Intel IXP43X manual Decoupling Capacitance Recommendations, VCC Decoupling, 14.3 VCC33 Decoupling

Intel® IXP43X Product Line of Network Processors—Hardware Design Guidelines

	Nominal	Description
Name	voltage
	†
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.
		1.3-V power supply input pins are used for internal logic of the analog phase lock-loop circuitry.
VCCA	1.3V	Requires special power filtering circuitry. See the Intel® IXP43X Product Line of Network
		Processors Datasheet

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".

3.14.2VCC 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.

3.14.3VCC33 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.

3.14.4VCCDDR 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.

3.14.5Power 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.

3.14.6Reset 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.

Intel® IXP43X Product Line of Network Processors
HDG	April 2007
54	Document Number: 316844; Revision: 001US