ltc4253a-adj Linear Technology Corporation, ltc4253a-adj Datasheet - Page 30

• Manufacturer Part Number: ltc4253a-adj
• Description: 48v Hot Swap Controller With Sequencer
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
LTC4253A-ADJ
reflected in V
zero. V
when V
time point 6. SEL tied low chooses this SS servo mode
during soft-start while SEL set high allows the SS pin to do
an open-loop ramp-up as in Figures 15a and 15b. The
stability of the SS servo loop requires a C
Large values of C
time-out as V
tial during the circuit breaker delay. The load capacitor is
unable to achieve full charge in one GATE start-up cycle.
A more serious side effect of a large C
duration may be exceeded during soft-start into a low
impedance load. A soft-start voltage below V
activate the circuit breaker TIMER.
Power Limit Circuit Breaker
Figure 16 shows the LTC4253A-ADJ in a power limit
circuit breaking application. The SENSE pin is modulated
by board voltage V
set to be the same as the lowest operating voltage,
V
operating voltage, V
power as available at V
30
SUPPLY(MIN)
– 48V RTN
(LONG PIN)
RESET
(LONG PIN)
– 48V RTN
(SHORT PIN)
– 48V
(LONG PIN)
SENSE
ACL
2.05k
20k
1%
1%
(t) already has a substantial offset from zero at
R2
R1
does not show a large kink as in Figure 15b
ACL
SENSE
= 43V. If the goal is to have the high supply
2k
1%
255k
1%
(t) may marginally exceed the V
SS
SUPPLY
C1
10nF
R3
) that ramps up smoothly from near
U
can cause premature circuit breaker
0.1µF
C
SUPPLY(MAX)
C
SQ
SS
SUPPLY(MIN)
33nF
. The zener voltage, V
U
C
0.68µF
T
UVL
UV
OVL
OV
SS
SQTIMER
TIMER
20k(1/4W)/2
RESET
LTC4253A-ADJ
SEL
10k
R
IN
PWRGD1
PWRGD2
PWRGD3
, then resistors R4 and
= 71V give the same
V
V
SENSE
DRAIN
IN
EE
W
GATE
BZV85C43
EN3
EN2
SS
Figure 16. Power Limit Circuit Breaker Application
value is that SOA
31.6k
D1
R4
SS
1µF
> 5nF.
C
22Ω
IN
R5
R9 22k
CB
Z
U
CB
of D1, is
will not
10nF
poten-
C
C
R
Q2
FZT857
D
R6
2.2k
1M
R
10Ω
C
†
Q1
IRF530S
R
0.02Ω
R5 are selected by:
If R5 is 22Ω, then R4 is 31.6k. The peak circuit breaker
power limit is:
when V
The peak power at the fault current limit occurs at the
supply overvoltage threshold. The fault current limited
power is:
POWER MAX
S
R7
2.2k
POWER FAULT
R
R
(
EN2
V
5
4
V
SUPPLY
IN1
†
=
R
SUPPLY
V
†
(
S
IN1
V
SUPPLY MAX
(
R8
2.2k
)
100µF
)
V
•
= 0.5 • (V
= 57V
C2
CB
=
=
⎡
⎢
⎣
•
†
V
+
POWER AT V
(
1 064
(
4
ACL
V
.
)
0.1µF
•
SUPPLY MIN
=
C3
POWER
MODULE 1
OUTPUT
V
)
−
SUPPLY MIN
•
(
SUPPLY(MIN)
POWER AT V
V
SUPPLY
MODULE 1
EN
(
POWER
EN3
(
SUPPLY MIN
)
+
)
−
V
•
SUPPLY MAX
†
V
V
V
+ V
†
MOC207
IN1
Z
SUPPLY MAX
(
SUPPLY MIN
) •
EN
MODULE 2
SUPPLY(MAX)
MODULE 2
POWER
OUTPUT
POWER
R
R
)
(
5
4
4253A F16
⎤
⎥
⎦
(
(
)
)
EN
2
)
4253a-adjf
)
LOAD 3
(17)
(18)
)
(19)