JAJSC32E September 2012 – June 2019 DP83848-EP
PRODUCTION DATA.
The DP83848-EP supports an external CMOS level oscillator source or a crystal resonator device.
Oscillator
If an external clock source is used, X1 should be tied to the clock source and X2 should be left floating.
Specifications for CMOS oscillators: 25 MHz in MII Mode and 50 MHz in RMII Mode are listed in Table 6-1 and Table 6-2.
Crystal
A 25-MHz, parallel, 20-pF load crystal resonator should be used if a crystal source is desired. Figure 6-4 shows a typical connection for a crystal resonator circuit. The load capacitor values will vary with the crystal vendors; check with the vendor for the recommended loads.
The oscillator circuit is designed to drive a parallel resonance AT cut crystal with a minimum drive level of 100 mW and a maximum of 500 µW. If a crystal is specified for a lower drive level, a current limiting resistor should be placed in series between X2 and the crystal.
As a starting point for evaluating an oscillator circuit, if the requirements for the crystal are not known, CL1 and CL2 should be set at 33 pF, and R1 should be set at 0 Ω.
Specification for 25-MHz crystal are listed in Table 6-3.
PARAMETER | MIN | TYP | MAX | UNIT | CONDITION |
---|---|---|---|---|---|
Frequency | 25 | MHz | |||
Frequency Tolerance | ±50 | ppm | Operational Temperature | ||
Frequency Stability | ±50 | ppm | 1 year aging | ||
Rise / Fall Time | 6 | nsec | 20% - 80% | ||
Jitter | 800(1) | psec | Short term | ||
Jitter | 800(1) | psec | Long term | ||
Symmetry | 40% | 60% | Duty Cycle |
PARAMETER | MIN | TYP | MAX | UNIT | CONDITION |
---|---|---|---|---|---|
Frequency | 50 | MHz | |||
Frequency Tolerance | ±50 | ppm | Operational Temperature | ||
Frequency Stability | ±50 | ppm | Operational Temperature | ||
Rise / Fall Time | 6 | nsec | 20% - 80% | ||
Jitter | 800(1) | psec | Short term | ||
Jitter | 800(1) | psec | Long term | ||
Symmetry | 40% | 60% | Duty Cycle |
PARAMETER | MIN | TYP | MAX | UNIT | CONDITION |
---|---|---|---|---|---|
Frequency | 25 | MHz | |||
Frequency Tolerance | ±50 | ppm | Operational Temperature | ||
Frequency Stability | ±50 | ppm | 1 year aging | ||
Load Capacitance | 25 | 40 | pF |