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FPF2100-FPF2107 Rev. H

Description of Operation

The FPF2100-FPF2107 are current limited switches that protect

systems and loads which can be damaged or disrupted by the

application of high currents. The core of each device is a

0.125Ω P-channel MOSFET and a controller capable of

functioning over a wide input operating range of 1.8-5.5V. The

controller protects against system malfunctions through current

limiting, under-voltage lockout and thermal shutdown. The

current limit is preset for either 200mA or 400mA.

On/Off Control

The ON pin controls the state of the switch. Active HI and LO

versions are available. Refer to the Ordering Information for

details. Activating ON continuously holds the switch in the on

state so long as there is no fault. For all versions, an under-

overrides the ON control to turn off the switch. In addition,

excessive currents will cause the switch to turn off in FPF2100-

FPF2102 and FPF2104-FPF2107. The FPF2100, FPF2101,

FPF2104 and FPF2105 have an Auto-Restart feature which will

automatically turn the switch on again after 160ms. For the

FPF2102 and FPF2106, the ON pin must be toggled to turn-on

the switch again. The FPF2103 and FPF2107 do not turn off in

response to a over current condition but instead remain

operating in a constant current mode so long as ON is active

and the thermal shutdown or under-voltage lockout have not

activated.

Fault Reporting

Upon the detection of an over-current, an input under-voltage,

or an over-temperature condition, the FLAGB signals the fault

mode by activating LO. For the FPF2100-FPF2102 and

FPF2104-FPF2106, the FLAGB goes LO at the end of the

blanking time while FLAGB goes LO immediately for the

FPF2103 and FPF2107. FLAGB remains LO through the Auto-

Restart Time for the FPF2100, FPF2101 FPF2104 and

FPF2105. For the FPF2102 and FPF2106, FLAGB is latched

LO and ON must be toggled to release it.With the FPF2103 and

FPF2107, FLAGB is LO during the faults and immediately

returns HI at the end of the fault condition. FLAGB is an open-

drain MOSFET which requires a pull-up resistor between VIN

and FLAGB. During shutdown, the pull-down on FLAGB is

disabled to reduce current draw from the supply.

Current Limiting

The current limit ensures that the current through the switch

doesn't exceed a maximum value while not limiting at less than

a minimum value. For the FPF2100-FPF2103 the minimum

current is 200mA and the maximum current is 400mA and for

the FPF2104-FPF2107 the minimum current is 400mA and the

maximum current is 800mA. The FPF2100-FPF2103 have a

blanking time of 10ms, nominally, during which the switch will

act as a constant current source. At the end of the blanking

time, the switch will be turned-off and the FLAGB pin will

activate to indicate that current limiting has occurred. The

FPF2103 and FPF2107 have no current limit blanking period so

immediately upon a current limit condition FLAGB is activated.

These parts will remain in a constant current state until the ON

pin is deactivated or the thermal shutdown turns-off the switch.

Reverse Voltage

currents may flow and can cause permanent damage to the

device. FPF2100-FPF2107 is designed to control current flow

Under-Voltage Lockout

The under-voltage lockout 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 which limits current over-shoots.

Thermal Shutdown

The thermal shutdown protects the part from internally or

externally generated excessive temperatures. During an over-

temperature condition the FLAGB is activated and the switch is

turned-off. The switch automatically turns-on again if the

temperature of the die drops below the threshold temperature.