LTC1421 LINER [Linear Technology], LTC1421 Datasheet - Page 10

• Manufacturer Part Number: LTC1421
• Description: Hot Swap Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
LTC1421/LTC1421-2.5
Figure 8c shows how the comparator can be used to
generate a reset when the 12V supply (V
below 10.8V. The 5V supply (V
reset when it dips below 4.65V. When the 12V supply
drops below 10.8V, COMPOUT will pull the FB pin low
setting the internal threshold voltage for comparator 1 to
5.88V. Since V
ately goes low and a reset is generated 200ms later.
Figure 8d shows how the comparator can be used to
override the internal reset voltage for a 5V supply on
V
10
OUTLO
6
7
6
7
V
V
CCLO
CCLO
Figure 8c. Reset 12V at 10.8V, Reset 5V at 4.65V
.
V
V
20 A
20 A
CCLO
CCLO
Figure 8b. Monitor 5V, Reset 3.3V at 2.9V
20 A
20 A
TIMING
TIMING
RESET
1.232V
1.232V
RESET
OUTLO
COMP1
COMP1
U
is less than 5.88V, PWRGD immedi-
–
+
–
+
INFORMATION
U
3.3V
COMP2
COMP2
5V
20
20
OUTLO
73.5k
26.7k
73.5k
26.7k
W
71.5k
71.5k
LTC1421
LTC1421
) also generates a
+
–
+
–
1421 F08b
16
11
15
13
14
8
1421 F08c
16
11
15
13
14
8
OUTHI
U
10k
5%
) drops
12V
5V
107k
1%
38.3k
1%
107k
1%
13.7k
1%
internal threshold to about 2.9V. The new reset threshold
voltage is set by the external resistive divider connected to
COMP2. When V
COMPOUT pulls FB to ground, changing the internal
threshold at COMP1 to 5.88V and generating a reset.
Finally, the comparator may be used to monitor a negative
supply as shown in Figure 8e. The external resistor divider
A 5k resistor is tied from the FB pin to V
6
7
6
7
V
V
CCLO
Figure 8e. Monitor – 12V at – 10.8V, Reset 5V at 4.65V
CCLO
V
20 A
V
20 A
CCLO
CCLO
20 A
20 A
TIMING
RESET
1.232V
TIMING
1.232V
RESET
Figure 8d. Reset 5V at 4.5V
OUTLO
COMP1
COMP1
drops below the new threshold,
–
+
–
+
COMP2
COMP2
5V
5V
20
20
73.5k
26.7k
73.5k
26.7k
71.5k
71.5k
LTC1421
LTC1421
+
–
+
–
OUTLO
1421 F08e
1421 F08d
16
11
15
13
14
8
16
11
15
13
14
8
– 12V
, setting the
5%
12V
12V
5k
13.7k
1%
107k
1%
10k
5%
102k
1%
38.3k
1%