The UCC3915 programmable hot swap power manager provides complete power-management, hot-swap
capability, and circuit breaker functions. The only external component required to operate the device, other than
power 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 2% 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 trip level or to a full 4 A 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 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 50 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.
The UCC3915 can be put into sleep mode, drawing only 100 uA of supply current. Other features include an
open-drain fault-output indicator, thermal shutdown, undervoltage lockout, 7-V to 15-V operation, and
low-thermal resistance SOIC and TSSOP power packages.
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