Technical information
USBUFxxW6
2.6
Transition times
This low pass filter has been designed in order to meet the USB 1.1 standard requirements
that implies the signal edges are maintained within the 4 -20 ns stipulated USB specification
limits. To verify this point, we have measured the rise time of VD+ voltage with and without
the USBUFxxW6 device.
Figure 14. Typical rise and fall times:
measurement configuration
Figure 15. Typical rise times with and
without protection device
without
74HC04
D+
+5V
+5V
+5V
74HC04
Square
Pulse
Generator
USBDF
01W6
D-
with
shows the circuit used to perform measurements of the transition times. In
we see the results of such measurements:
trise = 3.8 ns driver alone
trise = 7.8 ns with protection device
The adding of the protection device causes the rise time increase of roughly 4ns.
Note:
Rise time has been measured between 10% and 90% of the signal (resp. 90% and 10%)
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