EL5287CY INTERSIL [Intersil Corporation], EL5287CY Datasheet - Page 8

• Manufacturer Part Number: EL5287CY
• Description: Window 4ns High-Speed Comparator
• Manufacturer: INTERSIL [Intersil Corporation]

voltages greater than the supply voltage should be avoided
to prevent damages to the input stage.
Input Slew Rate
Most high speed comparators oscillate when the voltage of
one of the inputs is close to or equal to the voltage on the
other input due to noise or undesirable feedback. For clean
output waveform, the input must meet certain minimum slew
rate requirements. In some applications, it may be helpful to
apply some positive feedback (hysteresis) between the
output and the positive input. The hysteresis effectively
causes one comparator's input voltage to move quickly past
the other, thus taking the input out of the region where
oscillation occurs. For the EL5287, the propagation delay
increases when the input slew rate increases for low
overdrive voltages. With high overdrive voltages, the
propagation delay does not change much with the input slew
rate.
Latch Pin Dynamics
The EL5287 contains a “transparent” latch for each channel.
The latch pin is designed to be driven with either a TTL or
CMOS output. When the latch is connected to a logic high
level or left floating, the comparator is transparent and
immediately responds to the changes at the input terminals.
When the latch is switched to a logic low level, the
comparator output remains latched to its value just before
the latch’s high-to-low transition. To guarantee data
retention, the input signal must remain the same state at
least 1ns (hold time) after the latch goes low and at least 2ns
(setup time) before the latch goes low. When the latch goes
high, the new data will appear at the output in approximately
4ns (latch propagation delay).
Power Dissipation
When switching at high speeds, the comparator's drive
capability is limited by the rise in junction temperature
caused by the internal power dissipation. For reliable
operation, the junction temperature must be kept below
T
An approximate equation for the device power dissipation is
as follows. Assume the power dissipation in the load is very
small:
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JMAX
(125°C).
P
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DISS
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V
S
×
I
S
8
+
V
SD
×
I
SD
)
×
N
EL5287
where:
I
Please refer to the performance curve to choose the input
driving frequency. Having obtained the power dissipation, the
maximum junction temperature can be determined as
follows:
where:
Window Detector
If V
go high and the input in range is high. If V
range set by V
SD
V
I
V
I
N is the number of comparators in the package
T
θ
S
SD
JA
IN
S
SD
MAX
strongly depends on the input switching frequency.
is the analog quiescent supply current per comparator
is the analog supply voltage from V
is in the range of V
is the digital supply current per comparator
is the thermal resistance of the package
is the digital supply voltage from V
V
V
is the maximum ambient temperature
REFH
REFL
V
IN
REFH
T
JMAX
and V
+
+
-
-
=
REFL
T
MAX
REFL
< V
+
, the input in range is low.
Θ
IN
JA
< V
×
P
DISS
REFH
S
SD
IN
+ to V
is out of the
to ground
, both outputs
OUTH
Input In
Range
OUTL
S
-