IntelliMAX™ Advanced Load Management Switches
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To introduce the IntelliMAX™ Advanced Load Management Switches and their key features
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IntelliMAX™ Advanced Load Management Switches
- 11. Typical Application Circuit For normal operation: Power Dissipation = (I LIM ) 2 x R DS IntelliMAX Load Switch Input Capacitor to limit the voltage drop on the input supply Output Capacitor to prevent parasitic board inductances
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- Welcome to the training module on Fairchild IntelliMAX ™ Advanced Load Management Switches. This training module introduces the IntelliMAX ™ Advanced Load Management Switches and their key features.
- The IntelliMAX family combines conventional MOSFET performance with a unique combination of protection, control and fault monitoring features to enhance power management design. This level of integration helps designers achieve efficiency and reliability, while minimizing board space requirements. This family has wide operating voltage range which fulfills today’s portable device’s supply requirement. It also has other features, including slew rate control, under voltage lockout, over current limit protection, thermal shutdown, and fault monitoring.
- Here is functional block diagram for IntelliMAX family. It consists of different protection circuits, such as short circuit & thermal protection, and current limiting protection, turn-on and in-rush control block, and reverse current blocking circuit. However, not every member in this family contains all these features.
- As the IntelliMAX family features a wide operating range from 1.2V to 5.5V to address the voltage specifications for most portable devices, such as mobile phones, PDAs, digital cameras, MP3 players and portable bar code readers. These load switches have low quiescent current which helps to prolong battery life. Here list a series of applications supported by IntelliMAX load switches.
- 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. When the load current exceeds the maximum current, some load switches have a blanking time during which the switches will act as a constant current source. At the end of the blanking time, the switches will be turn-off and the fault flag pin will be activated to indicate that current limiting has occurred. If the load switches have no current limit blanking period immediately upon a current limit condition the fault flag pin 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.
- 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 undervoltage lockout threshold will cause a controlled turn-on of the switch which limits current over-shoots. If the device is in the UVLO condition, the fault flag goes low and indicates the fault.
- If the voltage at the V OUT pin is larger than the V IN pin, large currents may flow and can cause permanent damage to the device. The load switch is designed to control current flow from V IN to V OUT . So the reverse current blocking prevents current from flowing when the MOSFET is off and the output voltage is higher than the input voltage. The slew rate control feature turns the switch on over a defined period of time, which limits the current through the device and into the load. When balanced with the load capacitance this feature helps to prevent current spikes on the load and minimize voltage sags on the input. The Thermal Shutdown protects the device from internally or externally generated excessive temperatures. During an over temperature condition the fault flag is activated and the switch is turned-off. The switch automatically turns-on again if temperature of the die drops below the threshold temperature.
- Upon the detection of an over-current, an input under-voltage, or an over-temperature condition, the fault flag signals the fault mode by activating LOW. If the device has a blanking time and the fault condition persists beyond the blanking time, the fault flag goes LOW and the switch is turned off at the end of the blanking time. If the device does not have the blanking time, the fault flag goes LOW and the switch is shut off immediately. The fault flag is LOW during the faults and immediately turns HIGH at the end of the fault condition. The fault flag pin (FLAGB) is an open drain MOSFET which requires a pull-up resistor between V IN and FLAGB. During shutdown, the pull-down and FLAGB is disabled to reduce current draw from the supply.
- Switch control is by a logic input (ON) capable of interfacing directly with low voltage control signal. The ON pin controls the state of the switch. Active HIGH and LOW versions are available to accommodate various application requirements. Refer to the datasheet for details. Applying a continuous high or low signal depending on the switch configuration, will hold the switch in the ON state as long as there is no fault. The load switch will move into the OFF state when the ON pin is inactive. For all versions, an undervoltage on V IN or a junction temperature in excess of the rated temperature overrides the ON control and turns off the switch. For an over current condition, there are two responses for it, please refer to datasheet for details. One case is that the load switch moves into the OFF state if a current fault is encountered for longer duration than the Blanking Time. Another is that the load switch do not turn off in response to a over current condition but instead remain operating in a constant current mode as long as ON is active and the thermal shutdown or under voltage lockout have not activated.
- To limit the voltage drop on the input supply caused by transient in-rush currents when the switch turns-on into a discharged load capacitor or short-circuit, a capacitor (C1) needs to be placed between V IN and GND. A output capacitor (C2) should be placed between V OUT and GND to prevent parasitic board inductances from forcing V OUT below GND when the switch turns-off. For best performance, all traces in the PCB should be as short as possible. To be most effective, the input and output capacitors should be placed close to the device to minimize the effects that parasitic trace inductances may have on normal and short-circuit operation. Using wide traces for V IN , V OUT and GND will help minimize parasitic electrical effects along with minimizing the case to ambient thermal impedance.
- different package solutions in this family are available in WL-CSP, MLP, SOT-23 and SC-70. Here shows the dimension for each package.
- Thank you for taking the time to view this presentation on “ IntelliMAX ™ Advanced Load Management Switches” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the FAIRCHILD SEMICONDUCTOR site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility.