AM1705DPTPA3 Datasheet, PDF (43/164 Pages) Texas Instruments – AM1705 ARM Microprocessor

AM1705
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SPRS657D – FEBRUARY 2010 – REVISED MARCH 2013
5.6 Crystal Oscillator or External Clock Input
The 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 5-6 and Figure 5-7. 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 5-6 illustrates the option that uses on-chip 1.2V oscillator with external crystal circuit.
• Figure 5-7 illustrates the option that uses an external 1.2V clock input.
C₂
OSCIN
X₁
OSCOUT
C₁
Clock Input
to PLL
OSCV_SS
Figure 5-6. On-Chip 1.2V Oscillator
Table 5-3. Oscillator Timing Requirements
PARAMETER
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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