIR, IR-range) in high-speed applications, such as industrial sensors (light grid, length, level, position, thickness and clearance measurement), in dynamic measurement systems for surface analysis (spectral and color measurements, gloss, roughness), temperature measurement (thermal imaging, combustion monitoring) but also with in-line detectors for alpha-, beta-and gamma-rays, X-rays and ions.

The ASIC sensors are available in SMD housing or can be ordered as a naked chip for subsequent hybrid or MCM-processing. In connection with the MAZeT True Color Sensors, the amplifiers are available as full color sensor modules or SMD sensor components.