OMAP3525-HIREL_16 Datasheet, PDF (134/262 Pages) Texas Instruments – OMAP3525-HiRel and OMAP3530-HiRel Applications Processor

OMAP3525-HiRel, OMAP3530-HiRel
SPRS599D – JUNE 2009 – REVISED AUGUST 2010
www.ti.com
• sys_clkout2 can output the oscillator clock (12, 13, 16.8, 19.2, 26, or 38.4 MHz), core_clk (core DPLL
output), 96 MHz or 54 MHz. It can be divided by 2, 4, 8, or 16 and its off state polarity is
programmable. This output is active only when the core power domain is active.
For more information on the OMAP3525 and OMAP3530 Applications Processor clocking structure, see
the Power, Reset, and Clock management (PRCM) chapter of the OMAP35x Applications Processor TRM
(literature number SPRUFA5).
4.1 Input Clock Specifications
The clock system accepts three input clock sources:
• 32-kHz digital CMOS clock
• Crystal oscillator clock or CMOS digital clock (12, 13, 16.8, 19.2, 26, or 38.4 MHz)
• Alternate clock (48 or 54 MHz, or other up to 59 MHz)
4.1.1 Clock Source Requirements
Table 4-1 illustrates the requirements to supply a clock to the OMAP3525 and OMAP3530 device.
Table 4-1. Clock Source Requirements
PAD
sys_xtalout
sys_xtalin
sys_altclk
CLOCK FREQUENCY
12, 13, 16.8, or 19.2 MHz
Crystal
12, 13, 16.8, 19.2, 26, or 38.4 MHz Square
48,54 or up to 59 MHz
STABILITY
± 25 ppm
± 50 ppm
± 50 ppm
DUTY CYCLE
na
45% to 55%
40% to 60%
JITTER
na
< 1%
< 1%
TRANSITION
na
< 3.6 ns
< 5 ns
4.1.2 External Crystal Description
To supply a 12-, 13-, 16.8-, or 19.2-MHz clock to the OMAP3525 and OMAP3530 , an external crystal can
be connected to the sys_xtalin and sys_xtalout pins. Figure 4-2 describes the crystal implementation.
OMAP Device
sys_xtalin
sys_xtalout
Optional R_bias
Optional R_d
C_f1
C_f2
Crystal
030-008
Figure 4-2. Crystal Implementation(1) (2) (3) (4)
(1) On the PCB, the oscillator components (crystal, foot capacitors, optional R_bias and R_d) must be located close to the package. All these
components must be routed first with the lowest possible number of board vias.
(2) An optional resistor R_d can be added in series with the crystal to debug or filter the harmonics; a footprint must be reserved on the PCB
for use with 10-MHz crystals and feature low-drive levels.
(3) A 120-kΩ internal bias resistor R_bias is used. The feedback resistor R_bias provides negative feedback to the oscillator to put it in the
134 CLOCK SPECIFICATIONS
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