TMS320C6205 Datasheet, PDF (26/70 Pages) Texas Instruments – FIXED-POINT DIGITAL SIGNAL PROCESSOR

TMS320C6205
FIXED-POINT DIGITAL SIGNAL PROCESSOR
SPRS106E − OCTOBER 1999 − REVISED MARCH 2004
clock PLL
Most of the internal C6205 clocks are generated from a single source through the CLKIN pin. This source clock
either drives the PLL, which multiplies the source clock in 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 5,
Table 3, and Table 4 show the external PLL circuitry for either x1 (PLL bypass) or x4 PLL multiply modes.
Figure 6 shows the external PLL circuitry for a system with ONLY x1 (PLL bypass) mode.
To minimize the clock jitter, a single clean power supply should power both the C6205 device and the external
clock oscillator circuit. Noise coupling into PLLF directly impacts PLL clock jitter. 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.
3.3V
C3
10 mF
C4
0.1 mF
PLLV
ED[31,27,23]
(see Table 3)
CLKMODE0
(see Table 3)
CLKIN
PLL
PLLMULT _PLLCLK
CLKIN
LOOP FILTER
Internal to C6205
1
CPU
0
CLOCK
C2
C1
R1
NOTES: A. Keep the lead length and the number of vias between pin PLLF, pin PLLG, R1, C1, and C2 to a minimum. In addition, place all PLL
components (R1, C1, C2, C3, C4, and EMI Filter) as close to the C6000 DSP device as possible. Best performance is achieved
with the PLL components on a single side of the board without jumpers, switches, or components other than the ones shown.
B. For reduced PLL jitter, maximize the spacing between switching signals and the PLL external components (R1, C1, C2, C3, C4,
and the EMI Filter).
C. The 3.3-V supply for the EMI filter must be from the same 3.3-V power plane supplying the I/O voltage, DV_DD.
D. EMI filter manufacturer: TDK part number ACF451832-333, 223, 153, 103. Panasonic part number EXCCET103U.
E. At power up, the PLL requires a falling edge of RESET to initialize the PLL engine. It may be necessary to toggle reset in order to
establish proper PLL operation.
Figure 5. External PLL Circuitry for Either PLL Multiply Modes or x1 (Bypass) Mode
3.3V
PLLV
CLKMODE0
CLKIN
PLLMULT
PLL
PLLCLK
CLKIN
LOOP FILTER
Internal to C6205
1
CPU
0
CLOCK
NOTES: A. For a system with ONLY PLL x1 (bypass) mode, short the PLLF to PLLG.
B. The 3.3-V supply for PLLV must be from the same 3.3-V power plane supplying the I/O voltage, DV_DD.
Figure 6. External PLL Circuitry for x1 (Bypass) PLL Mode Only
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