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Intel
®
IXP43X Product Line of Network Processors—Hardware Design Guidelines
Intel
®
IXP43X Product Line of Network Processors
HDG April 2007
54 Document Number: 316844; Revision: 001US
3.14.1 Decoupling Capacitance Recommendations
It is common practice to place decoupling capacitors between the supply voltages and
ground. Placement can be near the input supply pins and ground, with one 100-nF
capacitor per pin. Additional decoupling capacitors can be place all over the board
every 0.5" to 1.0". This ensures good return path for currents and reduce power surges
and high-frequency noise.
It is also recommended that 4.7-µF to 10-µF capacitors be placed every 2" to 3".
3.14.2 VCC Decoupling
Connect one 100-nF capacitor per each VCC pin. Placement should be as close as
possible to the pin. It is also recommended to place a 4.7-µF capacitor near the device.
Use traces as thick as possible to eliminate voltage drops in the connection.
3.14.3 VCC33 Decoupling
Connect one 100-nF capacitor per each Vcc33 pin. Placement should be as close as
possible to the pin. It is also recommended to place a 4.7-µF capacitor near the device.
Use traces as thick as possible to eliminate voltage drops in the connection.
3.14.4 VCCDDR Decoupling
Connect one 100-nF capacitor per each VCCDDR pin. Placement should be as close as
possible to the pin. It is also recommended to place a 4.7-µF capacitor near the device.
Use traces as thick as possible to eliminate voltage drops in the connection.
3.14.5 Power Sequence
Power sequence is crucial for proper functioning of the IXP43X network processors. For
a complete description of power sequencing, see the Intel
®
IXP43X Product Line of
Network Processors Datasheet.
3.14.6 Reset Timing
Proper reset timing is also a crucial requirement for proper functioning of the IXP43X
network processors. There are two reset signal PWRON_RESET_N and RESET_IN_N
which required assertion sequence.
For a complete description of their functionality, see the Intel
®
IXP43X Product Line of
Network Processors Datasheet and its section titled Reset Timings. PWRON_RESET_N
is used as a Power Good and RESET_IN_N is used for resetting internal registers.
VCCPUSB 3.3V 3.3-V power supply input pins are used for USB IO.
VCCUSBCORE 1.3V 1.3-V power supply input pins are used for USB IO core.
VCCA 1.3V
1.3-V power supply input pins are used for internal logic of the analog phase lock-loop circuitry.
Requires special power filtering circuitry. See the Intel
®
IXP43X Product Line of Network
Processors Datasheet
Name
Nominal
voltage
†
Description