EL2252 Elantec Semiconductor, EL2252 Datasheet - Page 10

• Manufacturer Part Number: EL2252
• Description: Dual 50 MHz Comparator/Pin Receiver
• Manufacturer: Elantec Semiconductor

Applications Information
One of the few ways in which oscillations can be
induced is by connecting a high-Q reactive source
impedance to the EL2252 inputs Such sources
are long wires and unterminated coaxial lines
The source impedance should be de-Q’ed One
method is to connect a series resistor to the
EL2252 input of around 100
ance will calm the system more effectively but at
the expense of comparator response time Anoth-
er method is to install a ‘‘snubber’’ network from
comparator input to ground A snubber is a resis-
tor in series with a small capacitor around 100
and 33 pF Each physical and electrical environ-
ment will require different treatments although
many need none
The major use of the HYS pin is to suppress
noise superimposed on the input signal By
shorting the HYS pin to V
sis is placed around the V
input Leaving the pin open or more appropri-
ately grounding the HYS pin removes all hyster-
esis Connecting a resistor between HYS and
V
hysteresis level Unfortunately an external resis-
tor cannot track the internal devices properly so
temperature and unit-to-unit variations of hys-
EL2252C
Dual 50 MHz Comparator Pin Receiver
b
allows an adjustment of the peak-to-peak
OS
b
a
value More resist-
of the comparator
g
30 mV hystere-
Contd
10
teresis are increased The relationship between
the resistor and resulting hysteresis level is not
linear but a 1 5k resistor will approximately
halve the nominal value
The time delay of the EL2252 will increase by
about 0 7 ns when using full hysteresis
The EL2252 is specifically designed to be tolerent
of large inputs It will exhibit very much in-
creased delay times for input overdrives below
100 mV If very small overdrives must be sensed
the EL2018 or EL2019 comparators would be
good choices although they lose accuracies with
signal input Slew Rates above 400 V
EL2252 keeps its timing accuracy with input
Slew Rates between 100 V
input Slew Rate
The output stage drives tens of pF load capaci-
tances without increased overshoot but propaga-
tion delay increases about 1 ns per 10 pF The
output circuit is not a traditional TTL stage and
using an external pullup resistor will not change
the V
TTL (by grounding the TTL pin) will optimize
overall propagation delay and
try
OH
In general setting the output swing to
s and 4000 V
g
swing symme-
s The
s of