LTC4252A-1CMS#TR Linear Technology, LTC4252A-1CMS#TR Datasheet - Page 30

• Manufacturer Part Number: LTC4252A-1CMS#TR
• Description: IC CTRLR HOTSWAP NEG VOLT 10MSOP
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC4252A-1CMS#TR

• Applications: General Purpose
• Internal Switch(s): No
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
APPLICATIONS INFORMATION
Circuit Breaker with Foldback Current Limit
Figure 20 shows the LTC4252A in a foldback current limit
application. When V
current flows through resistors R4 and R5. This results in
a voltage drop across R5 and a corresponding reduction
in voltage drop across the sense resistor, R
amplifier servos the sense voltage between the SENSE
and V
through R
an output short-circuit condition. Without foldback current
limiting resistor R5, the current is limited to 3A during
analog current limit. With R5, the short-circuit current is
limited to 0.5A when V
Inrush Control Without a Sense Resistor
During Power-Up
Figure 21 shows the LTC4252A in an application where the
inrush current is controlled without a sense resistor during
power-up. This setup is suitable only for applications that
don’t require short-circut protection from the LTC4252A.
Resistor R4 and capacitor C2 act as a feedback network
to accurately control the inrush current. The C2 capacitor
can be calculated with the following equation:
where I
30
C2=
EE
I
GATE
GATE
I
INRUSH
pins to about 60mV. The short-circuit current
S
reduces as the V
= 58μA and C
•C
(SHORT PIN)
L
–48RTN
–48RTN
OUT
–48V
OUT
is shorted to the –48V RTN supply,
*FMMT493
30.1k
392k
1%
1%
L
R1
R2
is shorted to 71V.
is the total load capacitance.
OUT
voltage increases during
C1
10nF
**DIODES, INC
†
RECOMMENDED FOR HARSH ENVIRONMENTS
Figure 19. Power Limit Circuit Breaking Application
C
0.68μF
T
S
10
, as the ACL
9
8
3
UV
OV
TIMER
SS
C
68nF
SS
LTC4252A-1
(19)
V
V
EE
IN
5
1
R
3× 1.8k
1/4W EACH
IN
PWRGD
SENSE
D
DDZ13B
DRAIN
GATE
IN
†
Capacitor C3 and resistor R4 prevent Q1 from momen-
tarily turning on when the power pins first make contact.
Without C3 and R4, capacitor C2 pulls the gate of Q1 up
to a voltage roughly equal to V
LTC4252A powers up. By placing capacitor C3 in parallel
with the gate capacitance of Q1 and isolating them from
C2 using resistor R4, the problem is solved. The value of
C3 is given by:
where V
and V
Diode-ORing
Figure 22 shows the LTC4252 used as diode-oring with Hot
Swap capability in a dual – 48V power supply application.
The conventional diode-OR method uses two high power
diodes and heat sinks to contain the large heat dissipation
of the diodes. With the LTC4252 controlling the external
FETs Q2 and Q3 in a diode-OR manner, the small turn-on
voltage across the fully enhanced Q2 and Q3 reduces the
power dissipation significantly.
**
2
7
6
4
C3 ≈ 35 • C2 for V
C3=
SUPPLY(MAX)
C
1μF
IN
V
GS(TH),Q1
SUPPLY(MAX)
V
GS(TH),Q1
R4
38.3k
D1
BZV85C43
R
10Ω
C
C
10nF
C
is the MOSFET’s minimum gate threshold
is the maximum operating input voltage.
R6 27Ω
R
D
1M
SUPPLY(MAX)
R5
100k
• C2+C
(
*
+
GD(Q1)
EE
Q1
IRF530S
V
R
0.02Ω
425212 F19
OUT
S
C
100μF
• C2/C
= 71V
L
EN
LOAD
)
GS(Q1)
before the
425212fc
(20)