ISL6118

The ISL6118 is a dual channel, fully independent overcurrent  (OC) fault protection IC for the +2.5V to +5.5V environment. This device features internal current monitoring, accurate current limiting, integrated power switches and current limited delay to latch-off for system protection. The ISL6118 current sense and limiting circuitry sets the current limit to a nominal 0.6A, which is well suited for the 3.3VAUX ACPI application. The ISL6118 is the ideal  companion chip to the HIP1011D and HIP1011E dual PCI hot plug controllers. Together these and the ISL6118 fully control the four legacy PCI voltages (±12V, +3.3V, +5V) and the 3.3V AUX, respectively, for power control of two PCI slots compliant to PCI Bus Power Management Interface Spec Rev 1.1. Designed to be co located with the HIP1011D on the motherboard, the ISL6118 provides OC fault notification, accurate current limiting and a consistent timed latch-off thus isolating and protecting the voltage bus in the presence of an OC event or short circuit during all PCI Bus Power States as defined by the PCI specification.

The 12ms time to latch-off is independent of the adjoining switch's electrical or thermal condition and the OC response time is inversely related to the OC magnitude. each ISL6118 incorporates in a single 8-lead SOIC package two 80mΩ N-channel MOSFET power switches for power control. Each 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. Independent enabling inputs and fault reporting outputs for each channel are compatible with 3V and 5V logic to allow external control and monitoring.

The ISL6118 undervoltage (UV) feature prevents turn-on of  the outputs unless the correct ENABLE state and VIN>2.5V are present. During initial turn-on the ISL6118 prevents fault reporting by blanking the fault signal. Rising and falling outputs are current-limited voltage ramps 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 appropriate output is current limited for 12ms to allow transient conditions 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 correspondingFAULT low. The FAULT  signal is latched low until reset by the ENABLE signal being de-asserted at which time the FAULT signal will clear.