PNX1500E NXP Semiconductors, PNX1500E Datasheet - Page 74

• Manufacturer Part Number: PNX1500E
• Manufacturer: NXP Semiconductors

Specifications of PNX1500E

• Lead Free Status / Rohs Status: Not Compliant

NXP Semiconductors
Volume 1 of 1
10. Board Design Guidelines
PNX15XX_PNX952X_SER_N_4
Product data sheet
10.1 Power Supplies Decoupling
The following sections discuss the fundamentals of board design for the PNX1500
system. The intent is to give general guidelines on the subject, not the complete in
depth coverage.
A minimum of four layers board is recommended.
Power supply regulators require large smoothing capacitors to deliver the current until
the regulator can follow the load conditions. These smoothing capacitors are typically
large electrolytic capacitors with considerable parasitic inductance, typically in the
order of 10 nH. This high inductance does not allow for rapid supply of varying
currents required in high speed processors as the PNX1500. The following
recommendations assume a load transient of up to 1 A within 2 ns which is
considered conservative for the PNX1500. However, this does guarantee adequate
decoupling.
In “high frequency” applications, each power plane VCCP, VCCM and VDD should be
decoupled with at least 10 capacitor of 0.1 F. Capacitors should be chosen such that
the total series inductance is approximately within the order of 0.2 nH (i.e. 2 nH per
capacitor). The parasitic series resistance per capacitor should be in the order of 0.1
placed as closely as possible to the power pins of the PNX1500. If board space
allows an additional ten 0.01
and VCCM planes.
For “medium frequency”, each power plane VCCP, VCCM and VDD should be
decoupled with at least 10 capacitors of 47 F. Capacitors should be chosen such
that the total series inductance is approximately with the order of 0.5 nH. The
parasitic series resistance per capacitor should be in the order of 0.1 . Aluminum or
wet “wound foil” tantalum capacitors should not be used. Instead, dry tantalum
capacitors or equivalent total series resistor and inductance capacitors like the new
ceramic or polymer tantalum can be used. Despite the larger footprint these surface
mount “medium frequency” decoupling capacitors should still be placed as closely as
physically possible to the PNX1500 power pins.
Last step before the power regulator itself is the bulk decoupling. The bulk decoupling
can be achieved with five 100 F, 220 F or even 330 F capacitors. These
capacitors usually have an inductance of 10 nH and internal equivalent series
resistance (ESR) of 0.1 . The amount and size are dependant on how fast the
regulator operates. Tantalum capacitors are preferred.
The VIA connection to the power planes should be as wide as the capacitor soldering
lead which is different from a VIA of a regular signal. The routing and VIA inductance
and resistance must be included when computing the total series inductance and
resistance. same diameter power and ground via should be used.
. Ceramic capacitors may be used. These surface mount capacitors should be
Rev. 4.0 — 03 December 2007
F ceramic capacitor is recommended for each VDD
PNX15xx/952x Series
Chapter 1: Integrated Circuit Data
© NXP B.V. 2007. All rights reserved.
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