LTC1422
Hot Swap Controller
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Allows Safe Board Insertion and Removal
from a Live Backplane
System Reset Output with Programmable Delay
Programmable Electronic Circuit Breaker
User-Programmable Supply Voltage Power-Up Rate
High Side Driver for an External N-Channel FET
Controls Supply Voltages from 2.7V to 12V
Undervoltage Lockout
Soft Reset Input
Glitch Filter on RESET
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.
APPLICATIO S
s
s
Hot Board Insertion
Electronic Circuit Breaker
TYPICAL APPLICATIO
5V Hot Swap
Q1
R1
0.005Ω MTB50N06V
V
CC
R2
10Ω
5%
R3
6.81k
1%
C1
0.1µF
5
R4
2.43k
1%
V
OUT
5V
C
LOAD
+
CONNECTOR 2
CONNECTOR 1
8
2
V
CC
ON
7
6
FB
SENSE GATE
ON/RESET
LTC1422
RESET
TIMER
3
GND
C2
0.33µF
4
1
µP
RESET
GND
1422 TA01
BACKPLANE
PLUG-IN CARD
U
U
U
1
LTC1422
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RESET 1
ON 2
TIMER 3
GND 4
N8 PACKAGE
8-LEAD PDIP
8 V
CC
7 SENSE
6 GATE
5 FB
S8 PACKAGE
8-LEAD PLASTIC SO
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
ORDER PART
NUMBER
LTC1422CN8
LTC1422CS8
LTC1422IN8
LTC1422IS8
S8 PART MARKING
1422
1422I
T
JMAX
= 150°C,
θ
JA
= 130°C/W (N)
T
JMAX
= 150°C,
θ
JA
= 150°C/W (S)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
I
CC
V
LKO
V
LKH
V
FB
∆V
FB
V
FBHST
V
TM
∆V
TM
V
TMHST
I
TM
V
CB
I
CP
∆V
GATE
V
ONHI
V
ONLO
V
ONHYST
V
OL
I
PU
t
RST
PARAMETER
V
CC
Supply Current
V
CC
Undervoltage Lockout
V
CC
Undervoltage Lockout Hysteresis
FB Pin Voltage Threshold
FB Pin Threshold Line Regulation
FB Pin Voltage Threshold Hysteresis
TIMER Pin Voltage Threshold
TIMER Pin Threshold Line Regulation
TIMER Pin Voltage Threshold Hystersis
TIMER Pin Current
Circuit Breaker Trip Voltage
GATE Pin Output Current
External N-Channel Gate Drive
ON Pin Threshold High
ON Pin Threshold Low
ON Pin Hysteresis
Output Low Voltage
Logic Output Pull-Up Current
Soft Reset Time
DC Characteristics
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.
CONDITIONS
ON = V
CC
q
q
MIN
TYP
0.65
MAX
1.00
2.55
1.244
2.5
1.256
15
– 1.5
64
–8
14
1.35
1.26
0.4
38
UNITS
mA
V
mV
V
mV
mV
V
mV
mV
µA
mA
mV
µA
mA
V
V
V
mV
V
µA
µs
2.40
1.220
2.47
120
1.232
0.5
2.0
q
3V
≤
V
CC
≤
12V
q
q
1.208
1.232
2
45
3V
≤
V
CC
≤
12V
Timer On, GND
≤
V
TIMER
≤
1.5V
Timer Off, V
TIMER
= 1.5V
V
CB
= (V
CC
– V
SENSE
)
Charge Pump On, V
GATE
= GND
Charge Pump Off, V
GATE
= V
CC
V
GATE
– V
CC
q
q
q
q
q
q
q
– 2.5
44
– 12
10
1.25
1.20
– 2.0
10
50
– 10
10
12
1.30
1.23
80
0.14
– 12
RESET, I
O
= 3mA
RESET = GND
q
q
22
30
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
2
U
W
U
U
W W
W
LTC1422
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
1200
T
A
= 25°C
1000
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
800
600
400
200
GATE VOLTAGE (V)
0
2
4
6
8
10
SUPPLY VOLTAGE (V)
Gate Voltage vs Temperature
18.2
18.0
17.8
GATE CURRENT (µA)
16
V
CC
= 5V
I
G
= 0A
GATE CURRENT (µA)
GATE VOLTAGE (V)
17.6
17.4
17.2
17.0
16.8
16.6
16.4
– 55 – 35 –15
4
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G04
Feedback Threshold Voltage
vs Supply Voltage
1.2350
1.237
FEEDBACK THRESHOLD VOLTAGE (V)
T
A
= 25°C
FEEDBACK THRESHOLD VOLTAGE (V)
1.2345
1.2340
1.2335
1.2330
1.2325
1.2320
2
4
HIGH THRESHOLD
GLITCH FILTER TIME (µs)
LOW THRESHOLD
6
8
10
SUPPLY VOLTAGE (V)
U W
12
12
Supply Current vs Temperature
775
V
CC
= 5V
750
725
700
675
650
625
600
5
20
15
10
25
30
Gate Voltage vs Supply Voltage
T
A
= 25°C
I
G
