PCB Design

A printed circuit board (PCB) was designed to test the performance of the chip. The block diagram is shown in Fig. 8

The block diagram of the PCB
FIG 8. The block diagram of the PCB.

The PCB provides all the signals that the chip needs to work, including a 3.3V and a 1.2V power supply generated by the on board LDO (Linear Technology, LTC1963A, LTC3021). Two DACs (Linear Technology, LTC1448) are used to generate bias voltages for the transimpedance amplifier to work. Current sources (Texas Instrument, LM234) are used to bias the Opamp inside the chip. An Opal Kelly XEM6010LX45 FPGA was used to generate all the clocks and control signals for the chip. All this digital signals are translated into 1.2V power domain using the level shifter (Texas Instrument, SN74AVC8T245) on the board. Computer programs (written in Python 2.7) were written to allow fast configuration of the chips working mode. A Sallan-Key filter was designed to filter the output of the amplifier, but turned out not working because of a inappropriate choice of the Opamp. Extra prototyping area was added in case of mistakes on the board.

The picture of the PCB
FIG 9. The picture of the PCB.


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