LT1719CS8 Linear Technology, LT1719CS8 Datasheet - Page 12

• Manufacturer Part Number: LT1719CS8
• Description: IC COMP R-R I/O SGL 3/5V 8-SOIC
• Manufacturer: Linear Technology
• Series: UltraFast™r
• Type: General Purposer

Specifications of LT1719CS8

• Number Of Elements: 1
• Output Type: CMOS, Rail-to-Rail, TTL
• Voltage - Supply: 2.7 V ~ 10.5 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: Q1357287

LT1719
APPLICATIONS INFORMATION
The exact amount of hysteresis will vary from part to part
as indicated in the specifi cations table. The hysteresis level
will also vary slightly with changes in supply voltage and
common mode voltage. A key advantage of the LT1719
is the signifi cant reduction in these effects, which is im-
portant whenever an LT1719 is used to detect a threshold
crossing in one direction only. In such a case, the relevant
trip point will be all that matters, and a stable offset volt-
age with an unpredictable level of hysteresis, as seen in
competing comparators, is useless. The LT1719 is many
times better than prior comparators in these regards. In
fact, the CMRR and PSRR tests are performed by check-
ing for changes in either trip point to the limits indicated
in the specifi cations table. Because the offset voltage is
the average of the trip points, the CMRR and PSRR of the
offset voltage is therefore guaranteed to be at least as good
as those limits. This more stringent test also puts a limit
12
Figure 4. Additional External Hysteresis
V
REF
R2
R1
INPUT
+
–
LT1719S8
R3
on the common mode and power supply dependence of
the hysteresis voltage.
Additional hysteresis may be added externally. The rail-
to-rail outputs of the LT1719 make this more predictable
than with TTL output comparators due to the LT1719’s
small variability of V
To add additional hysteresis, set up positive feedback
by adding additional external resistor R3 as shown in
Figure 4. Resistor R3 adds a portion of the output to the
threshold set by the resistor string. The LT1719 pulls the
outputs to + V
with light loads, and to within 400mV with heavy loads.
For the load of most circuits, a good model for the voltage
on the right side of R3 is 300mV or +V
total voltage swing of (+V
– 600mV.
1719 F04
S
and ground to within 200mV of the rails
OH
(output high voltage).
S
– 300mV) – (300mV) = +V
S
– 300mV, for a
1719fa
S