USBUFxxW6

8/9

Figure A13 shows the circuit used to perform measurements of the transition times. In Figure A14, we see

the results of such measurements:

trise = 3.8ns

driver alone

trise = 7.8ns

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%)

D+

D-

+5V

+5V

+5V

74HC04

+5V

Square

Pulse

Generator

74HC04

USBUF

-xxW6

VD+

Fig. A13: Typical rise and fall times: measure-

ments configuration

without

with

Fig. A14: Typical rise times with and without pro-

tection device

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 4ns-20ns stipulated USB specification limits. To verify this point, we

have measured the rise time of VD+ voltage (please refer to Fig. A13) with and without the USBUFxxW6

device.

TRANSITION TIMES