1

LTC1642

Hot Swap Controller

May 1999

Final Electrical Specifications

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

DESCRIPTIO

The LTC

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 2.97V to

16.5V.

The SENSE pin allows foldback limiting of the load current,

with circuit breaker action after a programmable delay

time. The delay allows the part to power-up in current

limit. The CRWBR output can be used to trigger an SCR

for crowbar load protection after a programmable delay if

the input supply exceeds a programmable voltage. The

RESET output can be used to generate a system reset with

programmable delay when the supply voltage falls below

a programmable voltage. The ON pin can be used to cycle

the board power. The LTC1642 is available in the 16-pin

SSOP package.

s

Single Channel Positive NFET Driver

s

Programmable Undervoltage and Overvoltage

Protection

s

Foldback Current Limit

s

Adjustable Current Limit Time-Out

s

Latch Off or Automatic Retry on Current Fault

s

Driver for SCR Crowbar on Overvoltage

s

Programmable Reset Timer

s

Reference Output with Uncommitted Comparator

s

Against Surges to 33V.

s

16-Pin SSOP Package

s

Hot Board Insertion

s

Electronic Circuit Breaker

APPLICATIO S

, LTC and LT are registered trademarks of Linear Technology Corporation.

FEATURES

TYPICAL APPLICATIO

Hot Swap is a trademark of Linear Technology Corporation.

12V

SENSE

GATE

GND

BRK TMR

LTC1642

RST TMR

16

15

14

823

COMPOUT

ON

FAULT

OV

10

4

6

9

RESET

FB

CRWBR

REF

5

7

1

11

13

12

C3

0.33

µF

C2

0.33

µF

C5

0.1

µF

Q2

2N2222

Q3

MCR

12DC

D1

1N4148

R6

2.87k

1%

R5

110k

1%

R2

100

Ω

5%

R3

107k

1%

R4

13k

1%

R9

220

Ω

5%

Q1

FDR9410A

C6

0.01

µF

C1

0.047

µF

12V

AT 2.5A

R8

330

Ω

5%

R1

0.010

Ω

5%

R7

11.3k

1%

POWER-GOOD = 11.4V

1642 TA01

LATCH OFF: FLOAT FAULT

AUTOMATIC RETRY: TIE FAULT TO ON

RESET TIME = 200ms

CURRENT LIMIT TIME = 20ms

CROWBAR TIME = 90

µs

UNDERVOLTAGE = 10.8V

OVERVOLTAGE = 13.2V

+

C7

0.1

µF

R9 REQUIRED ONLY WITH SENSITIVE GATE SCRs,

NOT NEEDED WITH MCR12