The Standardization Group for Embedded Technologies (SGET) released SMARC Design Guide v2․2, following SMARC Module Specification v2․2․ This guide offers insights into architecture, compliance, and best practices for SMARC module design, covering power, thermal, and firmware fas integration․!
History of SMARC Specification
SMARC, short for Small Form Factor Computer Platform, emerged in the early 2010s as a response to the growing demand for compact, high‑performance embedded solutions․ The initial specification, SMARC 1․0, was published by the Standardization Group for Embedded Technologies (SGET) in 2012, drawing heavily on the success of the PC‑104 and CompactPCI standards while introducing a unified, low‑profile form factor․ Early adopters included automotive infotainment, industrial control, and portable medical devices, all of which required a tight footprint without sacrificing connectivity or power efficiency․ Over the next few years, the community rallied around the specification, contributing enhancements that addressed real‑world challenges such as thermal management, power delivery, and signal integrity․ By 2015, SMARC 1․1 was released, incorporating a revised pinout that supported higher data rates and a broader range of voltage rails, thereby extending the platform’s applicability to more demanding applications․ The 2017 update, SMARC 2․0, marked a significant milestone: it introduced a new mechanical envelope that reduced the module height from 20 mm to 16 mm, enabling integration into even smaller systems․ This revision also formalized the use of a 12‑pin power connector and standardized the placement of high‑speed interfaces, which simplified board‑level design and improved interoperability․ Subsequent minor revisions—SMARC 2․1 in 2019 and SMARC 2․2 in 2021—focused on refining the specification for emerging technologies, such as 5G connectivity, AI acceleration, and enhanced security features․ Throughout its evolution, the SMARC specification has maintained a strong emphasis on backward compatibility, ensuring that newer modules can coexist with legacy systems․ Today, the SMARC ecosystem is supported by a robust set of design guides, reference boards, and a growing community of developers, all of whom continue to push the boundaries of what can be achieved within a small, modular footprint․
Manufacturers worldwide rely on SMARC’s architecture to accelerate time‑to‑market for solutions today now!
Current SMARC Versions and Revisions
As of the latest release, SMARC 2․2 remains the prevailing standard, offering a 16 mm height and a 20 mm width that accommodates a full complement of interfaces while preserving a minimal footprint․ The 2․2 revision introduces several critical enhancements over its predecessor, SMARC 2․1, including a revised power rail layout that supports up to 12 V on the VDD rail, expanded USB‑Type‑C support, and a dedicated 5 V DC‑DC converter pin for external power supplies․ Additionally, the specification now mandates a 12‑pin power connector, replacing the older 8‑pin variant, which simplifies power delivery and reduces board complexity․ The revision also formalizes the use of the 3․3 V rail for high‑speed I/O, ensuring consistent voltage levels across all modules․ In parallel, the SMARC 2․2 specification has been aligned with the latest PCI‑Express 4․0 and PCI‑Express 5․0 standards, enabling higher data throughput for compute‑intensive applications․ The updated mechanical envelope maintains the same footprint as earlier releases, ensuring backward compatibility with existing carrier boards․ The specification also incorporates a new thermal pad design that improves heat dissipation for high‑power processors․ Finally, SMARC 2․2 introduces a new firmware update mechanism that allows for over‑the‑air updates via the USB‑Type‑C interface, a feature that was previously limited to carrier‑board‑controlled methods․ These changes collectively position SMARC 2․2 as a versatile platform for next‑generation embedded systems, from automotive infotainment to industrial automation and edge‑AI deployments․ The community has embraced these updates, and a growing number of reference designs now target SMARC 2․2, reflecting its maturity and widespread adoption․
Manufacturers have begun to release new boards that fully exploit the expanded interface set, such as dual‑lane PCI‑Express 4․0, SATA III, and high‑bandwidth memory (HBM) support, all within the same 16 mm height․ The specification also clarifies the use of the 12 V rail for power‑hungry modules, allowing designers to integrate GPUs or high‑performance DSPs without additional external power stages․ In addition, the updated pinout provides dedicated pins for 5G NR and LTE‑Advanced modems, making SMARC 2․2 an attractive choice for telecom edge nodes․ The revised thermal pad now features a higher thermal conductivity material, reducing the need for bulky heat sinks and enabling slimmer chassis designs․ Finally, the firmware update mechanism leverages a secure boot process that verifies the integrity of the firmware image before execution, thereby enhancing system security for critical applications․ With these features, SMARC 2․2 is poised to become the de‑facto standard for compact, high‑performance embedded computing across a broad spectrum of industries!!!
