LT1720/LT1721
4
17201fc
TYPICAL PERFORMANCE CHARACTERISTICS
SUPPLY VOLTAGE (V)
2.5
V
OS
AND TRIP POINT VOLTAGE (mV)
3
2
1
0
–1
–2
–3
4.0 5.0
17201 G01
3.0 3.5
4.5 5.5 6.0
V
TRIP
+
V
OS
V
TRIP
–
25°C
V
CM
= 1V
TEMPERATURE (°C)
–3
V
OS
AND TRIP POINT VOLTAGE (mV)
–1
1
3
–2
0
2
–25 25 100
17201 G02
–50 0 50 75 125
V
TRIP
+
V
OS
V
TRIP
–
TEMPERATURE (°C)
–50
3.6
3.8
4.2
25 75
17201 G03
0.2
0
–25 0
50 100 125
–0.2
–0.4
4.0
COMMON MODE INPUT VOLTAGE (V)
V
CC
= 5V
Input Offset and Trip Voltages
vs Supply Voltage
Input Offset and Trip Voltages
vs Temperature
Input Common Mode Limits
vs Temperature
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: If one input is within these common mode limits, the other input
can go outside the common mode limits and the output will be valid.
Note 3: The LT1720/LT1721 comparators include internal hysteresis.
The trip points are the input voltage needed to change the output state in
each direction. The offset voltage is defi ned as the average of V
TRIP
+
and
V
TRIP
–
, while the hysteresis voltage is the difference of these two.
Note 4: The common mode rejection ratio is measured with V
CC
= 5V
and is defi ned as the change in offset voltage measured from V
CM
= –0.1V
to V
CM
= 3.8V, divided by 3.9V.
Note 5: The power supply rejection ratio is measured with V
CM
= 1V and
is defi ned as the change in offset voltage measured from V
CC
= 2.7V to
V
CC
= 6V, divided by 3.3V.
ELECTRICAL CHARACTERISTICS
The l denotes specifi cations that apply over the full operating temperature
range, otherwise specifi cations are at T
A
= 25°C. V
CC
= 5V, V
CM
= 1V, C
OUT
= 10pF, V
OVERDRIVE
= 20mV, unless otherwise specifi ed.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Δt
PD
Differential Propagation Delay (Note 9) Between Channels 0.3 1.0 ns
t
SKEW
Propagation Delay Skew (Note 10) Between t
PDLH
/t
PDHL
0.5 1.5 ns
t
r
Output Rise Time 10% to 90% 2.5 ns
t
f
Output Fall Time 90% to 10% 2.2 ns
t
JITTER
Output Timing Jitter V
IN
= 1.2V
P-P
(6dBm), Z
IN
= 50Ω t
PDLH
V
CM
= 2V, f = 20MHz t
PDHL
15
11
ps
RMS
ps
RMS
f
MAX
Maximum Toggle Frequency V
OVERDRIVE
= 50mV, V
CC
= 3V
V
OVERDRIVE
= 50mV, V
CC
= 5V
70.0
62.5
MHz
MHz
Note 6: Because of internal hysteresis, there is no small-signal region
in which to measure gain. Proper operation of internal circuity is ensured
by measuring V
OH
and V
OL
with only 10mV of overdrive.
Note 7: Propagation delay measurements made with 100mV steps.
Overdrive is measured relative to V
TRIP
±
.
Note 8: t
PD
cannot be measured in automatic handling equipment with
low values of overdrive. The LT1720/LT1721 are 100% tested with a
100mV step and 20mV overdrive. Correlation tests have shown that
t
PD
limits can be guaranteed with this test, if additional DC tests are
performed to guarantee that all internal bias conditions are correct.
Note 9: Differential propagation delay is defi ned as the larger of the two:
Δt
PDLH
= t
PDLH(MAX)
– t
PDLH(MIN)
Δt
PDHL
= t
PDHL(MAX)
– t
PDHL(MIN)
where (MAX) and (MIN) denote the maximum and minimum values
of a given measurement across the different comparator channels.
Note 10: Propagation Delay Skew is defi ned as:
t
SKEW
= |t
PDLH
– t
PDHL
|
