Datasheet

Microprocessor
Power IC
sys_32k
sys_altclk
sys_clkout1
Alternate Clock Source Selectable (54, 48 MHz or other [up
to 59 MHz])
To Quartz (Oscillator output) or Unconnected
From Quartz (Oscillator input), Square Clock, or Crystal
Clock Request. To Square Clock Source or from Peripherals
Oscillator
is Used
Oscillator
is Bypassed
Unconnected
Square
Clock
Source
To Peripherals (From OSC_CLK: 26 MHz, core_clk
[DPLL, up to 166 MHz], DPLL-96 MHZ or DPLL-54 MHz
outputs with a divider of 1, 2, 4, 8, or 16)
GPin
To Peripherals (From OSC_CLK: 26 MHz)
sys_clkout2
sys_xtalout
sys_xtalin
sys_clkreq
sys_xtalout
sys_xtalin
sys_clkreq
sys_xtalout
sys_xtalin
sys_clkreq
Ethernet input 50-MHz clock
rmii_50mhz_clk
AM3517, AM3505
www.ti.com SPRS550E –OCTOBER 2009–REVISED MARCH 2013
4 Clock Specifications
The AM3517/05 device has three external input clocks, a low frequency (sys_32k), a high frequency
(sys_xtalin), and an optional (sys_altclk). The AM3517/05 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.
Figure 4-1. Clock Interface
The AM3517/05 device operation requires the following three input clocks:
• The 32-kHz clock can be generated using one of the following options and can be selected via the
sys_boot7 pin. See Figure 4-2.
– External: Supplied by an oscillator on the sys_32k pin.
– Internal: 32-kHz clock generation using a fixed divider on the HS system clock (26MHz).
• 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 (26 MHz) is used to generate the main source clock of the AM3517/05 device.
It supplies the DPLLs as well as several AM3517/05 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.
Copyright © 2009–2013, Texas Instruments Incorporated Clock Specifications 91
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