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TCM series
1005,1210,1608, 2010 type
TDK CORPORATION
2
TCM
Offering the optimal frequency characteristic for
USB2.0(480Mbps) and IEEE1394(400Mbps/100Mbps)
Requirements of USB2.0 regarding transmission waveform
DEVICE
HUB
USB2.0
Controller
IC
USB2.0
Controller
IC
USB Cable
TP4
TP3
TP2
TP1
DATA
D+/ D- lines
480Mbps
VDD
D+
D-
FG
USB2.0
CONTROLLER
TCM1005,1210
Chip Bead
Four observational points of
eye-pattern standard
While USB2.0 transmits data in 400mVp-p differential
signals, the eye-pattern standard, as shown in the
diagram below, represents the templates specifying
the limitation ranges of waveform distortion at four
observational points on the standard transmission
model connected by a USB cable between the
transmitting (HUB) and receiving sides (DEVICE).
It is required that the transmission waveform
does not enter the red area on the template.
Satisfying the USB2.0 eye pattern standard, SYNC
field (32 bit interval signal) standard with the industry's
highest-level performance, offers an ideal imped-
ance characteristic without distorting the speed
signal waveform, even with IEEE1394.
Of course, superb absorption /stabilization effects
against the common-mode elements (skew fluctua-
tion) due to the phase lag, or voltage difference of
differential signals, are offered, making it optimal as
a countermeasure against the radiation from the
VDS lines of laptop PCs and high- definition digital
display DVI lines, and for reinforcing the immunity.
Diverse standards are set for USB2.0 in order to pre-
vent operational troubles. The eye-pattern standard,
where the allowable range of transmitted differen-
tial signal waveform is specified, and the require-
ment of the first bit's voltage lower limit of the 32bit
interval signal (SYNC field), which is sent at the start
of every data transmission, should be especially con-
sidered in connection with EMI countermeasures.
The template TP1 at the USB2.0 transreceiver output end of the transmitting
side is strictest; TP2, TP3, and TP4 are less strict: the further they are from the
output end, the less strict. Also, the longer the cable length is, the smaller
the pulse voltage width (D+ and D- values) of the operational signal will
become due to cable resistance.