LTC4253AIGN#TR Linear Technology, LTC4253AIGN#TR Datasheet - Page 14

• Manufacturer Part Number: LTC4253AIGN#TR
• Description: MS-Hot Swap/High Voltage, Neg. 48V Hot Swap With 1% UV, Sequencer
• Manufacturer: Linear Technology

Specifications of LTC4253AIGN#TR

• Family Name: LTC4253A
• Package Type: SSOP N
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3.99mm
• Product Height (mm): 1.5mm
• Mounting: Surface Mount
• Pin Count: 16
• Lead Free Status / Rohs Status: Not Compliant

APPLICATIO S I FOR ATIO
LTC4253/LTC4253A
SHUNT REGULATOR
A fast responding regulator shunts the LTC4253/LTC4253A
V
current limiting resistor. The shunt regulator clamps V
to 13V (V
supply transients and contributes a short delay at start-up.
R
current and the drive required for three optocouplers used
by the PWRGD signals. Higher current through R
in higher dissipation for R
well as higher V
NPN buffer as in Figure 3, V
cascodes as in Figure 17 or V
MOSFET cascodes replacing the NPNs in Figure 17. Mul-
tiple 1/4W resistors can replace a single higher power R
resistor.
INTERNAL UNDERVOLTAGE LOCKOUT (UVLO)
A hysteretic comparator, UVLO, monitors V
undervoltage. The thresholds are defined by V
hysteresis V
enabled; below (V
pulled low. The UVLO function at V
14
IN
IN
pin. Power is derived from – 48RTN by an external
should be chosen to accommodate both V
– 48V RTN
(LONG PIN)
– 48V RTN
(SHORT PIN)
– 48V
(LONG PIN)
30.1k
392k
Z
1%
1%
R2
R1
). A 1µF decoupling capacitor at V
LKH
IN
47k
. When V
R9
noise. Alternative circuits are V
LKO
U
– V
C1
10nF
IN
0.1µF
LKH
C
C
RESET
U
PUSH
IN
IN
SS
SQ
rises above V
33nF
driving base resistors of NPN
and LTC4253/LTC4253A as
), it is disabled and GATE is
20k(1/4W)/2
C
0.68µF
UV
OV
RESET
SS
SQTIMER
TIMER
T
IN
10k
R
LTC4253A
W
driving the gates of
IN
V
V
EE
Figure 3. –48V/2.5A Application for the LTC4253A
IN
PWRGD1
PWRGD2
PWRGD3
IN
SENSE
DRAIN
GATE
LKO
EN3
EN2
should not be
1µF
C
IN
, the chip is
LKO
U
IN
IN
R3 22k
IN
IN
with an
results
supply
and its
IN
R
(Refer to Block Diagram)
filters
R
10Ω
D
C
C
10nF
1M
C
for
Q2
FZT857
IN
IN
R4
2.2k
Q1
IRF530S
R
0.02Ω
†
S
confused with the UV and OV pins. These are completely
separate functions.
UV/OV COMPARATORS (LTC4253)
A UV hysteretic comparator detects undervoltage condi-
tions at the UV pin, with the following thresholds:
An OV hysteretic comparator detects overvoltage condi-
tions at the OV pin, with the following thresholds:
The UV and OV trip point ratio is designed to match the
standard telecom operating range of 43V to 82V when
connected together as in the Typical Application. A resis-
tive divider is used to scale the supply voltage. Using 402k
and 32.4k gives a typical operating range of 43.2V to 82.5V.
The undervoltage shutdown and overvoltage recovery
thresholds are then 39.2V and 78.4V. 1% divider resistors
are recommended to preserve threshold accuracy.
UV low-to-high (V
UV high-to-low (V
OV low-to-high (V
OV high-to-low (V
EN2
R5
2.2k
V
IN1
V
†
†
IN1
R6
2.2k
100µF
R7
†
C
L
+
UVHI
UVLO
OVHI
OVLO
POWER
MODULE 1
OUTPUT
) = 3.225V
) = 6.150V
) = 2.925V
) = 5.850V
EN3
MODULE 1
EN
POWER
†
V
MOC207
†
IN1
MODULE 2
EN
MODULE 2
OUTPUT
POWER
POWER
R8
MODULE 3
EN
POWER
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