= 0A
575
14
1422 G01
550
– 55 – 35 –15
0
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G02
2
4
6
8
10
SUPPLY VOLTAGE (V)
12
14
1422 G03
Gate Current vs Supply Voltage
10.4
Gate Current vs Temperature
10.2
10.0
V
CC
= 5V
V
G
= 0V
14
12
10
8
6
T
A
= 25°C
V
G
= 0V
9.8
9.6
9.4
9.2
9.0
8.8
2
4
6
8
10
SUPPLY VOLTAGE (V)
12
14
1422 G05
8.6
– 55 – 35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G06
Feedback Threshold Voltage
vs Temperature
70
1.236
HIGH THRESHOLD
1.235
1.234
1.233
LOW THRESHOLD
1.232
1.231
1.230
1.229
1.228
– 55 – 35 –15
Glitch Filter Time
vs Feedback Transient
T
A
= 25°C
60
50
40
30
20
10
14
1422 G07
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G08
0
40
200
80
120
160
FEEDBACK TRANSIENT (mV)
240
1422 G09
3
LTC1422
TYPICAL PERFORMANCE CHARACTERISTICS
TIMER Threshold Voltage
vs Supply Voltage
1.244
T
A
= 25°C
TIMER THRESHOLD VOLTAGE (V)
TIMER THRESHOLD VOLTAGE (V)
1.242
1.240
1.238
1.236
1.234
1.232
2
4
6
8
10
SUPPLY VOLTAGE (V)
12
14
1422 G10
1.239
1.238
1.237
1.236
1.235
V
CC
= 5V
TIMER CURRENT (µA)
TIMER Current vs Temperature
2.45
ON PIN THRESHOLD VOLTAGE (V)
1.32
2.40
2.35
TIMER CURRENT (µA)
V
CC
= 5V
1.30
HIGH THRESHOLD
1.28
1.26
1.24
ON PIN THRESHOLD VOLTAGE (V)
2.30
2.25
2.20
2.15
2.10
2.05
2.00
– 55 – 35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G13
Current Limit Threshold
vs Temperature
85
V
CC
= 5V
CURRENT LIMIT THRESHOLD (mV)
80
RESET PULL-UP CURRENT (µA)
75
70
65
60
55
50
45
40
– 55 – 35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G17
4
U W
TIMER Threshold Voltage
vs Temperature
1.242
1.241
1.240
V
CC
= 12V
TIMER Current vs Supply Voltage
2.6
T
A
= 25°C
2.5
2.4
2.3
2.2
2.1
V
CC
= 3V
1.234
1.233
– 55 – 35 –15
2.0
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G11
2
4
6
8
10
SUPPLY VOLTAGE (V)
12
14
1422 G12
ON Pin Threshold Voltage
vs Supply Voltage
1.38
ON Pin Threshold Voltage
vs Temperature
T
A
= 25°C
1.36
1.34
1.32
1.30
1.28
1.26
1.24
1.22
1.20
– 55 – 35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G15
V
CC
= 5V
INPUT HIGH
LOW THRESHOLD
1.22
1.20
2
4
6
8
10
SUPPLY VOLTAGE (V)
12
14
1422 G14
INPUT LOW
RESET Pull-Up Current
vs Temperature
22
V
CC
= 5V
20
18
16
14
12
10
8
6
4
– 55 – 35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G18
LTC1422
TYPICAL PERFORMANCE CHARACTERISTICS
RESET Voltage vs Temperature
0.24
0.22
0.20
V
CC
= 5V
3mA PULL-UP
55
50
0.18
0.16
0.14
0.12
0.10
0.08
0.06
– 55 – 35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G19
ON PIN PULSE TIME (µs)
RESET VOLTAGE (V)
PIN FUNCTIONS
RESET (Pin 1) :
Open drain output to GND with a 12µA
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 40µs, 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 15µs a soft reset
will occur. The charge pump remains on, and the RESET
pin is pulled low for one timing cycle starting 30µs 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.
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 2µA
current from V
CC
is connected to the TIMER pin and the
voltage starts to ramp up with a slope given by: dV/dt =
2µA/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
)/2µA.
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.
U W
ON Pin Pulse (Soft Reset) Time
vs Temperature
45
40
35
30
25
20
15
10
– 55 – 35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1422 G20
V
CC
= 3V
V
CC
= 5V
V
CC
= 12V
U
U
U
5
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