UCC1913

UCC2913

UCC3913

DESCRIPTION

The UCC1913 family of negative voltage circuit breakers provides com-

plete power management, hot swap, and fault handling capability. The IC is

referenced to the negative input voltage and is driven through an external

resistor connected to ground, which is essentially a current drive as op-

posed to the traditional voltage drive. The on-board 10V shunt regulator

protects the IC from excess voltage and serves as a reference for program-

ming the maximum allowable output sourcing current during a fault. All

control and housekeeping functions are integrated, and externally program-

mable. These include the fault current level, maximum output sourcing cur-

rent, maximum fault time, soft start time, and average power limiting. In the

event of a constant fault, the internal timer will limit the on-time from less

than 0.1% to a maximum of 3%. The duty cycle modulates depending on

the current into the PL pin, which is a function of the voltage across the

FET, and will limit average power dissipation in the FET. The fault level is

fixed at 50mV across the current sense amplifier to minimize total dropout.

The fault current level is set with an external current sense resistor. The

maximum allowable sourcing current is programmed with a voltage divider

from VDD to generate a fixed voltage on the IMAX pin. The current level,

desired, a controlled current startup can be programmed with a capacitor

on the IMAX pin.

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

switched on. When the output current exceeds the fault level, but is less

than the maximum sourcing level programmed by the IMAX pin, the output

remains switched on, and the fault timer starts charging CT. Once CT

charges to 2.5V, the output device is turned off and performs a retry some

time later. When the output current reaches the maximum sourcing current

level, the output appears as a current source, limiting the output current to

the set value defined by IMAX.

Other features of the UCC1913 family include undervoltage lockout, and

8-pin small outline (SOIC) and Dual-In-Line (DIL) packages.

Negative Voltage Hot Swap Power Manager

FEATURES

• Precision Fault Threshold

• Programmable Average Power

Limiting

• Programmable Linear Current Control

• Programmable

• Overcurrent Limit

• Programmable Fault Time

• Fault Output Indication

• Shutdown Control

• Undervoltage Lockout

• 8-Pin SOIC

SLUS274 - JANUARY 1999

1

2

LINEAR

CURRENT

AMPLIFIER

PL

7OUT

IMAX

V

DD

50

Ω

8

V

DD

6

SENSE

5

VSS

4CT

ON-TIME

CONTROL

3

VDD

UVLO

5.0V

REF

LOGIC

SUPPLY

9.5V SHUNT REGULATOR

20

µA

1=

UNDERVOLTAGE

SOURCE

ONLY

SD/FLT

V

DD

0.2V

OVERCURRENT

COMPARATOR

DISABLE

5.0V

OVERLOAD COMPARATOR

50mV

BLOCK DIAGRAM

UDG-99001