SPI_Layout_Guide_AN

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针对高速SPI FLASH的PCB走线规则。

Spansion® Serial Peripheral Interface (SPI) FL Flash Layout Guide

Application Note

1.Introduction

The Spansion serial peripheral interface (SPI) flash devices are high speed synchronous access non-volatile memory devices. Standard high speed layout practices should be followed when performing printed circuit board (PCB) design with SPI flash. This application note outlines PCB layout recommendations for Spansion SPI flash devices, including S25FL-P, S70FL-P, S25FL-S, and S70FL-S flash families.

2.Basic SPI Flash Connectivity

All S25FL devices feature one flash die per package and are enabled via a single chip select control input. All S70FL devices feature two identical die per package which are individually enabled via two chip select control inputs and all other control inputs and I/O are shared between die. Figures2.1 and Figure2.2 illustrate basic Host to SPI Flash configuration options for S25FL flash and S70FL flash, respectively.

Figure 2.1 Simplified Connection Diagrams for S25FL Single and Multi I/O Configurations

PublicationNumberSPI_Layout_Guide_ANRevision02IssueDateApril8,2011

针对高速SPI FLASH的PCB走线规则。

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Figure 2.2 Simplified Connection Diagrams for S70FL Single and Multi I/O Configurations

Often multiple SPI devices are connected to a single host. Figure2.3 illustrates such a configuration. Use of a dual die S70FL device can be viewed as use of Device 1 and Device 2 in Figure2.3.

Figure 2.3 Simplified Multi- SPI Device Connection Diagram

Many SPI flash applications do not utilize the ACC, WP# or HOLD# functions. In those applications where an input is not utilized, the unused I/O should be pulled up to VCC, or VIO if present, via a suitable resistor, e.g. 4.7 to 10 kohms.

针对高速SPI FLASH的PCB走线规则。

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3.SPI Flash Packaging

The FL-P and FL-S SPI Flash families provide a user configurable high speed single, dual or quad channel interface to the host controller. Spansion SPI flash are available in a variety of packages, including SOIC-8 and SOIC-16 leaded packages, USON-8 and WSON-8 leadless packages and FAB024 and FAC024 ball grid array (BGA) packages. Table3.1 provides a matrix of package options for all FL-P and FL-S devices.

Table 3.1 Device Availability Matrix

Package \ DensitySOC008SO3 016

32 MbitS25FL032PS25FL032P

64 Mbit

S25FL064P

128 Mbit

S25FL128P S25FL129P S25FL128S

256 Mbit

S25FL256S

512 Mbit

S25FL512S

1024 Mbit

SL3S70FL256PUSONWSON

S25FL0

32PS25FL032P

S25FL064P

S25FL128P

S25FL129P S25FL128SS25FL129P S25FL128SS25FL129P S25FL128S

S25FL256S

FAB024FAC024ZSA024other BGA (planned)

S25FL032PS25FL032P

S25FL064PS25FL064P

S25FL256SS25FL256S

S25FL512S S70FL512S

S70FL01GS

S70FL256P

3.1SPI Flash Package Connection Diagrams

Applicable package connection diagrams are provided in each SPI Flash data sheet. These diagrams are

included here in Figure3.1 through Figure3.11 for reference.

Figure 3.1 SOC 008 wide – S25FL032P

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Figure 3.2 SO3 016 – S25FL128P

Figure 3.3 016 – S25FL032P/064P/129P

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Figure 3.4 SO3 016 – S29FL128S/256S/512S

Figure 3.5 SL3 016 – S70FL256P

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Figure 3.6 USON – S25FL032P

Figure 3.7 WSON – S25FL128P

Figure 3.8 WSON – S25FL032/064/129P, S25FL128/256SH

Figure 3.9 FAB024 – S25FL032/064/129P, S25FL128/256S

Note:

RESET# and VIO inputs apply to S25FL-S models only.

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Figure 3.10 FAC024 – S25FL032/064/129P, S25FL128/256S

Note:

RESET# and VIO inputs apply to S25FL-S models only.

Figure 3.11 ZSA024 – S70FL256P

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3.2SPI Flash Package Drawings

Applicable package drawings are provided in each SPI Flash data sheet. These drawings are included here in Figure3.12 through Figure3.17 for reference.

Figure 3.12 SOC 008 – Wide 8-Pin Plastic Small Outline 208 mils Body Width Package

针对高速SPI FLASH的PCB走线规则。

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针对高速SPI FLASH的PCB走线规则。

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Figure 3.14 USON 8-contact (5 x 6 mm) No-Lead Package

针对高速SPI FLASH的PCB走线规则。

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针对高速SPI FLASH的PCB走线规则。

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Figure 3.16 FAB024 and ZSA024 24-ball Ball Grid Array (6 x 8 mm) Packages

针对高速SPI FLASH的PCB走线规则。

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Figure 3.17 FAC024 24-ball Ball Grid Array (6 x 8 mm) Package

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nd Patterns Recommendations

Applicable PCB land pattern recommendations for SOC 008, SO3 016, SL3 016, USON, WSON, FAB024, FAC024, and ZSA024 packages are provided here in Figure4.1 through Figure4.6.Note: All dimensions are in mm.

