fw802a ETC-unknow, fw802a Datasheet - Page 12

• Manufacturer Part Number: fw802a
• Description: Low-power Ieee 1394a-2000 Two-cable Transceiver/arbiter Device
• Manufacturer: ETC-unknow

Two-Cable Transceiver/Arbiter Device
Crystal Selection Considerations
Load Capacitance
The frequency of oscillation is dependent upon the load capacitance specified for the crystal, in parallel resonant
mode crystal circuits. Total load capacitance (CL) is a function of not only the discrete load capacitors, but also
capacitances from the FW802A board traces and capacitances of the other FW802A connected components.
The values for load capacitors (C
C
Where:
C
C
Board Layout
The layout of the crystal portion of the PHY circuit is important for obtaining the correct frequency and minimizing
noise introduced into the FW802A PLL. The crystal and two load capacitors should be considered as a unit during
layout. They should be placed as close as possible to one another, while minimizing the loop area created by the
combination of the three components. Minimizing the loop area minimizes the effect of the resonant current that
flows in this resonant circuit. This layout unit (crystal and load capacitors) should then be placed as close as possi-
ble to the PHY XI and XO terminals to minimize trace lengths. Vias should not be used to route the XI and XO sig-
nals.
Absolute Maximum Ratings
Stresses in excess of the absolute maximum ratings can cause permanent damage to the device. These are abso-
lute stress ratings only. Functional operation of the device is not implied at these or any other conditions in excess
of those given in the operational sections of the data sheet. Exposure to absolute maximum ratings for extended
periods can adversely affect device reliability.
Table 2. Absolute Maximum Ratings
* Except for 5 V tolerant I/O (CTL0, CTL1, D0—D7, and LREQ) where V
12
12
Supply Voltage Range
Input Voltage Range*
Output Voltage Range at Any Output
Operating Free Air Temperature
Storage Temperature Range
A
L
stray
= load capacitance specified by the crystal manufacturer
= C
= capacitance of the board and the FW802A, typically 2—3 pF
B
= (C
L
– C
stray
Parameter
) × 2
A
and C
B
) should be calculated using this formula:
(continued)
Symbol
V
T
V
T
V
DD
stg
O
A
I
I
max = 5.5 V.
−0.5
−0.5
Min
–65
3.0
0
V
V
DD
DD
Max
150
3.6
70
Agere Systems Inc.
+ 0.5
+ 0.5
June 2001
Unit
°C
°C
V
V
V