G650-04686-01

    M.2 Accelerator datasheet  Version 1.5      Features    ● ● ● ● ● Google Edge TPU ML accelerator  ○ 4 TOPS total peak performance (int8)  ○ 2 TOPS per watt  Integrated power management  PCIe Gen2 x1 interface  Available in two M.2 form factors:  ○ M.2-2230-A-E-S3 (A+E key)  ○ M.2-2280-B-M-S3 (B+M key)  Operating temp: -20 to +85 °C        Description    The Coral M.2 Accelerator is an M.2 module (either A+E or B+M key) that brings the Edge TPU ML accelerator to existing  systems and products.    The Edge TPU is a small ASIC designed by Google that accelerates TensorFlow Lite models in a power efficient manner: it's  capable of performing 4 trillion operations per second (4 TOPS), using 2 watts of power—that's 2 TOPS per watt. For  example, one Edge TPU can execute state-of-the-art mobile vision models such as MobileNet v2 at almost 400 frames per  second. This on-device ML processing reduces latency, increases data privacy, and removes the need for a constant  internet connection.    The M.2 form-factor allows you to add local ML acceleration to products such as embedded platforms, mini-PCs, and  industrial gateways that have a compatible M.2 card slot.    Ordering information    Part number  Description  G650-04527-01  Coral M.2 Accelerator with A+E key  G650-04686-01  Coral M.2 Accelerator with B+M key    See https://coral.ai/products/m2-accelerator-ae.         Coral.ai | Copyright 2019 Google LLC.      M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        Table of contents    Features 1  Description 1  Ordering information 1  Table of contents 2  1 Specifications 3  2 Dimensions 4  2.1 A+E key dimensions 2.2 B+M key dimensions 3 Electrical characteristics 3.1 Absolute maximum ratings 3.2 Power consumption 3.3 Peak performance 4 Connector pinout 4.1 A+E key pinout 4.2 B+M key pinout 5 Application details 5.1 Software requirements 5.2 Power delivery and management 5.3 Thermal management 5.3.1 Thermal limits 5.3.2 Top-side cooling options 5.3.3 Bottom-side cooling options 5.3.4 Temperature warnings and frequency scaling 6 Document revisions       4  4  5  5  5  6  7  7  8  9  9  9  9  10  10  11  11  12         Coral.ai | Copyright 2019 Google LLC.    2    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        1 Specifications    For in-depth mechanical details, refer to the PCI-SIG's PCI Express M.2 specification.    Table 1. Technical specifications  Physical specifications  Dimensions  A+E key: 22.00 x 30.00 x 2.35 mm  B+M key: 22.00 x 80.00 x 2.35 mm  Weight  A+E key: 3.1 g  B+M key: 5.8 g  Host interface  Hardware interface  M.2 A+E key (M.2-2230-A-E-S3)  or M.2 B+M key (M.2-2280-B-M-S3)  Serial interface  PCIe Gen2 x1  Operating voltage  DC supply  3.3 V +/- 10 %  Environmental  Storage temperature  -40 to +85 °C  Operating temperature  -20 to +85 °C 1  Relative humidity  0 to 90% (non-condensing)  Mechanical (non-op)  Shock  100 G, 11 ms (persistent)  1000 G, 0.5 ms (stress)  1000 G, 1.0 ms (stress)  Vibration  (random/sinusoidal)  0.5 Grms, 5 - 500 Hz (persistent)  3 Grms, 5 - 800 Hz (stress)  Compliance  Countries 2  Unit shipped as a component. Final system certification/compliance to be done by the  customer.  ESD 3  1 kV HBM, 250 V CDM  The max operating temperature depends on the power consumption and thermal management in your system.  2 We can provide a certification example to show that a reasonably designed system can meet certification requirements.  3 Always handle in a static safe environment.        1      Coral.ai | Copyright 2019 Google LLC.    3    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        2 Dimensions    2.1 A+E key dimensions    ● ● ● ● ● PCB width: 22.00 mm ± 0.15 mm  PCB height: 30.00 mm ± 0.15 mm  PCB thickness: 0.80 mm ± 0.08 mm  Top-side component height: 1.55 mm ± 0.10 mm  Bottom-side component height: 0 mm    For in-depth mechanical specs, refer to the PCI Express M.2 Specification.      Figure 1. A+E key card dimensions (in millimeters)    2.2 B+M key dimensions    ● ● ● ● ● PCB width: 22.00 mm ± 0.15 mm  PCB height: 80.00 mm ± 0.15 mm  PCB thickness: 0.80 mm ± 0.05 mm  Top-side component height: 1.55 mm ± 0.10 mm  Bottom-side component height: 0 mm    For in-depth mechanical specs, refer to the PCI Express M.2 Specification.      