Datasheet

OSCOUT
OSCIN
OSCV
SS
Clock
Input
toPLL
NC
AM1808
SPRS653E –FEBRUARY 2010–REVISED MARCH 2014 www.ti.com
Figure 6-7. External 1.2V Clock Source
Table 6-3. OSCIN Timing Requirements for an Externally Driven Clock
MIN MAX UNIT
f
OSCIN
OSCIN frequency range 12 50 MHz
t
c(OSCIN)
Cycle time, external clock driven on OSCIN 20 ns
t
w(OSCINH)
Pulse width high, external clock on OSCIN 0.4 t
c(OSCIN)
ns
t
w(OSCINL)
Pulse width low, external clock on OSCIN 0.4 t
c(OSCIN)
ns
t
t(OSCIN)
Transition time, OSCIN 0.25P or 10
(1)
ns
t
j(OSCIN)
Period jitter, OSCIN 0.02P ns
(1) Whichever is smaller. P = the period of the applied signal. Maintaining transition times as fast as possible is recommended to improve
noise immunity on input signals.
6.6 Clock PLLs
The device has two PLL controllers that provide clocks to different parts of the system. PLL0 provides
clocks (though various dividers) to most of the components of the device. PLL1 provides clocks to the
mDDR/DDR2 Controller and provides an alternate clock source for the ASYNC3 clock domain. This allows
the peripherals on the ASYNC3 clock domain to be immune to frequency scaling operation on PLL0.
The PLL controller provides the following:
• Glitch-Free Transitions (on changing clock settings)
• Domain Clocks Alignment
• Clock Gating
• PLL power down
The various clock outputs given by the controller are as follows:
• Domain Clocks: SYSCLK [1:n]
• Auxiliary Clock from reference clock source: AUXCLK
Various dividers that can be used are as follows:
• Post-PLL Divider: POSTDIV
• SYSCLK Divider: D1, ¼, Dn
Various other controls supported are as follows:
• PLL Multiplier Control: PLLM
• Software programmable PLL Bypass: PLLEN
76 Peripheral Information and Electrical Specifications Copyright © 2010–2014, Texas Instruments Incorporated
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