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test-and-measurement:analog-discovery-2:hardware-design-guide [2022/02/18 20:11] – typo Arthur Browntest-and-measurement:analog-discovery-2:hardware-design-guide [2022/10/04 11:38] (current) – external edit 127.0.0.1
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-====== Analog Discovery 2 Hardware Design Guide (Under Construction) ======+====== Analog Discovery 2 Hardware Design Guide ======
 ~~TechArticle~~ ~~TechArticle~~
-<WRAP round todo> 
-== Under Construction == 
-</WRAP> 
  
 The Analog Discovery 2 is equipped with 13 test and measurement instruments providing the functionality of an entire benchtop worth of equipment in one device. The Oscilloscope, Waveform Generator, Logic Analyzer, Protocol Analyzer, Spectrum Analyzer, Power Supplies, and more provide a device that can become a pop-up electronics laboratory anywhere. The physical design of the Analog Discovery 2 provides BNC connectors or MTE cables for the analog inputs and outputs, MTE cables for the digital I/O, triggers, and power supplies, and a large removable and breadboardable design surface supporting a large variety of designs or projects.  The Analog Discovery 2 is equipped with 13 test and measurement instruments providing the functionality of an entire benchtop worth of equipment in one device. The Oscilloscope, Waveform Generator, Logic Analyzer, Protocol Analyzer, Spectrum Analyzer, Power Supplies, and more provide a device that can become a pop-up electronics laboratory anywhere. The physical design of the Analog Discovery 2 provides BNC connectors or MTE cables for the analog inputs and outputs, MTE cables for the digital I/O, triggers, and power supplies, and a large removable and breadboardable design surface supporting a large variety of designs or projects. 
  
