Linear Technology LTC1422 Datasheet

FEATURES

■

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

U

APPLICATIO S

LTC1422

Hot Swap Controller

U

DESCRIPTIO

TM

The LTC®1422 is an 8-pin Hot Swap
allows a board to be safely inserted and removed from a
live backplane. Using an external N-channel pass transis­tor, 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.

controller that

■

Hot Board Insertion

■

Electronic Circuit Breaker

TYPICAL APPLICATIO

5V Hot Swap

Q1

R1

MTB50N06V

VCCSENSE GATE
ON

CONNECTOR 1

0.005Ω

R2
10Ω
5%

8

76

FB

LTC1422

RESET

GNDTIMER

34

C2

0.33µF

52

1

V

ON/RESET

GND

CC

CONNECTOR 2

PLUG-IN CARDBACKPLANE

U

C1

0.1µF

R3

6.81k
1%

R4

2.43k
1%

µP

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.

V

OUT

+

5V

C

LOAD

1422 TA01

1

LTC1422

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

WW

W

U

ABSOLUTE MAXIMUM RATINGS

PACKAGE

/

O

RDER I FOR ATIO

WU

(Note 1)

Supply Voltage (VCC) ........................................... 13.2V

Input Voltage (TIMER, SENSE) ... – 0.3V to (VCC + 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

ORDER PART

NUMBER

LTC1422CN8
LTC1422CS8
LTC1422IN8
LTC1422IS8

LTC1422C ............................................... 0°C to 70°C

T

LTC1422I........................................... –40°C to 85°C

Storage Temperature Range ................ –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

Consult factory for Military grade parts.

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

DC Characteristics

I

CC

V

LKO

V

LKH

V

FB

∆V
V

FBHST

V

TM

∆V
V

TMHST

I

TM

V

CB

I

CP

∆V
V

ONHI

V

ONLO

V

ONHYST

V

OL

I

PU

t

RST

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

VCC Supply Current ON = V
VCC Undervoltage Lockout ● 2.40 2.47 2.55 V
VCC Undervoltage Lockout Hysteresis 120 mV
FB Pin Voltage Threshold ● 1.220 1.232 1.244 V
FB Pin Threshold Line Regulation 3V ≤ V

FB

FB Pin Voltage Threshold Hysteresis 2.0 mV
TIMER Pin Voltage Threshold ● 1.208 1.232 1.256 V
TIMER Pin Threshold Line Regulation 3V ≤ VCC ≤ 12V ● 215 mV

TM

TIMER Pin Voltage Threshold Hystersis 45 mV
TIMER Pin Current Timer On, GND ≤ V

Timer Off, V
Circuit Breaker Trip Voltage VCB = (VCC – V
GATE Pin Output Current Charge Pump On, V

Charge Pump Off, V
External N-Channel Gate Drive V

GATE

ON Pin Threshold High ● 1.25 1.30 1.35 V
ON Pin Threshold Low ● 1.20 1.23 1.26 V
ON Pin Hysteresis 80 mV
Output Low Voltage RESET, IO = 3mA ● 0.14 0.4 V
Logic Output Pull-Up Current RESET = GND –12 µA
Soft Reset Time ● 22 30 38 µs

GATE

The ● denotes the specifications which apply over the full operating

= 25°C. V

A

CC

≤ 12V ● 0.5 2.5 mV

CC

– V

CC

= 5V unless otherwise noted.

CC

≤ 1.5V ● –2.5 –2.0 –1.5 µA

TIMER

= 1.5V 10 mA

TIMER

) ● 44 50 64 mV

SENSE

= GND ● –12 –10 –8 µA

GATE

= V

GATE

= 150°C, θJA = 130°C/W (N)

JMAX

= 150°C, θJA = 150°C/W (S)

T

JMAX

CC

S8 PART MARKING

1422
1422I

● 0.65 1.00 mA

10 mA

● 10 12 14 V

2

U

UW

TYPICAL PERFORMANCE CHARACTERISTICS

LTC1422

Supply Current vs Supply Voltage Supply Current vs Temperature

1200

TA = 25°C

1000

800

600

400

SUPPLY CURRENT (µA)

200

0

2

6810

4

SUPPLY VOLTAGE (V)

Gate Voltage vs Temperature

18.2
VCC = 5V

= 0A

I

18.0

G

17.8

17.6

17.4

17.2

17.0

GATE VOLTAGE (V)

16.8

16.6

16.4

–55

–35

5

–15

25

TEMPERATURE (°C)

45

12 14

1422 G01

125

85

105

65

1422 G04

775

VCC = 5V

750

725

700

675

650

625

SUPPLY CURRENT (µA)

600

575

550

–55

–35

5

–15

25

TEMPERATURE (°C)

45

Gate Current vs Supply Voltage

16

TA = 25°C

= 0V

V

G

14

12

10

8

GATE CURRENT (µA)

6

4

2

6810

4

SUPPLY VOLTAGE (V)

Gate Voltage vs Supply Voltage

30

TA = 25°C

= 0A

I

G

25

20

15

10

GATE VOLTAGE (V)

