UCC3923, UCC3924, UCC3925, UCC3926, UCC3927, UCC3928

HIGHVOLTAGE HOT SWAP POWER MANAGER

SLUS471 – NOVEMBER 2000

3

POST OFFICE BOX 655303

Terminal Functions

TERMINAL

NO.

DESCRIPTION

NAME

UCC3923

UCC3926

UCC3924

UCC3927

UCC3925

UCC3928

I/O

DRAINSENS

–

10

16

I

Power good detection input

FAULT

1

1

6

O

Logic fault output

FLTTIME

2

2

7

I

Programming for fault timeout

GATE

3

3

8

O

Gate drive output

GND

4

4

9

I

Ground

INSA

–

5

10

I

Insertion detection input A

INSB

–

6

11

I

Insertion detection input B

IRAMP

5

7

12

I

Programming for current ramping

ISENS

6

8

13

I

Current sense input

ON

7

9

14

O

Logic command to turn on power to load

OVLO

–

–

15

I

Input overvoltage detection input

PG1

–

12

1

O

Enable for first downstream load

PG2

–

–

2

O

Enable for second downstream load

PG3

–

–

3

O

Enable for third downstream load

PG4

–

–

4

O

Enable for fourth downstream load

PG5

–

–

5

O

Enable for fifth downstream load

REF

–

11

17

O

Reference output

SEQTIME

–

–

18

I

Programming for downstream load sequencing

UVLO

–

13

19

I

Input undervoltage detection input

–VIN

8

14

20

I

Negative supply input

detailed description

power good detection input (UCC3924 and UCC3925 only)

DRAINSENS is an input that senses the voltage across the power FET. When the voltage on DRAINSENS is

less than 1V with respect to –VIN and IRAMP is greater than or equal to 5 V with respect to –VIN, then the power

FET is considered fully on and the PG outputs are allowed to begin sequencing the loads.

logic fault output (UCC3923, UCC3924, UCC3925)

FAULT is an open-drain, active-low driver that asserts when the fault latch is set. The UCC3923 UCC3924 and

UCC3925 controls the load inrush during starting by closed-loop regulation of load current. When the ON input

is low, IRAMP, FLTTIME, and SEQTIME are held low. When ON is asserted high, IRAMP is released and allows

I

LOAD v

0.01

V

IRAMP

R

SENSE

latch sets, the load is immediately turned off, and FAULT pulls low. The fault latch is cleared when ON is pulled

low.