LM3500  Product Folder

The LM3500 is a fixed frequency synchronous step-up DC/DC converter in a small 8-bump thin micro SMD package. The LM3500 is ideal for white LED applications for cellular phone back-lighting requiring low current and high efficiency. Its fixed 1MHz operating frequency allows the use of small, low ESR capacitors as well as a more predictable frequency spectrum, which is important in cellular phone applications. The LM3500 can drive 2 to 4 white LEDs in series from a single Li-Ion battery or 3 cell NiMH with no external rectification diode. For white LED applications, a single external resistor is used to set the maximum LED current. The white LED current can easily be adjusted using a pulse width modulated (PWM) signal on the shutdown pin. The LM3500 uses special protection circuitry on the output to prevent an overvoltage event if the primary white LED network should be disconnected eliminating the need of an extra protection Zener diode. In shutdown, the LM3500 disconnects the input and output creating a true isolation preventing any LED light from emitting over the full input operating voltage range and temperature.

• Synchronous rectification, high efficiency and no external schottky diode required
• Uses small surface mount components
• Can drive up to 3 (or 4 low V_F) white LEDs in series
• 2.7V to 7V input range
• True shutdown isolation
• Input undervoltage lockout
• Output overvoltage protection, no external zener diode required
• Requires only a small 16V ceramic capacitor at the output
• Thermal Shutdown
• 0.1µA shutdown current
• Small 8-bump thin micro SMD package

• LCD Bias Supplies
• White LED Back-Lighting
• Handheld Devices
• Digital Cameras
• Portable Applications