Hardware Requirements
SMARC modules demand 12 V, 5 V, 3․3 V rails, 20 mm width, 16 mm height, 20‑pin power header, USB‑C, PCIe, I²C, UART, and thermal pads․ Design must meet 2․2 spec, support 12 V power, secure boot, and provide EMI shielding All dimensions meet the 16 mm height rule!
Power and Voltage Specifications
According to SMARC Design Guide v2․2, modules must support a minimum of 12 V input with a tolerance of ±5 %․ The guide specifies that the primary power rail is 12 V, with secondary rails of 5 V and 3․3 V for logic․ The power connector is a 20‑pin header, with pins 1–4 dedicated to 12 V, pins 5–8 to 5 V, pins 9–12 to 3․3 V, and pins 13–16 for ground․ The guide also mandates that the power supply must provide at least 2 A on the 12 V rail, 1 A on the 5 V rail, and 0․5 A on the 3․3 V rail to accommodate typical embedded processors and peripheral devices․ Voltage regulators must be capable of handling peak currents up to 3 A on the 12 V rail, with a dropout voltage not exceeding 0․3 V under load․ The design must include protection features such as over‑current, over‑voltage, and reverse‑polarity protection on the power input․ Additionally, the guide recommends the use of low‑dropout (LDO) regulators for the 3․3 V rail to minimize noise, and switching regulators for the 12 V and 5 V rails to improve efficiency․ Thermal considerations require that the regulator package be able to dissipate at least 5 W under typical operating conditions․ Finally, the guide specifies that the power connector must be a USB‑C type with 20 pinned configuration, providing both power and data lines, and that the module must support hot‑plug detection and power sequencing compliant with the SMARC specification․ The SMARC Design Guide v2․2 also defines acceptable voltage ripple limits: 12 V rail ripple must be less than 50 mV peak‑to‑peak, 5 V less than 30 mV, and 3․3 V less than 20 mV․ These limits ensure reliable operation of high‑speed interfaces such as PCIe and USB‑C․ Furthermore, the guide recommends the use of a dedicated power‑management IC that can handle simultaneous power‑up of the CPU, GPU, and I/O subsystems, with a minimum rise time of 10 ms to avoid brown‑out conditions․ The power sequencing must follow the sequence: 12 V → 5 V → 3․3 V, with a 100 µs delay between each rail to allow voltage regulators to stabilize․ The design should also incorporate a power‑on reset (POR) circuit that asserts a reset signal to the processor until all rails are within spec․ These detailed requirements help ensure that SMARC modules meet the stringent reliability and performance expectations of modern embedded systems․
Connector Pinout and Mechanical Dimensions
SMARC modules employ a 20‑pin connector that aligns with the SMARC Module Specification v2․2․ The mechanical layout is a 12 mm × 12 mm footprint with a 1 mm pitch․ The connector is a USB‑C type with a 20‑pin configuration, providing power, data, and I/O signals․ Pin 1 is 12 V, pin 2 is ground, pin 3 is 5 V, pin 4 is ground, pin 5 is 3․3 V, pin 6 is ground, pin 7 is USB‑C data‑+ , pin 8 is USB‑C data‑–, pin 9 is PCIe lane‑0, pin 10 is PCIe lane‑1, pin 11 is I²C SDA, pin 12 is I²C SCL, pin 13 is UART TX, pin 14 is UART RX, pin 15 is SPI MOSI, pin 16 is SPI MISO, pin 17 is SPI SCK, pin 18 is SPI CS, pin 19 is GPIO, and pin 20 is a reset line․ The connector’s mechanical tolerances allow for ±0․1 mm alignment, and the module’s edge‑mount design requires a 2 mm clearance on all sides․ The pin spacing is 1 mm, and the connector’s width is 12 mm, height 12 mm, with a 1․5 mm thickness․ The guide specifies that the connector must be a 20‑pin USB‑C type, with a 1 mm pitch, and that the module must support a 12 V input, 5 V, and 3․3 V rails․ The connector’s mechanical dimensions are critical for ensuring proper mating with host boards, and the guide recommends using a 3‑D printed mount that matches the 12 mm × 12 mm footprint․ The connector must also support a 1․5 mm thick housing to accommodate the USB‑C type, and the module must be able to withstand a 100 kg force during insertion․ The SMARC Design Guide v2․2 also details the need for a 1․5 mm‑deep keying slot on the connector to prevent mis‑orientation․ The pinout must be verified with a multimeter before soldering, and the connector’s mechanical tolerances are specified to ensure reliable electrical contact and to avoid signal degradation․ The guide recommends using a 20‑pin USB‑C connector with a 1 mm pitch, 12 mm × 12 mm footprint, and a 1․5 mm thickness, providing a robust interface for power, data, and I/O signals in embedded systems․
Thermal Management
SMARC Design Guide v2․2 recommends heat-sink placement on the module’s top surface, using a 0․5 mm thermal pad․ A 10 mm × 10 mm copper plane aids heat spread, and a 1 mm thick silicone gasket improves thermal contact․ Test at 80°C․ Ensure airflow and use thermal greas
