Texas Instruments TMS320DM355 2 MXI2 27-MHz Oscillator optional oscillator, Esr, MXI2 MXO2

PRODUCT PREVIEW

TMS320DM355

Digital Media System-on-Chip (DMSoC)

www.ti.com

SPRS463A –SEPTEMBER 2007 –REVISED SEPTEMBER 2007

Table 5-3. Switching Characteristics Over Recommended Operating Conditions for 24-MHz System

Oscillator

PARAMETER	MIN	TYP	MAX	UNIT
Start-up time (from power up until oscillating at stable frequency)			4	ms
Oscillation frequency		24 or 36		MHz
ESR			60	Ω
Frequency stability			+/-50	ppm

5.5.2MXI2 (27-MHz) Oscillator (optional oscillator)

The MXI2 (27 MHz) oscillator provides an optional reference clock for the 'sVPSS module. The on-chip oscillator requires an external 27-MHz crystal connected across the MXI2 and MXO2 pins, along with two load capacitors, as shown in Figure 5-6. The external crystal load capacitors must be connected only to

the 27-MHz oscillator ground pin (VSS_MX2). Do not connect to board ground (VSS). Also, the PLL power pin (VDDA_PLL2) should be connected to the power supply through a ferrite bead, L1 in the example circuit

shown in Figure 5-6.

MXI2	MXO2	VSS_MX2	VDDA_PLL2	VSSA_PLL2
Crystal
27￿MHz			0.1	F
C1		C2	1	F
			L1

Figure 5-6. MXI2 (27-MHz) System Oscillator

The load capacitors, C1 and C2, should be chosen such that the equation is satisfied (typical values are C1 = C2 = 10 pF). CL 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 (MXI and MXO) and to the VSS_MX2 pin.

CL	C1C2
	(C1	C2)

Table 5-4. Switching Characteristics Over Recommended Operating Conditions for 27-MHz System

Oscillator

PARAMETER	MIN	TYP	MAX	UNIT
Start-up time (from power up until oscillating at stable frequency)			4	ms
Oscillation frequency			27	MHz
ESR			60	Ω
Frequency stability			+/-50	ppm

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