FEATURES

Precision Fault Threshold

Programmable Average Power Limiting

Programmable Linear Current Control

Programmable Overcurrent Limit

Programmable Fault Time

Fault Output Indicator

Shutdown Control

Undervoltage Lockout

8-Pin SOIC

APPLICATIONS

–48-V Distributed Power Systems

Central Office Switching

Wireless Base Stations

DESCRIPTION

The UCCx913 family of negative voltage circuit

breakers provides complete power management,

hot-swap, and fault handling capability. The

device is referenced to the negative input voltage

and is driven through an external resistor

connected to ground, which is essentially a

current drive as opposed to the traditional voltage

drive. The on-board 10-V shunt regulator protects

the device from excess voltage and serves as a

reference for programming the maximum

allowable output sourcing current during a fault. In

the event of a constant fault, the internal timer

limits 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 limits

average power dissipation in the FET. The fault

level is fixed at 50 mV across the current-sense

resistor 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, when the output appears as a

current source, is equal to VIMAX/RSENSE. If

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

2.5 V, 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 UCCx913 family include

undervoltage lockout, and 8-pin small outline

(SOIC) and dual-in-line (DIP) packages.