The current limit function ensures that the current
through the switch does not exceed a maximum value
while not limiting at less than a minimum value. The
minimum current at which the parts will limit the load
current is internally set to 100 mA.
The switch current limiting circuitry is active at all times
(Sleep and Wakeup mode) and protects the FPF2024-
FPF2027 against excessive load currents in all modes.
The proprietary current limiting circuit responds to an
over-current condition in 15 μs (typical).
Under-Voltage Lockout (UVLO)
The under-voltage lockout feature turns-off the switch if
the input voltage drops below the under-voltage lockout
threshold. With the ON pin active, the input voltage
rising above the under-voltage lockout threshold will
cause a controlled turn-on of the switch and will limit
current over-shoots. The UVLO feature is disabled
during Sleep mode. If device is in the UVLO condition,
FLAGB goes low and indicates the fault. If the input
voltage goes below UVLO voltage but remains above
1.3 V (typical) during Sleep mode, the switch is kept on
until the next Wakeup cycle, where the UVLO violation
will be detected. If the input voltage falls below 1.3 V in
Sleep mode, the switch is immediately turned off.
The Thermal Shutdown protects the device from
internally or externally generated excessive
temperatures. The Thermal shutdown feature is
disabled during Sleep mode. However, excessive load
currents that may result in high power dissipation will be
detected during Sleep mode and will activate the full
function Wakeup mode, which has thermal shutdown
protection. During an over-temperature condition the
FLAGB is pulled low and the switch is turned-off. If the
temperature of the die drops below the threshold
temperature, the switch automatically turns on again, To
avoid unwanted thermal oscillations, a 10°C (typical)
thermal hysteresis is implemented between thermal
shutdown entry and exit temperatures.
Figure 25. State Diagram with Blanking and Auto-Restart (FPF2024/5)
© 2008 Fairchild Semiconductor Corporation
FPF2024/25/26/27 • Rev. 1.1