Thermal management is the area concerned with making sure that the system and its components operate within defined temperature ranges, to guarantee the reliable operation of the whole system. It involves concepts such as power consumption, heat dissipation, and system temperature, which are related to the following topics:
This article provides an overview of thermal management solutions applied to the Toradex system SoMs. It goes through the hardware and software BSP specifics as well as cooling solutions.
This section goes through the hardware specifics related to thermal management.
Note: Additional information can be found in the respective Toradex SoMs datasheets, under the Thermal Specification section. The datasheets are available in the corresponding product pages, under the Datasheets tab.
The following table provides the maximum junction temperature for a specific SoC. Notice that this is the maximum temperature at the semiconductor level, measured by a sensor internal to the SoC die. This temperature is higher than the die/case temperature and is monitored by the underlying operating system and/or additional hardware mechanisms. If temperature throttling mechanisms fail to keep the SoC from reaching the junction temperature, a forced system shutdown is issued to prevent permanent damage.
Browse the dropdown table below for information about maximum junction temperature sorted by SoC:
The operating temperature of all the electrical components in an SoM defines the final module specification. As a consequence, the most critical element regarding temperature limits may not be the SoC, but instead another part. The dropdown tables below list the operating temperature range by Toradex SoM:
This section goes through the software and BSP specifics related to thermal management.
Dynamic Voltage and Frequency Scaling (DVFS) is a mechanism in which the operating system optimizes power consumption by adjusting the CPU clocks and voltage based on demand. A side-effect of power consumption optimization is that the system generates less heat in workloads that don't make full use of the CPU.
Thermal Throttling is a mechanism implemented in the operating system to preserve the integrity of the processor. It forces reduction of the system clock when it reaches certain temperatures, independent of DVFS.
Note: DVFS is disabled by default on WinCE. Please see DVFS on Windows Embedded Compact for further information.
It may be possible to enable/disable CPU cores dynamically if both the SoC and operating system support it, which saves power, thus generating less heat.
This section has some tips on how to save power, which may help reduce heat generation and other aspects of the software that may affect thermal management.
Note: We recommend the measuring of the system's power consumption, before and after making the changes. It helps in getting a better understanding of the power management of the system.
Choose your OS from the tabs below:
Using Linux, DVFS can be disabled, and the CPU frequency manually set. See the CPU Frequency (Linux) article.
An application in the userspace can monitor the temperature. How to read it and which sensors are available is module-dependent. See the Temperature Sensor (Linux) article and Apalis/Colibri T30 Temperature Monitoring for additional information.
The Linux kernel executes the Thermal Throttling, and the generic Thermal Sysfs API provides access to its settings. The section below includes information about how to set temperature trip points in Linux:
There are two temperature trip points used on iMX SoCs.
passive This is the point where Linux starts to throttle the CPU.
critical This is the point where Linux shuts itself down to protect the CPU.
Toradex decided to use the T_junction_max stated in the datasheet for the critical temperature and 10°C less for the passive trip point.
The following patch should be a guideline how to change these trip-points for iMX related SoCs:
diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
index 28072a7..591d6be 100644
--- a/drivers/thermal/imx_thermal.c
+++ b/drivers/thermal/imx_thermal.c
@@ -656,10 +656,10 @@ static int imx_get_sensor_data(struct platform_device *pdev)
}
/*
- * Set the critical trip point at 5C under max
+ * Set the critical trip point at max
* Set the passive trip point at 10C under max (can change via Sysfs)
*/
- data->temp_critical = data->temp_max + (1000 * 10);
+ data->temp_critical = data->temp_max;
data->temp_passive = data->temp_max - (1000 * 10);
return 0;
data->temp_max in this driver is used for the T_junction_max that is read out from the fuses.
data->temp_passive and data->temp_critical are the temperatures described above that a developer should set with the desired temperature in milli-degree Celsius.
The i.MX 8/8X power management and temperature monitoring are entirely handled by the System Controller Firmware (SCFW).
The critical and passive points threshold set in their dtsi file and specify CONFIG_IMX8M_THERMAL in defconfig.