Figure 2. B+M key card dimensions (in millimeters)       Coral.ai | Copyright 2019 Google LLC.    4    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        3 Electrical characteristics    3.1 Absolute maximum ratings    Exceeding the absolute ratings can cease operation and possibly cause permanent damage. Exposure to absolute ratings  for extended periods of time can also adversely affect reliability.     Table 2. Absolute maximum ratings  Parameter  Min  Max  Storage temperature  -40 °C  85 °C  Operating temperature  -20 °C  85 °C 1  Edge TPU junction temperature (Tj)  -40 °C  115 °C  Power supply (3.3 V)  -0.3 V  6.0 V   The maximum operating temperature is for the entire assembly and assumes that the Edge TPU junction temperature (Tj)  does not exceed its absolute maximum rating, which depends on the power consumption and thermal management in your  system.    1 3.2 Power consumption    The power consumed by the card module depends on the ML model, the number of inferences per second, and the  operating frequency of the Edge TPU. For some examples of average sustained power consumption, see table 3. However,  it's also important that you consider the peak current transients that occur during inferencing.    The maximum current drawn by the Edge TPU is typically much higher than the average current. That's because when the  Edge TPU executes an ML model, it repeatedly activates a large number of arithmetic logic units (ALUs) simultaneously,  resulting in a pattern of brief but large current transients. Each model architecture also activates a different set and different  number of ALUs, meaning the magnitude and the shape of the transient current very much depends on the model.    Although the average current drawn from the 3.3V supply is typically less than 500 mA, brief current transients that occur  during inferencing can reach roughly 3 A. These spikes also occur suddenly: even a simple model can generate current  transients in excess of 1 A/μs. However, these numbers are representative of only the models tested at Google, and your  numbers will vary. To determine the actual peak supply current, you should observe the current when running the models  you will deploy in production.    For more information, see section 5.2 Power delivery and management.    Table 3. Examples of long-term sustained power during inferencing  1 Model 1  Low operating frequency  125 MHz  Reduced operating frequency  250 MHz  Max operating frequency  500 MHz  MobileNet v2  0.6 W (7.1 ms @ 141 fps)  0.9 W (3.9 ms @ 256 fps)  1.4 W (2.4 ms @ 416 fps)  Inception v3  0.5 W (58.7 ms @ 17 fps)  0.6 W (51.7 ms @ 19.3 fps)  0.7 W (48.2 ms @ 20.7 fps)  Pre-compiled models were tested using models_benchmark.cc    Typical idle power consumption is 375 - 400 mW.       Coral.ai | Copyright 2019 Google LLC.    5    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        3.3 Peak performance    Peak performance when the Edge TPU is running at the maximum operating frequency:    ● 4 trillion operations per second (TOPS), 8-bit fixed-point math  ● 2 TOPS per watt             Coral.ai | Copyright 2019 Google LLC.    6    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        4 Connector pinout    4.1 A+E key pinout    Table 4. A+E key card pinout  Bottom side pins  Top side pins  Pin  Signal  Signal  Pin  74  3.3V  GND  75  72  3.3V  NC  73  70  NC  NC  71  68  NC  GND  69  66  NC  NC  67  64  NC  NC  65  62  NC  GND  63  60  NC  NC  61  58  NC  NC  59  56  NC  GND  57  54  NC  NC  55  52  PERST0# (3.3V)  CLKREQ0# (3.3V)  53  50  NC  GND  51  48  NC  REFCLKn0  49  46  NC  REFCLKp0    47  44  NC  GND  45  42  NC  PETn0   43  40  NC  PETp0   41  38  NC  GND  39  36  NC  PERn0  37  34  NC  PERp0  35  32  NC  GND  33  30  Key E Slot  Key E Slot  31  28  Key E Slot  Key E Slot  29  26  Key E Slot  Key E Slot  27  24  Key E Slot  Key E Slot  25  22  NC  NC  23  20  NC  NC  21  18  GND  NC  19  16  NC  NC  17  14  Key A Slot  Key A Slot  15  12  Key A Slot  Key A Slot  13  10  Key A Slot  Key A Slot  11  8  Key A Slot  Key A Slot  9  6  NC  GND  7  4  3.3V  NC  5  2  3.3V  NC  3      GND  1       Coral.ai | Copyright 2019 Google LLC.    7    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        4.2 B+M key pinout    Table 5. B+M key card pinout  Bottom side pins  Top side pins  Pin  Signal  Signal  Pin  74  3.3V  