LTC1440 LINER [Linear Technology], LTC1440 Datasheet - Page 8

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

LTC1440/LTC1441/LTC1442
APPLICATIONS
Hysteresis
Hysteresis can be added to the LTC1440 by connecting a
resistor (R1) between the REF and HYST pins and a
second resistor (R2) from HYST to V
The difference between the upper and lower threshold
voltages, or hysteresis voltage band (V
the voltage difference between the REF and HYST pins.
When more hysteresis is added, the upper threshold
increases the same amount as the low threshold de-
creases. The maximum voltage allowed between REF and
HYST pins is 50mV, producing a maximum hysteresis
voltage band of 100mV. The hysteresis band could vary by
8
TO
5V
8V
Figure 3a. Reference Transient Response Test Circuit
V
Figure 3b. Reference and Comparator Output
Transient Response
+
V
OUT
REF
8V
5V
R3
2.4M
10k
R2
U
R1
430
C1
1 F
INFORMATION
3
4
5
6
U
2ms/DIV
IN
IN
HYST
REF
–
+
V
2
+
–
–
W
V
+
HB
LTC1440
–
7
(Figure 4).
GND
), is equal to twice
1440/1/2 F03b
1
U
8
1440/1/2 F03a
OUT
up to 15%. If hysteresis is not wanted, the HYST pin
should be shorted to REF. Acceptable values for I
from 0.1 A to 5 A. If 2.4M is chosen for R2, then the value
of R1 is equal to the value of V
Level Detector
The LTC1440 is ideal for use as a micropower level
detector as shown in Figure 5. R1 and R2 form a voltage
divider from V
and R4 set the hysteresis voltage, and R5 and C1 bypass
the reference output. The following design procedure can
be used to select the component values:
1. Choose the V
V
IN
Figure 5. Glitch-Free Level Detector with Hysteresis
R2
3.4M
1%
R1
1.18M
1%
I
REF
R4
2.4M
1%
Figure 4. Programmable Hysteresis
R1
R2
15k
IN
1%
R3
IN
to the noninverting comparator input. R3
voltage trip level, in this example 4.65V.
6
5
R5
430
5%
HYST
REF
C1
1 F
LTC1440
3
4
5
6
V
IN
IN
HYST
REF
–
2
–
+
HB
V
2
+
–
–
.
5V
V
R1 =
R2 =
+
LTC1440
7
GND
(2)(I
1.182V –
V
1
HB
REF
I
REF
1440/1/2 F04
)
V
1440/1/2 F05
2
HB
8
REF
OUT
range