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Description
X-ray fluorescence with silicon drift detectors (SDDs) is an effective method for raw material extraction and recycling. These systems require a large number of detectors to be fitted in a very small space. Therefore, miniaturizing the current external power supply by means of an integrated, space-saving charge pump circuit is very advantageous
This work presents an application-specific integrated circuit (ASIC) manufactured using 180 nm silicon-on-insulator (SOI) technology, which can generate all negative high voltages required for SDD operation, ranging from -20 V to -200 V.
The central element of the ASIC is a CMOS DC/DC converter based on a Pelliconi charge pump.
The Pelliconi-type charge pump topology uses low-voltage transistors and a simple two-phase clock scheme. This enables higher frequency operation, as well as higher current output and efficiency, while simultaneously reducing the size of the chip.
An appropriate control concept has been implemented to adjust the output voltage of the charge pumps required for the SDD.
The presented prototype compares the performance of an SDD supplied by charge pumps using two different control concepts:
One concept is based on a common two-point control system, whereby the pumping process is regulated by a comparator. As an alternative, the concept of controlling the supply voltage of the clock circuit to generate the desired output voltage is being investigated.
The result is a comparison of both control concepts with an external power supply in terms of stability, noise, and spectral performance of the detector.