LP3931ISQX/NOPB

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LP3931ISQX/NOPB is classified as PMIC - LED Drivers. It is a low quiescent current, constant frequency, step-down DC/DC converter designed for driving a low-power LED. LP3931ISQX/NOPB integrates an internal MOSFET and current regulator which provide constant LED current over wide input voltage range. It\'s high performance and small package make LP3931ISQX/NOPB the ideal choice for driving low-power LEDs in portable devices.

Application Field

Typical applications include Cellphones, MP3 Players, Digital Cameras, Notebooks, Bluetooth headsets and other portable electronic devices. LP3931ISQX/NOPB can further be used to drive LEDs for a variety of applications, from LCD backlight display to alarm systems, automotive or building interior lighting.

Working Principle

LP3931ISQX/NOPB is a high-efficiency, constant frequency, step-down DC/DC converter designed for driving a low-power LED. This device offers an integrated internal MOSFET and current regulator that provide constant LED current over a wide input voltage range. Its architecture is a single loop current mode control. When the LED current drops, the converter will automatically increase its frequency to ensure stable LED current operation.

The step-down converter operates between a wide input voltage range, typically from 2.5 V to 6.5 V. Its frequency range can be adjusted by changing the values of an external resistor and capacitor. The LED current can be adjusted by an external resistor and is determined by the LED current set voltage, which is supplied to the VLED terminal. The output current is sourced from the VLED terminal and is accurate within ±3%. An internal compensation network ensures stability across a wide input voltage range.

LP3931ISQX/NOPB also features low quiescent current consumption, typically 57 μA for a load of 2 mA. Other features include soft start, open LED protection, over temperature protection, under voltage lockout and a programmable open LED safety timer. In the event of an over current condition, a -40 mV hysteresis is incorporated to allow a smooth recovery from the fault condition.

LP3931ISQX/NOPB will shut-off the output current when an open LED fault is detected. The current will be ramped down slowly as the voltage across the LED is monitored and the IC is reset when the voltage has dropped below the voltage set level. The soft start and open LED protection ensure reliability and safety throughout the system.

LP3931ISQX/NOPB is packaged in a 16-pin QFN package and is available from Texas Instruments in both commercial (0°C to 70°C) and automotive (-40°C to 125°C) temperature ranges. Other family members include LP3931ISQX-5.5/NOPB, a member which offers an extended 5.5 V to 6.5 V input voltage range, and LP3931ISQX-0.3/NOPB, a member which offers an output current of up to 300 mA.

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