UCC39151

SLUS184A – FEBRUARY 1999 – REVISED OCTOBER 2001

5

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Terminal Functions

TERMINAL

NAME

PACKAGE

I/O

DESCRIPTION

DP

N

PWP

I/O

DESCRIPTION

B0

9

9

13

I

B1

8

8

12

I

Provides digital input to the DAC, which sets the fault current threshold. These

B2

7

7

11

I

Provides digital in ut to the DAC, which sets the fault current threshold. These

can be used to provide a digital soft-start and adaptive current limiting.

B3

6

6

10

I

gg

CT

11

11

15

I/O

Capacitor connects to ground and sets the maximum fault time.

EGND

5

5

9

–

Serves as lowest impedance to the electrical ground.

FAULT

16

16

24

O

Open-drain output, which pulls low upon any fault or interrupt condition, or

thermal shutdown.

GND

4, 12, 13

–

5, 6, 7, 8,

17, 18, 19,

20

–

Heat sink/ground pins. These pins should be connected to large etch areas to

help dissipate heat.

IMAX

10

10

14

I

When this pin is set low, the maximum sourcing current is 1 A above the

programmed fault level. When set high, the maximum sourcing current is a

constant 4 A for applications which require fast charging of load capacitance.

SHTDWN

1

1

1

I

When this pin is brought low, the device is put into a sleep mode drawing

typically less than 100

µA of ICC (with VOUT unloaded). The input threshold is

hysteretic, allowing the user to program a start-up delay with an external RC

circuit.

VIN

2, 3

2, 3

2, 3

I

Input voltage. The recommended voltage range is 7 V to 15 V. Both VIN pins

should be connected together and connected to power source.

VOUT

14, 15

14, 15

22, 23

O

Output voltage.VOUT must not exceed VIN by more than 0.3 V.

detailed pin descriptions

CT: A capacitor connected to ground sets the maximum fault time. The maximum fault time must be more than

the time required to charge the external capacitance in one cycle. The maximum fault time is defined as:

t

FAULT +

16.1

103

C

T

Once the fault time is reached the output shuts down for a time given by:

t

SD +

833

103

C

T

This equates to a 1.9% duty cycle.

VOUT: Output voltage from the UCC39151. Both VOUT pins should be connected together and connected to

the load. When switched:

V

OUT ^

V

IN *

0.15

W

I

OUT

VOUT must not exceed VIN by more than 0.3V.

(1)

(2)

(3)