Detection And Control Electronics

Each SPAD is biased and driven by appropriate detection and control electronics. The core of the detection electronics are the integrated Active-Quenching Circuits (iAQC), one for each SPAD. Each iAQC is able to bias the corresponding SPAD above the breakdown voltage, generate a digital pulse each time a photon is detected and quickly quench the SPAD (by lowering its bias below breakdown). At the end of the cycle, the SPAD is ready to detect a new photon. Figure 4 shows the block diagram of each iAQC. The iAQCs are packaged with a possible five on one chip.

Figure 4. Block diagram of each one of the 60 integrated iAQC needed to bias the SPADA.

The entire detection board provides not only the 12 chips containing a total of 60 iAQCs , but also 15 quad output drivers that output 60 differential lines through two SCSI connectors (requested by ESO for backward compatibility with the existing MACAO systems).

Figure 5. Schematic block diagram of the detection board.

Moreover, an 8-bit micro-controller manages all settings, diagnostics, and signal communication. Commands and telemetry (temperature, over voltage, hold-off duration) will be transferred through an USB interface. Figure 5 shows the block diagram of the detection board.

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