LT4220
Dual Supply
Hot Swap Controller
U
FEATURES
DESCRIPTIO
Hot SwapTM Controller for Positive
The LT®4220 16-pin dual voltage Hot Swap controller
allows a board to be safely inserted and removed from a
live backplane. The device operates with any combination
of 2.7V to 16.5V and –2.7V to –16.5V supplies. Using two
external N-channel pass transistors, the board supply
voltages can be ramped up at an adjustable rate. A select-
able tracking mode allows dual supply tracking control for
ramping the positive and negative supplies together.
■
and Negative Supplies
■
Supply Tracking Mode
■
±2.7V to ±16.5V Operation
■
Analog Current Limit with Foldback
■
Allows Safe Board Insertion and Removal
from a Live Backplane
■
Open-Collector Power Good Comparators
■
Automatic Retry or Latchoff After a Current Fault
The LT4220 features foldback current limit and latches off
both gates if either supply remains in current limit longer
than an adjustable time period. The IC can be configured
for automatic restart after a delay set by the same timer.
■
Dual Undervoltage Lockout Comparator Inputs
■
Current Fault IndUication
APPLICATIO S
A power good signal indicates when the output voltages
monitoredby thetwoFBcomparatorsarewithintolerance,
and the gate drive signals are at their full on voltage.
■
Live Board Insertion
■
RAID Systems
■
–5.2V ECL Supplies
The LT4220 is available in a 16-lead narrow SSOP
package.
■
Industrial Controls
■
Split Supply Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
U
TYPICAL APPLICATIO
±12V 10A Hot Swap Controller
+
R
Q1
S
+
0.005Ω
SUB85N03-04
V
12V
CC
IN
12V
OUT
+
V
V
R13
10Ω
C1
10nF
+
Z1*
R5
10Ω
R6
1k
C4
100nF
CL1
7
16
15
SENSE
14
GATE
+
+
R15
20k
12V
IN
R1
V
TRACK
D1
CC
R9
10
13
V
+
36.5k
IN4001
PWRGD
12
36.5k
+
ON
R16, 20k
+
FB
11
8
R2
4.99k
FAULT
TIMER
12V
+
R10
4.99k
C7
V
OUT
10nF
C6
1µF
LT4220
9
6
R12
4.99k
GND
–12V
5
R4
4.99k
C8
10nF
–
V
–
IN
FB
R11
36.5k
–
ON
D2
IN4001
–
–
–12V
V
EE
SENSEK SENSE
GATE
R3
36.5k
C2
10nF
V
–
OUT
1
2
3
4
R8
1k
C5
1µF
TIME (10ms/DIV)
C3
100nF
+
R7
CL2
10Ω
Z2*
R14
10Ω
–
R
S
–
0.005Ω
V
IN
–12V
–12V
–
V
OUT
V
Q2
SUB85N03-04
EE
* 1SMA13AT3 TRANSIENT
VOLTAGE SUPPRESSOR
4220 TA01
4220f
1