Heat Sink and Thermal Pad Considerations
According to SMARC Design Guide v2․2, the recommended heat‑sink thickness is 1․5 mm, with a minimum area of 12 mm × 12 mm to accommodate the module’s power‑dissipating components․ A thermal pad thickness of 0․5 mm and a thermal conductivity of at least 2․5 W m⁻¹ K⁻¹ is required to ensure efficient heat transfer from the silicon die to the sink․ The pad should be placed directly beneath the processor and any high‑power voltage regulators, with a 0․2 mm clearance from the edge of the module to avoid shorting․ The guide specifies that the heat‑sink material should be aluminum or copper, with a surface finish that allows for a 0․1 mm silicone gasket to improve contact pressure․ The gasket material must be compliant with the SMARC mechanical tolerance of 0․05 mm․ In addition, the guide recommends using a thermal grease with a thermal resistance of less than 0․3 °C W⁻¹ for any gaps larger than 0․1 mm․ The heat‑sink mounting pattern must align with the module’s mounting holes, and the mounting screws should be tightened to 0․8 Nm to achieve the necessary clamping force․ Finally, the guide advises performing a thermal imaging test after assembly to verify that the maximum junction temperature does not exceed 80 °C under full load․ This ensures compliance with the SMARC Module Specification v2․2 and provides reliable operation in embedded applications․
Thermal Test Procedures
SMARC Design Guide v2․2 outlines a step‑by‑step thermal validation flow that ensures modules meet the 80 °C junction limit under maximum rated load․ The procedure begins with a baseline measurement: place the module on a calibrated thermal‑plate test fixture, apply the nominal 5 V/3․3 V supply, and allow the system to reach steady state for at least 10 minutes․ Use an IR camera with 0;5 °C resolution to capture the temperature map of the processor die, voltage regulator, and any other high‑power blocks․ Record the peak temperature and compare it to the 80 °C threshold․ Next, perform a load‑step test by raising the processor frequency from 1 GHz to 2․5 GHz in 0․5 GHz steps, logging the temperature rise; The guide specifies that the temperature differential between successive steps should not exceed 5 °C; if it does, investigate bottlenecks such as insufficient pad contact or inadequate heat‑sink mounting․ After the frequency sweep, conduct a power‑density test by increasing the supply voltage to the maximum rated 5․5 V while keeping the frequency constant, and verify the temperature stays below the limit․ Finally, repeat the sequence with the module mounted on its carrier board, applying the same thermal pad and heat‑sink configuration․ The results must be documented in a thermal test report that includes the IR images, temperature logs, and any corrective actions taken․ This rigorous testing guarantees compliance with SMARC Module Specification v2․2 and supports field operation․
Signal Integrity and EMI
SMARC Design Guide v2․2 emphasizes controlled impedance traces, 90 Ω differential pairs, and minimal stubs․ Use ground planes, via stitching, and proper decoupling to reduce EMI․ Follow EMC test limits per spec․ All measurements use 0․1 °C accuracy for compliance
PCB Layout Guidelines
SMARC Design Guide v2․2 specifies that high‑speed differential pairs must be routed with 90 Ω impedance and a 2 mm clearance from other signals․ Maintain a continuous ground plane on the adjacent layer to provide return paths and reduce loop area․ Place vias near power and ground pins to lower inductance and improve decoupling․ Use 0․1 µF ceramic capacitors close to each regulator pin, and add 10 µF tantalum for bulk filtering․ Keep signal stubs under 5 mm; longer stubs increase reflection․ For clock lines, route with matched length and use differential pairs when possible․ Avoid crossing high‑frequency traces with low‑frequency analog signals; separate them by at least 5 mm․ Implement via stitching around the board perimeter to shield EMI․ Place thermal vias under the processor and power modules, spacing them 2 mm apart, and connect them to a dedicated copper pour․ Follow the recommended 1 mm spacing between power and analog ground traces to prevent noise coupling․ Finally, perform a signal integrity simulation using a 10 GHz bandwidth tool to verify eye diagrams and return loss before fabrication․ During the simulation, monitor the eye diagram at 1 Gbps to ensure the vertical opening exceeds 80 % of the supply voltage and the horizontal opening is within 10 % of the bit period․ Verify the return loss is below –15 dB across the 0․1–5 GHz band․ Document all test vectors and keep the simulation file in the repository․ and ensure traceability․
Grounding and Shielding Techniques
