LTC1443/LTC1444/LTC1445
8
144345fe
applicaTions inForMaTion
The LTC1443/LTC1444/LTC1445 is a family of quad
micropower comparators with a built-in reference (1.182V
for the LTC1443 and 1.221V for the LTC1444/LTC1445).
Features include programmable hysteresis (LTC1444/
LTC1445), wide supply voltage range (2V to 11V) and the
ability of the reference to drive up to a 0.01µF capacitor with-
out oscillation. The comparator CMOS outputs (LTC1443/
LTC1445) can source up to 40mA while the LTC1444 has
an open-drain output to V
–
. The supply current glitches
that normally occur when the comparator output switches
states have been eliminated.
Power Supplies
The comparator family operates from a single 2V to 11V
supply. The LTC1443 includes a separate ground for the
comparator output stage, allowing a split supply ranging
from ±1V to ±5.5V. Connecting V
–
to GND on the LTC1443
allows single supply operation. If the comparator output
is required to source more than 1mA or the supply source
impedance is high, V
+
should be bypassed with a 0.1µF
capacitor.
Comparator Inputs
The comparator inputs can swing from the negative sup-
ply (V
–
) to within 1.3V maximum of the positive supply
(V
+
). The inputs can be forced 300mV below V
–
or above
V
+
without damage, and the typical input leakage current
is only ±10pA.
Comparator Outputs
The LTC1443 comparator output swings between GND
and V
+
to assure TTL compatibility with a split supply.
The LTC1444 and LTC1445 outputs swing between V
–
and V
+
. The outputs are capable of sourcing up to 40mA
(LTC1443/LTC1445) and sinking up to 5mA while still
maintaining microampere quiescent currents. The output
stage does not generate crowbar switching currents dur-
ing transitions which helps minimize parasitic feedback
through the supply pins.
Voltage Reference
The internal bandgap reference has a voltage of 1.182V for
LTC1443 or 1.221V for LTC1444/LTC1445 referenced to
V
–
. The reference accuracy is 1.5% from –40°C to 85°C.
It can source up to 200µA and sink up to 15µA with a 5V
supply. The reference can drive a bypass capacitor of up to
0.01µF without oscillation and by inserting a series resistor,
capacitance values up to 100µF can be used (Figure 1).
Figure 2 shows the resistor value required for different
capacitor values to achieve critical damping.
CAPACITOR VALUE (µF)
0.001
0.1
RESISTOR VALUE (kΩ)
10
1000
0.01 0.1 101
144345 F02
1
100
Figure 2. Damping Resistance vs Bypass Capacitor Value
LTC144X
V
–
REF
R1
C1
REFERENCE
OUTPUT
144345 F01
1.2V
+
–
Figure 1. Damping the Reference Output
