dp83848qsqx/nopb National Semiconductor Corporation, dp83848qsqx/nopb Datasheet - Page 28

• Manufacturer Part Number: dp83848qsqx/nopb
• Description: Phyter Extended Temperature Single Port 10/100 Mb/s Ethernet Physical Layer Transceiver
• Manufacturer: National Semiconductor Corporation

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11.0 Design Guidelines
11.1 TPI NETWORK CIRCUIT
Figure 10
twisted pair interface. To the right is a partial list of recom-
mended transformers. It is important that the user realize that
variations with PCB and component characteristics requires
11.2 ESD PROTECTION
Typically, ESD precautions are predominantly in effect when
handling the devices or board before being installed in a sys-
tem. In those cases, strict handling procedures need be im-
plemented during the manufacturing process to greatly
reduce the occurrences of catastrophic ESD events. After the
system is assembled, internal components are less sensitive
from ESD events.
See section
rating.
11.3 CLOCK IN (X1) REQUIREMENTS
The DP83848Q 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
shows the recommended circuit for a 10/100 Mb/s
Section 15.0 AC and DC Specifications
Table 7
FIGURE 10. 10/100 Mb/s Twisted Pair Interface
and
Table
for ESD
8.
28
that the application be tested to ensure that the circuit meets
the requirements of the intended application.
Crystal
A 25 MHz, parallel, 20 pF load crystal resonator should be
used if a crystal source is desired.
connection for a crystal resonator circuit. The load capacitor
values will vary with the crystal vendors; check with the ven-
dor for the recommended loads.
The oscillator circuit is designed to drive a parallel resonance
AT cut crystal with a minimum drive level of 100mW 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 be-
tween X2 and the crystal.
As a starting point for evaluating an oscillator circuit, if the
requirements for the crystal are not known, C
should be set at 33 pF, and R
Specification for 25 MHz crystal are listed in
Pulse H1102
Pulse H2019
Pulse J0011D21
Pulse J0011D21B
1
should be set at 0Ω.
Figure 12
Table
shows a typical
30152511
L1
9.
and C
L2