-===== Oscilloscope ===== +This document, the hardware design guide, describes the architecture and implementation of many of the key circuits and features of the Analog Discovery 2. Those users looking for deep and detailed information on the operation of their device may find this of particular interest. For a summary of the key specifications of the device, check out the [[specifications]]. For a high-level overview of the key features of the device, check out the [[reference-manual]].
- +
-{{reference/test-and-measurement/analog-discovery-2/analog-discovery-2-7.png?direct |}} +
- +
- +
-The Digilent Analog Discovery 2™ is a multi-function instrument that allows users to measure, visualize, generate, record, and control mixed signal circuits of all kinds. The low-cost Analog Discovery 2 is small enough to fit in your pocket, but powerful enough to replace a stack of lab equipment, providing engineering students, hobbyists, and electronics enthusiasts the freedom to work with analog and digital circuits in virtually any environment, in or out of the lab. +
- +
-For more information on the analog input ("Scope") channels, please visit the [[test-and-measurement:analog-discovery-pro-3x50:specifications]]. For a walkthrough of the different features of WaveForms' Oscilloscope instrument, please visit the [[test-and-measurement:guides:waveforms-oscilloscope]] guide. +
- +
- +
- +
-===== Features ===== +
- +
-The analog and digital inputs and outputs can be connected to a circuit using simple wire probes; alternatively, the [[ reference:test-and-measurement:bnc-adapter-board:start | BNC Adapter Board]] +
- and BNC probes can be used to connect and utilize the Oscilloscope functions with probes. Driven by the free WaveForms software, the Analog Discovery 2 can be configured to work as any one of several traditional instruments, which include: +
- +
-  * Two-channel oscilloscope (1MΩ, ±25V, differential, 14-bit, 100MS/s, 30MHz+  bandwidth - with the Analog Discovery BNC Adapter Board) +
-  * Two-channel arbitrary function generator (±5V, 14-bit, 100MS/s, 12MHz+  bandwidth - with the Analog Discovery BNC Adapter Board) +
-  * Stereo audio amplifier to drive external headphones or speakers with replicated AWG signals +
-  * 16-channel digital logic analyzer (3.3V CMOS, 100MS/s)((These 16 digital lines are shared by the Logic Analyzer, Pattern Generator and Digital I/O. They are always inputs, some of them can be set to be outputs also. Digital I/O has precedence in case of output conflict with the Pattern Generator.)) ((When inputs, these lines can be set to be 1.8V CMOS compatible.)) +
-  * 16-channel pattern generator (3.3V CMOS, 100MS/s)((These 16 digital lines are shared by the Logic Analyzer, Pattern Generator and Digital I/O. They are always inputs, some of them can be set to be outputs also. Digital I/O has precedence in case of output conflict with the Pattern Generator.)) ((When inputs, these lines can be set to be 1.8V CMOS compatible.)) +
-  * 16-channel virtual digital I/O including buttons, switches, and LEDs – perfect for logic training applications ((These 16 digital lines are shared by the Logic Analyzer, Pattern Generator and Digital I/O. They are always inputs, some of them can be set to be outputs also. Digital I/O has precedence in case of output conflict with the Pattern Generator.)) ((When inputs, these lines can be set to be 1.8V CMOS compatible.)) +
-  * Two input/output digital trigger signals for linking multiple instruments (3.3V CMOS)((When inputs, these lines can be set to be 1.8V CMOS compatible.)) +
-  * Two programmable power supplies (0…+5V , 0…-5V). The maximum available output current and power depend on the Analog Discovery 2 powering choice: +
-      * 500mW total when powered through USB  +
-      * 2.1W max for each supply when powered by an auxiliary supply +
-  * Two-channel voltmeter (AC, DC, ±25V) +
-  * Network analyzer – Bode, Nyquist, Nichols transfer diagrams of a circuit. Range: 1Hz to 10MHz +
-  * Spectrum Analyzer – power spectrum and spectral measurements (noise floor, SFDR, SNR, THD, etc.) +
-  * Digital Bus Analyzers (SPI, I²C, UART, Parallel, CAN) +
- +
- +
-The Analog Discovery 2 was designed for students in typical university-based circuits and electronics classes. Its features and specifications, as well as the additional requirements of operating from USB or external power, maintaining the small and portable form factor, the robustness to withstand student use in a variety of environments, and low-cost are based directly on feedback that was obtained from numerous professors from several universities. Meeting all of these requirements proved challenging; however, the task ultimately generated some new and innovative circuits. This document describes the Analog Discovery 2's circuits, with the intent of providing a better understanding of its electrical functions, operations, and a more detailed description of the hardware’s features and limitations. It is not intended to provide enough information to enable complete duplication of the Analog Discovery 2, or to allow users to design custom configurations for programmable parts in the design. +
- +
- +
-Analog Discovery 2 is the next generation of the very popular Analog Discovery. The main improvements are: +
-  * Ability to use an external power supply and consequently deliver more power to user supplies. When USB-powered, the Analog Discovery 2 delivers the same power as the Analog Discovery. +
-  * New enclosure with enhanced design and improved connector reliability. +
-  * Improved signal/noise and crosstalk performances for both the scope and waveform generator.  +
-  * Better defined bandwidth for both the scope and waveform generator. +
- +
---> Important Note: Grounding Circuitry # +
- +
-The Analog Discovery Studio 2's GND reference is connected to the USB GND. Depending on the PC powering scheme, and other PC connections (Ethernet, audio, etc. – which might also be grounded) the Analog Discovery Pro's GND reference might be connected to the whole GND system and ultimately to the power network protection (earth ground). The circuit under test might also be connected to earth or possibly floating. +
- +
-For safety reasons, it is the user’s responsibility to understand the powering and grounding scheme, and to make sure that there is a common GND reference between the Analog Discovery Studio 2 and the circuit under test, and that the common mode and differential voltages do not exceed specifications. Furthermore, for distortion-free measurements, the common mode and differential voltages need to meet specifications. +
- +
-<-- +
- +
---> Important Note: Pinout Diagram # +
- +
-{{ :analog_discovery_2:analogdiscovery2-pinout-600.png?nolink&450 |Analog Discovery 2 Pinout.}} +
- +
-<--+
  
 +----
 +===== Pinout Diagram =====
 +For reference, the pinout of the Analog Discovery 2 is presented in Figure 1.
  
