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=== The DAC ===
=== The DAC ===
The purpose of the control board is to allow remotely programmable bias voltages for the SiPMs. For this purpose a DAC is required. The current design of the tagger microscope calls for 16 SiPMs per electronics card. Various designs were considered, but based on availability of components in the 50V range (DACs and op-amps primarily) the most suitable choice found was the Analog Devices' AD5535. It can go up to 200V with a resolution of 14 bit (roughly 12mV at 200V scale, roughly 3mV at a 50V scale) on 32 channels. As there are so many channels built in to this system, the tagger may be slightly restructured so as to include 32 SiPMs per board instead of 16 per board. This DAC defines its own serial interface for communication with the FPGA.
=== The ADC ===
In order to monitor the voltage levels of the power lines, an ADC is to be included in the design. The Analog Devices' AD7928 is an eight-channel ADC. Based on the selection of components there are six necessary power lines and two necessary grounds, so the AD7928 is capable of monitoring the entire system if need be. It uses a serial protocol that is compatible with the SPI bus to communicate with the FPGA.
=== Temperature sensor ===
In order to monitor the ambient temperature, a temperature sensor is to be included in the design. The Analog Devices' AD7314 has ten-bit resolution on temperature and is compatible with the SPI bus for communication with the FPGA.