LT4250L Datasheet, PDF (1/12 Pages) Linear Technology – Negative 48V Hot Swap Controller

LT4250L/LT4250H
Negative 48V
Hot Swap Controller
FEATURES
s _{Allows Safe Board Insertion and Removal}
from a Live – 48V Backplane
s _{Circuit Breaker Immunity to Voltage Steps and}
Current Spikes
s _{Programmable Inrush and}
Short-Circuit Current Limits
s _{Pin Compatible with LT1640L/LT1640H}
s _{Operates from –20V to – 80V}
s _{Programmable Overvoltage Protection}
s _{Programmable Undervoltage Lockout}
s _{Power Good Control Output}
s _{Bell-Core Compatible ON/OFF Threshold}
U
APPLICATIO S
s _{Central Office Switching}
s _{– 48V Distributed Power Systems}
s _{Negative Power Supply Control}
DESCRIPTIO
The LT^®4250L/LT4250H are 8-pin, negative 48V Hot Swap^TM
controllers that allow a board to be safely inserted and
removed from a live backplane. Inrush current is limited to
a programmable value by controlling the gate voltage of an
external N-channel pass transistor. The pass transistor is
turned off if the input voltage is less than the program-
mable undervoltage threshold or greater than the over-
voltage threshold. A programmable current limit protects
the system against shorts. After a 500µs timeout the
current limit activates the electronic circuit breaker. The
PWRGD (LT4250L) or PWRGD (LT4250H) signal can be
used to directly enable a power module. The LT4250L is
designed for modules with a low enable input and the
LT4250H for modules with a high enable input.
The LT4250L/LT4250H are available in 8-pin PDIP and SO
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
–48V RTN
(SHORT PIN)
–48V RTN
R4^†
549k
1%
UV =
38.5V
UV
RELEASE
AT 43V
OV =
71V
R5^†
6.49k
1%
R6^†
10k
1%
3
UV
2
OV
V_EE
4
SENSE
5
*
–48V
INPUT 1
0.1µF
10V
R1^†
0.02Ω
5%
–48V
INPUT 2
* DIODES INC. SMAT70A
† _{THESE COMPONENTS ARE APPLICATION}
SPECIFIC AND MUST BE SELECTED BASED
UPON OPERATING CONDITIONS AND DESIRED
PERFORMANCE. SEE APPLICATIONS
INFORMATION.
8
V_DD
LT4250L
1
PWRGD
GATE
DRAIN
6
7
R3^†
1k, 5%
C1^†
R2
470nF 10Ω
25V
5%
C2^†
15nF
100V
V_EE AND
DRAIN
20V/DIV
I_D (Q1)
5A/DIV
Q1
IRF530
C3 +
0.1µF
100V
C4
100µF
100V
2
1
ON/OFF
V_IN+
V_OUT+
SENSE ⁺
9
8
7
+
TRIM
SENSE ^{– 6}
4 _VIN–
V_OUT– ⁵
5V
C5
100µF
16V
LUCENT
JW050A1-E
4250 TA01
Voltage Step On Input Supply
500µs/DIV
4250lhf
1