feature

1.8 to 5.5V Input Voltage Range Control Turn On 50mA and 100mA Current Limit Options Undervoltage Lockout Thermal Shutdown <1µA Shutdown Current Auto Restart Blanking RoHS Compliant

application

PDA Mobile Phone GPS Device MP3 Player Digital Camera Peripheral Port Hot Swap Supplies General Description fpf2000 to fpf2007 are a series of load switches that provide comprehensive protection for systems and loads that may encounter high current conditions. These devices contain a 0.7µm current-limited p-channel MOSFET that operates on one input. Voltage range 1.8-5.5V. Switch control can be interfaced directly with low voltage control signals through a logic input (on). Each part includes thermal shutdown protection that shuts down the switch to prevent damage to the part when a persistent overcurrent condition causes overheating. Running in constant current mode to prohibit excessive current when the switch current reaches the current limit will not cause harm. For fpf2000-fpf2002 and fpf2004-FPF2006, if the constant current state still exists after 10ms, these parts will turn off the switch and pull the fault signal pin (flag) low. The fpf2000, fpf2001, fpf2004, and fpf2005, have an auto-restart function that turns the switch on again after 80ms, if the ON pin is still active. The FPF2002 and FPF2006 do not have this auto-restart feature, so the switch will remain off until the on pin is cycled. For the fpf2003 and fpf2007, a current limit condition will immediately pull the fault signal pin low and the part will remain in constant current mode until the switch current falls below the current limit. For FPF2000 through FPF2003, the minimum current limit is 50mA, while for fpf2004 to fpf2007 it is 100mA. These parts are provided in a space saving 5-pin SC-70 package.

Instructions

The fpf2000-fpf2007 are current limit switches used to protect systems and loads that can be destroyed or destroyed in high current applications. At the heart of each device is a 0.7Ω p-channel mosfet and controller with a wide input operating range of 1.8-5.5V. Controller protection protects against system failures through current limiting, undervoltage lockout, and thermal shutdown. The current limit is preset to 50mA or 100mA. On/Off Control The ON pin controls the state of the switch. Activation high and low versions are available. See ordering information for details. Activate ON Continue to hold the switch in the ON position as long as there is no fault to speak. For all models, an undervoltage on the VIN or a joint temperature over 150°C overrides the open control to close the switch. Also, excessive current will cause the switches in FPF2000 to close - fpf2002 and fpf2004 - fpf2007. fpf2000, fpf2001, fpf2004 and fpf2005 have auto-restart function, which will automatically turn on the switch again after 80ms. FPF2002 and FPF2006, the ON pin must be switched to turn on and off again. The fpf2003 and fpf2007 are responsive to overcurrent conditions, but remain operating in constant current mode as long as ON is active and thermal shutdown or undervoltage lockout is active. Fault Reporting Once overcurrent, input undervoltage, or overtemperature is detected, a signal lamp will signal a fault to activate LO mode. For FPF2000-FPF2002 and fpf2004-fpf2006, the flags are fpf2003 and fpf2007 immediately when flagb. in fpf2000, fpf2001, fpf2004 and FPF2005. For fpf2002 and fpf2006, flagb is locked and must toggle Lo and On to release it. With the FPF2003 and FPF2007, flag B is low during the fault and returns hi immediately at the end of the fault condition. FlagB is an open-drain mosfet that requires a pull-up resistor between Vin and the flagpole. During shutdown, the drop-down menu on flagb is disabled to reduce the current consumption of the power supply. Current Limit The current limit ensures that the current through the switch does not exceed the maximum value, but is not limited to less than the minimum value. For fpf2000-fpf2003, the minimum current is 50mA and the maximum current is 100mA, and for fpf2004-fpf2007, the minimum current is 100mA and the maximum current is 200mA. fpf2000-fpf2002 and fpf2004-fpf2006, the blanking time is 10ms, nominally, the switch will act as a constant current source during this time. At the end of the AT blanking time, the switch will close and the FlagB pin will activate to indicate that the current limit has occurred. The fpf2003 and fpf2007 have no current limit and the blanking period flag B is activated immediately under the current limit conditions. These sections will remain in their current state until the ON pin is disabled or thermal shutdown turns off the switch. Reverse Voltage If the voltage at the output pin is greater than the VIN pin, a large current may flow and may cause permanent damage. device. fpf2000-fpf2007 are used to control the current from vin to vout. Undervoltage lockout if the input voltage falls below the undervoltage lockout threshold. Using the ON pin to activate the switch where the input voltage rises below the undervoltage lockout threshold will result in limited current overshoot. Thermal Shutdown Thermal shutdown protects the mold from excessively high temperatures generated internally or externally. In an overtemperature condition, flag B is activated and the switch is turned off. If the mold temperature drops below the threshold temperature.

Input capacitors limit the input supply voltage drop caused by transients Inrush current when the switch is turned on to discharge the load capacitors or short circuits, a capacitor needs to be placed between the VIN and ground. A 0.1µf ceramic capacitor, CIN, placed close to the pin is usually sufficient. Higher cin-can values are used to further reduce voltage drop. The output capacitor should be at vout and GND. This capacitor prevents parasitic plate inductance from driving the output voltage below ground when the switch is open. For the fpf2000-fpf2002 and fpf2004-fpf2006, the total output capacitance needs to be kept below the maximum value, cout(max), to prevent the part from registering overcurrent regulation and closing the switch. The maximum output capacitance can be determined by the following formula, CIN is strongly recommended to be larger than cout due to the integrated body diode in the PMOS switch. cannot be greater than when the system power is remote. This can cause current to flow through the body from VOUT to the VIN diode. Power dissipation During normal operation of the switch, power dissipation is small for the part. A part with a higher current limit will dissipate the most power only if the part goes into current limit, the maximum power dissipation occurs when the output is shorted to ground. For fpf2000, fpf2001, fpf2004 and fpf2005, power dissipation will be by auto-restart time, trestart and overcurrent blanking time tblank, so that the dissipated energy is, when using FPF2002 and FPF2006, care must be taken to manually reset the parts. Continuous reset When there is an output short circuit, part at high duty cycle can cause part temperature to rise. The junction temperature is only allowed to rise up to the shutdown threshold. Once this temperature is reached, before the intersection, opening the switch is not going to drop the temperature. For the fpf2003 and fpf2007, the short-circuit output will cause the part to dissipate worst-case power while operating at constant current, as calculated in (3), until thermal shutdown is initiated. Then loop in and out as long as the ON pin is active and the short circuit is present. Layout For best performance, all traces should be as short as possible. To be most effective, input and output capacitors should be placed close to the device to minimize the effects of parasitics during normal and short-circuit operation that may have slight inductance. Using wide traces for VIN (vin), VIN (vout), and ground (gnd) will help minimize parasitic electrical effects while minimizing the thermal impedance of the enclosure to the environment.