OMAP3530_08 Datasheet, PDF (134/264 Pages) Texas Instruments – Applications Processor

OMAP3530/25 Applications Processor
SPRS507B – FEBRUARY 2008 – REVISED JULY 2008
4 CLOCK SPECIFICATIONS
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The OMAP3530/25 device has three external input clocks, a low frequency (sys_32k), a high frequency
(sys_xtalin), and an optional (sys_altclk). The OMAP3530/25 device has two configurable output clocks,
sys_clkout1 and sys_clkout2.
Figure 4-1 shows the interface to the external clock sources and clock outputs.
OMAP
sys_32k
sys_altclk
sys_clkout1
sys_clkout2
sys_xtalout
Power IC
Alternate Clock Source Selectable (54, 48 MHz or other [up
to 54 MHz])
To Peripherals (From OSC_CLK: 12, 13,16.8, 19.2, 26, or
38.4 MHz)
To Peripherals (From OSC_CLK: 12,13, 16.8, 19.2, 26, or
38.4 MHz, core_clk [DPLL, up to 332 MHz], DPLL-96 MHz
or DPLL-54 MHz outputs with a divider of 1, 2, 4, 8, or 16)
To Quartz (Oscillator output) or Unconnected
sys_xtalin
To Quartz (Oscillator input) or Square Clock
sys_clkreq
Clock Request. To Square Clock Source or from Peripherals
Oscillator
is Used
sys_xtalout
sys_xtalin
sys_clkreq
Oscillator
is Bypassed
sys_xtalout
sys_xtalin
GPin
sys_clkreq
Figure 4-1. Clock Interface
Unconnected
Square
Clock
Source
030-007
The OMAP3530/25 device operation requires the following three input clocks:
• The 32-kHz frequency is used for low frequency operation. It supplies the wake-up domain for
operation in lowest power mode (off mode). This clock is provided through the sys_32k pin.
• The system alternative clock can be used (through the sys_altclk pin) to provide alternative 48 or 54
MHz or other clock source (up to 54 MHz).
• The system clock input (12, 13, 16.8, 19.2, 26, or 38.4 MHz) is used to generate the main source clock
of the OMAP3530/25 device. It supplies the DPLLs as well as several OMAP modules. The system
clock input can be connected to either:
– A crystal oscillator clock managed by sys_xtalin and sys_xtalout. In this case, the sys_clkreq is
used as an input (GPIN).
– A CMOS digital clock through the sys_xtalin pin. In this case, the sys_clkreq is used as an output to
request the external system clock.
The OMAP3530/25 outputs externally two clocks:
• sys_clkout1 can output the oscillator clock (12, 13, 16.8, 19.2, 26, or 38.4 MHz) at any time. It can be
controlled by software or externally using sys_clkreq control. When the device is in the off state, the
sys_clkreq can be asserted to enable the oscillator and activate the sys_clkout1 without waking up the
device. The off state polarity of sys_clkout1 is programmable.
134 CLOCK SPECIFICATIONS
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