LTC1445 Linear Technology, LTC1445 Datasheet - Page 7

• Manufacturer Part Number: LTC1445
• Description: Ultralow Power Quad Comparators with Reference
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
PI FU CTIO S
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 0.01 F capacitor
without oscillation. The comparator CMOS outputs
(LTC1443/LTC1445) can source up to 40mA while the
LTC1444 has an open-drain output to V
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
allows single supply operation. If the comparator output
is required to source more than 1mA or the supply source
impedance is high, V
capacitor.
Comparator Inputs
The comparator inputs can swing from the negative sup-
ply (V
(V
V
is only 10pA.
Comparator Outputs
The LTC1443 comparator output swings between GND
and V
LTC1444 and LTC1445 outputs swing between 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 during transi-
OUT D (Pin 15): Comparator D Output. (Open-drain
output for LTC1444). Output can source up to 40mA
(LTC1443, LTC1445) and sink 5mA.
+
+
U
without damage, and the typical input leakage current
). The inputs can be forced 300mV below V
+
–
to assure TTL compatibility with a split supply. The
) to within 1.3V maximum of the positive supply
U
U
U
+
should be bypassed with a 0.1 F
U
–
to GND on the LTC1443
W
–
. The supply
U
–
–
or above
and V
+
.
OUT C (Pin 16): Comparator C Output. (Open-drain output
for LTC1444). Output can source up to 40mA (LTC1443,
LTC1445) and sink 5mA.
tions 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
It can source up to 200 A and sink up to 15 A with a 5V
supply. The reference can drive a bypass 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.
–
. The reference accuracy is 1.5% from – 40 C to 85 C.
Figure 2. Damping Resistance vs Bypass Capacitor Value
LTC1443/LTC1444/LTC1445
Figure 1. Damping the Reference Output
1000
100
0.1
10
REFERENCE
0.001
1
OUTPUT
0.01
CAPACITOR VALUE ( F)
R1
C1
0.1
V
–
LTC1443/44/45 • F01
REF
LTC144X
1
LTC1443/44/45 • F02
10
7