Datasheet

PRODUCTPREVIEW
AM335x
XTALIN
VSS_OSC
XTALOUT
C
1
C
2
Optional R
d
Crystal
Optional R
bias
AM3359, AM3358, AM3357
AM3356, AM3354, AM3352
SPRS717E –OCTOBER 2011–REVISED JANUARY 2013 www.ti.com
A. Oscillator components (Crystal, C
1
, C
2
, optional R
bias
and R
d
) must be located close to the AM335x package.
Parasitic capacitance to the printed circuit board (PCB) ground and other signals should be minimized to reduce noise
coupled into the oscillator. The VSS_OSC terminal provides a Kelvin ground reference for the external crystal
components. External crystal component grounds should only be connected to the VSS_OSC terminal and should not
be connected to the PCB ground plane.
B. C
1
and C
2
represent the total capacitance of the respective PCB trace, load capacitor, and other components
(excluding the crystal) connected to each crystal terminal. The value of capacitors C
1
and C
2
should be selected to
provide the total load capacitance, C
L
, specified by the crystal manufacturer. The total load capacitance is C
L
=
[(C
1
*C
2
)/(C
1
+C
2
)] + C
shunt
, where C
shunt
is the crystal shunt capacitance (C
0
) specified by the crystal manufacturer
plus any mutual capacitance (C
pkg
+ C
PCB
) seen across the AM335x XTALIN and XTALOUT signals. For
recommended values of crystal circuit components, see Table 4-2.
Figure 4-8. OSC0 Crystal Circuit Schematic
Table 4-2. OSC0 Crystal Circuit Requirements
NAME DESCRIPTION MIN TYP MAX UNIT
f
xtal
Crystal parallel resonance Fundamental mode oscillation only 19.2, 24.0, MHz
frequency 25.0, or
26.0
Crystal frequency stability -50.0 50.0 ppm
and tolerance
C
C1
C
1
capacitance 12.0 24.0 pF
C
C2
C
2
capacitance 12.0 24.0 pF
C
shunt
Shunt capacitance 5.0 pF
ESR Crystal effective series f
xtal
= 19.2 MHz, oscillator has nominal 54.4 Ω
resistance negative resistance of 272 Ω and worst-
case negative resistance of 163 Ω
f
xtal
= 24.0 MHz, oscillator has nominal 48.0 Ω
negative resistance of 240 Ω and worst-
case negative resistance of 144 Ω
f
xtal
= 25.0 MHz, oscillator has nominal 46.6 Ω
negative resistance of 233 Ω and worst-
case negative resistance of 140 Ω
f
xtal
= 26.0 MHz, oscillator has nominal 45.3 Ω
negative resistance of 227 Ω and worst-
case negative resistance of 137 Ω
104 Power and Clocking Copyright © 2011–2013, Texas Instruments Incorporated
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