LTC1440(RevC) View Datasheet(PDF) - Linear Technology
Part Name
Description
Manufacturer
LTC1440 Datasheet PDF : 16 Pages
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LTC1440/LTC1441/LTC1442
APPLICATIONS INFORMATION
3 IN+
4 IN–
7
V+
+
–
8 OUT
5V
5 HYST
TO
8V
R2
10k
6 REF
LTC1440
R3
2.4M
R1
430Ω
C1
1µF
V–
GND
2
1
up to 15%. If hysteresis is not wanted, the HYST pin
should be shorted to REF. Acceptable values for IREF range
from 0.1µA to 5µA. If 2.4M is chosen for R2, then the value
of R1 is equal to the value of VHB.
IREF
R1
R2
6 REF
LTC1440
5
HYST
V–
2
R1 = VHB
(2)(IREF)
( ) 1.182V – VHB
R2 =
2
IREF
1440/1/2 F04
1440/1/2 F03a
Figure 4. Programmable Hysteresis
Figure 3a. Reference Transient Response Test Circuit
8V
V+
5V
VREF
OUT
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 VIN to the noninverting comparator input. R3
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 VIN voltage trip level, in this example 4.65V.
2ms/ DIV
1440/1/2 F03b
Figure 3b. Reference and Comparator Output
Transient Response
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 – (Figure 4).
The difference between the upper and lower threshold
voltages, or hysteresis voltage band (VHB), is equal to twice
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
VIN
R2
3.4M
1%
R1
1.18M
1%
3 IN+
4 IN–
5V
7
V+
+
–
8
OUT
R3
15k
1%
R4
2.4M
1%
5 HYST
6 REF
R5
430Ω
5%
V–
C1
2
1µF
LTC1440
GND
1
1440/1/2 F05
Figure 5. Glitch-Free Level Detector with Hysteresis
144012fc
11
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