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Texas Instruments AM570x Thermal Considerations Application notes
Application Report
SPRACG1 – June 2018
AM570x Thermal Considerations
Ahmad Rashed
ABSTRACT
This application report discusses thermal performance of the Sitara™ AM570x series processors. The
data presented demonstrates the effects of different thermal management strategies in terms of processor
junction temperature and power consumption across MPU loading and ambient temperature.
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Contents
Overview ......................................................................................................................
Important Notes ..............................................................................................................
Test Overview ................................................................................................................
Data and Results ............................................................................................................
References ...................................................................................................................
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7
List of Figures
........................................................................
..........................................................................
Junction Temperature vs Ambient Temperature ........................................................................
Power Consumption vs Ambient Temperature ..........................................................................
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Junction Temperature vs Ambient Temperature
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2
Power Consumption vs Ambient Temperature
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3
4
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List of Tables
1
Supported OPP vs Max Frequency
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Trademarks
Sitara is a trademark of Texas Instruments.
Arm, Cortex are registered trademarks of Arm Limited.
Linux is a registered trademark of Linus Torvalds.
All other trademarks are the property of their respective owners.
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Overview
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Overview
An internal AM570x board was used in this experiment to gather thermal data with different processor
loading and ambient temperature. Ambient temperature was controlled with programmable environmental
chamber.
The collected data can be utilized to correlate the thermal performance of the processor and power
consumption at a given processor load and junction temperature, based on ambient temperature and
thermal management.
Tests were repeated with the following thermal management:
• Bare package (no heatsink)
• Low-cost heatsink
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Important Notes
The environmental chamber used to collect this data circulates air internally to maintain homogeneous
internal temperature, and does not accurately simulate the environment on the bench or end product. This
is important to consider in passive cooling applications where air circulation can significantly impact PCB,
package, and heatsink power dissipation efficiency.
The data presented in this test was gathered with a typical device, representing nominal silicon process
and leakage. Thermal performance and power consumption can vary significantly due to process
variation. Extra margin must be designed in to account for worst case process variation (leakage).
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Test Overview
The following CPU loading schemes were characterized with the internal AM570x board for this report.
3.1
OS Idle
The AM570x processor is idling after booting the out-of-box configuration of Processor SDK Linux®
v04.02.00. No display was connected to the AM570x board. MPU, GPU, and IVA cores are powered but
automatically clock gated while the DSP and IPU cores are both power and clock gated.
3.2
Dhrystone
Dhrystone is a single-threaded benchmark, capable of utilizing approximately 100% of one Arm® Cortex®A15 core. Dhyrstone is included in the TI Processor SDK. Tests were conducted with the A15 running at
1.0 GHz (OPP_NOM).
3.3
Temperature Measurement
Reported temperature data is measured by on-die sensors to the approximate actual junction temperature.
Temperature for each use-case is measured after soaking for 5 minutes. Under lab conditions, it was
determined a 5 minute period allows the processor to reach stable temperature.
The TI Processor SDK provides Linux drivers for these sensors, and can be queried from the commandline, for example:
# cat /sys/class/thermal/thermal_zone0/temp
71800
3.4
OPP Definitions
Operating performance points (OPP) levels define a max frequency per fixed voltage level in each voltage
domain. Table 1 lists frequency of each subsystem per OPP for the AM570x processor.
Dynamic Voltage Frequency Scaling (DVFS) refers to a software technique where the system-on-chip
(SoC) supplies with AVS support are changed from one OPP level (voltage and frequency pair) to another
in order to either adapt to a changing work-load, or in order to avoid device operation outside of desired
temperature bounds.
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AM570x Thermal Considerations
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Data and Results
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This SoC does not support DVFS on any rails. OPP levels should be set during boot by the initial
bootloader. Ensure that the selected OPP level meets the application's needs and all thermal testing is
conducted at the desired OPP level.
Table 1. Supported OPP vs Max Frequency
OPP_NOM
OPP_HIGH
Voltage Domain
Clock Domain
Max Frequency (MHz)
Max Frequency (MHz)
VD_CORE
MPU_CLK
1000
N/A
GPU_CLK
425.6
N/A
CORE_IPUx_CLK
212.8
N/A
L3_CLK
266
N/A
DDR3 / DDR3L
667 (DDR3-1333)
N/A
IVA_GCLK
388.3
532
DSP_CLK
600
750
VD_DSP
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Data and Results
This section contains the raw data and graphs of the test experiments described above. All of the data
was gathered running the latest Linux Processor SDK. All tests were conducted without an external
display installed.
4.1
OPP Settings and Linux Thermal Framework
Tests were conducted with Processor SDK 04.02.00, with following default OPP levels:
Default OPP Levels
MPU
GPU
DSP
IVA
NOM
NOM
HIGH
HIGH
The MPU, GPU, DSP and IVA cores are operating at fixed OPP levels. Only the OPP levels for DSP and
IVA cores can be changed and that must be done by editing the U-Boot defconfig file with the desired
OPP level and recompiling.
While not applicable to the AM570x, other devices can utilize the CPUFreq driver if they support multiple
OPPs for the MPU domain. In that case, a desired max frequency must be set if seeking power
consumption at a lower than max frequency.
Additionally, the Linux thermal framework needs to be disabled, otherwise, the max fequency is reduced
as the MPU heats up to prevent thermal shutdown. This should only be done for data gathering purposes
when the junction temperature exceeds the levels defined in the device tree and is not recommended for a
production system.
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Data and Results
4.2
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Power and Thermal Chamber Measurements
The tables shown in the following sections contain power consumption and junction temperature
measured running OS Idle and Dhrystone single-core use cases at different controlled ambient
temperatures with and without an attached heatsink. This silicon process type is nominal. Dhrystone tests
were repeated with MPU at OPP_NOM (1.0 GHz).
Junction temperature and power reported in the following sections were sampled at the same time, and
are presented in separate tables to aid comprehension.
4.3
OS Idle
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (°C)
35
51
71
94
107
Heatsink (°C)
31
47
66
87
98
Figure 1. Junction Temperature vs Ambient Temperature
4
AM570x Thermal Considerations
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Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (mW)
1338.2
1450.9
1700.6
2245.9
2684.1
Heatsink (mW)
1255.7
1427.4
1632.8
2004.0
2358.2
Figure 2. Power Consumption vs Ambient Temperature
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Data and Results
4.4
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Dhrystone
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (°C)
40
56
77
101
114
Heatsink (°C)
33
49
69
90
102
Figure 3. Junction Temperature vs Ambient Temperature
6
AM570x Thermal Considerations
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References
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Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (mW)
2198.7
2335.4
2682.8
3314.7
3893.5
Heatsink (mW)
2116.7
2281.7
2553.4
2980.5
3412.7
Figure 4. Power Consumption vs Ambient Temperature
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References
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•
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To learn more about thermal management, visit http://www.ti.com/thermal
Thermal Design Guide for DSP and ARM Application Processors
Thermal models can be found in the Models section of Tools and Software in the product folder:
http://www.ti.com/product/AM5708/toolssoftware
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