DM816x C6A816x AM389x Power Estimation

Power Estimation Spreadsheet

Abstract

This article discusses the power consumption of the Texas Instruments TMS320DM816x DaVinci™ digital media processors, TMS320C6A816x C6000™ DSP+ARM processors, and AM389x Sitara™ ARM® Processors. For the rest of the document, the word "device" represents the device chosen by the user (DM816x, C6A816x or AM389x).

Power consumption on the device is highly application-dependent, therefore a spreadsheet is provided to model power consumption for a user’s application and to present some measured scenarios. The spreadsheet supports configurability of device core modules such as the ARM Cortex-A8, C674x and most peripherals. The data in the accompanying spreadsheet are indicative of the expected maximums of power consumption for production units. Thus, the spreadsheet values may be used for board thermal analysis and power supply design as a maximum long-term average. The spreadsheet takes into account power savings possible with SmartReflex features such as adaptive voltage scaling (AVS).

The data presented in the Version 3.0 power estimation spreadsheet are based on measurements performed on DM816x revision 1.0 silicon.

The Power Estimation Spreadsheet

The spreadsheet applies to DM816x, C6A816x and AM389x devices. In the document, the word "device" represents the device chosen by the user (DM816x, C6A816x or AM389x). The power spreadsheet is available here: File:DM816x C6A816x AM389x Power spreadsheet RevE.zip

Section 1.5 outlines how to use the existing power estimation spreadsheet to estimate power consumption of device speed range 4 (CYG4) devices

Modeling Power for an Active Scenario

Power consumption estimates in the spreadsheet are separated by the major modules of the device, so that their contribution can be gauged independent of each other. The options in the spreadsheet are intended to provide some flexibility in customizing the worst case power consumption estimate for a specific application.

Power consumption in the device consists of:

• static power – due to leakage current, and dependent on temperature; and
• active power – due to transistor switching, and independent of temperature.

The DM816x Power Estimation Spreadsheet models temperature effects on device power consumption. The user is allowed to specify case temperature of the device to be used in the power estimate. This is used to scale the baseline power estimate in the spreadsheet, which consists of device static power and power consumption from interconnects and clock trees.

Active power consumption is the power that is consumed by portions of the device that are performing some processing. Active power is independent of temperature, but dependent on voltage and module activity levels. The DM816x Power Estimation Spreadsheet allows configuration of activity for some modules in the DM816x device. For other modules, measured scenarios are provided for the module, and the user is expected to select the usage scenario most closely aligned to the intended application.

Using the Power Estimation Spreadsheet

Note: The power spreadsheet uses circular references. To avoid any error, ensure that the power spreadsheet is the first spreadsheet in an "Excel session". In other words, the MS Excel should not be open before you open the power spreadsheet.

Using the power estimation spreadsheet involves entering appropriate usage parameters for modules. Cells that are designed for user input are white in color. To use the spreadsheet, simply configure the white cells to a value most closely aligned with your intended scenario. The spreadsheet will display the details of power consumption for the configuration selected.

The following sections shall explain the usage of the spreadsheet, specifically the cells that need user inputs.

Device level entries

This section explains the entries that are not module-dependent.

1. First-of-all, the user needs to select the device intended to be used in the end application. This can be done by selecting the appropriate button for the cell marked "DEVICE". Version 3.0 of the spreadsheet includes the option to select PG2.0 versions of the devices, and Speed Range 5 versions of the C6A816x and AM389x devices.

2. Enter the case temperature of the device in the cell marked "Case Temp".

3. Based on the above two inputs, a baseline power value is calculated which is the static power of Always-On, Active and Default power domains and the power of low power modules (like McASP, McBSP, SPI, Timers, UART, GPIO).

4. The device selection buttons at top (DM8168, C6A8168, AM394) can be used to quickly generate the power estimate for typical use cases of these devices.

