DP83934CVUL-25 National Semiconductor, DP83934CVUL-25 Datasheet - Page 75

• Manufacturer Part Number: DP83934CVUL-25
• Description: IC CTRLR ORIENT NETWORK 160PQFP
• Manufacturer: National Semiconductor

Specifications of DP83934CVUL-25

• Controller Type: Network Interface Controller (NIC)
• Interface: Twisted Pair
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 140mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-MQFP, 160-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *DP83934CVUL-25

8 0 Network Interfacing
Resonant frequency
Tolerance (see text)
Accuracy
Fundamental Mode Series Resistance
Specified Load Capacitance
Type
Circuit
8 1 3 2 Clock Oscillator Module
The SONIC-T also allows an external clock oscillator to be
used The connection configuration is shown in Figure 8-5
This connection requires an oscillator with the following
specifications
1 TTL or CMOS output with a 0 01% frequency tolerance
2 40% –60% duty cycle
3 One CMOS load output drive
These specifications assume that no other circuitry is driv-
en In this configuration the OSCOUT pin must be left open
8 1 3 3 PCB Layout Considerations
Care should be taken when connecting a crystal Stray ca-
pacitance (e g from PC board traces and plated through-
holes around the OSCIN and OSCOUT pins) can shift the
crystal’s frequency out of range causing the transmitted fre-
quency to exceed the 0 01% tolerance specified by IEEE
The layout considerations for using an external crystal are
rather straightforward The oscillator layout should locate all
components close to the OSCIN and OSCOUT pins and
FIGURE 8-5 Oscillator Module Connection
TABLE 8-1 Crystal Specifications
to the SONIC-T
FIGURE 8-6 External Circuitry to Connect the SONIC-T to Twisted Pair Cable
g
0 005% (50 ppm) at 0 to 70 C
(Continued)
Parallel Resonance
g
0 01% at 25 C
TL F 11719– 55
20 MHz
s
AT cut
s
18 pF
25
75
should use short traces that avoid excess capacitance and
inductance A solid ground should be used to connect the
ground legs of the two capacitors
When connecting an external oscillator the only considera-
tions are to keep the oscillator module as close to the
SONIC-T as possible to reduce stray capacitance and in-
ductance and to give the module a clean V
ground
8 1 4 Power Supply Considerations
In general power supply routing and design for the
SONIC-T need only follow standard practices In some situ-
ations however additional care may be necessary in the
layout of the analog supply Specifically special care may be
needed for the TXV
and TPV
PLLGND OSCGND TPGND and ANGND In most cases
the analog and digital power supplies can be interconnect-
ed However to ensure optimum performance of the
SONIC-T’s analog functions power supply noise should be
minimized To reduce analog supply noise any of several
techniques can be used
1 Route analog supplies as a separate set of traces or
2 Provide noise filtering on the analog supply pins by insert-
3 Utilize a separate regulator to generate the analog sup-
8 2 TWISTED PAIR INTERFACE MODULE
Transmitter Considerations The transmitter consists of
four signals the true and complement Manchester encoded
data (TXO
These four signals are resistively combined (Figure 8-6)
TXO
ration referred to as pre-emphasis This digital pre-emphasis
is required to compensate for the low-pass filter effects of
the twisted pair cable which cause greater attenuation to
the 10 MHz (50 ns) pulses of the Manchester encoded
waveform than the 5 MHz (100 ns) pulses
planes from the digital supplies with their own decoupling
capacitors
ing a low pass filter Alternatively a ferrite bead could be
used to reduce high frequency power supply noise
ply
a
with TXOd
CC
g
) and these signals delayed by 50 ns (TXOd
power supplies and the TXGND RXGND
b
CC
and TXO
RXV
CC
b
TL F 11719 – 56
PLLV
with TXOd
CC
OSCV
a
CC
in a configu-
CC
and a solid
RXTV
g
CC
)