Design and prototyping of SiPM electronics



The pages listed here describe the work in electronics undertaken to support Silicon Photomultiplier (SiPM) based readout of the Tagger Microscope for JLab Hall-D and the GlueX experiment in particular. The working design concept for the Tagger's readout involves an array of PCB boards with SiPMs and their amplifiers, summing circuits etc. suspended in a light-tight box out of the plane of incoming electrons. Each of these "amplifier" or "analog" boards are connected across a light-sealing bus board to a "control" or "digital" board. The latter set of boards principally contain bias voltage control circuitry and an architecture that allows Ethernet-based communication with a controlling PC. An added advantage of this two-tier design is the ease with which the tagger can be wired without introducing light leaks: the SiPM signals are passed into a chamber more tolerant of ambient light. (The coaxial cables can then take the SiPM signals off digital boards.) The adjacent diagram outlines this scheme.

Analog Amplifier
The suitability of commercially-available SiPMs have been evaluated with "AMP_0604" amplifier by Photonique.

The following pages provide analysis of this circuit:
 * SiPM Amplifier - analog amplifier circuit supplied by for use with the SiPMs.
 * MATLAB amplifier in detail - more information regarding the implementation of the MATLAB-based simulation of the amplifier circuit.

A similar amplifier circuit is necessary replicated for each SiPM in the tagger microscope. However, microscope readout calls for somewhat different design requirements and operating condition constraints. The following is a brief outline the demands on the amplifier design:
 * adjustable gain, ranging from readout of hundreds of pixels to calibration with single-photon counting
 * less than 15% gain variability on transistor $$\beta$$ ($$h_{FE}$$) parameter
 * summing circuit to pool SiPM signals in groups of 5
 * minimized pulse duration
 * minimized power consumption

A full discussion of these along with steps taken to meet the new design goals are outlined in:
 * SiPM Amplifier Optimization
 * SiPM Amplifier Signal Analysis
 * SiPM Amplifier Components

Current Progress
The PCB layout of the digital control board is complete. Three prototype identical prototype boards are currently being tested. Documentation for these boards can be found here: Digital control board documentation

For debugging notes, including all currently known problems, see Digital control board debugging notes.

Design Tree

 * SiPM digital control board - design of the digital PCB for controlling the SiPMs.
 * Programming the FPGA
 * Programming the Ethernet controller - discussion of the design for the core of the FPGA which handles the complex needs of the FPGA - Ethernet controller chip interface.
 * Reset and Initialization - discussion of the design for the reset and initialization part of the core
 * Ethernet packets - a detail of the packets we intend to use on our network.
 * Programming the DAC - discussion of the design for the DAC.
 * Programming the SPI - discussion of the hybrid module that controls both the ADC and the temperature sensor over a single SPI bus. This design incorporates the (now obsolete) predecessor modules:
 * Programming the temperature sensor - discussion of the design for the temperature sensor.
 * Programming the ADC - discussion of the design for the ADC.

Resources

 * Presentation on FPGA programming PPT PDF
 * VHDL Tutorial
 * The Hamburg VHDL Archive

VHDL Overview

 * VHDL tutorial - a brief guide to VHDL design with a design example; the introduction and core of the tutorial.
 * VHDL: Where to start - section one of the tutorial, focusing on preparing your design for coding.
 * VHDL: Enter the code monkey - section two of the tutorial, focusing on outlining the framework of your code.
 * VHDL: The real code - section three of the tutorial, focusing on coding the body of your design.
 * VHDL: Xilinx ISE - section four of the tutorial, focusing on using the development environment.

To-do list
Ethernet module
 * Upload ADC module block diagrams
 * Combine ADC & temperature sensor into single "SPI" module
 * Complete Ethernet controller module
 * Registers
 * Idler
 * Reader
 * Querier
 * Programmer
 * Transmitter
 * Transceiver, extra debugging quasi-emulators in progress
 * Reset module
 * Check all modules for proper async reset support
 * Execute on startup
 * Execute on command
 * Soft reset - load and report MAC and location addresses.


 * Integrate all modules and simulate the device as a whole
 * Determine size of FPGA
 * Design or purchase connector to bus board
 * Purchase all components (including EEPROM, RJ-45 female jack, etc)
 * Obtain footprints of all chips, connectors, jacks, etc
 * PCB layout [in progress]
 * Prototype PCB
 * Design bus board
 * Design analog board

Schematics and PCB Designs
Electronics board design project by Woody Underwood