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6.4.2

PLL1 Controller Operating Modes

6.4.3

PLL1 Stabilization, Lock, and Reset Times

6.4.4

PLL1 Controller Input and Output Clock Electrical Data/Timing

CLKIN

TMS320DM647/TMS320DM648

Digital Media Processor

SPRS372A – MAY 2007 – REVISED JUNE 2007

The PLL1 controller has two modes of operation: bypass mode and PLL mode. The mode of operation is

determined by the PLLEN bit of the PLL control register (PLLCTL). In PLL mode, SYSREFCLK is

generated from the device input clock CLKIN1 using the divider PREDIV and the PLL multiplier PLLM. In

bypass mode, CLKIN1 is fed directly to SYSREFCLK.

All hosts (HPI, PCI, etc.) must hold off accesses to the DSP while the frequency of its internal clocks is

changing. A mechanism must be in place such that the DSP notifies the host when the PLL configuration

has completed.

The PLL stabilization time is the amount of time that must be allotted for the internal PLL regulators to

become stable after device power-up. The PLL should not be operated until this stabilization time has

expired.

The PLL reset time is the amount of wait time needed when resetting the PLL (writing PLLRST = 1), in

order for the PLL to properly reset, before bringing the PLL out of reset (writing PLLRST = 0). For the

PLL1 reset time value, see Table 6-7.

Table 6-7. PLL1 Stabilization, Lock, and Reset Times

MIN

TYP

MAX

UNIT

PLL stabilization time

150

μs

PLL lock time

2000*C(1)

μs

PLL reset time

128*C(1)

μs

(1)

C = CLKIN1 cycle time in ns. For example, when CLKIN1 frequency is 50 MHz, use C = 20 ns.

Table 6-8. Timing Requirements for CLKIN1 (1)(2)(3) (see Figure 6-6)

-720

-900

PLL MODES

NO.

UNIT

x1 (Bypass), x15, x20,

x25, x30, x32

MIN

MAX

tc(CLKIN1)

Cycle time, CLKIN1

30.3

tw(CLKIN1H)

Pulse duration, CLKIN1 high

0.4C

tw(CLKIN1L)

Pulse duration, CLKIN1 low

0.4C

tt(CLKIN1)

Transition time, CLKIN1

1.2

tJ(CLKIN1)

Period jitter, (peak-to-peak), CLKIN1

100

(1)

The reference points for the rise and fall transitions are measured at 3.3-V VIL MAX and VIH MIN.

(2)

C = CLKIN1 cycle time in ns. For example, when CLKIN1 frequency is 50 MHz, use C = 20 ns.

(3)

The PLL1 multiplier factors (x1 [BYPASS], x 15, x20, x25, x30, x32) further limit the MIN and MAX values for tc(CLKIN1). For more

detailed information on these limitations, see Section 6.3.5, Power and Clock Domains.

Figure 6-6. CLKIN1 Timing

Peripheral Information and Electrical Specifications

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