ZHCSGV3G June 2009 – January 2017 TMS320C6748
PRODUCTION DATA.
The processor supports multiple operating points by scaling voltage and frequency to minimize power consumption for a given level of processor performance.
Frequency scaling is achieved by modifying the setting of the PLL controllers’ multipliers, post-dividers (POSTDIV), and system clock dividers (SYSCLKn). Modification of the POSTDIV and SYSCLK values does not require relocking the PLL and provides lower latency to switch between operating points, but at the expense of the frequencies being limited by the integer divide values (only the divide values are altered the PLL multiplier is left unmodified). Non integer divide frequency values can be achieved by changing both the multiplier and the divide values, but when the PLL multiplier is changed the PLL must relock, incurring additional latency to change between operating points. Detailed information on modifying the PLL Controller settings can be found in the TMS320C6748 DSP System Reference Guide (SPRUGJ7).
Voltage scaling is enabled from outside the device by controlling an external voltage regulator. The processor may communicate with the regulator using GPIOs, I2C or some other interface. When switching between voltage-frequency operating points, the voltage must always support the desired frequency. When moving from a high-performance operating point to a lower performance operating point, the frequency should be lowered first followed by the voltage. When moving from a low-performance operating point to a higher performance operating point, the voltage should be raised first followed by the frequency. Voltage operating points refer to the CVdd voltage at that point. Other static supplies must be maintained at their nominal voltages at all operating points.
The maximum voltage slew rate for CVdd supply changes is 1 mV/us.
For additional information on power management solutions from TI for this processor, follow the Power Management link in the Product Folder on www.ti.com for this processor.
The processor supports multiple clock domains some of which have clock ratio requirements to each other. SYSCLK1:SYSCLK2:SYSCLK4:SYSCLK6 are synchronous to each other and the SYSCLKn dividers must always be configured such that the ratio between these domains is 1:2:4:1. The ASYNC and ASYNC3 clock domains are asynchronous to the other clock domains and have no specific ratio requirement.
Table 6-5 summarizes the maximum internal clock frequencies at each of the voltage operating points.
| CLOCK SOURCE | CLOCK DOMAIN | 1.3V NOM | 1.2V NOM | 1.1V NOM | 1.0V NOM | |
|---|---|---|---|---|---|---|
| PLL0_SYSCLK1 | DSP subsystem | 456 MHz | 375 MHz | 200 MHz | 100 MHz | |
| PLL0_SYSCLK2 | SYSCLK2 clock domain peripherals and optional clock source for ASYNC3 clock domain peripherals | 228 MHz | 187.5 MHz | 100 MHz | 50 MHz | |
| PLL0_SYSCLK3 | Optional clock for ASYNC1 clock domain
(See ASYNC1 row) |
|||||
| PLL0_SYSCLK4 | SYSCLK4 domain peripherals | 114 MHz | 93.75 MHz | 50 MHz | 25 MHz | |
| PLL0_SYSCLK5 | Not used on this processor | - | - | - | - | |
| PLL0_SYSCLK6 | Not used on this processor | - | - | - | - | |
| PLL0_SYSCLK7 | Optional 50 MHz clock source for EMAC RMII interface | 50 MHz | 50 MHz | - | - | |
| PLL1_SYSCLK1 | DDR2/mDDR Interface clock source
(memory interface clock is one-half of the value shown) |
312 MHz | 312 MHz | 300 MHz | 266 MHz | |
| PLL1_SYSCLK2 | Optional clock source for ASYNC3 clock domain peripherals | 152 MHz | 150 MHz | 100 MHz | 75 MHz | |
| PLL1_SYSCLK3 | Alternate clock source input to PLL Controller 0 | 75 MHz | 75 MHz | 75 MHz | 75 MHz | |
| McASP AUXCLK | Bypass clock source for the McASP | 50 MHz | 50 MHz | 50 MHz | 50 MHz | |
| PLL0_AUXCLK | Bypass clock source for the USB0 and USB1 | 48 MHz | 48 MHz | 48 MHz | 48 MHz | |
| ASYNC1 | ASYNC Clock Domain (EMIFA) | Async Mode | 148 MHz | 148 MHz | 75 MHz | 50 MHz |
| SDRAM Mode | 100 MHz | 100 MHz | 66.6 MHz | 50 MHz | ||
| ASYNC2 | ASYNC2 Clock Domain (multiple peripherals) | 50 MHz | 50 MHz | 50 MHz | 50 MHz | |
Some interfaces have specific limitations on supported modes/speeds at each operating point. See the corresponding peripheral sections of this document for more information.
TI provides software components (called the Power Manager) to perform DVFS and abstract the task from the user. The Power Manager controls changing operating points (both frequency and voltage) and handles the related tasks involved such as informing/controlling peripherals to provide graceful transitions between operating points. The Power Manager is bundled as a component of DSP/BIOS.