UCC2912

UCC3912

PROGRAMMABLE HOT SWAP POWER MANAGER

SLUS241D − MARCH 1994 - REVISED NOVEMBER 2003

1

www.ti.com

D Integrated 0.15-Ω Power MOSFET

D 3-V to 8-V Operation

D Digital Programmable Current Limit

from 0 A to 3 A

D Electronic Circuit Breaker Function

D 1µA ICC When Disabled

D Programmable On-Time

D Programmable Start Delay

D Fixed 3% Duty Cycle

D Unidirectional Switch

D Thermal Shutdown

D Fault-Output Indicator

D Maximum-Output Current Can Be Set to 1 A

Above the Programmed Fault Level or to a

Full 4 A

D Power SOIC, Low-Thermal Resistance

Packaging

description

The UCC3912 family of hot swap power managers provides complete power management, hot swap capability,

and circuit breaker functions. The only component required to operate the device, other than supply bypassing,

is the fault timing capacitor, CT. All control and 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 3% duty cycle ratio limits average output

power.

The internal 4-bit DAC allows programming of the fault level current from 0 A to 3 A with 0.25-A resolution. The

IMAX control pin sets the maximum sourcing current to 1 A above the fault level when driven low, and to a full

4 A when driven high for applications which require 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

Ω. When the output current 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 remains off for 30 times the programmed fault time. When the output current reaches

the maximum sourcing level, the MOSFET transitions from a switch to a constant current source. (continued)

block diagram

UDG-99146

B1

B0

6

7

8

2

3

9

11

16

0 A−3 A

0.25

RES

B3

B2

5

4

13

12

CT

ON TIME

CONTROL

3% DUTY

CYCLE

+

−

THERMAL

SHUTDOWN

INTERNAL

BIAS

+

−

1

SHTDWN

14

15

1.5 V

H = OPEN

FAULT

CURRENT SENSE

+

−

CHARGE

PUMP

30 mV

VOUT

REVERSE VOLTAGE

COMPARATOR

+

−

LINEAR CURRENT AMPLIFIER

1 A

ABOVE

FAULT

10

IMAX

GND

HEATSINK

GND PINS

CURRENT FAULT

LEVEL 0A TO 3 A

OVERCURRENT

COMPARATOR

MAX CURRENT

LEVEL

4 A

H = 4 A

VIN

VIN

VOUT

VOUT

POWER

FET

4 BIT DAC

Copyright

 2003, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.