SMSC USB3280 - Manual (Page 26)

Hi-Speed USB Device PHY with UTMI Interface
Datasheet
Revision 1.5 (11-15-07) 26 SMSC USB3280
DATASHEET
7.6 USB 2.0 Transceiver
The SMSC Hi-Speed USB 2.0 Transceiver consists of the High Speed and Full Speed Transceivers,
and the Termination resistors.
7.6.1 High Speed and Full Speed Transceivers
The USB3280 transceiver meets all requirements in the USB 2.0 specification.
The receivers connect directly to the USB cable. This block contains a separate differential receiver
for HS and FS mode. Depending on the mode, the selected receiver provides the serial data stream
through the multiplexer to the RX Logic block. The FS mode section of the FS/HS RX block also
consists of a single-ended receiver on each of the data lines to determine the correct FS linestate. For
HS mode support, the FS/HS RX block contains a squelch circuit to insure that noise is never
interpreted as data.
The transmitters connect directly to the USB cable. The block contains a separate differential FS and
HS transmitter which receive encoded, bit stuffed, serialized data from the TX Logic block and transmit
it on the USB cable.
7.6.2 Termination Resistors
The USB3280 transceiver fully integrates all of the USB termination resistors. The USB3280 includes
the 1.5k
Ω pull-up resistor on DP. In addition the 45Ω high speed termination resistors are also
integrated. These integrated resistors require no tuning or trimming. The state of the resistors is
determined by the operating mode of the PHY. The possible valid resistor combinations are shown in
Table 7.1 .
„ RPU_DP_EN activates the 1.5k Ω DP pull-up resistor
„ HSTERM_EN activates the 45 Ω DP and DM high speed termination resistors
Table 7.1 DP/DM Termination vs. Signaling Mode
SIGNALING MODE
UTMI+ INTERFACE SETTINGS
RESISTOR
SETTINGS
XCVRSELECT TERMSELECT OPM
O
DE[1:0]
RPU_D
P
_
E
N
HS
TER
M
_
E
N
Tri-State Drivers Xb Xb 01b 0b 0b
Power-up 1b 0b 00b 0b 0b
Peripheral Chirp 0b 1b 10b 1b 0b
Peripheral HS 0b 0b 00b 0b 1b
Peripheral FS 1b 1b 00b 1b 0b
Peripheral HS/FS Suspend 1b 1b 00b 1b 0b
Peripheral HS/FS Resume 1b 1b 10b 1b 0b
Peripheral Test J/Test K 0b 0b 10b 0b 1b