5. The button Typical DVR Application can be used to generate the power estimate for typical 16 channel DVR application.

6. The button mW / mA, can be used to convert the power estimate on each rail to corresponding current estimate and vice versa. The rail wise power estimates are available in row 269.

7. A new entry has been added for AVS Enable. Select “Enable” in this cell to estimate the power when AVS control is functioning normally in the system. Select “Disable” in this cell to estimate the power if the AVS control is disabled or there is an unexpected fault in the system and constant 1.05V is supplied on AVS voltage rail.

Note: AVS enable mode is required for normal operation of the device. The AVS disable option has been provided to (optionally) estimate the worst case power in the scenario where AVS control fails in the system. The AVS disable option shall be useful in designing fault tolerant power supply.

Module level entries

This section illustrates the various entries expected for the modules. The spreadsheet presents information for the full-featured DM816x device in the DaVinci family. However, since the spreadsheet breaks out the power consumption by each module in the DM816x, estimates for the C6816x and AM398x can be obtained by choosing the "Off" option in status for the module not present in the device under consideration. This will ensure active and static power from the non-applicable module is not included in the power tally. The calculations in the power spreadsheet assumes that with exception of Always-on power domain, the rest of power domains are switched off when all the modules corresponding to that power domain are not used. For more details on Power domains, please refer the Power Management section of the device TRM.

The frequency for some of the modules is dependent on the device option chosen. The current maximum device frequencies (in MHz) supported are:

Device	ARM	C674x	HDVICP2	SGX
TMS320DM8168BCYG2	1200	1000	600	300
TMS320C6A8168BCYG5	1500	1250	Not Applicable	375
AM3894BCYG150	1500	Not Applicable	Not Applicable	375

Cortex A8

1. Status: If Cortex A8 is used, select "Active", else if A8 is in WFI (stand-by) state, select "Idle"

2. Frequency: Enter the frequency of Cortex A8

3. Utilization %: Enter the percentage of Cortex A8 CPU utilization in your use case

C674x

1. Status: If C674x is used, choose "Active" else choose "Off"

2. Frequency: Enter the frequency of C674x

3. Utilization %: Enter the percentage of C674x CPU utilization in your use case

Media Controller

The power of Media Controller is included in the power numbers of HDVICPs and HDVPSS.

HDVICP2-0, HDVICP2-1, HDVICP2-2

1. Status: If HDVICP2 is used, choose "Active", else choose "Off"

2. Frequency: Enter the frequency of HDVICP2

|Note:
While reducing the frequency of HDVICP, ensure the resolution and/or frame rate is changed accordingly.

3. Resolution: Enter the resolution of encode/decode being performed in HDVICP2

4. Enc/Dec: Select HDVICP2 is using H.264 Enc or H.264 Dec

5. Number of channels: Enter the number of channels/instances of Encoder/Decoder executed on HDVICP2

6. FPS per channel: Number of frames per second per channel/instance of Encoder/Decoder

7. Max FPS* No. Channel: This value can not be changed by the user. It indicates the upper limit for FPS * No. channels based on the resolution and Encoder/Decoder being used in the HDVICP2.

Note: When the same HDVICP is used for encode and decode operation, it is recomended to use Encode power for sum of encoder and decoder channels. For example, if an application uses X instances of encode and Y instances of decode on the same HDVICP, the maximum power can be obtained by configuring the HDVICP to encode X+Y channels/instances

HDVPSS

1. Status: If HDVPSS is used, choose "Active", else choose "Off"

2. Scenario: The following use cases are available to be chosen from. For use case not listed below, add the power of all the components of the HDVPSS use case.

