OMAP-L137 Low-Power Applications Processor
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SPRS563A–SEPTEMBER 2008–REVISED OCTOBER 2008
6.5 Crystal Oscillator or External Clock Input
The OMAP-L137 device includes two choices to provide an external clock input, which is fed to the
on-chip PLL to generate high-frequency system clocks. These options are illustrated in Figure 6-5 and
Figure 6-6.
•
•
Figure 6-5 illustrates the option that uses on-chip 1.2V oscillator with external crystal circuit.
Figure 6-6 illustrates the option that uses an external 1.2V clock input.
C2
OSCIN
Clock Input
to PLL
X1
OSCOUT
C1
OSCVSS
Figure 6-5. On-Chip 1.2V Oscillator
Clock
Input
to PLL
OSCIN
OSCOUT
NC
OSCVSS
Figure 6-6. External 1.2V Clock Source
Table 6-1. CLKIN Timing Requirements
MIN
12
MAX
30
UNIT
MHz
MHz
ns
fosc
Oscillator frequency range (OSCIN/OSCOUT)
fPLL
Freuency range of PLL input , external clock source only
Cycle time, external clock driven on OSCIN
12
50
tc(CLKIN)
20
tw(CLKINH) Pulse width high, external clock on OSCIN
0.4
ns
tc(CLKIN)
tw(CLKINL) Pulse width low, external clock on OSCIN
0.4
tc(CLKIN)
ns
ns
tt(CLKIN)
Transition time, CLKIN
5
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