LM3501TL-25

• Synchronous rectification is required with high efficiency and no external Schottky diode
• Use small surface mount components
• Can drive 2-5 series white LEDs (possible functions with more.)_inexpensiveV F indicator)
• Input voltage range of 2.7V to 7V
• True off-isolation, no LED leakage current
• LED current control of DC voltage
• Input undervoltage lockout
• Internal Output Overvoltage Protection (OVP) Circuit, LM3501-16 Required, No External Zener Diode Required: 15.5V OVP; LM3501 - 21: 20.5V OVP.
• All that is required for input and output is a tiny 16V (LM3501 - 16) or 25V (LM3501 - 21) ceramic capacitor
• Thermal shutdown
• 0.1μA shutdown current
• Small 8-ball low profile micro SMD package

illustrate

The LM3501 is a fixed frequency step-up DC/DC converter ideal for driving white LED display backlighting and other lighting functions. Fully integrated with synchronous switching (no external Schottky diode required) and low feedback voltage (515 mV), the LM3501 circuit is optimized for power efficiency in lighting applications in wireless handsets and other portable products (single-cell Li-ion battery or 3-NiMH battery powered). The LM3501 operates a fixed 1 MHz switching frequency. The LM3501 ceramic input and output capacitors, when used together, provide a small, low-noise, low-cost solution.

Two LM3501 options are available with different output voltage capabilities. The LM3501-21 has a maximum output voltage of 21V and is usually suitable for driving 4 or 5 white LEDs in series. The LM3501-16 has a maximum output voltage of 16V and is usually suitable for driving 3 or 4 white LEDs in series (the maximum number of LEDs in series depends on the forward voltage of the LED). If the main white LED network should be disconnected, the LM3501 uses an internal protection circuit to prevent damaging overvoltage events.

A single external resistor is used to set the maximum LED current for LED drive applications. LED current can easily adjust the analog control voltage on different control pins or turn off pins by using pulse-width modulation (PWM) signals. The LM3501 shuts down completely, disconnecting the output inputs, creating complete isolation and preventing any leakage current from trickling from the LEDs.

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• LCD bias power supply
• White LED backlight
• Handheld devices
• Digital cameras
• Portable applications