Cypress Semiconductor FX2LP Instrukcja Użytkownika Pobierz pdf (Strona 58)

CY7C68013A/CY7C68014A

CY7C68015A/CY7C68016A

Document #: 38-08032 Rev. *K Page 58 of 60

13.0 PCB Layout Recommendations

[24]

The following recommendations should be followed to ensure

reliable high-performance operation.

• At least a four-layer impedance controlled boards are re-

quired to maintain signal quality.

• Specify impedance targets (ask your board vendor what

they can achieve).

• To control impedance, maintain trace widths and trace spac-

ing.

• Minimize stubs to minimize reflected signals.

• Connections between the USB connector shell and signal

ground must be done near the USB connector.

• Bypass/flyback caps on VBus, near connector, are recom-

mended.

• DPLUS and DMINUS trace lengths should be kept to within

2 mm of each other in length, with preferred length of

20–30 mm.

• Maintain a solid ground plane under the DPLUS and DMI-

NUS traces. Do not allow the plane to be split under these

traces.

• It is preferred is to have no vias placed on the DPLUS or

DMINUS trace routing.

• Isolate the DPLUS and DMINUS traces from all other signal

traces by no less than 10 mm.

14.0 Quad Flat Package No Leads (QFN)

Package Design Notes

Electrical contact of the part to the Printed Circuit Board (PCB)

is made by soldering the leads on the bottom surface of the

package to the PCB. Hence, special attention is required to the

heat transfer area below the package to provide a good

thermal bond to the circuit board. A Copper (Cu) fill is to be

designed into the PCB as a thermal pad under the package.

Heat is transferred from the FX2LP through the device’s metal

paddle on the bottom side of the package. Heat from here, is

conducted to the PCB at the thermal pad. It is then conducted

Package Diagrams (continued)

TOP VIEW

PIN A1 CORNER

0.50

3.50

5.00±0.10

BOTTOM VIEW

0.10(4X)

3.50

5.00±0.10

0.50

Ø0.15MCAB

Ø0.05 M C

Ø0.30±0.05(56X)

A1 CORNER

-B-

-A-

1.0 max

0.160 ~0.260

0.080 C

0.45

SEATING PLANE

0.21

0.10 C

-C-

SIDE VIEW

5.00±0.10

REFERENCE JEDEC: MO-195C

PACKAGE WEIGHT: 0.02 grams

13265486

7856 2341

001-03901-*B

Figure 12-5. 56 VFBGA (5 x 5 x 1.0 mm) 0.50 Pitch, 0.30 Ball BZ56

Note:

24. Source for recommendations: EZ-USB FX2™PCB Design Recommendations, http://www.cypress.com/cfuploads/support/app_notes/FX2_PCB.pdf and High

Speed USB Platform Design Guidelines, http://www.usb.org/developers/docs/hs_usb_pdg_r1_0.pdf.

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