 +{{ :analog_discovery_2:analogdiscovery2-pinout-600.png?nolink&450 |Analog Discovery 2 Pinout Diagram.}}
 +//{{anchor:figure_1:Figure 1. Analog Discovery 2 Pinout Diagram.}}//
  
 +----
 ===== 1.1 Architectural Overview and Block Diagram ===== ===== 1.1 Architectural Overview and Block Diagram =====
  
-Analog Discovery 2's high-level block diagram is presented in [[analog_discovery_2:refmanual#figure_2|Fig. 2]] below. The core of the Analog Discovery 2 is the [[http://www.xilinx.com/|Xilinx®]] [[http://www.xilinx.com/products/silicon-devices/fpga/spartan-6/index.htm|Spartan®-6]] FPGA (specifically, the XC6SLX16-1L device). The WaveForms application automatically programs the Discovery’s FPGA at start-up with a configuration file designed to implement a multi-function test and measurement instrument. Once programmed, the FPGA inside the Discovery communicates with the PC-based WaveForms application via a USB 2.0 connection. The WaveForms software works with the FPGA to control all the functional blocks of the Analog Discovery 2, including setting parameters, acquiring data, and transferring and storing data.+Analog Discovery 2's high-level block diagram is presented in [[analog_discovery_2:refmanual#figure_2|Fig. 2]] below. The core of the Analog Discovery 2 is the [[https://www.xilinx.com/|Xilinx®]] [[https://www.xilinx.com/products/silicon-devices/fpga/spartan-6.html|Spartan®-6]] FPGA (specifically, the XC6SLX16-1L device). The WaveForms application automatically programs the Discovery’s FPGA at start-up with a configuration file designed to implement a multi-function test and measurement instrument. Once programmed, the FPGA inside the Discovery communicates with the PC-based WaveForms application via a USB 2.0 connection. The WaveForms software works with the FPGA to control all the functional blocks of the Analog Discovery 2, including setting parameters, acquiring data, and transferring and storing data.
  
  
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 ---- ----
  
-====== 2. Oscilloscope ====== +====== 2. Scope ======
- +
-{{reference:test-and-measurement:analog-discovery-pro-3x50:oscilloscope.png?nolink&800}}+
  
 //**Important Note**: Unlike traditional inexpensive scopes, the Analog Discovery 2 inputs are fully differential. However, a GND connection to the circuit under test is needed to provide a stable common mode voltage. The Analog Discovery 2 GND reference is connected to the USB GND. Depending on the PC powering scheme, and other PC connections (Ethernet, audio, etc. – which might also be grounded) the Analog Discovery 2 GND reference might be connected to the whole GND system and ultimately to the power network protection (earth ground). The circuit under test might also be connected to earth or  possibly floating. For safety reasons, it is the user’s responsibility to understand the powering and grounding scheme and make sure that there is a common GND reference between the Analog Discovery 2 and the circuit under test, and that the common mode and differential voltages do not exceed the limits shown in equation \ref{1}. Furthermore, for distortion-free measurements, the common mode and differential voltages need to fit into the linear range shown in Figs. [[analog_discovery_2:refmanual#figure_12|12]] and [[analog_discovery_2:refmanual#figure_13|13]]. //**Important Note**: Unlike traditional inexpensive scopes, the Analog Discovery 2 inputs are fully differential. However, a GND connection to the circuit under test is needed to provide a stable common mode voltage. The Analog Discovery 2 GND reference is connected to the USB GND. Depending on the PC powering scheme, and other PC connections (Ethernet, audio, etc. – which might also be grounded) the Analog Discovery 2 GND reference might be connected to the whole GND system and ultimately to the power network protection (earth ground). The circuit under test might also be connected to earth or  possibly floating. For safety reasons, it is the user’s responsibility to understand the powering and grounding scheme and make sure that there is a common GND reference between the Analog Discovery 2 and the circuit under test, and that the common mode and differential voltages do not exceed the limits shown in equation \ref{1}. Furthermore, for distortion-free measurements, the common mode and differential voltages need to fit into the linear range shown in Figs. [[analog_discovery_2:refmanual#figure_12|12]] and [[analog_discovery_2:refmanual#figure_13|13]].
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-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_15.png |Figure 14. Scope spectral characteristic diagram. Low gain (up), high gain (down).}}+{{ :analog_discovery_2:ad2_15.png |Figure 14. Scope spectral characteristic diagram. Low gain (up), high gain (down).}}
 //{{anchor:figure_14:Figure 14. Scope spectral characteristic diagram. Low gain (up), high gain (down).}}// //{{anchor:figure_14:Figure 14. Scope spectral characteristic diagram. Low gain (up), high gain (down).}}//
  
