UCC3921

Latchable Negative Floating Hot Swap Power Manager UCC1921 UCC2921 UCC3921 FEATURES Precision Fault Threshold Programmable: Average Power Limiting, Linear Current Control, Overcurrent Limit and Fault Time Fault Output Indication Signal Automatic Retry Mode or Latched Operation Mode Shutdown Control Undervoltage Lockout 250µs Glitch Filter on the SDFLTCH pin 8-Pin DIL and SOIC DESCRIPTION The UCC3921 family of negative floating hot swap power managers provides complete power management, hot swap, and fault handling capability. The IC is referenced to the negative input voltage and is powered through an external resistor connected to ground, which is essentially a current drive as opposed to the traditional voltage drive. The onboard 10V shunt regulator protects the IC from excess voltage and serves as a reference for programming the maximum allowable output sourcing current during a fault. All control and housekeeping functions are integrated and externally programmable. These include the fault current level, maximum output sourcing current, maximum fault time, selection of Retry or Latched mode, 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% duty cycle. The duty cycle modulation depends on the current into PL, which is a function of the voltage across the FET, thus limiting average power dissipation in the FET. The fault level is fixed at 50mV ac...