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Texas Instruments AM574x thermal considerations Application notes
Application Report
SPRACL7 – March 2019
AM574x thermal considerations
Ahmad Rashed
ABSTRACT
This application report discusses the thermal performance of the Sitara™ AM574x 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 ...................................................................................................................... 2
Important Notes .............................................................................................................. 2
Test Overview ................................................................................................................ 2
Data and Results ............................................................................................................ 3
References .................................................................................................................. 13
List of Figures
............................................................. 4
...................................................... 5
Dyrystone (Core 1) at OPP_NOM (Junction Temp vs Ambient Temp) ............................................... 6
Dyrystone (Core 1) at OPP_NOM (Power Consumption vs Ambient Temp) ........................................ 7
Dyrystone (Core 1 and Core 2) at OPP_NOM (Junction Temp vs Ambient Temp) ................................ 8
Dyrystone (Core 1 & Core 2) at OPP_NOM (Power Consumption vs Ambient Temp) ............................ 9
Dyrystone (Core 1) at OPP_HIGH (Junction Temp vs Ambient Temp) ............................................ 10
Dyrystone (Core 1) at OPP_HIGH (Power Consumption vs Ambient Temp) ...................................... 11
Dyrystone (Core 1 & Core 2) at OPP_HIGH (Junction Temp vs Ambient Temp) ................................ 12
Dyrystone (Core 1 & Core 2) at OPP_HIGH (Power Consumption vs Ambient Temp) ........................... 13
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OS Idle - OPP_NOM (Junction Temp vs Ambient Temp)
2
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
1
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Overview
In this experiment, an internal AM574x board is used to gather thermal data with different processor
loading and ambient temperature. Ambient temperature is controlled with a 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 (31-mm x 31-mm x 19.5-mm, #ATS-54310R-C1-R0)
• Low-cost heatsink + Fan (5 V, 9500 RPM, 4.9 CFM, #MC30060V1-000U-A99)
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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 is 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 are characterized with the internal AM574x board for this report.
3.1
OS Idle
The AM574x processor is idling after booting the out-of-box configuration of Processor SDK Linux®
v05.02.00. No display was connected to the AM574x 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 are conducted with the A15 running at 1.0
GHz (OPP_NOM) and 1.5 GHz (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 five minutes. Under lab conditions, it is
determined a five 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 the frequency of each subsystem per OPP for the AM574x 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
to either adapt to a changing work-load, or to avoid device operation outside of desired temperature
bounds.
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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 must be
set during boot by the initial bootloader. Ensure that the selected OPP level meets the needs of the
application and all thermal testing is conducted at the desired OPP level.
Table 1. Supported OPP vs Max Frequency
OPP_NOM
OPP_OD
OPP_HIGH
Maximum Frequency
(MHz)
Maximum Frequency
(MHz)
Maximum Frequency
(MHz)
Voltage Domain
Clock Domain
VD_MPU
MPU_CLK
1000
1176
1500
VD_DSP
DSP_CLK
600
700
750
EVE_FCLK
535
650
650
VD_IVA
IVA_GCLK
388.3
430
532
VD_GPU
GPU_CLK
425.6
500
532
VD_CORE
DDR3 / DDR3L
667 (DDR3-1333)
N/A
N/A
212.8
N/A
N/A
266
N/A
N/A
0.034
N/A
N/A
CORE_IPUx_CLK
L3_CLK
VD_RTC
4
RTC_FCLK
Data and Results
This section contains the raw data and graphs of the test experiments described above. All data is
gathered running the latest Linux Processor SDK. All tests are conducted without an external display
installed.
4.1
OPP Settings and Linux Thermal Framework
Tests are conducted with Processor SDK 04.02.00 at 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 AM574x, the Linux kernel on this device uses the CPUFreq driver to support multiple
OPPs for the MPU domain and dynamically changes between them. As such, a desired maximum
frequency must be set if you are seeking power consumption at a frequency lower than the maximum.
Additionally, the Linux thermal framework needs to be disabled, otherwise, the maximum frequency is
reduced as the MPU heats up to prevent thermal shutdown. This must 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
are repeated with MPU at each supported OPP.
Junction temperature and power reported in the following sections are sampled at the same time, and are
presented in separate tables to aid comprehension.
