The ISL6121 is a single supply Overcurrent (OC) fault
protection IC for 2.5V to 5V applications where 2A current
limiting is desired. This device features internal current
monitoring and limiting along with a 50mΩ integrated power
switch and a current limited time out to latch-off feature for
system protection. The time to latch-off is independent of
device temperature, and magnitude of OC.
Each ISL6121 incorporates in a 8 lead SOIC package a
50mΩ N-channel MOSFET power switch for power control.
The switch is driven by a constant current source giving a
controlled ramp up of the output voltage. This provides a soft
start turn-on eliminating bus voltage drooping caused by inrush current while charging heavy load capacitances.
(Enable high (ISL6121H) and enable low (ISL6121L) options
are) available with a fault reporting output compatible with 3V
and 5V logic level signals allowing for external control and
monitoring.
The Under Voltage (UVLO) lockout feature prevents turn-on
of the output unless the correct ENABLE signal and VIN >
2.5V are both present. During initial turn-on the ISL6121
design prevents a fault from being presented by blanking the
fault signal, unlike other vendor devices needing additional
external circuitry to accomplish this. Rising and falling
output is a current-limited voltage ramp so that both the
inrush current and voltage slew rate are limited,
independent of load. This reduces supply droop due to
surge and eliminates the need for external EMI filters.
During operation once an OC condition is detected the
output is current limited to 2A to allow for a transient
condition to pass. If still in current limit after the current limit
period has elapsed the output is latched off and the fault is
reported by pulling the FAULT low. The FAULT signal is
latched low until reset by the enable signal being deasserted
at which time the FAULT signal will clear.

Features
• 0.05Ω Integrated Power N-channel MOSFET Switch
• Accurate Current Sensing and Limiting
• 12ms Timed Fault Latch-Off, No thermal Dependency
• 2.5V to 5.5V Operating Range
• Under Voltage Lockout
• Disabled Output Internally Pulled Low
• Controlled Turn On/Off Ramp Times
• Fault Output Signal
• Logic Level Enable High Inputs (ISL6121H) or Enable Low
Inputs (ISL6121L)
• Logic Level Compatible Enable Input and Fault Output
• Pb-Free Available (RoHS Compliant)

Applications
• Fibre Channel
• Industrial Power Control
• Hot Plug