• Display: Onchip HDMI  : Only on-chip HDMI is used for Display (capture and other processing is not used)
• Display: Offchip HDMI  : Only off-chip HDMI (DVO) is used for Display (capture and other processing is not used)
• Display: HDCOMP  : Only HDCOMP Display is used (capture and other processing is not used)
• Display: SDVENC  : Only SDVENC Display is used (capture and other processing is not used)
• Tridisplay (without GPX): Three displays (on-chip, offchip HDMI and SD VENC) without Graphics
• Tridisplay (with GPX)  : Three displays (on-chip, offchip HDMI and SD VENC) with Graphics
• Capture: 16 D1  : 16 channel D1 capture is used (display and other processing is not used)
• Capture: 8 D1  : 8 channel D1 capture is used (display and other processing is not used)
• Capture: 4 D1  : 4 channel D1 capture is used (display and other processing is not used)
• Capture: 2 1080p  : 2 1080p channel capture is used (display and other processing is not used)
• Capture: 1 1080p  : 1 1080p channel capture is used (display and other processing is not used)
• DEI Primary  : DEI Primary path with scalar bypassed
• Scalar+DEI Primary  : DEI Primary path with scalar enabled
• DEI Auxillary  : DEI Auxillary path is enabled
• NF  : Only Noise filter is enabled
• Scalar  : Only 1 scalar is enabled
• 1 ch DVR  : Typical capture, processing and display for 1 channel DVR scenario
• 4 ch DVR  : Typical capture, processing and display for 4 channel DVR scenario
• 8 ch DVR  : Typical capture, processing and display for 8 channel DVR scenario
• 16 ch DVR  : Typical capture, processing and display for 16 channel DVR scenario

SGX530

1. Status: If SGX530 is used, choose "Active", else choose "Off"

2. Frequency: Enter the frequency for SGX530

3. Frames per Sec (1080p): Enter the number of 1080p frames processed by SGX. If any other resolution is used, the total processing need to be converted to appropriate 1080p frames per second

EDMA

1. Status: If EDMA is used, choose "Active", else choose "Off"

Note:
Since the power of EDMA is low, it is not split further into the number of EDMA channels being used.

EMIF_0, EMIF_1

1. Status: If EMIF is used, choose "Active", else choose "Off". Please note that EMIF1_1 can not be independently be marked Active/Off. It follows the status of EMIF_0.

2. Frequency: Enter the frequency for EMIF operation. The upper frequency limit for DDR3 is 800 MHz and for DDR2 is 400 MHz.

3. DDR2/DDR3: Select the memory type (DDR2/DDR3) being used.

4. Transfer Rate (MBps): Specify the transfer rate for each EMIF in terms of Mega Bytes per Second. The upper limit for the transfer rate is fixed at 4480 MBps and 2240 MBps for DDR3 and DDR2 respectively (assuming 70% efficiency)

5. Write %: Specify the percentage of data being written to DDR memory with respect to the Transfer Rate mentioned above. (Rest of the data is assumed to be read from DDR memory)

Note:
For the same frequency of operation and data transfer rate, DDR3 consumes much less power than DDR2.

PCIe

1. Status: If PCIe is used, choose "Active", else choose "Off"

2. Mode: Select the mode of operations for PCIe (Full Duplex: 1X, Half Duplex: 1X, Full Duplex: 2X, Half Duplex: 2X)

SATA

1. Status: If SATA is used, choose "Active", else choose "Off"

USB

1. Status: If USB is used, choose "Active", else choose "Off"

2. No. of Instances: Select the number of USB Instances used

EMAC

1. Status: If EMAC is used, choose "Active", else choose "Off"

2. No. of Instances: Select the number of EMAC Instances used

Device Speed Range 4 (CGY4) Power Consumption Estimation

Procedure to estimate power consumption

Follow the steps below to estimate the power consumption for Device Speed Range (CYG4) devices:

