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1
LTC1422
Hot Swap Controller
s
Allows Safe Board Insertion and Removal
from a Live Backplane
s
System Reset Output with Programmable Delay
s
Programmable Electronic Circuit Breaker
s
User-Programmable Supply Voltage Power-Up Rate
s
High Side Driver for an External N-Channel FET
s
Controls Supply Voltages from 2.7V to 12V
s
Undervoltage Lockout
s
Soft Reset Input
s
Glitch Filter on RESET
5V Hot Swap
The LTC
1422 is an 8-pin Hot Swap
TM
controller that
allows a board to be safely inserted and removed from a
live backplane. Using an external N-channel pass transis-
tor, the board supply voltage can be ramped up at a
programmable rate. A high side switch driver controls the
N-channel gate for supply voltages ranging from 2.7V to
12V.
A programmable electronic circuit breaker protects
against shorts. The RESET output can be used to generate
a system reset when the supply voltage falls below a
programmable voltage. The ON pin can be used to cycle
the board power or to generate a soft reset.
The LTC1422 is 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.
s
Hot Board Insertion
s
Electronic Circuit Breaker
+
V
CC
SENSE GATE
LTC1422
GND
TIMER
ON
8
3
4
7
6
R2
10
5%
R3
6.81k
1%
R4
2.43k
1%
R1
0.005
Q1
MTB50N06V
C1
0.1
F
C
LOAD
V
OUT
5V
V
CC
ON/RESET
GND
1422 TA01
PLUG-IN CARD
BACKPLANE
C2
0.33
F
5
2
1
FB
RESET
RESET
P
CONNECTOR 1
CONNECTOR 2
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
U
2
LTC1422
W
U
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
T
JMAX
= 150
C,
JA
= 130
C/W (N)
T
JMAX
= 150
C,
JA
= 150
C/W (S)
1
2
3
4
8
7
6
5
TOP VIEW
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
RESET
ON
TIMER
GND
V
CC
SENSE
GATE
FB
Supply Voltage (V
CC
) ........................................... 13.2V
Input Voltage (TIMER, SENSE) ... 0.3V to (V
CC
+ 0.3V)
Input Voltage (FB, ON) ........................... 0.3V to 13.2V
Output Voltage (RESET) ........................ 0.3V to 13.2V
Output Voltage (GATE) ............................. 0.3V to 20V
Operating Temperature Range
LTC1422C ............................................... 0
C to 70
C
LTC1422I ........................................... 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................. 300
C
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
Consult factory for Military grade parts.
LTC1422CN8
LTC1422CS8
LTC1422IN8
LTC1422IS8
S8 PART MARKING
ELECTRICAL CHARACTERISTICS
1422
1422I
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC Characteristics
I
CC
V
CC
Supply Current
ON = V
CC
q
0.65
1.00
mA
V
LKO
V
CC
Undervoltage Lockout
q
2.40
2.47
2.55
V
V
LKH
V
CC
Undervoltage Lockout Hysteresis
120
mV
V
FB
FB Pin Voltage Threshold
q
1.220
1.232
1.244
V
V
FB
FB Pin Threshold Line Regulation
3V
V
CC
12V
q
0.5
2.5
mV
V
FBHST
FB Pin Voltage Threshold Hysteresis
2.0
mV
V
TM
TIMER Pin Voltage Threshold
q
1.208
1.232
1.256
V
V
TM
TIMER Pin Threshold Line Regulation
3V
V
CC
12V
q
2
15
mV
V
TMHST
TIMER Pin Voltage Threshold Hystersis
45
mV
I
TM
TIMER Pin Current
Timer On, GND
V
TIMER
1.5V
q
2.5
2.0
1.5
A
Timer Off, V
TIMER
= 1.5V
10
mA
V
CB
Circuit Breaker Trip Voltage
V
CB
= (V
CC
V
SENSE
)
q
44
50
64
mV
I
CP
GATE Pin Output Current
Charge Pump On, V
GATE
= GND
q
12
10
8
A
Charge Pump Off, V
GATE
= V
CC
10
mA
V
GATE
External N-Channel Gate Drive
V
GATE
V
CC
q
10
12
14
V
V
ONHI
ON Pin Threshold High
q
1.25
1.30
1.35
V
V
ONLO
ON Pin Threshold Low
q
1.20
1.23
1.26
V
V
ONHYST
ON Pin Hysteresis
80
mV
V
OL
Output Low Voltage
RESET, I
O
= 3mA
q
0.14
0.4
V
I
PU
Logic Output Pull-Up Current
RESET = GND
12
A
t
RST
Soft Reset Time
q
22
30
38
s
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V unless otherwise noted.
