TMS320DM641 datasheet(99/171 Pages) TI

99 / 171 page

Clock PLL

June 2003 − Revised August 2004

SPRS222C

4.7

Clock PLL

The PLL controller features hardware-configurable PLL multiplier controller, dividers (/2, /4, /6, and /8), and

reset controller. The PLL controller accepts an input clock, as determined by the logic state on the

CLKMODE[1:0] pins, from the CLKIN pin. The resulting clock outputs are passed to the DSP core, peripherals,

and other modules inside the C6000

 DSP.

4.7.1

Clock PLL Device-Specific Information

Most of the internal C64x

 DSP clocks are generated from a single source through the CLKIN pin. This source

clock either drives the PLL, which multiplies the source clock frequency to generate the internal CPU clock,

or bypasses the PLL to become the internal CPU clock.

To use the PLL to generate the CPU clock, the external PLL filter circuit must be properly designed.

Figure 4−10 shows the external PLL circuitry for either x1 (PLL bypass) or other PLL multiply modes.

To minimize the clock jitter, a single clean power supply should power both the C64x

 DSP device and the

external clock oscillator circuit. The minimum CLKIN rise and fall times should also be observed. For the input

clock timing requirements, see the input and output clocks electricals section.

Rise/fall times, duty cycles (high/low pulse durations), and the load capacitance of the external clock source

must meet the DSP requirements in this data sheet (see the electrical characteristics over recommended

ranges of supply voltage and operating case temperature table and the input and output clocks electricals

section).

TMS320DM641 Datasheet(PDF) 99 Page - Texas Instruments