DP83907VF National Semiconductor, DP83907VF Datasheet - Page 21

• Manufacturer Part Number: DP83907VF
• Description: IC CONTROLLR AT/LANII TP 160PQFP
• Manufacturer: National Semiconductor

Specifications of DP83907VF

• Controller Type: Network Interface Controller (NIC)
• Interface: Twisted Pair
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 150mA
• 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: *DP83907VF

4 0 Functional Description
If a crystal is connected to the DP83907 it is recommended
that the circuit shown in Figure 19 be used and that the
components used meet the following
Crystal XT1 AT cut parallel resonant crystal
The recommended values for capacitors C1 and C2 should
be 26 pF minus the board capacitance on that pin There-
fore if both X1 and X2 have 4 pF of board capacitance then
a 22 pF capacitor should be used
According to the IEEE 802 3 standard the entire oscillator
circuit (crystal and amplifier) must be accurate to 0 01%
When using a crystal the X2 pin is not guaranteed to pro-
vide a TTL compatible logic output and should not be used
to drive external standard logic If additional logic needs to
be driven then an external oscillator should be used as
described in the following section
Oscillator Module Operation
If the designer wishes to use a crystal clock oscillator one
that provides the following should be employed
1) TTL or CMOS output with a 0 01% frequency tolerance
2) 40 –60% duty cycle
The circuit is shown in Figure 20 When using a clock oscil-
lator it is recommended that the designer connect the oscil-
lator output to the X1 pin and leave the X2 pin floating
Series Resistance
Specified Load Capacitance
Accuracy 0 005% (50 ppm)
Typical Load 50 W– 75 W
FIGURE 21 Connection from DP83907’s AUI Port to a AUI Connector
s
25
s
(Continued)
20 pF
21
Manchester Encoder and DIfferential Driver
The differential transmit pair on the secondary of the em-
ployed transformer drives up to 50 meters of twisted pair
AUI cable
The DP83907 allows full-step to be compatible with IEEE
802 3 Transmit
state providing zero differential voltage to operate with
transformer coupled loads
FIGURE 20 DP83907 Connection for Oscillator Module
a
and Transmit
b
are equal in the idle
TL F 12082 – 15
TL F 12082 – 16