AM1810_15 Datasheet, PDF (75/262 Pages) Texas Instruments – AM1810 ARM® Microprocessor For PROFIBUS

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AM1810
SPRS709D – NOVEMBER 2010 – REVISED MARCH 2014
6.5 Crystal Oscillator or External Clock Input
The device includes two choices to provide an external clock input, which is fed to the on-chip PLLs to
generate high-frequency system clocks. These options are illustrated in Figure 6-6 and Figure 6-7. For
input clock frequencies between 12 and 20 MHz, a crystal with 80 ohm max ESR is recommended. For
input clock frequencies between 20 and 30 MHz, a crystal with 60 ohm max ESR is recommended.
Typical load capacitance values are 10-20 pF, where the load capacitance is the series combination of C1
and C2.
The CLKMODE bit in the PLLCTL register must be 0 to use the on-chip oscillator. If CLKMODE is set to 1,
the internal oscillator is disabled.
Figure 6-6 illustrates the option that uses on-chip 1.2V oscillator with external crystal circuit. Figure 6-7
illustrates the option that uses an external 1.2V clock input.
C₂
OSCIN
X₁
OSCOUT
C₁
Clock Input
to PLL
OSCV_SS
Figure 6-6. On-Chip Oscillator
Table 6-2. Oscillator Timing Requirements
f_osc
Oscillator frequency range (OSCIN/OSCOUT)
MIN
MAX
UNIT
12
30
MHz
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Peripheral Information and Electrical Specifications
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