DP83916VF National Semiconductor, DP83916VF Datasheet - Page 71

• Manufacturer Part Number: DP83916VF
• Description: IC CTRLR ORIENT NETWK IN 132PQFP
• Manufacturer: National Semiconductor
• Series: SONIC™r

Specifications of DP83916VF

• Controller Type: Network Interface Controller (NIC)
• Interface: Bus
• Mounting Type: Surface Mount
• Package / Case: 132-MQFP, 132-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Supply: -
• Voltage - Supply: -
• Operating Temperature: -
• Other names: *DP83916VF

6 0 Network Interfacing
Note 1 The X1 pin is not guaranteed to provide a TTL compatible logic
Note 2 The frequency marked on the crystal is usually measured with a
Resonant frequency
Tolerance (see text)
Accuracy
Fundamental Mode Series Resistance
Specified Load Capacitance
Type
Circuit
6 1 3 2 Clock Oscillator Module
If an external clock oscillator is used the SONIC-16 can be
connected to the external oscillator in one of two ways The
first configuration is shown in Figure 6-5 In this case an
oscillator that provides the following should be used
1 TTL or CMOS output with a 0 01% frequency tolerance
2 40% –60% duty cycle
3
Again the above assumes no other circuitry is driven
The second configuration shown in Figure 6-6 connects to
the X2 input This connection requires an oscillator with the
same specifications as the previous circuit except that the
t
put drive may be necessary if the oscillator must also
drive other components )
5 TTL loads output drive (I
output and should not be used to drive any external logic If addi-
tional logic needs to be driven then an external oscillator should be
used as described in the following section
fixed load capacitance specified in the crystal’s data sheet The
actual load capacitance used should be the specified value minus
the stray capacitance
TABLE 6-1 Crystal Specifications
FIGURE 6 4 Crystal Connection
FIGURE 6 5 Oscillator Module
Connection to the SONIC-16
to the SONIC-16 (see text)
g
0 005% (50 ppm) at 0 to 70 C
OL
e
8 mA) (Additional out-
(Continued)
Parallel Resonance
g
0 01% at 25 C
TL F 11722– 55
TL F 11722– 56
20 MHz
s
AT cut
s
18 pF
25
71
output drive specification need only be one CMOS load
This circuit configuration also offers the advantage of slight-
ly lower power consumption In this configuration the X1 pin
must be left open and should not drive external circuitry
Also as shown by Figure 6-6 there is a 180 phase differ-
ence between connecting an oscillator to X1 compared to
X2 This difference only affects the relationship between
TXC and the oscillator module output The operation of the
SONIC-16 is not affected by this phase change
6 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 X1 and X2 pins) can shift the crystal’s
frequency out of range causing the transmitted frequency
to exceed the 0 01% tolerance specified by IEEE The lay-
out considerations for using an external crystal are rather
straightforward The oscillator layout should locate all com-
ponents close to the X1 and X2 pins and should use short
traces that avoid excess capacitance and inductance A sol-
id 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-16 as possible to reduce stray capacitance and in-
ductance and to give the module a clean V
ground
6 1 4 Power Supply Considerations
In general power supply routing and design for the SONIC-
16 need only follow standard practices In some situations
however additional care may be necessary in the layout of
the analog supply Specifically special care may be needed
for the TXVCC RXVCC and PLLVCC power supplies and
the TXGND and ANGND In most cases the analog and
digital power supplies can be interconnected However to
ensure optimum performance of the SONIC-16’s analog
functions power supply noise should be minimized To re-
duce 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-
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
Module Connection to the SONIC-16
FIGURE 6 6 Alternate Oscillator
CC
TL F 11722 – 57
and a solid