LM3S8970 Datasheet, PDF (464/494 Pages) Texas Instruments – Stellaris® LM3S8970 Microcontroller

Electrical Characteristics
Table 20-16. Ethernet Reference Crystal^a
Name
Value
Condition
Frequency
Load capacitance^b
25.00000
4^c
MHz
pF
Frequency tolerance
±50
PPM
Aging
±2
PPM/yr
Temperature stability (0° to 70°)
±5
PPM
Oscillation mode
Parallel resonance, fundamental mode
Parameters at 25° C ±2° C; Drive level = 0.5 mW
Drive level (typ)
50-100
µW
Shunt capacitance (max)
10
pF
Motional capacitance (min)
10
fF
Serious resistance (max)
60
Ω
Spurious response (max)
> 5 dB below main within 500 kHz
a. If the internal crystal oscillator is used, select a crystal with the following characteristics.
b. Equivalent differential capacitance across XTLP/XTLN.
c. If crystal with a larger load is used, external shunt capacitors to ground should be added to make up the equivalent
capacitance difference.
Figure 20-3. External XTLP Oscillator Characteristics
T_r
T_f
T_clkhi
T_clkper
T_clklo
Table 20-17. External XTLP Oscillator Characteristics
Parameter Name Symbol Min Nom Max Unit
XTLN Input Low Voltage XTLN_ILV - - 0.8 -
XTLP Frequency^a XTLP_f - 25.0 - -
XTLP Period^b
T_clkper
- 40 -
-
XTLP Duty Cycle _XTLPDC 40 - 60 %
40
60
Rise/Fall Time
Absolute Jitter
T_r , T_f
- - 4.0 ns
- - 0.1 ns
a. IEEE 802.3 frequency tolerance ±50 ppm.
464
Luminary Micro Confidential-Advance Product Information
June 13, 2007