feature

Has 1.8 to 5.5V input voltage range Controls turn on 200mA and 400mA current limit options Under voltage lockout Thermal shutdown < 1UA shutdown current Auto restart Player Digital Camera Peripheral Ports Hot Swap Power Supplies Overview The fpf2100 to fpf2107 are a family of load switches that provide comprehensive protection for systems and loads that may experience high current conditions. These devices contain a 0.125 Ω current-limited p-channel mosfet that operates over an input voltage range of 1.8-5.5v . Switch control is achieved through a logic input (on) that interfaces directly with low voltage control signals. Each part has thermal shutdown protection that shuts off the switch to prevent damage to the part when a persistent overcurrent condition causes overheating. When the switch current reaches the current limit, the part operates in constant current mode to prevent damage from excessive current. For the fpf2100-fpf2102 and fpf2104-fpf2106, if the constant current condition still exists after 10ms, these parts will turn off the switch and pull the fault signal pin (flagb) low. The fpf2100, fpf2101, fpf2104, and fpf2105 have an auto-restart feature that will turn on the switch again after 160ms if the turn-on pin is still active. The FPF2102 and FPF2106 do not have an auto-restart feature, so the switch will remain off until the on pin is cycled. For the FPF2103 and FPF2107, the current limit condition will immediately pull the fault signal pin low and the part will remain in constant current mode until the switch current drops below the current limit. For FPF2100 to FPF2103, the minimum current limit is 200mA, and for FPF2104 to FPF2107, the minimum current limit is 400mA. These parts are available in a space-saving 5-pin SOT33 package.

Instructions

The FPF2100-FPF2107 are current limiting switches used to protect systems and loads that may be damaged or interrupted by applying high currents. At the heart of each device is a 0.125Ω p-channel mosfet and a controller capable of operating over a wide input operating range of 1.8-5.5v. The controller protects against system failures through current limiting, undervoltage lockout, and thermal shutdown. Current limit is 200mA or 400mA. On/Off Control The ON pin controls the state of the switch. Active HI and LO versions are available. See ordering information for details. Activating ON will keep the switch ON as long as there is no fault. For all versions, an undervoltage on the VIN or a connection temperature over 150°C will override the open control to close the switch. Additionally, excessive current will cause the switches in the FPF2100-FPF2102 and FPF2104-FPF2107 to open. The fpf2100, fpf2101, fpf2104 and fpf2105 have an auto-restart function that automatically turns the switch on again after 160ms. For the fpf2102 and fpf2106, the ON pin must be toggled to turn the switch on again. The FPF2103 and FPF2107 do not shut down due to an overcurrent condition, but remain operating in constant current mode as long as ON is active and thermal shutdown or undervoltage lockout is not active. Fault report flag B signals fault mode by activating the LO when overcurrent, input undervoltage, or overtemperature is detected. For fpf2100-fpf2102 and fpf2104-fpf2106, flag b changes to lo at the end of the blanking time, while for fpf2103 and fpf2107, flag b changes to lo immediately. During the auto-restart time of fpf2100, fpf2101, fpf2104 and fpf2105, flagb is always lo. For fpf2102 and fpf2106, flagb is locked to lo and must be opened to release it. For fpf2103 and fpf2107, flagb is lo during the fault and returns hi immediately when the fault ends. flagb is an open-drain mosfet that requires a pull-up resistor between vin and flagb.

During shutdown, the drop-down menu on flag B will be disabled to reduce the current draw of the power supply. Current Limit The current limit ensures that the current through the switch does not exceed the maximum value while not falling below the minimum value. For the FPF2100-FPF2103, the minimum current is 200 mA and the maximum current is 400 mA; for the FPF2104-FPF2107, the minimum current is 400 mA and the maximum current is 800 mA. The blanking time of the fpf2100-fpf2103 is nominally 10ms, during which the switch will act as a constant current source. At the end of the blanking time, the switch will close and the Flag B pin will activate to indicate that a current limit has occurred. The fpf2103 and fpf2107 do not have a current limit blanking period, so they are activated as soon as the current limit condition flag b is activated. These parts will remain in a constant current state until the turn-on pin is disabled or thermal shutdown turns off the switch. Reverse Voltage If the voltage at the VOUT pin is greater than the VIN pin, a large current may flow and may cause permanent damage to the device. The FPF2100-FPF2107 are designed to control the current flow from VIN to VIN. If the input voltage falls below the undervoltage lockout threshold, the undervoltage lockout will turn off the switch. With the ON pin active, the input voltage rising below the voltage lockout threshold will result in a controlled turn-on of the switch, limiting overshoot current. Thermal Shutdown Thermal shutdown protects components from excessively high temperatures generated internally or externally. In the overtemperature state, the flag B is activated and the switch is closed. If the mold temperature falls below the threshold temperature, the switch automatically opens again.

Input Capacitor To limit the input supply voltage drop caused by transient inrush currents when the switch is turned on as a discharged load capacitor or short circuit, a capacitor needs to be placed between the VIN and ground. A 0.1°F ceramic capacitor, CIN, placed near the pin is usually sufficient. Higher cin values can be used to further reduce the voltage drop. The output capacitor A 0.1 should be placed between VOUT and GND if the capacitor cannot. This capacitor will prevent parasitic plate inductance from forcing VOUT below GND when the switch is open. For the fpf2100-fpf2102 and fpf2104-fpf2106, the total output capacitance needs to be kept below the maximum value cout(max) to prevent the part from registering an overcurrent condition and turning off. Due to the integrated body diode in the PMOS switch, it is strongly recommended that CIN be larger than COUT. When system power is removed, COUT greater than CIN will cause VOUT to exceed the VIN. This can cause current to flow from VOUT to the VIN through the body diode. When the power loss is used as a switch in normal operation, the power loss is small and has little effect on the operating temperature of the parts. Parts with higher current limit will dissipate the most power, typically if the part goes into current limit, the maximum power dissipation will occur when the output is shorted to ground.

For fpf2100, fpf2101, fpf2104 and fpf2105, the power consumption will be scaled by the auto-restart time trstrt and the overcurrent blanking time tblank, so the maximum power consumption is usually , when using the FPF2102 and FPF2106, care must be taken to manually reset the part. When the output is shorted, continuously resetting the part at a high duty cycle can cause the part to heat up. The connection temperature is only allowed to increase up to the thermal shutdown threshold. Once that temperature is reached, opening the switch will not open the switch until the temperature of the joint has dropped. For the FPF2103 and FPF2107, an output short circuit will cause the part to operate in a constant current state, consuming the worst-case power calculated in (3), until thermal shutdown is activated. It will then cycle into and out of thermal shutdown as long as the ON pin is active and there is a short circuit. For best performance, all trajectories should be as short as possible. For best results, input and output capacitors should be placed close to the device to minimize the effects of parasitic trace inductances on normal and short-circuit operation. Using wide traces for VIN (vin), output voltage (vout), and ground (gnd) will help minimize parasitic electrical effects while minimizing the impact on ambient thermal impedance.