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 ---- ----
-====== 3. Waveform Generator ====== +====== 3. Arbitrary Waveform Generator ======
- +
-{{reference:test-and-measurement:analog-discovery-pro-3x50:waveform-generator.png?nolink&800}}+
  
 ===== 3.1. AWG DAC ===== ===== 3.1. AWG DAC =====
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-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_19.png?700 |Figure 19. AWG I/V and out.}}+{{ :analog_discovery_2:ad2_19.png?700 |Figure 19. AWG I/V and out.}}
 //{{anchor:figure_19:Figure 19. AWG I/V and out.}}// //{{anchor:figure_19:Figure 19. AWG I/V and out.}}//
 ---- ----
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 $$ - 5.45V <  - 5V < V_{ACoutAWG\;HG} < 5V < 5.45V$$ $$ - 5.45V <  - 5V < V_{ACoutAWG\;HG} < 5V < 5.45V$$
-$$ - 1.36V < 1.25V < V_{ACoutAWG\;LG} < 1.25V < 1.36V\label{39}\tag{39}$$+$$ - 1.36V < - 1.25V < V_{ACoutAWG\;LG} < 1.25V < 1.36V\label{39}\tag{39}$$
  
  
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 $$at\;Low\;Gain:\;\;\;\frac{{2.72V}}{{{2^{14}}}} = 166\mu V$$ $$at\;Low\;Gain:\;\;\;\frac{{2.72V}}{{{2^{14}}}} = 166\mu V$$
-$$at\;High\;Gain:\;\;\;\;\;\frac{{10.9V}}{{{2^{14}}}} = 665\mu V\label{40}\tag{40}$$+$$at\;High\;Gain:\;\;\;\;\frac{{10.9V}}{{{2^{14}}}} = 665\mu V\label{40}\tag{40}$$
  
 The second term in equation \ref{38} shows the DC component (AWG offset), with a range of (for either LowGain or HighGain): The second term in equation \ref{38} shows the DC component (AWG offset), with a range of (for either LowGain or HighGain):
  
-$$ - 5.5V < 5V < V_{DCoutAWG} < 5V < 5.5V\label{41}\tag{41}$$+$$ - 5.5V < - 5V < V_{DCoutAWG} < 5V < 5.5V\label{41}\tag{41}$$
  
 AD8067 is supplied with $\pm 5.5V$; to avoid saturation the user should keep the sum of AC and DC components in \ref{38} to: AD8067 is supplied with $\pm 5.5V$; to avoid saturation the user should keep the sum of AC and DC components in \ref{38} to:
  
-$$ - 5.5V < 5V < V_{outAWG} < 5V < 5.5V\label{42}\tag{42}$$+$$ - 5.5V < - 5V < V_{outAWG} < 5V < 5.5V\label{42}\tag{42}$$
  
 Only **bolded** ranges are used in equations \ref{39}, \ref{41}, and \ref{42}, for providing tolerance margins. Only **bolded** ranges are used in equations \ref{39}, \ref{41}, and \ref{42}, for providing tolerance margins.
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 As shown in [[analog_discovery_2:refmanual#figure_23|Fig. 23]], the Analog Discovery 2's power can be supplied either from the USB port (VBUS) or from an external power supply (J4 connector).  As shown in [[analog_discovery_2:refmanual#figure_23|Fig. 23]], the Analog Discovery 2's power can be supplied either from the USB port (VBUS) or from an external power supply (J4 connector). 
  
-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_24.png |Figure 23. USB power control.}}+{{ :analog_discovery_2:ad2_24.png |Figure 23. USB power control.}}
 //{{anchor:figure_23:Figure 23. USB power control.}}// //{{anchor:figure_23:Figure 23. USB power control.}}//
  
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 IC46A/B op amps insert the command voltages $V_{SET+\_USR}$ and $V_{SET-\_USR}$, respectively, in the feedback loop. Additionally, IC46B introduces the required inversion for the negative supply.  IC46A/B op amps insert the command voltages $V_{SET+\_USR}$ and $V_{SET-\_USR}$, respectively, in the feedback loop. Additionally, IC46B introduces the required inversion for the negative supply. 
  
