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Philips Semiconductors
USB 2-port hub
V
DD
UPSTREAM-
DIFFERENTIAL
DATA
V
SS
DOWNSTREAM-
DIFFERENTIAL
DATA
V
SS
A. DOWNSTREAM HUB DELAY
SOP DISTORTION
t
= t
(SOP) – t
SOP
HDD
LOW SPEED TIMINGS ARE DETERMINED IN THE SAME WAY FOR:
t
AND t
LHDD
LSOP
V
DD
UPSTREAM-
DIFFERENTIAL
DATA
V
SS
t
EOP–
DOWNSTREAM-
DIFFERENTIAL
DATA
V
SS
A. DOWNSTREAM EOP DELAY
1999 Jul 22
CROSSOVER
POINT
CROSSOVER
POINT
Hub Delay
Downstream
t
HDD
(NEXT J)
HDD
Figure 2. Hub Differential Data Delay and SOP distortion
CROSSOVER
POINT
EXTENDED
t
EOP+
CROSSOVER
POINT
EXTENDED
EOP DELAY
t
= t
EOPD
EOP–
EOP DELAY RELATIVE TO t
HDD
t
= t
– t
EOPDR
EOPD
HDD
EOP SKEW
t
= t
– t
HESK
EOP+
EOP–
LOW SPEED TIMINGS ARE DETERMINED IN THE SAME WAY FOR:
t
, t
, AND t
LEOPD
LEOPDR
LHESK
Figure 3. Hub EOP Delay and EOP Skew
CROSSOVER
POINT
DOWNSTREAM
DIFFERENTIAL
DATA
UPSTREAM
DIFFERENTIAL
DATA
B. UPSTREAM HUB DELAY
DOWNSTREAM
PORT
UPSTREAM
END OF CABLE
B. UPSTREAM EOP DELAY
22
Product specification
PDIUSBH12
CROSSOVER
POINT
Hub Delay
Upstream
t
HDD
SV00514
CROSSOVER
POINT
EXTENDED
t
t
EOP–
EOP+
CROSSOVER
POINT
EXTENDED
SV00515
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