TLK100_11 Datasheet, PDF (37/88 Pages) Texas Instruments – Industrial Temp, Single Port 10/100 Mb/s Ethernet Physical Layer Transceiver

TLK100
www.ti.com
SLLS931B – AUGUST 2009 – REVISED DECEMBER 2009
7.2.2 Crystal
The use of a 25MHz, parallel, 20pF-load crystal resonator is recommended if a crystal source is desired.
Figure 7-2 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
100μW and a maximum of 500μW. If a crystal is specified for a lower drive level, a current limiting resistor
should be placed in series between XO and the crystal.
As a starting point for evaluating an oscillator circuit, if the requirements for the crystal are not known, set
the values for C_L1 and C_L2 at 33pF, and R₁ should be set at 0Ω.
Specification for 25MHz crystal are listed in Table 7-2.
PARAMETER
Frequency
Frequency Tolerance
Frequency Stability
Rise / Fall Time
Jitter (Short term)
Jitter (Long term)
Symmetry
Load Capacitance
PARAMETER
Frequency
Frequency Tolerance
Frequency Stability
Load Capacitance
XI
XO
R₁
C_L1
C_L2
S0340-01
Figure 7-2. Crystal Oscillator Circuit
Table 7-1. 25 MHz Oscillator Specification
TEST CONDITIONS
Operational Temperature
1 year aging
10%–90%
Cycle-to-cycle
Accumulative over 10 ms
Duty Cycle
Table 7-2. 25 MHz Crystal Specification
TEST CONDITIONS
Operational Temperature
At 25°C
1 year aging
MIN
40%
TYP MAX UNIT
25
MHz
±50 ppm
±50 ppm
8 nsec
50
psec
1 nsec
60%
15
30 pF
MIN TYP MAX UNIT
25
MHz
±50 ppm
±50 ppm
±5 ppm
10
40 pF
Copyright © 2009, Texas Instruments Incorporated
Submit Documentation Feedback
Product Folder Link(s): TLK100
Design Guidelines
37