4.3
OS Idle at OPP_NOM
OPP Levels
MPU
GPU
DSP
IVA
NOM
HIGH
HIGH
HIGH
Ta (°C)
Thermal
Management
25
45
60
75
No Heatsink (°C)
39
59.8
78
100.8
Heatsink (°C)
32.6
53.3
69.8
85.6
102.2
Heatsink + Fan (°C)
31
49.6
66.3
81.8
99.6
90
Figure 1. OS Idle - OPP_NOM (Junction Temp vs Ambient Temp)
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Ta (°C)
Thermal
Management
25
45
60
75
No Heatsink (mW)
2319.1
2776.4
3427.2
4744
Heatsink (mW)
2212
2621.4
3124.9
3811.9
4877.3
Heatsink + Fan (mW)
2208.1
2518
2978.5
3641.7
4703.1
90
Figure 2. OS Idle - OPP_NOM (Power Consumption vs Ambient Temp)
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Data and Results
4.4
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Dhrystone 1 Core at OPP_NOM
OPP Levels
MPU
GPU
DSP
IVA
NOM
HIGH
HIGH
HIGH
Ta (°C)
Thermal
Management
25
45
60
75
No Heatsink (°C)
44.2
65
85.9
112
90
Heatsink (°C)
35.2
55.6
71.5
88.5
106.8
Heatsink + Fan (°C)
33
52.3
68.4
85.5
103.2
Figure 3. Dyrystone (Core 1) at OPP_NOM (Junction Temp vs Ambient Temp)
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Ta (°C)
Thermal
Management
25
45
60
75
No Heatsink (mW)
3157.5
3707.1
4610.1
6366.7
Heatsink (mW)
3010.6
3448.8
3952.1
4778.4
6071.4
Heatsink + Fan (mW)
2974.7
3399.1
3916
4614.9
5777.2
90
Figure 4. Dyrystone (Core 1) at OPP_NOM (Power Consumption vs Ambient Temp)
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Data and Results
4.5
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Dhrystone 2 Core at OPP_NOM
OPP Levels
MPU
GPU
DSP
IVA
NOM
HIGH
HIGH
HIGH
Ta (°C)
Thermal
Management
25
45
60
No Heatsink (°C)
50.5
73.3
93.4
Heatsink (°C)
38.2
58.4
Heatsink + Fan (°C)
35.3
54.8
75
90
75
91.8
111.4
71.5
88
105.8
Figure 5. Dyrystone (Core 1 and Core 2) at OPP_NOM (Junction Temp vs Ambient Temp)
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Ta (°C)
Thermal
Management
25
45
60
No Heatsink (mW)
4111.4
4869.1
5966
Heatsink (mW)
3852.5
4303.7
Heatsink + Fan (mW)
3849.7
4276.2
75
90
4916.3
5819.6
7247.3
4825.1
5592.9
6827.6
Figure 6. Dyrystone (Core 1 & Core 2) at OPP_NOM (Power Consumption vs Ambient Temp)
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Data and Results
4.6
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Dhrystone 1 Core at OPP_HIGH
OPP Levels
MPU
GPU
DSP
IVA
HIGH
HIGH
HIGH
HIGH
Ta (°C)
Thermal
Management
25
45
No Heatsink (°C)
54.2
81.2
Heatsink (°C)
38.6
60.6
77.5
96
Heatsink + Fan (°C)
36.4
57.7
73.9
91.3
60
75
90
Figure 7. Dyrystone (Core 1) at OPP_HIGH (Junction Temp vs Ambient Temp)
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Ta (°C)
Thermal
Management
25
45
No Heatsink (mW)
4949.6
6362
Heatsink (mW)
4397.9
5151.9
6007.6
7521
Heatsink + Fan (mW)
4361.2
5041.5
5803.9
7063.7
60
75
90
Figure 8. Dyrystone (Core 1) at OPP_HIGH (Power Consumption vs Ambient Temp)
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Data and Results
4.7
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Dhrystone 2 Core at OPP_HIGH
OPP Levels
MPU
GPU
DSP
IVA
HIGH
HIGH
HIGH
HIGH
Ta (°C)
Thermal
Management
25
45
No Heatsink (°C)
68.4
102.4
Heatsink (°C)
44.6
Heatsink + Fan (°C)
40.8
60
75
90
66.4
84.5
104.4
62.2
79
97.5
Figure 9. Dyrystone (Core 1 & Core 2) at OPP_HIGH (Junction Temp vs Ambient Temp)
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Ta (°C)
Thermal
Management
25
45
No Heatsink (mW)
7311.6
9999.8
Heatsink (mW)
6269.4
Heatsink + Fan (mW)
6162.4
60
75
7156.7
8338.7
10297.3
6958
7938.4
9487.3
90
Figure 10. Dyrystone (Core 1 & Core 2) at OPP_HIGH (Power Consumption vs Ambient Temp)
5
References
•
•
•
To learn more about thermal management, visit http://www.ti.com/thermal
Texas Instruments: 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/AM5748/toolssoftware
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