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FPF2000-FPF2007 Rev. H

Description of Operation

The FPF2000-FPF2007 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 0.7

Ω

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 50mA or 100mA.

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-

voltage on VIN or a junction temperature in excess of 150°C

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

excessive currents will cause the switch to turn off in FPF2000-

FPF2002 and FPF2004-FPF2007. The FPF2000, FPF2001,

FPF2004 and FPF2005 have an Auto-Restart feature which will

automatically turn the switch on again after 80ms. For the

FPF2002 and FPF2006, the ON pin must be toggled to turn-on

the switch again. The FPF2003 and FPF2007 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 FPF2000-FPF2002 and

FPF2004-FPF2006, the FLAGB goes LO at the end of the

blanking time while FLAGB goes LO immediately for the

FPF2003 and FPF2007. FLAGB remains LO through the Auto-

Restart Time for the FPF2000, FPF2001 FPF2004 and

FPF2005. For the FPF2002 and FPF2006, FLAGB is latched

LO and ON must be toggled to release it. With the FPF2003 and

FPF2007, FLAGB is LO during the faults and immediately

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

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 FPF2000-FPF2003 the minimum

current is 50mA and the maximum current is 100mA and for the

FPF2004-FPF2007 the minimum current is 100mA and the

maximum current is 200mA. The FPF2000-FPF2002 and the

FPF2004-FPF2006, 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 FPF2003 and FPF2007 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. FPF2000-FPF2007 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 die 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

temperature of the die drops below the threshold temperature.