VBUS054B-HS3
Vishay Semiconductors
One mode of use is,…
in the very first moment before any pulses have
arrived, all three diodes are completely discharged
(so the diode capacitances are empty of charge) the
first signal pulse with an amplitude > 0.5 V will drive
the upper PN-diode (D
1
) in a forward direction and
"sees" the empty capacitance of the Z-diode (ZD).
Depending on the duration of this pulse and the pause
to the next one the Z-diodes capacitance can be
charged up so that the next pulse "sees" a lower
capacitance. After some pulses the big Z-diode could
be completely charged up so that the following pulses
just see the small capacitance of both PN-diodes.
For some application this can work perfectly.....
For others applications the capacitance must be the
same all the time from the first till the last pulse.
For these applications the appropriate mode of use is
to connect the Z-diode to the supply voltage.
In this mode the Z-diode is charged up immediately by
the supply voltage and both PN-diodes are always
used in reverse. This keeps their capacitance at a
minimum.
D
1
ZD
I/O
D
2
Gnd
20405
V
BUS
D
1
ZD
I/O
D
2
Gnd
20406
www.vishay.com
6
For technical support, please contact: ESD-Protection@vishay.com
Document Number 81586
Rev. 1.4, 07-Oct-08
VISHAY [ VISHAY TELEFUNKEN ]