(Note 1)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
3
LTC1422
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
SUPPLY VOLTAGE (V)
2
0
GATE VOLTAGE (V)
5
10
15
20
30
4
6
8
10
1422 G03
12
14
25
T
A
= 25
C
I
G
= 0A
Gate Voltage vs Supply Voltage
Gate Current vs Temperature
SUPPLY VOLTAGE (V)
2
FEEDBACK THRESHOLD VOLTAGE (V)
1.2350
1.2345
1.2340
1.2335
1.2330
1.2325
1.2320
4
6
8
10
1422 G07
12
14
T
A
= 25
C
HIGH THRESHOLD
LOW THRESHOLD
Feedback Threshold Voltage
vs Supply Voltage
Glitch Filter Time
vs Feedback Transient
Gate Voltage vs Temperature
TEMPERATURE (
C)
55
16.4
GATE VOLTAGE (V)
16.6
17.0
17.2
17.4
65
18.2
1422 G04
16.8
5
35
85
25
15
105
45
125
17.6
17.8
18.0
V
CC
= 5V
I
G
= 0A
SUPPLY VOLTAGE (V)
2
0
SUPPLY CURRENT (
A)
200
400
600
800
1200
4
6
8
10
1422 G01
12
14
1000
T
A
= 25
C
Supply Current vs Supply Voltage
Supply Current vs Temperature
TEMPERATURE (
C)
55
550
SUPPLY CURRENT (
A)
575
625
650
675
65
775
1422 G02
600
5
35
85
25
15
105
45
125
700
725
750
V
CC
= 5V
Gate Current vs Supply Voltage
SUPPLY VOLTAGE (V)
2
4
GATE CURRENT (
A)
6
8
10
12
16
4
6
8
10
1422 G05
12
14
14
T
A
= 25
C
V
G
= 0V
FEEDBACK TRANSIENT (mV)
0
10
GLITCH FILTER TIME (
s)
20
30
40
50
70
40
80
120
160
1422 G09
200
240
60
T
A
= 25
C
Feedback Threshold Voltage
vs Temperature
TEMPERATURE (
C)
55
FEEDBACK THRESHOLD VOLTAGE (V)
65
1.237
1.236
1.235
1.234
1.233
1.232
1.231
1.230
1.229
1.228
1422 G08
5
35
85
25
15
105
45
125
HIGH THRESHOLD
LOW THRESHOLD
TEMPERATURE (
C)
55
8.6
GATE CURRENT (
A)
8.8
9.2
9.4
9.6
65
10.4
1422 G06
9.0
5
35
85
25
15
105
45
125
9.8
10.0
10.2
V
CC
= 5V
V
G
= 0V
4
LTC1422
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
SUPPLY VOLTAGE (V)
2
TIMER THRESHOLD VOLTAGE (V)
1.244
1.242
1.240
1.238
1.236
1.234
1.232
4
6
8
10
1422 G10
12
14
T
A
= 25
C
TIMER Threshold Voltage
vs Supply Voltage
SUPPLY VOLTAGE (V)
2
2.0
TIMER CURRENT (
A)
2.1
2.2
2.3
2.4
2.6
4
6
8
10
1422 G12
12
14
2.5
T
A
= 25
C
TIMER Current vs Supply Voltage
TEMPERATURE (
C)
55
TIMER THRESHOLD VOLTAGE (V)
65
1.242
1.241
1.240
1.239
1.238
1.237
1.236
1.235
1.234
1.233
1422 G11
5
35
85
25
15
105
45
125
V
CC
= 12V
V
CC
= 5V
V
CC
= 3V
TIMER Threshold Voltage
vs Temperature
ON Pin Threshold Voltage
vs Supply Voltage
TIMER Current vs Temperature
TEMPERATURE (
C)
55
TIMER CURRENT (
A)
65
2.45
2.40
2.35
2.30
2.25
2.20
2.15
2.10
2.05
2.00
1422 G13
5
35
85
25
15
105
45
125
V
CC
= 5V
SUPPLY VOLTAGE (V)
2
ON PIN THRESHOLD VOLTAGE (V)
1.32
1.30
1.28
1.26
1.24
1.22
1.20
4
6
8
10
1422 G14
12
14
T
A
= 25
C
LOW THRESHOLD
HIGH THRESHOLD
ON Pin Threshold Voltage
vs Temperature
TEMPERATURE (
C)
55
ON PIN THRESHOLD VOLTAGE (V)
65
1.38
1.36
1.34
1.32
1.30
1.28
1.26
1.24
1.22
1.20
1422 G15
5
35
85
25
15
105
45
125
V
CC
= 5V
INPUT HIGH
INPUT LOW
Current Limit Threshold
vs Temperature
TEMPERATURE (
C)
55
40
CURRENT LIMIT THRESHOLD (mV)
45
55
60
65
65
85
1422 G17
50
5
35
85
25
15
105
45
125
70
75
80
V
CC
= 5V