According to SMARC Design Guide v2․2, a single‑point ground reference is mandatory to minimize ground bounce․ The guide recommends a dedicated ground plane on the bottom layer, with a continuous copper pour that connects all ground pins via low‑impedance vias․ For high‑frequency signals, differential pairs should share a common reference plane on the same layer to reduce loop area․ The design guide specifies that all analog ground pins must be routed to a separate analog ground plane that is isolated from the digital ground plane by a 0․5 mm gap, then connected through a low‑inductance via at the board edge to the main ground plane․ Shielding is achieved by placing a metal shield layer between the processor core and the RF antenna, with a 0․2 mm clearance․ The shield must be connected to the system ground at both ends of the shielded trace to prevent standing waves․ For EMI compliance, the guide advises a 10 µm copper thickness on the shield layer and a 0․1 mm spacing to adjacent signal traces․ The ground plane must be continuous under the power regulator to reduce EMI coupling․ The guide also recommends using a ground stitching pattern of 0․3 mm pitch around the perimeter, with 0․2 mm spacing to the edge․ Finally, the design must include a ground reference point at the center of the board to serve as the return path for all high‑speed signals, ensuring a symmetrical return path and minimizing differential impedance variations․ Include 22 cs․
Software and Firmware Integration
SMARC Design Guide v2․2 outlines firmware integration: a modular bootloader must support secure OTA updates, with version tags in non‑volatile memory․ Firmware binaries are signed, verified, and flashed via UART or I²C ensuring compatibility across revisions․
Bootloader and Firmware Update Process
The SMARC Design Guide v2․2 specifies a robust, modular bootloader architecture that supports secure, over‑the‑air (OTA) firmware updates․ The bootloader must reside in a protected flash region and be capable of verifying digital signatures before executing firmware․ During power‑on, the bootloader checks the integrity of the active firmware; if a newer signed image on the external storage interface (e․g․, UART, I²C, or SD card), it initiates the update sequence․ The sequence includes: 1) downloading the image to a temporary buffer, 2) computing the hash and comparing it to the header value, 3) verifying the signature using the embedded public key, and 4) atomically swapping the firmware partition․ If any step fails, the bootloader falls back to the last known good image․ The guide recommends using a dual‑bank or dual‑partition scheme to avoid bricking the device․ All communication channels for updates must be encrypted (TLS 1․3 or equivalent) to prevent man‑in‑the‑middle attacks․ The design guide further advises implementing a watchdog timer that resets the system if the update process hangs, ensuring the device does not remain in an unusable state․ Finally, the bootloader should expose a status register that allows host software to query the current firmware version, update progress, and error codes, facilitating seamless integration into larger embedded ecosystems․ The bootloader logs update status to a serial console for debug
Firmware Compatibility and Versioning
According to the SMARC Design Guide v2․2, firmware compatibility follows a strict versioning schema aligned with the SMARC module specification․ Each image must embed a header with major, minor, patch numbers, a build timestamp, and a unique identifier for the target SMARC module family․ The major number changes only for backward‑incompatible updates; minor increments add new features while maintaining compatibility, and patch numbers fix bugs․ Firmware must declare the supported SMARC revision (e․g․, 2․2) so the bootloader can reject incompatible images․ The guide recommends a semantic versioning approach (MAJOR․MINOR․PATCH) and the use of a “compatibility matrix” in documentation to map releases to supported hardware revisions․ Each firmware binary must be signed with a public‑key infrastructure (PKI) embedded in the bootloader; the public key is tied to the module’s unique ID․ The bootloader verifies the signature before loading, ensuring only firmware compiled for the exact module variant runs․ For multi‑module ecosystems, a “module‑family” tag in the header allows a single bootloader to support several related variants while enforcing strict compatibility․ Developers must maintain a changelog documenting every change, including the reason for major version bumps, to aid troubleshooting․ The guide also requires that firmware updates be accompanied by a changelog entry recording the exact build hash, release notes, and any required hardware configuration changes, ensuring traceability and facilitating rollback procedures if a new version introduces regressions․ All updates are logged to a secure audit trail․ Versioning rules are documented in mod manual․!