The thermal driver can be accessed through the following interface:
/sys/class/thermal/thermal_zoneX for i.MX 8 and i.MX 8X./sys/class/thermal/thermal_zone0 for i.MX 8M Mini./sys/class/thermal/thermal_zoneX for i.MX 8M Plus.Inside the above directory, there are files named trip_point*. There you can read the type, current temperature, and hysteresis used by those trip points.
See the article CPU (Linux) for detailed information on supported modules.
Disable unused Display Interfaces
Use a Lower Frequency
Avoid Toggling Pins
Use Low Power Modes
Check CPU Load
Disable unused Drivers
DVFS and temperature throttling settings can be customized. See the Resource Manager Registry Settings and Apalis/Colibri iMX6 DVFS on Windows Embedded Compact articles. As an alternative to tweaking resources, as well as a means to monitor system frequency and temperature, Toradex provides a software tool named Toradex Task Manager. Notice that DVFS is available from WinCE Image 1.3b4 onwards.
For additional temperature monitoring information, see Apalis/Colibri T30 Temperature Monitoring and SoC Temperature Readout (WinCE).
See the article Resource Manager Registry Settings for detailed information on supported modules.
Disable unused Display Interfaces
BootupStyle = 1
HDMIHotplugBehavior = 2
Use a Lower Frequency
Avoid Toggling Pins
Use Low Power Modes
Check CPU Load
Disable unused Drivers
Colling solutions usually target the SoC and can be either passive or active. Passive means that the natural convection transports the heat from the surface to the air. By passive definition, it includes both having the SoC exposed to the environment with or without a heatsink. The efficiency of natural convection is dependent on the housings and the environment. This solution has no moving parts and does not produce noise. If the passive cooling is not sufficient, the most common active cooling solution for embedded systems is the use of a DC fan on top of the heat sink, which increases efficiency dramatically.
if a box encloses the hardware, there are two recommended approaches: The design of the enclosure should optimize the airflow The enclosure should thermally couple to the SoC ( or both).
The temperature inside the enclosing has to respect the SoM operating temperature range.
The Apalis family has a robust, rigid mounting mechanism to support thermal solutions. It is ready-to-use on Toradex carrier boards and, if you plan to design your carrier board, the thermal solution implementation guidelines are available in the Apalis Carrier Board Design Guide.
The optimized Apalis Heatsink is available for each version of the Toradex Apalis module. The following table shows the compatibility of the available Apalis heatsinks:
| Apalis Heatsink Type | Compatible Module |
|---|---|
| Type 1 | Apalis iMX6Q IT Apalis iMX6D IT |
| Type 2 | Apalis T30 |
| Type 3 | Apalis iMX6Q Apalis iMX6D Apalis TK1 |
| Type 4 | Apalis iMX8QM |
The Apalis heatsink has four holes intended for mounting a fan on top of it. Specifics are available in the Apalis Heatsink Fan article. Also, a 3D CAD model of the heatsink is available in the 3D CAD models page.
Apalis Carrier Boards Heatsink
The Colibri family of SoMs does not have a cooling solution officially provided by Toradex. Nevertheless, we have tested a few off-the-shelf heatsink solutions available in the market with Colibri T20 and T30 modules. For more details, please refer to the following test reports:
The Verdin family has a robust, rigid mounting mechanism to support thermal solutions. It is ready-to-use on Toradex carrier boards and, if you plan to design your carrier board, the thermal solution implementation guidelines are available in the Verdin Carrier Board Design Guide.
The optimized Verdin Industrial Heatsink is available for each version of the Toradex Verdin module. The following table shows the compatibility of the available Verdin Industrial Heatsink:
| Verdin Heatsink Type | Compatible Module |
|---|---|
| Type 1 | Verdin iMX8M Mini Verdin iMX8M Plus |
Verdin Industrial Heatsink
Colibri PXAxx modules run at a fixed frequency. Toradex provides ways to manually change the system frequency to tweak or optimize the system performance using software configurations. In most of the use cases, a cooling solution is not necessary. The maximum temperature is the case temperature of the PXA processor, which must not exceed 85°C. For more details, please refer to the respective Colibri module datasheet and Marvell's EMTS.