GND  75  72  3.3V  GND  73  70  3.3V  GND  71  68  NC  NC  69  66  Key M Slot  NC  67  64  Key M Slot  Key M Slot  65  62  Key M Slot  Key M Slot  63  60  Key M Slot  Key M Slot  61  58  NC  Key M Slot  59  56  NC  GND  57  54  NC  REFCLKp0    55  52  CLKREQ0# (3.3V)  REFCLKn0  53  50  PERST0# (3.3V)  GND  51  48  NC  PERp0   49  46  NC  PERn0   47  44  NC  GND  45  42  NC  PETp0   43  40  NC  PETn0   41  38  NC  GND  39  36  NC  NC  37  34  NC  NC  35  32  NC  GND  33  30  NC  NC  31  28  NC  NC  29  26  NC  GND  27  24  NC  NC  25  22  NC  NC  23  20  NC  GND  21  18  Key B Slot  Key B Slot  19  16  Key B Slot  Key B Slot  17  14  Key B Slot  Key B Slot  15  12  Key B Slot  Key B Slot  13  10  NC  NC  11  8  NC  NC  9  6  NC  NC  7  4  3.3V  NC  5  2  3.3V  GND  3      GND  1           Coral.ai | Copyright 2019 Google LLC.    8    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        5 Application details    5.1 Software requirements    The M.2 Accelerator must be operated by the Edge TPU runtime and Coral PCIe driver, which is compatible with the  following systems:    ● Linux:  ○ 64-bit version of Debian 10 or Ubuntu 16.04 (or newer)  ○ x86-64 or ARMv8 system architecture  ● Windows:  ○ 64-bit version of Windows 10  ○ x86-64 system architecture  ● All systems require support for MSI-X as defined in the PCI 3.0 specification    5.2 Power delivery and management    Caution: If you do not carefully consider the power demands of the ML models running the Edge TPU, along with the  ability of your host to handle the corresponding current transients, the peak currents might cause brownouts or other  abnormal behavior in the upstream power regulator.    As described in section 3.2 Power consumption, the current drawn by the Edge TPU is highly variable and depends on the  model being executed. Although the average current drawn by the Edge TPU might seem low (less than 500 mA), it can  repeatedly and rapidly spike up to 3 A, depending on the model you're running. These spikes also occur suddenly: even a  simple model can generate current transients in excess of 1 A/μs, which can last several tens of microseconds.     Ideally, your host system and M.2 socket can be designed to tolerate these higher currents, and your power supply can  provide fast transient response performance. Alternatively, you may use some software strategies to mitigate the effects of  the peak currents, such as underclocking the Edge TPU.    5.3 Thermal management    The Edge TPU dissipates power roughly proportional to its computational load. The resulting heat in the Edge TPU die must  be safely and reliably conducted away to avoid excessive die temperatures that can affect performance and reliability.     The primary heat-generating components on the card are the Edge TPU and power IC, located under the shield can as  indicated in figure 3. The shield can provides thermal coupling to these components with thermal pads—there is no air gap  between the components and the shield can. (For thermal resistance detail, see section 5.3.2 Top-side cooling options.)    During typical operation, approximately 90% of the system power dissipates from the Edge TPU, and the remaining 10%  dissipates from the power IC. Total power dissipation depends on the operating frequency and computational load.                     Coral.ai | Copyright 2019 Google LLC.    9    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01          Figure 3. Approximate location of the power IC (PMIC) and Edge TPU (coupled with the shield can using thermal pads)    5.3.1 Thermal limits    The Edge TPU’s junction temperature Tj must stay below the maximum operating specification:    ● Maximum Edge TPU junction temperature Tj: 115 °C    Warning: Exceeding the maximum temperature can result in permanent damage to the Edge TPU and surrounding  components, and can possibly cause fire and serious damage, injury, or death.    For information about how to read the Edge TPU temperature, see Manage the PCIe module temperature.    