Figure 4.1 SOC 008 Proposed Land Pattern

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Figure 4.2 SO3 016 & SL3 016 Proposed Land Pattern

针对高速SPI FLASH的PCB走线规则。

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Figure 4.3

USON Proposed Land Pattern

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Figure 4.4 WSON Proposed Land Pattern

The WSON8 land pattern is shown above. It is recommended that the center slug should be solder mask define (SMD) to avoid bridging. The mask opening should be 0.05 – 0.1 mm smaller than the center pad on all four sides. At the pin, it should be NSMD with the mask opening 3 mil larger than the copper pad on all sides. At center slug, the stencil should also has small multiple openings with solder paste coverage about

40 – 70% of the exposed pad area to prevent bridging between the center slug and pins.

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Figure 4.5 FAB024 and ZSA024 Proposed Land Pattern

Figure 4.6 FAC024 Proposed Land Pattern

4.1BGA Land Pad Recommendations

PCB solder-ball land pads can be either non-solder-mask defined (NSMD) or solder-mask-defined (SMD). For NSMD configurations, there is a small gap between the solder pad and the solder mask. Solder will flow into the gap between the pad and the solder mask (reference Figure4.7). For SMD configurations, the solder mask covers the outer edge of the solder pad. Solder is prevented from flowing over the edges of the pad by

the solder mask.

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Figure 4.7 SMD vs. NSMD Landing Pad Definition

SolderPadSolderPad

MaskMask

Mask Opening

Pad

Mask Board material

Pad

Board Material

NSMD

SMD

NSMD is generally the recommended land pad configuration because it enables a stronger bond between the solder pad and the solder ball with less stress concentration.

For SMD configurations, it is good practice to make the solder mask opening the same size as the diameter of the solder ball. On NSMD configurations, the solder pad should be between 80% and 100% of the solder ball diameter and the solder mask opening should be 0.15 mm larger than the solder pad to provide ample space for excess solder. Table4.1 provides dimensional recommendations for SMD and NSMD configurations suitable for use with the FAB024, FAC024 and ZSC024 packages.

Table 4.1 NSMD and SMD Dimensional Recommendations for BGA Packages

Configuration

SMDNSMD

OpeningSolder PadSolder MaskSolder PadSolder Mask

Recommended Dimension

0.55 mm0.45 mm0.45 mm0.60 mm

5.Printed Circuit Board Design Recommendations

This section contains general layout recommendations.

5.1Power Supply Decoupling

All S25FL and S70FL SPI Flash have one power supply input pin (VCC) and one ground pin (GND).

Additionally, certain models support a separate I/O supply input pin (VIO) for applications that require I/O levels to be less than VCC. Use of one 0.1 µF ceramic capacitor, normally in a 0603 or 0402 package, is recommended for decoupling each power supply input pin. A decoupling capacitor should be placed as close as possible to the VCC supply input pin, as well as the VIO supply input pin if present.

The routing of the decoupling capacitor should be optimized to achieve low inductance. Power supply trace lengths from the package pads to the vias should be as short as possible with a trace width of approximately 0.6 mm. It is recommended to avoid sharing the same via with 2 or more decoupling capacitors. Figure5.1 shows examples of routing the decoupling capacitor.

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Figure 5.1 Routing with Decoupling Capacitor

5.2Clock Signal Routing

For reliable high speed synchronous data transfers, it is essential for the clock signal to have very good signal

integrity. The following recommendations should be taken into consideration when routing the clock signal. Run the clock signal at least 3x of the trace width away from all other signal traces. This will help keep clock signal clean from noise, reference Figure5.2. Use as few vias as possible for the entire path of the clock signal. Each via will create impedance changes and signal reflections. Run the clock trace as straight as possible and avoid using serpentine routing, reference Figure5.3. Keep a continuous ground in the next layer as a reference plane.

Route the clock trace with controlled impedance, typically a 50 ohm trace impedance with ± 5% tolerance.

Figure 5.2 Separate Clock from other Traces

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Figure 5.3 Straight Trace Runs for Clock

5.3Data Signal Routing

The FL Flash support 1, 2 and 4-bit data bus configurations. In 2 and 4-bit multiple I/O configurations, it is

important that the I/O traces are routed such that they have identical lengths, within ~ 3 mm, to assure

equivalent propagation delays. To assure reliable data transfers for all configurations it is important that the propagation delays for the clock trace and all data traces are identical.

The data signals should be routed with traces of controlled impedance to reduce signal reflection. Data traces should have no 90° angle corners. The preferred method for implementing a 90° angle change is to cut the corner to smooth the trace, reference Figure5.4. To maximize signal integrity, avoid using multiple signal layers for data signal routing and ensure all signal traces have a continuous reference plane.

Figure 5.4 Signal Routing at the Corner

5.4Via Routing

Vias should not be placed within a land pad as this can cause solder wicking inside the via hole, resulting in

misshapen solder joints and electrical opens. Vias should be placed a minimum of 0.3 mm away from the solder pad as shown in Figure5.5

.

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