TMS320DM6446_15 Datasheet, PDF (101/227 Pages) Texas Instruments – Digital Media System-on-Chip

TMS320DM6446
www.ti.com
SPRS283H – DECEMBER 2005 – REVISED SEPTEMBER 2010
Table 6-10. Crystal Requirements for a 27-MHz System Oscillator
PARAMETER
Start-up time (from power up until oscillating at stable frequency of 27 MHz)
Oscillation frequency
ESR
Frequency stability
MIN
TYP
27
MAX
4
60
±50
UNIT
ms
MHz
Ω
ppm
6.5.1.2 24-MHz Crystal for USB Oscillator
In this option, a crystal is used as the external clock input to the DM6446 USB PLL.
The 24-MHz oscillator provides the reference clock for the DM6446 USB peripheral. The on-chip oscillator
requires an external 24-MHz crystal connected across the M24XI and M24XO pins, along with two load
capacitors, as shown in Figure 6-11.The external crystal load capacitors must be connected only to the
24-MHz oscillator ground pin (M24V_SS). Do not connect to board ground (V_SS).
M24XI
M24XO
RBIAS
(optional)
M24V_SS
M24V_DD
Crystal
24 MHz
C1
C2
1.8 V
Figure 6-11. 24-MHz USB Oscillator
The RBIAS resistor is optional. If the RBIAS resistor is used, it should equal 1 MΩ ±5%. 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
(M24XI and M24XO) and to the M24XV_SS pin.
C_L
+
C₁C₂
(C₁ ) C₂)
Table 6-11. Crystal Requirements for a 24-MHz USB Oscillator
PARAMETER
Start-up time (from power up until oscillating at stable frequency of 24 MHz)
Oscillation frequency
ESR
Frequency stability
MIN
TYP
24
MAX
4
60
±50
UNIT
ms
MHz
Ω
ppm
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