LT4250L_15 Datasheet, PDF (1/14 Pages) Linear Technology – Negative 48V Hot Swap Controller

FEATURES
n _{Allows Safe Board Insertion and Removal from a}
Live –48V Backplane
n _{Circuit Breaker Immunity to Voltage Steps and}
Current Spikes
n _{Programmable Inrush and Short-Circuit Current}
Limits
n _{Pin Compatible With LT1640L/LT1640H}
n _{Operates from –18V to –80V}
n _{Programmable Overvoltage Protection}
n _{Programmable Undervoltage Lockout}
n _{Power Good Control Output}
n _{Bell-Core Compatible ON/OFF Threshold}
APPLICATIONS
n _{Central Office Switching}
n _{–48V Distributed Power Systems}
n _{Negative Power Supply Control}
LT4250L/LT4250H
Negative 48V
Hot Swap Controller
DESCRIPTION
The LT^®4250L/LT4250H are 8-pin, negative 48V Hot Swap™
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 tran-
sistor is turned off if the input voltage is less than the
programmable undervoltage threshold or greater than
the overvoltage 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
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Hot Swap is a
trademark of Linear Technology Corporation.
TYPICAL APPLICATION
–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
PWRGD ¹
V_EE AND
DRAIN
20V/DIV
GATE
DRAIN
6
7
R3^†
1k, 5%
C1^†
R2
470nF 10Ω
25V
5%
C2^†
15nF
100V
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
TRIM ⁷
+
SENSE^{– 6}
4 _VIN–
V_OUT– ⁵
5V
C5
100μF
16V
LUCENT
JW050A1-E
4250 TA01a
Voltage Step on Input Supply
500μs/DIV
4250 TA01b
4250lhfa
1