1. Using the DM816x_C6A816x_AM389x_Power_spreadsheet_RevE, enter clock rates for all required processing elements equal to the maximum rated values for speed grade 2.
2. Enter the utilization percentages for the customer use case at target frequencies.
3. Select maximum operating case temp (spreadsheet limited to 85C).
4. Record power (mW) totals for each supply voltage. Also record the baseline power for CVDD and CVDDC (Cells K23 and L23 respectively).
5. Active power scale factor is 25% for CVDD only. Subtract CVDD baseline from CVDD total to obtain CVDD total active power. Multiply CVDD total active power times 0.25 to obtain power adjustment.
6. Refer to the CVDD leakage table below to obtain the coarse leakage adjustment - record the value at the next highest case temp.
7. Add CVDD active power adjustment and leakage adjustment to the previously recorded CVDD total to obtain the maximum CVDD power estimate for speed grade 4.
8. If CVDD current is desired rather than power, divide the CVDD power estimate by 0.8.

Device Case Temp (C)	CVDD Leakage Adjustment (mW)
45	897
65	1337
85	2000

Example

1. Open the DM816x_C6A816x_AM389x_Power_spreadsheet_RevE power estimation spreadsheet and enable macros.
2. Select "Typical DVR Application" and “mW”.
3. Note temp is 60C case and part is DM8168ACYG2.
4. Change Cortex A8 to 1100MHz, Active, 40%.
5. Change C674x DSP to 930MHz, Active, 40%.
6. Change all 3 HDVICP blocks to 550MHz, Active.
7. Leave all other settings in spreadsheet unchanged.
8. Record power totals for each supply rail: CVDD 5413 mW, CVDDC 1362 mW,DVDD33 312 mW,DVDD18 268 mW,DVDD15 1808 mW
9. Record CVDD and CVDDC baseline power: CVDD baseline 2794 mW, CVDDC baseline 968 mW
10. Calculate CVDD active power (CVDD total minus CVDD baseline): CVDD active 2619 mW
11. Calculate CVDD active power increase to SG4 rather than SG2 (CVDD active times 0.25): CVDD active increase 655 mW
12. Record the CVDD leakage power adjustment from the table for 65C:CVDD leakage adjustment 1337 mW
13. Calculate CVDD SG4 total power (sum CVDD total, CVDD active increase and CVDD leakage adjustment):CVDD total power for SG4 7405 mW
14. Calculate CVDD current, if desired (divide CVDD total for SG4 by 0.8):CVDD total current for SG4 9256 mA

Calculator Spreadsheet

Following excel spreadsheet is a helper calculator to do the above mentioned calculations: DM816x CYG4 Power Calculator

FAQ

Q: Why do I get circular reference error when I open the power spreadsheet?
A: The power spreadsheet uses circular references. To avoid any error, ensure that the power spreadsheet is the first spreadsheet in an "Excel session". In other words, the MS Excel should not be open before you open the power spreadsheet.

Q: What is the estimated current draw for 0.9V (USB Logic)? It is not specified in the datasheet nor in the power estimation spreadsheet.
A: It is very small (just a few mA) compared to the other power supplies. Hence. it was not included as a separate item.

Q: Can you provide information about the Power Management IC solutions suggested for use with these devices?
A: Please contact your local analog power FAE for the latest information on suggested PMIC solutions.

Q: Do the DDR2/DDR3 power estimates include the power consumption of the DDR devices or just the interface on the processor?
A: The power spreadsheet DOES NOT include the power consumed by DDR memories, only the processor.

Q: Why is case temperature used in the power spreadsheet and not junction temperature as in the datasheet?
A: It is easier for the end user to measure the case temperature of the device.

Q: The datasheet indicates that some kind of heat dissipative solution is required for this device. What heat dissipative solution was used for the power measurements in this spreadsheet?
A: Thermal inducing systems were used for regulating the case temperature during power measurement. This is needed only for power characterization at given temperature. However, the end user needs to use the heat dissipating solution while using the device on their board.

Q: How to estimate the power consumption for extended temperature devices operating at 105C case?
A: Add 1000mW to the CVDD baseline recorded at 85C case. Add 632mW to the CVDDC baseline recorded at 85C case.