UCC2915

UCC3915

SLUS198A - FEBRUARY 2000

FEATURES

• Integrated 0.15 Ohm Power

MOSFET

• 7V to 15V Operation

• Digital Programmable Current Limit

from 0A to 3A

• Programmable ON Time

• Programmable Start Delay

• Fixed 2% Duty Cycle

• Thermal Shutdown

• Fault Output Indicator

• Maximum Output Current can be set

to 1A above the Programmed Fault

Level or to a full 4A

• Power SOIC and TSSOP, Low

Thermal Resistance Packaging

DESCRIPTION

The UCC3915 Programmable Hot Swap Power Manager provides com-

plete power management, hot swap capability, and circuit breaker functions.

The only external component required to operate the device, other than

housekeeping functions are integrated, and externally programmable.

These include the fault current level, maximum output sourcing current,

maximum fault time, and startup delay. In the event of a constant fault, the

Internal fixed 2% duty cycle ratio limits average output power.

The internal 4 bit DAC allows programming of the fault level current from 0

to 3A with 0.25A resolution. The IMAX control pin sets the maximum

sourcing current to 1A above the trip level or to a full 4A of output current

for fast output capacitor charging.

When the output current is below the fault level, the output MOSFET is

switched ON with a nominal ON resistance of 0.15 . When the output cur-

rent exceeds the fault level, but is less than the maximum sourcing level,

the output remains switched ON, but the fault timer starts, charging CT.

Once CT charges to a preset threshold, the switch is turned OFF, and re-

mains OFF for 50 times the programmed fault time. When the output cur-

rent reaches the maximum sourcing level, the MOSFET transitions from a

switch to a constant current source.

6

7

8

9

1A

ABOVE

FAULT

OVER CURRENT

COMPARATOR

CURRENT FAULT

LEVEL 0–3 AMPS

10

H= 4A

MAX

CURRENT

LEVEL

4A

ON TIME

CONTROL

2% DUTY

CYCLE

0–3A

0.25

RES

11

13

12

4

5

B3

B2

B1

B0

4BIT DAC

GND

HEAT SINK

GND PINS

CT

CHARGE

PUMP

16

LINEAR CURRENT

AMPLIFIER

POWER

FET

2

3

V

OUT

REVERSE VOLTAGE

COMPARATOR

30mV

FAULT

THERMAL

SHUTDOWN

INTERNAL

BIAS

+

–

1

15

14

VOUT

VIN

CURRENT SENSE

H = OPEN

1.5V

SHTDWN

IMAX

*

*BODYDIODE

BLOCK DIAGRAM

15V Programmable Hot Swap Power Manager

UDG-99174

Note: Pin numbers refer to DIL-16 and SOIC-16 packages.