AM3874 Datasheet, PDF (188/345 Pages) Texas Instruments – AM387x Sitara ARM Microprocessors (MPUs)

AM3874, AM3872, AM3871
SPRS695 – SEPTEMBER 2011
www.ti.com
Table 7-13. SERDES_CLKN/P AC Coupling Capacitors Recommendations (continued)
PARAMETER
SERDES_CLKN/P AC coupling capacitor package size⁽¹⁾⁽²⁾
MIN
TYP
0402
MAX
0603
UNIT
EIA
(1) L x W, 10 Mil units, i.e., a 0402 is a 40 x 20 Mil surface mount capacitor.
(2) The physical size of the capacitor should be as small as practical. Use the same size on both lines in each pair placed side-by-side.
The differential clock source is required to meet the REFCLK AC Specifications outlined in the PCI
EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 2.0, at the input to the AC coupling
capacitors.
In addition, LVDS clock sources that are compliant to the above specification, but with the following
exceptions, are also acceptable:
Table 7-14. Acceptable Exceptions to the REFCLK AC Specifications for LVDS Clock Sources
PARAMETER
V_IH
Differential High-Level Input Voltage
V_IL
Differential Low-Level Input Voltage
MIN
125
-1000
MAX
1000
-125
UNIT
mV
mV
7.4.3 CLKIN32 Input Clock
An external 32768-Hz clock input can optionally be provided at the CLKIN32 pin to serve as a reference
clock in place of the RTCDIVIDER clock for the following Modules:
• RTC
• GPIO0/1/2/3
• TIMER1/2/3/4/5/6/7
• ARM Cortex-A8
• SYNCTIMER
The CLKIN32 source must meet the timing requirements shown in Table 7-17.
7.4.4 Output Clocks Select Logic
The device includes two selectable general-purpose clock outputs (CLKOUT0 and CLKOUT1). The source
for these output clocks is controlled by the CLKOUT_MUX register in the Control Module (see
Figure 7-11).
188 Power, Reset, Clocking, and Interrupts
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