5

0

125

85

105

65

1422 G02

2

6810

4

SUPPLY VOLTAGE (V)

12 14

1422 G03

Gate Current vs Temperature

10.4
VCC = 5V

= 0V

V

10.2

G

10.0

9.8

9.6

9.4

9.2

GATE CURRENT (µA)

9.0

8.8

12 14

1422 G05

8.6
–55

–35

–15

5

25

45

TEMPERATURE (°C)

65

125

85

105

1422 G06

Feedback Threshold Voltage
vs Supply Voltage

1.2350
TA = 25°C

1.2345

1.2340

1.2335

1.2330

1.2325

FEEDBACK THRESHOLD VOLTAGE (V)

1.2320

2

4

HIGH THRESHOLD

LOW THRESHOLD

6810

SUPPLY VOLTAGE (V)

12 14

1422 G07

Feedback Threshold Voltage
vs Temperature

1.237

1.236

1.235

1.234

1.233

1.232

1.231

1.230

1.229

FEEDBACK THRESHOLD VOLTAGE (V)

1.228

HIGH THRESHOLD

–55

–35

5

–15

25

TEMPERATURE (°C)

LOW THRESHOLD

45

Glitch Filter Time
vs Feedback Transient

70

60

50

40

30

GLITCH FILTER TIME (µs)

20

10

65

125

85

105

1422 G08

0

80 120 160

40

FEEDBACK TRANSIENT (mV)

TA = 25°C

200 240

1422 G09

3

LTC1422

UW

TYPICAL PERFORMANCE CHARACTERISTICS

TIMER Threshold Voltage
vs Supply Voltage

1.244

TA = 25°C

1.242

1.240

1.238

1.236

1.234

TIMER THRESHOLD VOLTAGE (V)

1.232

2

2.45
VCC = 5V

2.40

2.35

2.30

2.25

2.20

2.15

TIMER CURRENT (µA)

2.10

2.05

2.00

–55

–35

6810

4

SUPPLY VOLTAGE (V)

5

–15

25

TEMPERATURE (°C)

TIMER Threshold Voltage
vs Temperature

1.242

12 14

1422 G10

1.241

1.240

1.239

1.238

1.237

1.236

1.235

TIMER THRESHOLD VOLTAGE (V)

1.234

1.233
–55

VCC = 12V

–35

–15

VCC = 5V

VCC = 3V

5

25

45

TEMPERATURE (°C)

65

125

85

105

1422 G11

ON Pin Threshold Voltage
vs Supply VoltageTIMER Current vs Temperature

1.32

1.30

2

HIGH THRESHOLD

LOW THRESHOLD

6810

4

SUPPLY VOLTAGE (V)

1.28

1.26

1.24

1.22

ON PIN THRESHOLD VOLTAGE (V)

45

65

125

85

105

1422 G13

1.20

TA = 25°C

12 14

1422 G14

TIMER Current vs Supply Voltage

2.6
TA = 25°C

2.5

2.4

2.3

2.2

TIMER CURRENT (µA)

2.1

2.0

2

6810

4

SUPPLY VOLTAGE (V)

ON Pin Threshold Voltage
vs Temperature

1.38
VCC = 5V

1.36

1.34

1.32

1.30

1.28

1.26

1.24

ON PIN THRESHOLD VOLTAGE (V)

1.22

1.20

–55

–35

INPUT HIGH

INPUT LOW

5

–15

25

TEMPERATURE (°C)

45

12 14

1422 G12

65

125

85

105

1422 G15

4

Current Limit Threshold
vs Temperature

85

VCC = 5V

80

75

70

65

60

55

50

CURRENT LIMIT THRESHOLD (mV)

45

40

–35

–55

5

–15

25

TEMPERATURE (°C)

45

RESET Pull-Up Current
vs Temperature

22

VCC = 5V

20

18

16

14

12

10

8

RESET PULL-UP CURRENT (µA)

6

4

–35

125

85

105

65

1422 G17

–55

5

–15

25

TEMPERATURE (°C)

45

65

125

85

105

1422 G18

UW

TYPICAL PERFORMANCE CHARACTERISTICS

RESET Voltage vs Temperature

0.24
VCC = 5V

0.22

3mA PULL-UP

0.20

0.18

0.16

0.14

0.12

RESET VOLTAGE (V)

0.10

0.08

0.06

–55

–35

–15

5

25

45

TEMPERATURE (°C)

65

125

85

105

1422 G19

55
50

45

40

35

30

25

ON PIN PULSE TIME (µs)

20

15

10

UUU

PIN FUNCTIONS

ON Pin Pulse (Soft Reset) Time
vs Temperature

VCC = 3V

VCC = 5V

VCC = 12V

5

25

–55

–35

–15

TEMPERATURE (°C)

45

65

85

LTC1422

125

105

1422 G20

RESET (Pin 1) : Open drain output to GND with a 12µA
pull-up to VCC. 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
VCC.

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 VCC is connected to the TIMER pin and the
voltage starts to ramp up with a slope given by: dV/dt =
2µA/C

. When the voltage reaches the trip point

TIMER

(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.

5