-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_27.png |Figure 26. User power supplies.}}+{{ :analog_discovery_2:ad2_27.png |Figure 26. User power supplies.}}
 //{{anchor:figure_26:Figure 26. User power supplies.}}// //{{anchor:figure_26:Figure 26. User power supplies.}}//
  
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   * Forced PWM and automatic PWM/PSM modes   * Forced PWM and automatic PWM/PSM modes
  
-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_28.png |Figure 27. 3.3V internal analog power supply.}}+{{ :analog_discovery_2:ad2_28.png |Figure 27. 3.3V internal analog power supply.}}
 //{{anchor:figure_27:Figure 27. 3.3V internal analog power supply.}}// //{{anchor:figure_27:Figure 27. 3.3V internal analog power supply.}}//
  
-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_29.png |Figure 28. 1.8V internal analog power supply.}}+{{ :analog_discovery_2:ad2_29.png |Figure 28. 1.8V internal analog power supply.}}
 //{{anchor:figure_28:Figure 28. 1.8V internal analog power supply.}}// //{{anchor:figure_28:Figure 28. 1.8V internal analog power supply.}}//
  
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 The 5.5V and -5.5V supplies [[analog_discovery_2:refmanual#figure_30|Fig. 30]] are created with a Sepic-Cuk topology, built around a single [[http://www.analog.com/en/power-management/switching-regulators-integrated-fet-switches/adp1612/products/product.html|ADP1612]] Step-Up DC-to DC converter. Both Sepic and Cuk converters are connected to the same switching pin of the regulator. Only the positive Sepic output is regulated, while the negative output tracks the positive one. This is an accepted behavior, since similar load currents are expected on both positive and negative rails.  The 5.5V and -5.5V supplies [[analog_discovery_2:refmanual#figure_30|Fig. 30]] are created with a Sepic-Cuk topology, built around a single [[http://www.analog.com/en/power-management/switching-regulators-integrated-fet-switches/adp1612/products/product.html|ADP1612]] Step-Up DC-to DC converter. Both Sepic and Cuk converters are connected to the same switching pin of the regulator. Only the positive Sepic output is regulated, while the negative output tracks the positive one. This is an accepted behavior, since similar load currents are expected on both positive and negative rails. 
  
-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_31.png |Figure 30. ±5.5V internal analog supplies.}}+{{ :analog_discovery_2:ad2_31.png |Figure 30. ±5.5V internal analog supplies.}}
 //{{anchor:figure_30:Figure 30. ±5.5V internal analog supplies.}}// //{{anchor:figure_30:Figure 30. ±5.5V internal analog supplies.}}//
  
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   * Compact PCB footprint   * Compact PCB footprint
  
-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_33.png |Figure 32. 3.3V internal digital supply.}}+{{ :analog_discovery_2:ad2_33.png |Figure 32. 3.3V internal digital supply.}}
 //{{anchor:figure_32:Figure 32. 3.3V internal digital supply.}}// //{{anchor:figure_32:Figure 32. 3.3V internal digital supply.}}//
  
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   * Forced PWM and automatic PWM/PSM modes   * Forced PWM and automatic PWM/PSM modes
  
-{{ :test-and-measurement:analog-discovery-2:analog-discovery-2_34.png |Figure 33. 1.8V internal digital supply.}}+{{ :analog_discovery_2:ad2_34.png |Figure 33. 1.8V internal digital supply.}}
 //{{anchor:figure_33:Figure 33. 1.8V internal digital supply.}}// //{{anchor:figure_33:Figure 33. 1.8V internal digital supply.}}//
  
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 ====== 8. FPGA ====== ====== 8. FPGA ======
  
-The core of the Analog Discovery 2 is the Xilinx [[http://www.xilinx.com/products/silicon-devices/fpga/spartan-6/index.htm|Spartan-6]] FPGA circuit XC6SLX16-1L. The configured logic performs:+The core of the Analog Discovery 2 is the Xilinx [[https://www.xilinx.com/products/silicon-devices/fpga/spartan-6.html|Spartan-6]] FPGA circuit XC6SLX16-1L. The configured logic performs:
  
   * Clock management (12 MHz and 60 MHz for USB communication, 100 MHz for data sampling)   * Clock management (12 MHz and 60 MHz for USB communication, 100 MHz for data sampling)