Specification
NET2272 USB Peripheral Controller
______________________________________________________________________________
NetChip Technology, Inc., 2003
Patent Pending
335 Pioneer Way, Mountain View, California 94041
TEL (650) 526-1490
FAX (650) 526-1494
http://www.netchip.com
Rev 1.2, October 15, 2003
14
1.5.2.3 Analog VSS (ground)
•
Analog ground must be filtered from the digital ground using the recommended circuit provided.
•
Analog VSS and digital VSS must be connected via a 1
µH inductor.
•
AVSS, PVSS, COM pins, and RREF’s resistor should be connected to analog VSS.
1.5.2.4 Decoupling Capacitors
•
At least one 0.1
µF decoupling capacitor for every two pairs of digital/analog VDD and VSS should be
located near the NET2272 device.
•
At least one 0.01
µF decoupling capacitor for every two pairs of digital/analog VDD and VSS should be
located near the NET2272 device.
•
Decoupling capacitors may be placed on the solder side of the PCB.
•
At least one 10
µF filter capacitor for every five 0.1µF or 0.01µF decoupling capacitors.
•
Use capacitors that have good quality at high frequency for low ESR, such as tantalum or ceramic
capacitors. Do not use electrolytic capacitors.
1.5.2.5 EMI Noise Suppression
•
A common-mode choke coil may suppress EMI noise effectively, although such a coil could affect USB
2.0 signal quality.
•
Choose a good quality noise filter, if necessary.
•
For a typical implementation, a choke is not required.
•
Use good quality, shielded cables.
1.6
Terminology
Byte. 8-bit quantity of data.
Word. 16-bit quantity of data.
Scalar. Multi-byte data element.
Local Transaction. A read or write operation on the local bus. It includes an address phase followed by one data
transfer.
Local Transfer. During a transfer, data is moved from the source to the destination on the local bus.
Clock cycle. One period of the internal 60 MHz clock.
Big Endian. The most significant byte in a scalar is located at address 0.
Little Endian. The least significant byte in a scalar is located at address 0.
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