RESET Pull-Up Current
vs Temperature
TEMPERATURE (
C)
55
4
RESET PULL-UP CURRENT (
A)
6
10
12
14
65
22
1422 G18
8
5
35
85
25
15
105
45
125
16
18
20
V
CC
= 5V
5
LTC1422
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
PI
N
FU
N
CTIO
N
S
U
U
U
TIMER (Pin 3): Analog system timing generator pin. This
pin is used to set the delay before the charge pump turns
on after the ON pin goes high. It also sets the delay before
the RESET pin goes high, after the output supply voltage
is good, as sensed by the FB pin.
When the timer is off, an internal N-channel shorts the
TIMER pin to ground. When the timer is turned on, a 2
A
current from V
CC
is connected to the TIMER pin and the
voltage starts to ramp up with a slope given by: dV/dt =
2
A/C
TIMER
. When the voltage reaches the trip point
(1.232V), the timer will be reset by pulling the TIMER pin
back to ground. The timer period is given by: (1.232V
C
TIMER
)/2
A.
GND (Pin 4): Chip Ground.
FB (Pin 5): Analog comparator input used to monitor the
output supply voltage with an external resistive divider.
When the voltage on the FB pin is lower than the 1.232V,
the RESET pin will be pulled low. An internal filter helps
prevent negative voltage glitches from triggering a reset.
When the voltage on the FB pin rises above the trip point,
the RESET pin will go high after one timing cycle.
RESET (Pin 1) : Open drain output to GND with a 12
A
pull-up to V
CC
. This pin is pulled low when the voltage at
the FB (Pin 5) goes below the FB pin threshold. The RESET
pin will go high one timing cycle after the voltage at the FB
pin goes above the FB pin threshold. An external pull-up
resistor can be used to speed up the rising edge on the
RESET pin or pull the pin to a voltage higher or lower than
V
CC
.
ON (Pin 2): Analog Input Pin. The threshold is set at 1.30V
with 80mV hysteresis. When the ON pin is pulled high, the
timer turns on for one cycle, then the charge pump turns
on. When the ON pin is pulled low longer than 40
s, the
GATE pin will be pulled low and remain off until the ON pin
is pulled high.
If the ON pin is pulled low for less than 15
s a soft reset
will occur. The charge pump remains on, and the RESET
pin is pulled low for one timing cycle starting 30
s from
the falling edge of the ON pin.
The ON pin is also used to reset the electronic circuit
breaker. If the ON pin is cycled low and high following the
trip of the circuit breaker, the circuit breaker is reset and
a normal power-up sequence will occur.
RESET Voltage vs Temperature
TEMPERATURE (
C)
55
RESET VOLTAGE (V)
65
0.24
0.22
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
1422 G19
5
35
85
25
15
105
45
125
V
CC
= 5V
3mA PULL-UP
TEMPERATURE (
C)
55
ON PIN PULSE TIME (
s)
65
55
50
45
40
35
30
25
20
15
10
1422 G20
5
35
85
25
15
105
45
125
V
CC
= 12V
V
CC
= 5V
V
CC
= 3V
ON Pin Pulse (Soft Reset) Time
vs Temperature
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