As IoT devices become more capable, delivering the necessary performance to enable immersive experiences to users is a complex challenge owing to the power and thermal constraints on these devices. To address this challenge, a design approach that specifically caters to portable devices without a constant power source is essential. An optimal and thermal efficient design is only possible by taking a holistic approach to power management across the system including the choice of materials for the product enclosures.
Qualcomm does an excellent job on the Snapdragon platforms’ power and thermal management by designing specialized processing engines, smartly integrating them, and optimizing the system software. The different processing engines are specifically designed to perform a given task or enable a user experience at optimal power and thermal levels.
The Snapdragon platform includes the CPU, PMIC, graphics processing unit (GPU), digital signal processor (DSP), image signal processor (ISP), display engine, video engine, sensor engine, and many other specialized processing engines that are designed with optimized architecture for performance and power. The complete system architecture is custom designed by Qualcomm including interconnects, caches, memory systems, and more. This is critical for all these processing engines to work well together. The system software that run on these engines is optimized too to take advantage of power saving hardware features and to make intelligent power management decisions.
Qualcomm’s thermal management algorithm provides a safety net, preventing the device from causing damage to components or injury/discomfort to users. To accomplish this, one must lower power dissipation to keep the temperature at acceptable levels. Let us dig deeper to see how this accomplished. The Thermal core is part of the upstream Linux solution for thermal management and it includes:
- Thermal zone: Provides a means to expose thermal sensors through the sysfs as well as define thermal configurations based off of the sensor.
- Cooling device: Modules that can be throttled to reduce temperature. The different cooling devices(not exhaustive) available and their actions are tabulated below:
- Thermal governor: A temperature monitor algorithm that controls the temperature of a thermal zone within a limit by mitigating the cooling devices associated with the zone.
The inbuilt algorithm carefully monitors key temperatures within the Snapdragon platform using multiple on-die temperature sensors, additional sensors near power amplifiers and the Limits Management Hardware(LMH) protection circuit. The on-die sensors increases the algorithm’s capability to identify and target thermal problems more accurately. The LMH Manages the peak current consumed by the CPU subsystem within the specified capability of the PMIC supply rail and provides an extremely fast thermal management response if any of the CPUs are overheating. Though this reduces the CPU performance when an extreme current or thermal condition is detected, this performance reduction occurs without any other impact to the operation of the software running on the CPU subsystem. Passive cooling is also applied by reducing performance.
Thermal thresholds are configurable in the bootloader and Qualcomm provides default settings after due tuning for every processor. Typically the device boot threshold would be 150C and -150C. The algorithm and the default (tuned) thresholds manage the junction temperature to not exceed the processor’s maximum allowed through mitigation methods explained earlier.
What the Snapdragon offers has to be coupled with Thermal design guidelines at a product level. SMART Wireless Computing has been delivering multiple generations of Snapdragon processor-based embedded computing solutions partnering with Qualcomm and has expertise in creating solutions with excellent thermal dissipation to provide optimized performance of Snapdragon at industrial grade operating temperatures. Our solutions include high quality fan-less enclosures made of sheet metal or plastic and Aluminum heatsink for excellent emission control and heat dissipation that can clear all regulatory compliances.