TMS320DM6467CCUTA Datasheet, PDF (153/355 Pages) Texas Instruments – Digital Media System-on-Chip

TMS320DM6467
www.ti.com
SPRS403H – DECEMBER 2007 – REVISED JUNE 2012
7.4 External Clock Input From DEV_MXI/DEV_CLKIN and AUX_MXI/AUX_CLKIN Pins
The DM6467 device includes two options to provide an external clock input for both the system and
auxiliary oscillators:
• Use an on-chip oscillator with external crystal (fundamental parallel resonant mode only, no overtone
support).
• Use an external 1.8-V LVCMOS-compatible clock input.
The optimal external clock input frequency for the crystals are 27 MHz for the system oscillator
(DEV_MXI/DEV_CLKIN) and 24 MHz for the auxiliary oscillator. Section 7.4.1.1 provides more details on
Option 1, using an on-chip oscillator with external crystal for the 27-MHz system oscillator. Section 7.4.1.2
provides more details on Option 1, using an on-chip oscillator with external crystal for the 24-MHz auxiliary
oscillator. Section 7.4.2.1 provides details on Option 2, using an external 1.8-V LVCMOS-compatible clock
input for the 27-MHz system oscillator. Section 7.4.2 provides details on Option 2, using an external 1.8-V
LVCMOS-compatible clock input for the 24-MHz auxiliary oscillator.
7.4.1 Clock Input Option 1—Crystal
7.4.1.1 27-MHz for System Oscillator Clock Input Option 1—Crystal
In this option, a crystal is used as the external clock input to the DM6467 system oscillator.
The 27-MHz oscillator provides the reference clock for all DM6467 subsystems and peripherals. The on-
chip oscillator requires an external 27-MHz crystal connected across the DEV_MXI and DEV_MXO pins,
along with two load capacitors, as shown in Figure 7-8. The external crystal load capacitors must be
connected only to the 27-MHz oscillator ground pin (DEV_V_SS). Do not connect to board ground (V_SS).
The DEV_DV_DD18 pin can be connected to the same 1.8 V power supply as DV_DDR2.
DEV_MXI/
DEV_CLKIN
Crystal
27 MHz
DEV_MXO
DEV_V_SS
DEV_DV_DD18 DEV_DV_SS DEV_CV_DD
C1
C2
1.8 V
1.2 V
A. The DEV_CV_DD core voltage value is device dependent (e.g., when using SmartReflex, DEV_CV_DD can be either 1.2
V or 1.05 V).
Figure 7-8. 27-MHz System Oscillator^(A)
The load capacitors, C1 and C2, should be chosen such that the equation is satisfied (typical values are
C1 = C2 = 10 pF). C_L in the equation is the load specified by the crystal manufacturer. All discrete
components used to implement the oscillator circuit should be placed as close as possible to the
associated oscillator pins (DEV_MXI and DEV_MXO) and to the DEV_V_SS pin.
CL
=
C1C2
(C1 + C2 )
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Peripheral Information and Electrical Specifications 153
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