LTC1440 LINER [Linear Technology], LTC1440 Datasheet - Page 7

• Manufacturer Part Number: LTC1440
• Description: Ultralow Power Single/Dual Comparator with Reference
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
LTC1440/LTC1441/LTC1442 are a family of micropower
comparators with built-in 1.182V reference. Features
include programmable hysteresis (LTC1440/LTC1442),
wide supply voltage range (2V to 11V) and the ability of the
reference to drive up to a 0.01 F capacitor without oscil-
lation. The comparators’ CMOS outputs can source up to
40mA and the supply current glitches, that normally occur
when switching logic states, have been eliminated.
Power Supplies
The comparator family operates from a single 2V to 11V
supply. The LTC1440 includes a separate ground for the
comparator output stage, allowing a split supply ranging
from 1V to 5.5V. Connecting V
will allow single supply operation. If the comparator out-
put is required to source more than 1mA, or the supply
source impedance is high, V
0.1 F capacitor.
Comparator Inputs
The comparator inputs can swing from the negative sup-
ply V
inputs can be forced 300mV below V
damage and the typical input leakage current is only
Comparator Outputs
The LTC1440 comparator output swings between GND
and V
LTC1441 and LTC1442 outputs swing between V
The outputs are capable of sourcing up to 40mA and
sinking up to 5mA while still maintaining microampere
quiescent currents. The output stage does not generate
crowbar switching currents during transitions which helps
minimize parasitic feedback through the supply pins.
Voltage Reference
The internal bandgap reference has a voltage of 1.182V
referenced to V
– 40 C to 85 C. It can source up to 200 A and sink up to
20 A with a 5V supply. The reference can drive a bypass
10pA.
–
+
to within 1.3V max of the positive supply V
to assure TTL compatibility with a split supply. The
–
. The reference accuracy is 1.5% from
U
INFORMATION
U
+
should be bypassed with a
–
to GND on the LTC1440
W
–
or above V
U
+
–
without
and V
+
. The
+
.
capacitor of up to 0.01 F without oscillation and by
inserting a series resistor, capacitance values up to 100 F
can be used (Figure 1).
Figure 2 shows the resistor value required for different
capacitor values to achieve critical damping. Bypassing
the reference can help prevent false tripping of the com-
parators by preventing glitches on V
transients from disturbing the reference output voltage.
Figure 3 shows the bypassed reference output with a
square wave applied to the V
10mV of hysteresis voltage band while R1 damps the
reference response. Note that the comparator output
doesn’t trip.
Figure 2. Damping Resistance vs Bypass Capacitor Value
LTC1440/LTC1441/LTC1442
REFERENCE
Figure 1. Damping the Reference Output
1000
100
OUTPUT
0.1
10
0.001
1
0.01
CAPACITOR VALUE ( F)
R1
C1
+
0.1
pin. Resistors R2 and R3 set
REF
V
LTC144X
–
1440/1/2 F01
1
+
or reference load
1440/1/2 F02
10
7