5.3.2 Top-side cooling options    To ensure successful long-term operation, you might want to add a cooling solution on the top-side of the card module, on  top of the shield can. When selecting a thermal solution for the top, consider the following thermal resistance properties  with the shield can in place:     ● Edge TPU junction-to-shield-can thermal resistance θj-s: 11 °C/W    Although many applications can sustain proper thermal levels with the shield can in place, you can achieve higher thermal  dissipation (if necessary) by removing the shield can and placing a thermal solution in direct contact with the Edge TPU. If  you choose to do so, then consider the junction-to-case thermal resistance and component dimensions indicated in table 6.    Table 6. Thermal properties and dimensions for cooling solutions with the shield can removed  Component  Top-face dimensions  (X-Y)  Top-face height from PCB  (Z)  Junction-to-case thermal resistance θj-c  Edge TPU  5.0 x 5.0 mm  0.55 ± 0.03 mm  2.2 °C/W  Power IC  2.6 x 3.0 mm  0.48 ± 0.03 mm  0.5 °C/W  Shield can frame  N/A  ~1.35 mm  N/A  Other  N/A  1.00 ± 0.10 mm  N/A    Notice that other top-side components are taller than the primary heat-producing components, so your heat sink or other  enclosure must clear those components. For improved thermal conductivity, consider adding metal stubs that extend from  the heat sink to the surface of the Edge TPU, and fill the remaining gap to the Edge TPU with a thermal coupling material.       Coral.ai | Copyright 2019 Google LLC.    10    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        Caution: If you remove the shield can, it's important that your added heat sink or enclosure has sufficient clearance  above the tallest top-side components to prevent the risk of contact and electrical shorting.     If you remove the shield can, be sure to consider the distance between the PCB and heat sink or enclosure. This distance  determines the minimum allowable thermal pad thickness, as well as the maximum compressive force that can be exerted  on the card. To ensure safe operation, the sustained compressive pressure onto each component from the thermal pads  should not exceed 30 PSI (assuming there is an air gap below the card, and thermal pads on the entire top face of the Edge  TPU and power IC).     5.3.3 Bottom-side cooling options    A secondary thermal path for cooling the Edge TPU is a thermal epoxy or soft thermal pad on the underside of the card,  directly below the Edge TPU. This may dissipate some of the power through the card module and into the base PCB below.    The bottom-side cooling solution is less effective than the top-side solution and should be considered a supplemental  thermal path. In order to approximate the effectiveness of a bottom-side thermal path, you should use the junction-to-board  thermal resistance θj-b indicated in table 7.    Table 7. Thermal properties for bottom-side cooling solutions  Component  Top-face dimensions (X-Y)  Junction-to-board thermal resistance θj-b   Edge TPU  5.0 x 5.0 mm  15 °C/W 1  In this case, θj-b is the temperature difference between the Edge TPU junction and the surface of the card module when  measured from the bottom of the card, directly underneath the Edge TPU.    1 5.3.4 Temperature warnings and frequency scaling    The Edge TPU includes an internal temperature sensor to help you make power management decisions. You can manually  read the temperature, configure parameters that specify when the Edge TPU should shut down, and specify trip-points for  dynamic frequency scaling (DFS).     For details, read Manage the PCIe module temperature.             Coral.ai | Copyright 2019 Google LLC.    11    M.2 Accelerator datasheet v1.5  G650-04527-01 / G650-04686-01        6 Document revisions    Table 8. History of changes to this document  Version  Changes  1.5 (August 2020)  Changed max Edge TPU junction temperature (Tj) to 115 °C (was 125 °C, which is actually  used for HTOL and other qualifications).  Changed minimum operating temperature to -20 °C (was -40 °C).  1.4 (August 2020)  Added information about power consumption and thermal management.  Updated operating temperature and system requirements.  Removed description of DFS; added a link to a more detailed app note.  Miscellaneous edits. Restructured document to match similar products.  1.3 (April 2020)  Updated system architecture requirements  1.2 (December 2019)  Revised dimensions and added tolerances  1.1 (October 2019)  Added max power consumption  1.0 (August 2019)  Initial release         Coral.ai | Copyright 2019 Google LLC.    12