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Texas Instruments AM571x Thermal Considerations Application notes
Application Report
SPRACI0 – October 2018
AM571x Thermal Considerations
Ahmad Rashed
ABSTRACT
This application report discusses thermal performance of the Sitara™ AM571x 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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List of Figures
.............................................................
......................................................
Dyrystone(Core 1) @ OPP_NOM (Junction Temp vs Ambient Temp) ...............................................
Dyrystone(Core 1) @ OPP_NOM (Power Consumption vs Ambient Temp) ........................................
Dyrystone(Core 1) @ OPP_OD (Junction Temp vs Ambient Temp) ................................................
Dyrystone(Core 1) @ OPP_OD (Power Consumption vs Ambient Temp) ..........................................
Dyrystone(Core 1) @ OPP_HIGH (Junction Temp vs Ambient Temp) ..............................................
Dyrystone(Core 1) @ OPP_HIGH (Power Consumption vs Ambient Temp) ........................................
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OS Idle - OPP_NOM (Junction Temp vs Ambient Temp)
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OS Idle - OPP_NOM (Power Consumption vs Ambient Temp)
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List of Tables
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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 AM571x 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 AM571x board for this report.
3.1
OS Idle
The AM571x processor is idling after booting the out-of-box configuration of Processor SDK Linux®
v04.02.00. No display was connected to the AM571x 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), 1.188GHz (OPP_OD), and 1.5GHz (OPP_HIGH).
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 AM571x 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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AM571x Thermal Considerations
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Data and Results
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This SoC only supports DVFS on the MPU domain. For DSP and GPU domains, the 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_OD
OPP_HIGH
Max Frequency (MHz)
Max Frequency (MHz)
Max Frequency (MHz)
MPU_CLK
1000
1176
1500
DSP_CLK
600
700
750
VD_IVA
IVA_GCLK
388.3
430
532
VD_GPU
GPU_CLK
VD_CORE
DDR3 / DDR3L
Voltage Domain
Clock Domain
VD_MPU
VD_DSP
CORE_IPUx_CLK
L3_CLK
VD_RTC
4
RTC_FCLK
425.6
500
532
667 (DDR3-1333)
N/A
N/A
212.8
N/A
N/A
266
N/A
N/A
0.034
N/A
N/A
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 OPP levels:
Default OPP Levels
MPU
GPU
DSP
IVA
NOM
HIGH
HIGH
HIGH
The MPU domain OPP defaults to NOM when idle and increases to HIGH when under load. OPP levels
for DSP and IVA cores can be changed but that must be done by editing the U-Boot defconfig file with the
desired OPP level and recompiling.
Applicable to the AM571x, the Linux kernel on this device utilizes the CPUFreq driver to support multiple
OPPs for the MPU domain and dynamically change between them. As such a desired max frequency
must be set if seeking power consumption at a frequency lower than the max.
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 each supported OPP.
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 (MPU @ OPP_NOM)
OPP Levels
MPU
GPU
DSP
IVA
NOM
HIGH
HIGH
HIGH
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (°C)
33.6
48.4
68.6
90.2
102.8
Heatsink (°C)
31.6
45.6
65.8
87.2
99.4
Junction Temperature (qC)
105
85
65
45
No Heatsink
Heatsink
25
20
40
60
80
Ambient Temperature (qC)
100
D001
Figure 1. OS Idle - OPP_NOM (Junction Temp vs Ambient Temp)
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (mW)
2295
2392.7
2605.6
2962.6
3237.4
Heatsink (mW)
2239.7
2365.9
2562.1
2897.5
3162.9
3250
Power (mW)
3000
2750
2500
2250
No Heatsink
Heatsink
2000
20
40
60
80
Ambient Temperature (qC)
100
D002
Figure 2. OS Idle - OPP_NOM (Power Consumption vs Ambient Temp)
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4.4
Dhrystone (MPU @ OPP_NOM)
OPP Levels
MPU
GPU
DSP
IVA
NOM
HIGH
HIGH
HIGH
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (°C)
37.4
51.2
72
95
105.4
Heatsink (°C)
34.2
48.4
67.6
88.8
101.4
Junction Temperature (qC)
120
100
80
60
40
No Heatsink
Heatsink
20
20
40
60
80
Ambient Temperature (qC)
100
D003
Figure 3. Dyrystone(Core 1) @ OPP_NOM (Junction Temp vs Ambient Temp)
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (mW)
2987
3103.1
3336.9
3766.1
4035.6
Heatsink (mW)
2923.7
3091.3
3277.6
3651
3896.2
4050
Power (mW)
3800
3550
3300
3050
No Heatsink
Heatsink
2800
20
40
60
80
Ambient Temperature (qC)
100
D004
Figure 4. Dyrystone(Core 1) @ OPP_NOM (Power Consumption vs Ambient Temp)
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Data and Results
4.5
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Dhrystone (MPU @ OPP_OD)
OPP Levels
MPU
GPU
DSP
IVA
OD
HIGH
HIGH
HIGH
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (°C)
38.6
53.6
74.8
96.8
107.4
Heatsink (°C)
34.6
49
69
91.2
102.6
Junction Temperature (qC)
120
100
80
60
40
No Heatsink
Heatsink
20
20
40
60
80
Ambient Temperature (qC)
100
D005
Figure 5. Dyrystone(Core 1) @ OPP_OD (Junction Temp vs Ambient Temp)
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (mW)
3292.1
3421.1
3688.5
4145.3
4497.2
Heatsink (mW)
3258.1
3365.6
3567.9
4032.5
4306.4
4600
Power (mW)
4350
4100
3850
3600
3350
No Heatsink
Heatsink
3100
20
40
60
80
Ambient Temperature (qC)
100
D006
Figure 6. Dyrystone(Core 1) @ OPP_OD (Power Consumption vs Ambient Temp)
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AM571x Thermal Considerations
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4.6
Dhrystone (MPU @ OPP_HIGH)
OPP Levels
MPU
GPU
DSP
IVA
HIGH
HIGH
HIGH
HIGH
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (°C)
42.2
57.4
80.6
103.6
114.4
Heatsink (°C)
35.8
50.4
72.8
93.6
106.4
Junction Temperature (qC)
120
100
80
60
40
No Heatsink
Heatsink
20
20
40
60
80
Ambient Temperature (qC)
100
D007
Figure 7. Dyrystone(Core 1) @ OPP_HIGH (Junction Temp vs Ambient Temp)
Ta (°C)
Therm Mgmt
25
40
60
80
90
No Heatsink (mW)
4092.1
4269.2
4660.2
5344.1
5783.1
Heatsink (mW)
4037.1
4169.4
4589.8
5040.6
5414.9
6000
5750
Power (mW)
5500
5250
5000
4750
4500
4250
4000
20
No Heatsink
Heatsink
40
60
80
Ambient Temperature (qC)
100
D008
Figure 8. Dyrystone(Core 1) @ OPP_HIGH (Power Consumption vs Ambient Temp)
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References
•
•
•
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/AM5718/toolssoftware
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