WG82574L S LBA9 Intel, WG82574L S LBA9 Datasheet - Page 438

• Manufacturer Part Number: WG82574L S LBA9
• Description: CONTROLLER, ENET, INTEL 82574L, 64PQFN
• Manufacturer: Intel

Specifications of WG82574L S LBA9

• Ethernet Type: IEEE 802.3, IEEE 802.3u, IEEE 802.3ab
• Supply Voltage Range: 3V To 3.6V
• Operating Temperature Range: 0°C To +85°C
• Digital Ic Case Style: QFN
• No. Of Pins: 64
• Package / Case: QFN
• Interface Type: I2C, JTAG, PCI, SPI
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

13.3.1.5
13.3.1.6
Note:
Note:
438
Crystal Oscillation Mode
The terms series-resonant and parallel-resonant are often used to describe crystal
oscillator circuits. Specifying parallel mode is critical to determining how the crystal
frequency is calibrated at the factory.
A crystal specified and tested as series resonant oscillates without problem in a
parallel-resonant circuit, but the frequency is higher than nominal by several hundred
parts per million. The purpose of adding load capacitors to a crystal oscillator circuit is
to establish resonance at a frequency higher than the crystal’s inherent series resonant
frequency.
Figure 70
circuit. Note that pin X1 and X2 refers to XTAL1 and XTAL2 in the Ethernet device,
respectively. The crystal and the capacitors form a feedback element for the internal
inverting amplifier. This combination is called parallel-resonant, because it has positive
reactance at the selected frequency. In other words, the crystal behaves like an
inductor in a parallel LC circuit. Oscillators with piezoelectric feedback elements are
also known as “Pierce” oscillators.
Load Capacitance and Discrete Capacitors
The formula for crystal load capacitance is as follows:
Because 28 pF is not a standard value, use 27 pF capacitors for C1 and C2, which is the
closest standard value.
The oscillator frequency should be measured with a precision frequency counter where
possible. The values of C1 and C2 should be fine tuned for the design. As the actual
capacitive load increases, the oscillator frequency decreases.
Intel recommends COG or NPO capacitors with a tolerance of ±5% (approximately
±1 pF) or smaller.
where:
C
crystal circuit capacitors.
C
package. Individual stray capacitance components can be estimated and added
as parallel capacitances. Note that total C
Solve for the discrete capacitor values as follows:
C1 = C2 = 2 * [C
For example:
If total C
and C2 = 2 * [18 pF - 4.0 pF] = 28 pF.
L
stray
shows the recommended placement and layout of an internal oscillator
is the rated C
allows for additional capacitance from solder pads, traces and the 82574
stray
= 4.0 pF and if the C
load
load
of the crystal component and C1 and C2 are discrete
- C
C
L
stray
=
]
- - - - - - - - - - - - - - - - - - -


C1
C1 C2
+

load
C2
rating is 18 pF, then the calculated C1


82574 GbE Controller—Design Considerations
+
stray
C
stray
is typically 3 pF to 7 pF.