Datasheet

6
LTC1540
sn1540 1540fas
APPLICATIONS INFORMATION
WUU
U
V
+
R1
430Ω
R2
10k
C1
1µF
5V
TO
8V
OUT
V
–
21
7
8
GND
LTC1540
1540 • F03a
IN
+
IN
–
HYST
REF
3
4
5
6
R3
2.4M
–
+
LTC1540
V
–
REF
R1
C1
REFERENCE
OUTPUT
1540 • F01
Figure 1. Damping the Reference Output
Figure 2. Damping Resistance vs Bypass Capacitor Value
Figure 3 shows the bypassed reference output with a
square wave applied to the V
+
pin. Resistors R2 and R3 set
10mV of hysteresis voltage band while R1 damps the
reference response. Note that the comparator output
doesn’t trip.
Low Voltage Operation: V
+
= 1.6V
The guaranteed minimum operating voltage is 2V (or
±1V). As the total supply voltage is reduced below 2V, the
performance degrades and the supply current falls. At low
supply voltages, the comparator’s output drive is reduced
and the propagation delay increases. The V
REF
and V
OS
are
also slightly worse. The useful input voltage range extends
from the negative supply to 0.9V below the positive
supply. Test your prototype over the full
temperature and supply voltage range if operation below
2V is anticipated. Because of the increase in supply
current, operation below 1.5V is not recommended
(Figure 4).
Figure 4. Supply Current vs Supply Voltage
SUPPLY VOLTAGE (V)
0
SUPPLY CURRENT (µA)
3
4
5
2.0
1540 F04
2
1
0
0.5
1.0
1.5
2.5
V
–
= GND = 0V
IN
+
= 0V
IN
–
= REF = HYST
T
A
= 25°C
Figure 3a. Power Supply Transient Test Circuit
CAPACITOR VALUE (µF)
0.001
0.1
RESISTOR VALUE (kΩ)
10
1000
0.01 0.1 101
1540 • F02
1
100
Figure 3b. Power Supply Transient Rejection
2mV/DIV
2ms/DIV 1540 F03b
8V
V
+
5V
V
REF
OUT