LTC4251 LINER [Linear Technology], LTC4251 Datasheet - Page 17

• Manufacturer Part Number: LTC4251
• Description: Negative Voltage Hot Swap Controllers in SOT-23
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
SENSE pin is less than V
exceeds V
up and GATE pulls down immediately. In Figure 12c,
multiple momentary faults cause the TIMER capacitor to
integrate until it latches.
Analog Current Limit and Fast Current Limit
In Figure 13a, when SENSE exceeds V
lated by the analog current limit amplifier loop. When
SENSE drops below V
Figure 13b, when a severe fault occurs, SENSE exceeds
V
FCL
and GATE immediately pulls down until the analog
TMRH
, TIMER is latched high by the 5.8µA pull-
Figure 10. Undervoltage Timing with an Overvoltage Glitch (All Waveforms are Referenced to V
SENSE
U
TIMER
UV/0V
SENSE
GATE
TIMER
UV/0V
GATE
ACL
V
Figure 9. Undervoltage Lockout Timing (All Waveforms are Referenced to V
UVHI
V
V
UVLO
CB
, GATE is allowed to pull up. In
U
OVHI
. In Figure 12b, when TIMER
1
1
V
V
UV/0V
2
UV/0V
3
V
2
UV/0V
V
V
CLEARS V
V
UV/0V
V
OVLO
DROPS BELOW V
UV/0V
UVHI
W
OVERSHOOTS V
DROPS BELOW V
CLEARS V
ACL
UVHI
INITIAL TIMING CYCLE
INITIAL TIMING CYCLE
. CHECK TIMER < V
, GATE is regu-
5.8µA
UVHI
UVLO
5.8µA
OVHI
, CHECK TIMER < V
. TIMER, GATE, AND SENSE ARE PULLED TO V
OVLO
U
AND TIMER ABORTS INITIAL TIMING CYCLE.
AND TIMER RESTARTS INITIAL TIMING CYCLE.
TMRL
V
, GATE < V
V
TMRH
TMRH
TMRL
V
TMRL
V
, GATE < V
TMRL
GATEL
4 5
current amplifier can establish control. If TIMER reaches
V
Resetting a Fault Latch
As shown in Figure 14, a latched fault is reset by either
pulling UV/OV below V
An initial timing cycle is initiated if UV/OV is used for reset.
If TIMER is used for reset, the initial timing cycle is skipped.
Internal Soft-Start
An internal soft-start feature ramps the positive input of
the analog current limit amplifier during initial start-up.
58µA
3
58µA
AND SENSE < V
TMRH
START-UP CYCLE
GATEL
4
START-UP CYCLE
TIMER CLEARS V
6 7
TIMER CLEARS V
5 6
230µA
230µA
AND SENSE < V
, GATE pulls low and latches off.
8 9
EE
7 8 9
CB
.
58µA
10
.
58µA
TMRL
V
V
TMRL
V
V
ACL
CB
CB
ACL
CB
, CHECK GATE < V
.
LTC4251/LTC4251-1/
, CHECK GATE < V
5.8µA
5.8µA
UVLO
GATEL
GATEL
AND SENSE < V
or pulling TIMER below V
AND SENSE < V
5.8µA
425112 F10
5.8µA
425112 F09
EE
)
CB
CB
LTC4251-2
.
.
EE
)
17
425112fa
TMRL
.