Texas Instruments TMS320C6722 Floating-PointDigital Signal Processors, 44.PLL Power Supply Filter

		TMS320C6727, TMS320C6726, TMS320C6722
	www.ti.com	Floating-Point Digital Signal Processors
			SPRS268E –MAY 2005 –REVISED JANUARY 2007
	Table 4-40. Allowed PLL Operating Conditions
	PARAMETER	DEFAULT VALUE	ALLOWED SETTING OR RANGE
			MIN	MAX
1	PLLRST = 1 assertion time during initialization	N/A	125 ns
2	Lock time before setting PLLEN = 1. After changing D0, PLLM, or	N/A	187.5 µs
	input clock.
3	PLL input frequency (PLLREF after D0(1))		12 MHz	50 MHz
4	PLL multiplier values (PLLM)	x13	x4	x25
5	PLL output frequency (PLLOUT before dividers D1, D2, D3)(2)	N/A	140 MHz	600 MHz
6	SYSCLK1 frequency (set by PLLM and dividers D0, D1)	PLLOUT/1		Device Frequency
				Specification
7	SYSCLK2 frequency (set by PLLM and dividers D0, D2)	PLLOUT/2	/2, /3, or /4 of SYSCLK1
8	SYSCLK3 frequency (set by PLLM and dividers D0, D3)	PLLOUT/3		EMIF Frequency
				Specification

(1)Some values for the D0 divider produce results outside of this range and should not be selected.

(2)In general, selecting the PLL output clock rate closest to the maximum frequency will decrease clock jitter.

CAUTION

SYSCLK1, SYSCLK2, SYSCLK3 must be configured as aligned by setting ALNCTL[2:0] to '1';and the PLLCMD.GOSET bit must be written every time the dividers D1, D2, and D3 are changed in order to make sure the change takes effect and preserves alignment.

CAUTION

When changing the PLL parameters which affect the SYSCLK1, SYSCLK2, SYSCLK3 dividers, the bridge BR2 in Figure 2-4must be reset by the CFGBRIDGE register. See Table 2-7.

The PLL is an analog circuit and is sensitive to power supply noise. Therefore it has a dedicated 3.3-V power pin (PLLHV) that should be connected to DVDD at the board level through an external filter, as illustrated in Figure 4-44.

BOARD

DVDD (3.3 V)

Place Filter and Capacitors as Close

to DSP as Possible

EMI

Filter

10mF

+

0.1mF

PLLHV

EMI Filter: TDK ACF451832−333, −223, −153, or −103,

Panasonic EXCCET103U, or Equivalent

Figure 4-44. PLL Power Supply Filter

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