OMAP3530ECUS datasheet(134/264 Pages) TI1

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4.1 Input Clock Specifications

4.1.1

Clock Source Requirements

4.1.2

External Crystal Description

sys_xtalin

sys_xtalout

OMAP Device

Crystal

OptionalRbias

OptionalRd

Cf2

Cf1

030-008

OMAP3530/25 Applications Processor

SPRS507F – FEBRUARY 2008 – REVISED OCTOBER 2009

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 OMAP3530/25 Applications Processor clocking structure, see the Power,

Reset, and Clock management (PRCM) chapter of the OMAP35x Applications Processor TRM (literature

number SPRUFA5).

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)

Table 4-1 illustrates the requirements to supply a clock to the OMAP3530/25 device.

Table 4-1. Clock Source Requirements

PAD

CLOCK FREQUENCY

STABILITY

DUTY CYCLE

JITTER

TRANSITION

sys_xtalout

12, 13, 16.8, or 19.2 MHz

Crystal

± 25 ppm

sys_xtalin

12, 13, 16.8, 19.2, 26, or 38.4 MHz

Square

± 50 ppm

45% to 55%

< 1%

< 3.6 ns

sys_altclk

48,54 or up to 59 MHz

± 50 ppm

40% to 60%

< 1%

< 5 ns

To supply a 12-, 13-, 16.8-, or 19.2-MHz clock to the OMAP3530/25, an external crystal can be connected

to the sys_xtalin and sys_xtalout pins. Figure 4-2 describes the crystal implementation.

Figure 4-2. Crystal Implementation(1)(2)(3)(4)

(1) On the PCB, the oscillator components (crystal, foot capacitors, optional Rbias and Rd) 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 Rd 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-k

Ω internal bias resistor R

bias is used. The feedback resistor Rbias provides negative feedback to the oscillator to put it in the

CLOCK SPECIFICATIONS

134

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